Wikipedia - Benutzerbeiträge [de]

Der Herr der Karawane

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{{Infobox film
| name = Caravans
| image = Caravans_(1978).jpg
| image size =
| caption =
| alt =
| director = [[James Fargo]]
| producer = [[Elmo Williams]]
| based on = {{based on|''[[Caravans (novel)|Caravans]]''|[[James A. Michener]]}}
| screenplay = [[Nancy Voyles Crawford]], [[Thomas A. McMahon]] and [[Lorraine Williams]]
| starring = [[Anthony Quinn]] [[Behrouz Vossoughi]] [[Michael Sarrazin]] [[Christopher Lee]] [[Jennifer O'Neill]]
| music = [[Mike Batt]]
| cinematography = [[Douglas Slocombe]]
| studio = [[FIDCI]]
| editing = [[Richard Marden]]
| distributor = [[Universal Pictures]]
| released = {{film date|1978|11|2|[[Radio City Music Hall]]|ref1=<ref name="nyt" />}}
| runtime = 127 minutes
| country = United States Iran
| language = English Persian
| budget = $10 million<ref>{{cite web |url=http://catalog.afi.com/Film/56234-CARAVANS?sid=a1db55ec-1e67-4777-abfa-dff4bf6354a7&sr=0.8563489&cp=1&pos=0#1 |title=Caravans - History |website=[[AFI Catalog of Feature Films]] |publisher=[[American Film Institute]] |accessdate=May 18, 2019 }}</ref>
| gross = $1.965 million (US-Canada rentals)<ref>"Big Rental Films of 1979". ''[[Variety (magazine)|Variety]]''. January 9, 1980. 70.</ref>
}}

'''Caravans''' is a 1978 Iranian-American film directed by [[James Fargo]] based on [[Caravans (novel)|the novel]] by [[James A. Michener]]. Nancy Voyles Crawford wrote the screenplay. This movie represents people of [[Afghanistan]] and their tradition in [[Qandahar]], [[Badakhshan]] cities in that time and the [[Kochi people]] of afghanistan. The movie was shot in [[Afghanistan]] and [[iran]] and starred [[Anthony Quinn]], [[Jennifer O'Neill]], and [[Michael Sarrazin]].

==Plot==
The story is set in the fictional Middle Eastern country of Zadestan in 1948. Mark Miller is stationed at the U.S. Embassy in the fictional city of Kashkhan and is assigned to investigate the disappearance of and locate a young woman, Ellen Jasper, the daughter of a United States Senator, who vanished after her marriage to Colonel Nazrullah several months previously. Nazrullah is desperate to find her and becomes defensive when Miller asks about her. By law, Ellen has given up her rights as an American by becoming his wife. Miller traces her to a band of nomads who are running illegal guns. She doesn't want to leave, being estranged from both her parents and her husband. Miller doesn't want to return without proof she's alive and OK, which she refuses to give. Nazrullah lures the gun-runners into a trap. He separates Miller from the nomads and asks his wife to return to him but she refuses. Ellen at last gives Miller a note for her family. As the nomads leave, Nazrullah orders his troops to fire on them and Ellen is killed trying to rescue a child. A heart-broken Nazrullah carries away the body of his dead wife.

==Cast==
*[[Anthony Quinn]] as Zulffiqar
*[[Michael Sarrazin]] as Mark Miller
*[[Christopher Lee]] as Sardar Khan
*[[Jennifer O'Neill]] as Ellen Jasper
*[[Behrouz Vossoughi]] as Colonel Nazrullah
*[[Joseph Cotten]] as Crandall
*[[Barry Sullivan (American actor)|Barry Sullivan]] as Richardson
*[[Jeremy Kemp]] as Dr. Smythe
*Duncan Quinn as Moheb
*Behrouz Gramian as Peasant Boy (Behrooz Gueramian)
*[[Mohammad-Ali Keshavarz]] as Shakkur
*[[Parviz Gharib-Afshar]] as Nur Mohammad
*Fahimeh Amouzandeh as Mira
*Mohammad Kahnemoui as Maftoon (Mohammad Taghi Kahnemoui)
*Khosrow Tabatabai as Dancing Boy

==Changes from the source novel==
The film was not well received by James Michener as it strayed wildly from the plot of his book, even eradicating its main character, a Nazi war criminal on the run who falls in love with the female lead character. This omission and other story changes caused Michener to take legal action.{{Citation needed|date=May 2019}}

==Music==
[[Mike Batt]] wrote the score, which has been the most successful element of the film, remaining a bestseller for many years after the film's release. The song "Caravan Song" was written by Mike Batt and sung by the Scottish singer [[Barbara Dickson]]. It peaked at No. 41 in UK charts and featured on the album ''[[All for a Song]]''.

==Reception==
Harold C. Schonberg of ''[[The New York Times]]'' panned the film as a "fake epic," adding. "It has a fabricated plot, based on the James Michener novel, it has bad acting, it has unbelievably inane dialogue, and it has every cliché in the books, including an ending with the caravan silhouetted against the sunset. Even so reliable an actor as Anthony Quinn looks idiotic; he displays his macho by grunts and mutters, and occasionally there is a peculiar look on his face that suggests what he really thinks of all this nonsense."<ref name="nyt">[https://www.nytimes.com/1978/11/06/archives/arts-theater.html "Arts".] ''[[The New York Times]]''. November 6, 1978. 54.</ref> ''[[Variety (magazine)|Variety]]'' wrote, "The main trouble with 'Caravans' isn't the Iranians, it's Hollywood. Almost every fake moment in the film, and there are lots of them, has the touch of Hollywood laid on with a heavy coating. Take away the Americans, of course, and you wouldn't have such a slick film, but you might have a more honest one."<ref>"Film Reviews: Caravans". ''[[Variety (magazine)|Variety]]''. November 8, 1978. 18.</ref> [[Roger Ebert]] of the ''[[Chicago Sun-Times]]'' gave the film 2 stars out of 4 and wrote that it was "slow and obvious, and at the end rather pointless," but "if you're facing a slow Sunday afternoon with a lot of time before the roast is done, 'Caravans' could, in its own way, be fun."<ref>{{cite web |url=https://www.rogerebert.com/reviews/caravans-1979 |title=Caravans |last=Ebert |first=Roger |date=January 30, 1979 |website=[[RogerEbert.com]] |accessdate=May 18, 2019 }}</ref> [[Gene Siskel]] of the ''[[Chicago Tribune]]'' gave the film 1 star out of 4 and called it "a thoroughly laughable desert adventure" with the relationship between Quinn and O'Neill getting "short shrift" and the movie lacking "an action scene of any merit. Only at the very end is there a battle of sorts. But director James Fargo ... shoots these scenes in boring medium shots. They are as exciting as if they had been shot with models in a sandbox."<ref>Siskel, Gene (February 1, 1979). "'Caravans': Sandlot drama". ''[[Chicago Tribune]]''. Section 2, p. 5.</ref> [[Kevin Thomas (film critic)|Kevin Thomas]] of the ''[[Los Angeles Times]]'' called the film "a stirring romantic epic on a grand scale marred by patches of truly terrible dialogue. As a result, despite all that this Universal release has going for it in the way of visual splendor and high adventure, it is likely to be entertaining only for the least discriminating (or most indulgent)."<ref>Thomas, Kevin (December 22, 1978). "Iranian Adventure in 'Caravans'". ''[[Los Angeles Times]]''. Part IV, p. 16.</ref> Gary Arnold of ''[[The Washington Post]]'' wrote, "'Caravans' will be lucky if it's remembered as an expensive flop ... Ironically, the film's emptiness is magnified by the contrast between its drab, flimsy plot and vast, majestic landscapes. 'Caravans' is too inert to be salvaged by the photogenic advantages of impressive scenery."<ref>Arnold, Gary (March 27, 1979). [https://www.washingtonpost.com/archive/lifestyle/1979/03/27/wandering-caravans-trek-to-oblivion/bd007e2d-6b20-4c08-9b89-5489912d7e52/ "Wandering 'Caravans'".] ''[[The Washington Post]]''. B1.</ref> Tim Pulleine of ''[[The Monthly Film Bulletin]]'' wrote that "Ellen's twofold defection remains resolutely undramatised and the gun-running sub-plot is mainly demoted to a few cryptic reference to off-screen action. The movie thus becomes a tiresome exercise in anti-climax."<ref>{{cite journal |last=Pulleine |first=Tim |date=February 1980 |title=Caravans |journal=[[The Monthly Film Bulletin]] |volume=47 |issue=553 |page=20 }}</ref>

==References==
{{Reflist}}

==External links==
*{{IMDb title|id=0077296|title=Caravans}}

{{James Fargo}}

[[Category:English-language films]]
[[Category:1978 films]]
[[Category:Films set in the Middle East]]
[[Category:Films set in a fictional Asian country]]
[[Category:Films set in 1948]]
[[Category:Universal Pictures films]]
[[Category:American adventure drama films]]
[[Category:American films]]
[[Category:Films shot in Iran]]

Monolingualismus

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{{Use American English|date=January 2019}}
{{Use mdy dates|date=January 2019}}
{{Short description|The ability to only speak one language}}
'''Monoglottism''' ([[Greek language|Greek]] μόνος ''monos'', "alone, solitary", + γλῶττα ''glotta'', "tongue, language") or, more commonly, '''monolingualism''' or '''unilingualism''', is the condition of being able to speak only a single language, as opposed to [[multilingualism]]. In a different context, "unilingualism" may refer to a [[language policy]] which [[forced language|enforces]] an official or [[national language]] over others.

Being '''monolingual''' or '''unilingual''' is also said of a text, [[dictionary]], or conversation written or conducted in only one language, and of an [[entity]] in which a single language is either used or officially recognized (in particular when being compared with bilingual or multilingual entities or in the presence of individuals speaking different languages). Note that mono''glottism'' can only refer to lacking the ''ability'' to speak several languages. Multilingual speakers outnumber monolingual speakers in the world's population.<ref>G. Richard Tucker (1999)[http://www.cal.org/resources/Digest/digestglobal.html A Global Perspective on Bilingualism and Bilingual Education] {{webarchive|url=https://web.archive.org/web/20120822104004/http://www.cal.org/resources/Digest/digestglobal.html |date=2012-08-22 }} Carnegie Mellon University CALL Digest EDO-FL-99-04</ref>

Suzzane Romaine pointed out, in her 1995 book ''Bilingualism'', that it would be weird to find a book titled ''Monolingualism''.<ref>{{cite book |last=Romaine |first=Suzzane |year=1995 |publisher=Wiley-Blackwell |title=Bilingualism |pages=1 |isbn=978-0-631-19539-9}}</ref> This statement reflects the traditional assumption that linguistic theories often take on: that monolingualism is the norm.<ref>{{cite journal |last=Pavlenko |first=Aneta |title=L2 influence on L1 in late bilingualism. |journal=Issues in Applied Linguistics. |year=2000 |volume=11 |issue=2 |pages=175–206 }}</ref> Monolingualism is thus rarely the subject of scholarly publications, as it is viewed to be an unmarked or prototypical concept where it has the sense of being normal and [[multilingualism]] is the exception.<ref name="ellis">{{cite journal |last=Ellis |first=Elizabeth |title=Monolingualism: The unmarked case |journal=Estudios de Sociolingüística. |year=2006 |volume=7 |issue=2 |pages=173–196}}</ref>

The assumption of normative monolingualism is also often the view of monolinguals who speak a [[world language|global language]], like the [[English language]]. Crystal (1987) said that this assumption is adopted by many in Western society.<ref>{{cite book |last=Crystal |first=David |year=1987 |publisher=Cambridge University Press |title=The Cambridge Encyclopaedia of Language |isbn=978-0-521-55967-6}}</ref> One explanation is provided by Edwards, who in 2004 claimed that evidence of the "monolingual mindset" can be traced back to 19th century [[Europe]], when the nation was rising and a dominant group had control,{{what|date=December 2013}} and European mindsets on language were carried forth to its [[colonies]], further perpetuating the monolingual mindset.<ref>{{cite book |last1=Edwards |first1=Viv |title=Multilingualism in the English-speaking world. |publisher=Wiley-Blackwell |year=2004 |isbn=978-0-631-23613-9 |pages=3–5}}</ref>

Another explanation is that the nations who speak the [[English language]] are both “the producers and beneficiaries of English as a [[world language|global language]]” and the populations within these countries tend to be monolingual.<ref name="ellis"/>

==Comparison with multilingualism==
===Vocabulary size and verbal fluency===
According to a study on lexical access,<ref>{{cite journal |last1=Bialystok |first1=Ellen |last2=Craik |first2=Fergus I.M |last3=Luk |first3=Gigi. |title=Lexical access in bilinguals: Effects of vocabulary size and executive control |journal=Journal of Neurolinguistics |volume=21 |issue=6 |pages=522–538 |year=2008 |doi=10.1016/j.jneuroling.2007.07.001}}</ref> monolinguals often maintain a wider [[vocabulary]] in a target language relative to a comparable [[bilingual]], and that increases the efficiency of word retrieval in monolinguals. Monolinguals also access words more often than bilinguals in a target language.

In letter fluency tasks, monolinguals in the study were also able to respond with more words to the letter cue than bilinguals, but such an effect was not seen in bilinguals with a high [[vocabulary]] score.

Also, monolinguals performed better than bilinguals on verbal fluency in the study. If the [[vocabulary abilities]] were made to be more comparable, however, many of the differences would disappear, indicating that [[vocabulary]] size may be a factor that moderated a person's performance in verbal fluency and naming tasks. The same study also found that bilinguals, in a version of the letter fluency task that placed more demand on executive control, performed better than monolinguals. Thus, once [[vocabulary]] abilities were controlled, bilinguals performed better on letter fluency possibilities by the enhanced frontal executive processes in the [[brain]].

It is important to note here that bilinguals' overall vocabulary size in both languages combined was equivalent to monolinguals' in one language. While monolinguals may excel in vocabulary size for the one language they speak, their vocabulary content is not greater. Bilinguals may have smaller vocabularies in each individual language, but when their vocabularies were combined, the content size was approximately similar to that of the monolingual. Monolingual children demonstrated larger vocabulary scored than their bilingual peers, but bilingual children's vocabulary scores still increased with age, just like the monolingual children's vocabulary scores (Core et al., 2011). Despite a variation in vocabulary scores, there was absolutely no difference between monolingual and bilingual children in terms of total vocabulary size and total vocabulary gains (Core et al., 2011). Bilingual children and monolingual children have the same vocabulary size and gain the same vocabulary knowledge.

===Creative functioning===
In a study testing for creative functioning that involved monolingual and bilingual children in [[Singapore]],<ref>{{cite journal |last1=Torrance |first1=E. Paul |last2=Gowan |first2=John.C. |last3=Wu |first3=Jing-Jyi |last4=Aliotti |first4=Nicholas C. |title=Creative functioning of monolingual and bilingual children in Singapore |journal=Journal of Educational Psychology |volume=61 |issue=1 |pages=72–75 |year=1970 |doi=10.1037/h0028767}}</ref> researchers found that monolinguals performed better on fluency and flexibility than bilinguals. The trend was reversed, however, on tests for originality and elaboration.

===Mental well-being===
In another recent study in [[Canada]], it has been shown that monolinguals were worse at the onset of [[senility]] than bilinguals.<ref>{{cite news|url=http://www.biologynews.net/archives/2007/01/11/canadian_study_shows_bilingualism_has_protective_effect_in_delaying_onset_of_dementia_by_four_years.html|title=Canadian study shows bilingualism has protective effect in delaying onset of dementia by 4 years|work= Biology News Net|date=January 11, 2007}}</ref> In the study, it seems that being [[bilingual]] is associated with a delay of [[dementia]] by four years as compared to monolinguals. Bialystok's most recent work also shows that lifelong bilingualism can delay symptoms of [[dementia]].<ref name="university affairs">{{cite web|url=http://www.universityaffairs.ca/the-rise-of-the-monoglots.aspx |title=The rise of the monoglots |publisher=University Affairs.ca |date=August 5, 2008 |accessdate=11 March 2012}}</ref>

It is believed that bilingualism contributes to cognitive reserve by preventing effects of cognitive delay and prolonging the onset of sicknesses such as dementia. Cognitive reserve refers to the idea that engaging in stimulating physical or mental activity maintains cognitive functioning (Bialystok et al., 2012). In that case, knowing more than one language is similar to stimulating mental activity. To test whether or not bilingualism contributes to cognitive reserve, Bialystok et al. (2012) looked at hospital records among monolingual and bilingual adults who have dementia. The researchers found that elderly bilingual adults were diagnosed with dementia about three to four years later than elderly monolingual adults. The results have been replicated and validated, with outside factors being controlled. In fact, outside factors such as socioeconomic status and cultural differences always helped monolinguals, making the argument the bilingualism contributes to cognitive reserve even stronger (Bialystok et al., 2012). That finding enhances the fact that bilinguals are at an advantage because of their ability to speak two languages, not because of outside factors. A probable explanation for this phenomenon is that knowledge of multiple languages keeps the brain alert and therefore more mentally aware for a longer period of time.

===Emotion and behaviour===
A study conducted with children in their early school years suggested that there are emotional and behavioural benefits to being bilingual.<ref>{{cite journal |last1=Han |first1=Wen-Jui |last2=Huang |first2=Chien-Chung |title=The forgotten treasure: Bilingualism and Asian children's emotional and behavioural health |journal=American Journal of Public Health |year=2010 |volume=100 |issue=5 |pages=831–838 |doi=10.2105/ajph.2009.174219|pmc=2853634 }}</ref> In the same study, the findings show that monolingual children, in particular non-English monolingual children, display more poor behavioural and emotional outcomes in their school years. The non-English monolingual children had the highest level of externalizing and internalizing behaviourial problems by fifth grade(around 10–11 years of age), even though the children were all measured to have similar levels of internalizing and externalizing behaviourial problems at the start{{what|date=December 2013}}. In contrast, the fluent [[bilingual]] and non-English dominant bilingual children were found to have the lowest level of these behaviourial problems. The authors suggest that monolingualism seems to be a risk factor. However, if there is a supportive school environment with teachers who are experienced in [[ESL]] (English as a Second Language), children seem to have better emotional constitution.

===Memory performance===
In a study conducted at the [[University of Florida]], which compared Native-English [[bilingual]]s to English monolinguals, although there was no difference in accuracy between the two groups, there was an evident slower response rate from bilinguals on tasks that involve latency of recognition of a list of abstract words and [[lexical decision task]]s.<ref>{{cite journal |last1=Ransdell |first1=Sarah Ellen |last2=Fischler |first2=Ira |title=Memory in a monolingual mode:When are bilinguals at a disadvantage? |journal=Journal of Memory and Language |year=1987 |volume=26 |pages=392–405 |doi=10.1016/0749-596x(87)90098-2}}</ref> For these two tasks, language-specific and data driven processes were more prevalent, that is, the tasks were driven by the dominant language and the data (the words used in the task). The study differed from prior research that there is more balance in familiarity of the [[dominant language]]. Magiste's (1980) hypothesis that it could have been due to differential familiarity with the [[dominant language]] is suggested to be a possible reason for the bilingual disadvantage.<ref>{{cite journal |last=Magiste |first=Edith |year=1980 |title=Memory for numbers in monolinguals and bilinguals |journal=Acta Psychologica |volume=46 |pages=63–68 |doi=10.1016/0001-6918(80)90059-1}}</ref> They explained that for bilinguals, it could be because the acquiring and using of the [[second language]] meant that there was less time to process English, as compared to the monolingual participants in the study.

However, evidence from a research study shows that bilinguals have a faster reaction time in most working memory tasks. While a lot of research asserts that monolingual children outperform bilingual children, other research asserts the opposite. Research by Bialystok et al., as reported by Kapa and Colombo (2013, p. 233) shows that bilingual individuals perform better than monolingual individuals on a wide variety of cognitive tests, thus demonstrating cognitive control advantages. Two different concepts, attentional inhibition and attentional monitoring, are used to measure attentional control. In terms of attentional control, early bilingual learners showed the greatest advantage, compared to monolingual speakers and late bilingual speakers. In terms of overall performance on ATN, the three groups performed equally, but when age and verbal ability variables were controlled, there was a difference in reaction time. The early bilingual children's reaction time was tremendously faster than the monolingual children, and only slightly faster than the late bilingual children (Kapa & Colombo, 2013). Early bilingual learners showed that they simply responded most efficiently to the task at hand. The results from this study demonstrate the advantages bilingual children have with attentional control. This is likely because bilingual children are used to balancing more than one language at time, and are therefore used to focusing on which language is necessary at a certain time. By constantly being aware of what language to use and being able to successfully switch between languages, it makes sense that bilingual children would be better at directing and focusing their attention.

===Verbal and non-verbal cognitive development===
A 2012 study by the [[University of York]] published in ''Child Development'' journal<ref>{{cite web |url=http://www.dushi.ca/tor/education/bencandy.php/fid18/aid1819 |title=最新研究：双语儿童比单语小孩更聪慧 |publisher=加拿大都市网 |date=10 February 2012 |accessdate=23 March 2013}}</ref> reviewed the effects of the development of a child's verbal and non-verbal language, matched between monolinguals and bilinguals in a particular language. Researchers compared about 100 6-year-old monolingual and [[bilingual]] children (monolingual in English; bilingual in English and Mandarin, bilingual in French and English, bilingual in Spanish and English), to test their verbal and [[non-verbal communication]] [[cognitive development]]. The research takes into consideration factors like the similarity of the language, the cultural background and education experience. These students mostly come from public schools from various areas, having similar social and economic background.

Results show that in the child's early stage, multilingual kids are very different from one another in their language and [[cognitive]] skills development, and also when compared to monolingual children. When compared to monolinguals, multilingual children are slower in building up their [[vocabulary]] in every language. However, their metalinguistic development allowed them to understand better the structure of the language. They also performed better in non-verbal control tests. A non-verbal control test refers to the ability to focus and then able to divert their attention when being instructed to.

==Reasons for persistence==
===Convergence principle===
According to the convergence principle,<ref name="snow">{{cite book|title=Language Loyalties: A Source Book on the Official English Controversy. |chapter=The Costs of Monolingualism |last1=Snow |first1=Catherine E.|last2=Hakuta |first2=Kenji |editor=Crawford, J.|publisher=The University of Chicago |year=1992 |pages=384–394 |url=http://www.stanford.edu/~hakuta/Publications/(1992)%20-%20THE%20COST%20OF%20MONOLINGUALISM.pdf |accessdate=9 March 2012}}</ref> language style tends to change to that of people who are liked and admired. Conversations in which one party speaks a language different from the other persons both are hard to maintain and have reduced intimacy. Thus, speech is usually adapted and accommodated for convenience, lack of misunderstanding and conflict and the maintenance of intimacy. In intermarriages, one partner tends to become monolingual, which also usually applies to the children.

===Predominance of English===
{{see also|English-only movement}}
The predominance of [[English language|English]] in many sectors, such as world trade, [[technology]] and [[science]], has contributed to English-speaking societies being persistently monolingual, as there is no relevant need to learn a [[second language]] if all dealings can be done in their [[native language]];<ref>{{cite journal |last=Peel |first=Quentin |title=The monotony of monoglots |journal=Language Learning Journal |volume=23 |issue=1 |pages=13–14 |year=2001 |doi=10.1080/09571730185200041}}</ref> that is especially the case for English-speakers in the [[United States]], particularly the [[Northern United States]] and most of the [[Southern United States]], where everyday contact with other languages, such as [[Spanish language|Spanish]] and [[French language|French]] is usually limited. The country's large area and the most populous regions' distance from large non-English-speaking areas, such as [[Mexico]] and [[Quebec]], increase the geographic and economic barriers to foreign travel.<ref>{{cite news|url=http://news.gallup.com/poll/1825/about-one-four-americans-can-hold-conversation-second-language.aspx|title=About One in Four Americans Can Hold a Conversation in a Second Language}}</ref> Nevertheless, the requirement for all school children to learn a foreign language in some English speaking countries and areas works against this to some extent. Although the country is economically interdependent with trade partners such as [[China]], American corporations and heavily-Americanized subsidiaries of foreign corporations both mediate and control most citizens' contact with most other nations' products. There is a popular joke: "What do you call a person who speaks three languages? A trilingual. What do you call a person who speaks two languages? A bilingual. What do you call a person who speaks one language? An American."<ref>{{cite book|last1=Gramling|first1=David|title=The Invention of Monolingualism|date= 6 October 2016|publisher=Bloomsbury Publishing|isbn=1501318055|pages=60-61}}</ref>

There is also increasing pressure on [[multilingualism|bilingual]] [[immigrants]] to renounce their [[mother tongue]] and to adopt their host country's language. As a result, even though there may be immigrants from a wide variety of nationalities and cultures, the main language spoken in the country does not reflect them.{{Citation needed|date=February 2015}}

==Costs==
Snow and Hakuta<ref name="snow" /> write that in a cost-benefit analysis, the choosing of English as the official and national language often comes with additional costs on the society, as the alternative choice of multilingualism has its own benefits.

===Education===
Some of the education budget is allocated for foreign-language training, but [[fluency]] of foreign-language students is lower than those who learned it at home.<ref name="snow" />

===Economic===
[[International business]] may be impeded by a lack of people competent in other languages.<ref name="snow" />

===National security===
Money has to be spent to train foreign-service personnel in foreign languages.<ref name="snow" />

===Time and effort===
Compared to the maintenance of a language that is learned at home, more time, effort and hard work are required to learn it in school.<ref name="snow" />

===Job opportunities===
Kirkpatrick asserts that monolinguals are at a disadvantage to bilinguals in the international job market.<ref>{{cite journal |last=Kirkpatrick |first=Andy |year=2000 |title=The disadvantaged monolingual: Why English alone is not enough. |journal=Australian Language Matters |volume=8 |issue=3 |pages=5–7 }}</ref>

==In the media==
[[Lawrence Summers]], in an article published in the ''[[New York Times]]'',<ref>{{cite news |url=https://www.nytimes.com/2012/01/22/education/edlife/the-21st-century-education.html?pagewanted=all |last=Summers |first=Lawrence H. |title=What You (Really) Need to Know |work=New York Times |date=20 January 2012}}</ref> discusses how to prepare for the future advancement of America. He also questioned the importance and necessity of learning foreign languages by remarking that "English's emergence as the [[global language]], along with the rapid progress in [[machine translation]] and the fragmentation of languages spoken around the world, makes it less clear that the substantial investment necessary to speak a foreign tongue is universally worthwhile."

Others have disagreed with Summers' view. A week later, the ''New York Times'' hosted a discussion among six panelists,<ref>{{cite news |url=https://www.nytimes.com/roomfordebate/2012/01/29/is-learning-a-language-other-than-english-worthwhile |date=29 January 2012 |title=English Is Global, So Why Learn Arabic? |work=New York Times |last1=Berdan |first1=Stacie Nevadomski |last2=Jackson |first2=Anthony |last3=Erard |first3=Michael |last4=Ho |first4=Melanie |last5=Suarez-Orozco |first5=Marcelo M. |last6=Lewis |first6=Clayton}}</ref> all of whom were for learning foreign languages and cited the benefits and advantages and the changing global landscape.

==See also==
*[[Multilingualism]]
*[[Languages of the United Kingdom]]
*[[Languages of the United States]]
*[[Linguistic imperialism]]
*[[List of multilingual countries and regions]]

==References==
{{Reflist}}

* Bialystok, E., Craik, F. & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Neuropsychology & Neurology, Linguistics & Language & Speech, 16(4), 240-250.
* Core, C., Hoff, E., Rumiche, R., & Senor, M. (2011). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637-1649.
* Kapa, L., & Colombo, J. (2013). Attentional control in early and later bilingual children.Cognitive Development, 28(3), 233-246.

==External links==
{{Wiktionary|monoglottism|monolingualism|unilingualism}}
*[https://litigation-essentials.lexisnexis.com/webcd/app?action=DocumentDisplay&crawlid=1&crawlid=1&doctype=cite&docid=14+Cardozo+L.+Rev.+1713&srctype=smi&srcid=3B15&key=30ce6efd643c7fdf6f394561a88d0a65 Monolingualism and Judaism] by Jose Faur, contrasting the Greek monolingualism with the polyglot culture of the Hebrews

[[Category:Monolingualism]]

Benutzer:Robin16324/

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{{Use British English |date=April 2017}}
{{Use mdy dates|date=June 2018}}
{{Infobox anatomy
| Name = Human brain
| Latin = Cerebrum<ref>{{cite web |url=http://dictionary.reference.com/browse/cerebrum |title=''Cerebrum'' Etymology |publisher=''[[dictionary.com]]'' |accessdate=October 24, 2015 |deadurl=no |archiveurl=https://web.archive.org/web/20151024035732/http://dictionary.reference.com/browse/cerebrum |archivedate=October 24, 2015 }}</ref>
| Greek = ἐγκέφαλος (enképhalos)<ref>{{cite web |url=http://etymonline.com/index.php?allowed_in_frame=0&search=encephalo- |title=''Encephalo-'' Etymology |publisher=''[[Online Etymology Dictionary]]'' |accessdate=October 24, 2015 |deadurl=no |archiveurl=https://web.archive.org/web/20171002022623/http://etymonline.com/index.php?allowed_in_frame=0&search=encephalo- |archivedate=October 2, 2017 }}</ref>
| Image = Skull and brain normal human.svg
| Caption = Human brain and skull
| Width =
| Image2 = Cerebral lobes.png
| Caption2 = Cerebral lobes: the [[frontal lobe]] (pink), [[parietal lobe]] (green) and [[occipital lobe]] (blue)
| Precursor = [[Neural tube]]
| System = [[Central nervous system]] [[Neuroimmune system]]
| Artery = [[Internal carotid artery|Internal carotid arteries]], [[Vertebral artery|vertebral arteries]]
| Vein = [[Internal jugular vein]], [[internal cerebral veins]]; external veins: ([[superior cerebral veins|superior]], [[middle cerebral veins|middle]], and [[inferior cerebral veins|inferior]] [[cerebral veins]]), [[basal vein]], and [[cerebellar veins]]
| Nerve =
| Lymph =
}}
The '''human brain''' is the central [[organ (anatomy)|organ]] of the human [[nervous system]], and with the [[spinal cord]] makes up the [[central nervous system]]. The brain consists of the [[cerebrum]], the [[brainstem]] and the [[cerebellum]]. It controls most of the activities of the [[human body|body]], processing, integrating, and coordinating the information it receives from the [[Sensory nervous system|sense organs]], and making decisions as to the instructions sent to the rest of the body. The brain is contained in, and protected by, the [[neurocranium|skull bones]] of the [[human head|head]].

The cerebrum is the largest part of the human brain. It is divided into two [[cerebral hemisphere]]s. The [[cerebral cortex]] is an outer layer of [[grey matter]], covering the core of [[white matter]]. The cortex is split into the [[neocortex]] and the much smaller [[allocortex]]. The neocortex is made up of six [[Cerebral cortex#Layers|neuronal layers]], while the allocortex has three or four. Each hemisphere is conventionally divided into four [[lobes of the brain|lobes]] – the [[frontal lobe|frontal]], [[temporal lobe|temporal]], [[parietal lobe|parietal]], and [[occipital lobe]]s. The frontal lobe is associated with [[executive functions]] including [[self-control]], [[planning]], [[reason]]ing, and [[abstraction|abstract thought]], while the occipital lobe is dedicated to vision. Within each lobe, cortical areas are associated with specific functions, such as the [[sensory cortex|sensory]], [[motor cortex|motor]] and [[Cerebral cortex#Association areas|association]] regions. Although the left and right hemispheres are broadly similar in shape and function, some functions are [[lateralization of brain function|associated with one side]], such as [[language]] in the left and [[spatial visualization ability|visual-spatial ability]] in the right. The hemispheres are connected by [[Commissural fiber|commissural nerve tracts]], the largest being the [[corpus callosum]].

The cerebrum is connected by the brainstem to the spinal cord. The brainstem consists of the [[midbrain]], the [[pons]], and the [[medulla oblongata]]. The [[cerebellum]] is connected to the brainstem by [[cerebellar peduncle|pairs of tracts]]. Within the cerebrum is the [[ventricular system]], consisting of four interconnected [[Ventricular system#Structure|ventricles]] in which [[cerebrospinal fluid]] is produced and circulated. Underneath the cerebral cortex are several important structures, including the [[thalamus]], the [[epithalamus]], the [[pineal gland]], the [[hypothalamus]], the [[pituitary gland]], and the [[subthalamus]]; the [[limbic system|limbic structures]], including the [[amygdala]] and the [[hippocampus]]; the [[claustrum]], the various [[Nucleus (neuroanatomy)|nuclei]] of the [[basal ganglia]]; the [[basal forebrain]] structures, and the three [[circumventricular organ]]s. The [[Cell (biology)|cells]] of the brain include [[neuron]]s and supportive [[neuroglia|glial cells]]. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of [[neurotransmitter]]s in response to [[action potential|nerve impulses]]. Neurons connect to form [[neural pathway]]s, [[neural circuit]]s, and elaborate [[Large scale brain networks|network systems]]. The whole circuitry is driven by the process of [[neurotransmission]].

The brain is protected by the [[skull]], suspended in [[cerebrospinal fluid]], and isolated from the [[circulatory system|bloodstream]] by the [[blood–brain barrier]]. However, the brain is still susceptible to [[brain damage|damage]], [[Central nervous system disease|disease]], and [[infection]]. Damage can be caused by [[closed head injury|trauma]], or a loss of blood supply known as a [[stroke]]. The brain is susceptible to [[neurodegeneration|degenerative disorders]], such as [[Parkinson's disease]], [[dementia]]s including [[Alzheimer's disease]], and [[multiple sclerosis]]. [[Psychiatric condition]]s, including [[schizophrenia]] and [[major depressive disorder|clinical depression]], are thought to be associated with brain dysfunctions. The brain can also be the site of [[brain tumors|tumours]], both [[benign tumour|benign]] and [[cancer|malignant]]; these mostly [[metastasis|originate from other sites in the body]].

The study of the anatomy of the brain is [[neuroanatomy]], while the study of its function is [[neuroscience]]. A number of techniques are used to study the brain. [[Biological specimen|Specimens]] from other animals, which may be [[histology|examined microscopically]], have traditionally provided much information. [[Medical imaging]] technologies such as [[functional neuroimaging]], and [[electroencephalography]] (EEG) recordings are important in studying the brain. The [[medical history]] of people with [[brain damage|brain injury]] has provided insight into the function of each part of the brain.

In culture, the [[philosophy of mind]] has for centuries attempted to address the question of the nature of [[consciousness]] and the [[mind-body problem]]. The [[pseudoscience]] of [[phrenology]] attempted to localise personality attributes to regions of the cortex in the 19th century. [[Brain transplant#In science fiction|In science fiction, brain transplants]] are imagined in tales such as the 1942 ''[[Donovan's Brain]]''.
{{TOC limit |3}}

==Structure==
{{See also|List of regions in the human brain |Outline of the human brain}}

===Gross anatomy===
{{Further|Neuroscience of sex differences}}
The adult human brain weighs on average about {{convert|1.2-1.4|kg|abbr=on}} which is about 2% of the total body weight,<ref name=CarpenterCh1>{{cite book |title=Carpenter's Human Neuroanatomy |last1=Parent |first1=A. |last2=Carpenter |first2=M.B. |publisher=Williams & Wilkins |year=1995 |isbn=978-0-683-06752-1 |chapter=Ch. 1}}</ref><ref name="Bigos">{{cite book |last1=Bigos |first1=K.L. |last2=Hariri |first2=A. |last3=Weinberger |first3=D. |title=Neuroimaging Genetics: Principles and Practices |publisher=[[Oxford University Press]] |isbn=978-0199920228 |year=2015 |page=157 |url=https://books.google.com/books?id=TF_iCgAAQBAJ&pg=PA157}}</ref> with a volume of around 1260 [[cubic centimetre|cm3]] in men and 1130 cm3 in women, although there is substantial individual variation.<ref>{{cite journal |last1=Cosgrove |first1=K.P. |last2=Mazure |first2=C.M. |last3=Staley |first3=J.K. |title=Evolving knowledge of sex differences in brain structure, function, and chemistry |year=2007 |journal=Biol Psychiatry |volume=62 |pages=847–855 |pmid=17544382 |pmc=2711771 |doi=10.1016/j.biopsych.2007.03.001 |issue=8}}</ref> Neurological [[sex differences in intelligence|differences between the sexes]] have not been shown to correlate in any simple way with [[intelligence quotient|IQ]] or other measures of cognitive performance.<ref name="pmid10234034">{{cite journal |last1=Gur |first1=R.C. |last2=Turetsky |first2=B.I. |last3=Matsui |first3=M. |last4=Yan |first4=M. |last5=Bilker |first5=W. |last6=Hughett |first6=P. |last7=Gur |first7=R.E. |title=Sex differences in brain gray and white matter in healthy young adults: correlations with cognitive performance |journal=[[The Journal of Neuroscience]] |volume=19 |pages=4065–4072 |year=1999 |pmid=10234034 |issue=10|doi=10.1523/JNEUROSCI.19-10-04065.1999 }}</ref>

The [[cerebrum]], consisting of the [[cerebral hemisphere]]s, forms the largest part of the brain and overlies the other brain structures.{{sfn|Gray's Anatomy|2008|p=227-9}} The outer region of the hemispheres, the [[cerebral cortex]], is [[grey matter]], consisting of [[Cerebral cortex#Layers|cortical layers]] of [[neuron]]s. Each hemisphere is divided into four main [[lobes of the brain|lobes]] – the [[frontal lobe]], [[parietal lobe]], [[temporal lobe]], and [[occipital lobe]].{{sfn|Gray's Anatomy|2008|p=335-7}} Three other lobes are included by some sources which are a ''central lobe'', a [[limbic lobe]], and an [[Insular cortex|insular lobe]].<ref name="Ribas">{{cite journal |page=7 |pmid=20121437|year=2010|last1=Ribas|first1=G. C.|title=The cerebral sulci and gyri|journal=Neurosurgical Focus|volume=28|issue=2|doi=10.3171/2009.11.FOCUS09245}}</ref> The central lobe comprises the [[precentral gyrus]] and the [[postcentral gyrus]] and is included since it forms a distinct functional role.<ref name="Ribas"/><ref name="Frigeri">{{cite journal |pmid=25555079|year=2015|last1=Frigeri|first1=T.|title=Microsurgical anatomy of the central lobe|journal=Journal of Neurosurgery|volume=122|issue=3|pages=483–98|last2=Paglioli|first2=E.|last3=De Oliveira|first3=E.|last4=Rhoton Jr|first4=A. L.|doi=10.3171/2014.11.JNS14315}}</ref>

The [[brainstem]], resembling a stalk, attaches to and leaves the cerebrum at the start of the [[midbrain]] area. The brainstem includes the midbrain, the [[pons]], and the [[medulla oblongata]]. Behind the brainstem is the [[cerebellum]] ({{lang-la |little brain}}).{{sfn|Gray's Anatomy|2008|p=227-9}}

The cerebrum, brainstem, cerebellum, and spinal cord are covered by three membranes called [[meninges]]. The membranes are the tough [[dura mater]]; the middle [[arachnoid mater]] and the more delicate inner [[pia mater]]. Between the arachnoid mater and the pia mater is the [[Meninges#Subarachnoid spaces|subarachnoid space]] and [[subarachnoid cisterns]], which contain the [[cerebrospinal fluid]].{{sfn|Purves|2012|p=724}} The outermost membrane of the cerebral cortex is the basement membrane of the pia mater called the [[glia limitans]] and is an important part of the [[blood–brain barrier]].<ref name="Anatomy and Ultrastructure">{{Cite book |last1=Cipolla |first1=M.J. |title=Anatomy and Ultrastructure |url=https://www.ncbi.nlm.nih.gov/books/NBK53086/#s2.2 |publisher=Morgan & Claypool Life Sciences |date=January 1, 2009 |deadurl=no |archiveurl=https://web.archive.org/web/20171001170945/https://www.ncbi.nlm.nih.gov/books/NBK53086/#s2.2 |archivedate=October 1, 2017 }}</ref>
The living brain is very soft, having a gel-like consistency similar to soft tofu.<ref name="NPR">{{cite web |title=A Surgeon's-Eye View of the Brain |url=https://www.npr.org/templates/story/story.php?storyId=5396115 |website=NPR.org |deadurl=no |archiveurl=https://web.archive.org/web/20171107023155/http://www.npr.org/templates/story/story.php?storyId=5396115 |archivedate=November 7, 2017 }}</ref> The cortical layers of neurons constitute much of the cerebral [[grey matter]], while the deeper subcortical regions of [[myelin]]ated [[axon]]s, make up the [[white matter]].{{sfn|Gray's Anatomy|2008|p=227-229}} The white matter of the brain makes up about half of the total brain volume.<ref name="Neuron">{{cite journal |last1=Sampaio-Baptista |first1=C |last2=Johansen-Berg |first2=H |title=White Matter Plasticity in the Adult Brain. |journal=Neuron |date=20 December 2017 |volume=96 |issue=6 |pages=1239–1251 |doi=10.1016/j.neuron.2017.11.026 |pmid=29268094}}</ref>
{{multiple image

| align =center
| direction =horizontal
| total_width =700


| header_align =center
| header =Structural and functional areas of the human brain


| image1 =Sobo 1909 624.png
| width1 =3060
| height1 =2247
| alt1 =A diagram showing various structures within the human brain
| caption1 =Human brain bisected in the [[sagittal plane]], showing the white matter of the corpus callosum


| image2 =Blausen 0102 Brain Motor&Sensory (flipped).png
| width2 =1425
| height2 =951
| alt2 =A diagram of the functional areas of the human brain
| caption2 =Functional areas of the human brain. Dashed areas shown are commonly left hemisphere dominant

}}

====Cerebrum====
{{main|Cerebrum|Cerebral cortex}}
[[File:Gray726.png|thumb|Major gyri and sulci on the lateral surface of the cortex]]
[[File:Gehirn, medial - Lobi en.svg|thumb|Lobes of the brain]]

The cerebrum is the largest part of the brain, and is divided into nearly [[Symmetry in biology#Bilateral symmetry|symmetrical]] left and right [[cerebral hemisphere|hemisphere]]s by a deep groove, the [[longitudinal fissure]].<ref name="Davey">{{cite book |author=Davey, G. |title=Applied Psychology |isbn=978-1444331219 |publisher=[[John Wiley & Sons]] |year=2011 |page=153 |url=https://books.google.com/books?id=K1qq1SsgoxUC&pg=PA153}}</ref> The hemispheres are connected by five [[Commissural fiber#Structure|commissures]] that span the longitudinal fissure, the largest of these is the [[corpus callosum]].{{sfn|Gray's Anatomy|2008|p=227-9}}
Each hemisphere is conventionally divided into four main [[lobes of the brain|lobes]]; the [[frontal lobe]], [[parietal lobe]], [[temporal lobe]], and [[occipital lobe]], named according to the [[skull |skull bones]] that overlie them.{{sfn|Gray's Anatomy|2008|p=335-7}} Each lobe is associated with one or two specialised functions though there is some functional overlap between them.<ref name=Ackerman/> The surface of the brain is [[gyrification|folded]] into ridges ([[gyrus|gyri]]) and grooves ([[sulcus (neuroanatomy)|sulci]]), many of which are named, usually according to their position, such as the [[frontal gyrus]] of the frontal lobe or the [[central sulcus]] separating the central regions of the hemispheres. There are many small variations in the secondary and tertiary folds.{{sfn|Larsen|2001|pp=455–456}}

The outer part of the cerebrum is the [[cerebral cortex]], made up of [[grey matter]] arranged in layers. It is {{convert|2 |to |4 |mm}} thick, and deeply folded to give a convoluted appearance.<ref>{{cite book |last=Kandel |first=E.R. |author2=Schwartz, J.H. |author3=Jessel T.M. |title=Principles of Neural Science |year=2000 |publisher=McGraw-Hill Professional |isbn=978-0-8385-7701-1 |page=324}}</ref> Beneath the cortex is the cerebral [[white matter]]. The largest part of the cerebral cortex is the [[neocortex]], which has six neuronal layers. The rest of the cortex is of [[allocortex]], which has three or four layers.{{sfn|Gray's Anatomy|2008|pp=227–229}}

The cortex is [[brain mapping|mapped]] by divisions into about fifty different functional areas known as [[Brodmann's areas]]. These areas are distinctly different when [[Histology|seen under a microscope]].{{sfn|Guyton & Hall|2011|p=574}} The cortex is divided into two main functional areas – a [[motor cortex]] and a [[sensory cortex]].{{sfn|Guyton & Hall|2011|p=667}} The [[primary motor cortex]], which sends axons down to [[motor neuron]]s in the brainstem and spinal cord, occupies the rear portion of the frontal lobe, directly in front of the somatosensory area. The [[primary sensory areas]] receive signals from the [[sensory nerve]]s and [[nerve tract|tracts]] by way of [[Thalamus#Thalamic nuclei|relay nuclei]] in the [[thalamus]]. Primary sensory areas include the [[visual cortex]] of the [[occipital lobe]], the [[auditory cortex]] in parts of the [[temporal lobe]] and [[insular cortex]], and the [[somatosensory cortex]] in the [[parietal lobe]]. The remaining parts of the cortex, are called the [[association areas]]. These areas receive input from the sensory areas and lower parts of the brain and are involved in the complex [[cognition|cognitive processes]] of [[perception]], [[thought]], and [[decision-making]].<ref>Principles of Anatomy and Physiology 12th Edition – Tortora, Page 519.</ref> The main functions of the frontal lobe are to [[Attentional control|control attention]], abstract thinking, behaviour, problem solving tasks, and physical reactions and personality.<ref name="Freberg">{{cite book |author=Freberg, L. |title=Discovering Biological Psychology |publisher=[[Cengage Learning]] |year=2009 |pages=44–46 |isbn=978-0547177793 |url=https://books.google.com/books?id=-zyTMXAjzQsC&pg=PA44}}</ref><ref name="Kolb">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I. |title=Fundamentals of Human Neuropsychology |publisher=[[Macmillan Publishers|Macmillan]] |year=2009 |pages=73–75 |isbn=978-0716795865 |url=https://books.google.com/books?id=z0DThNQqdL4C&pg=PA73}}</ref> The occipital lobe is the smallest lobe; its main functions are visual reception, visual-spatial processing, movement, and [[Color vision#Color in the human brain|colour recognition]].<ref name="Freberg"/><ref name="Kolb"/> There is a smaller occipital lobule in the lobe known as the [[cuneus]]. The temporal lobe controls [[Echoic memory|auditory]] and [[visual memory|visual memories]], [[Language processing in the brain|language]], and some hearing and speech.<ref name="Freberg"/>

[[File:Visible Human head slice.jpg|thumb|upright|Cortical folds and white matter in horizontal bisection of head]]

The cerebrum contains the [[ventricular system|ventricles]] where the cerebrospinal fluid is produced and circulated. Below the corpus callosum is the [[septum pellucidum]], a membrane that separates the [[lateral ventricles]]. Beneath the lateral ventricles is the [[thalamus]] and to the front and below this is the [[hypothalamus]]. The hypothalamus leads on to the [[pituitary gland]]. At the back of the thalamus is the brainstem.{{sfn|Pocock|2006|p=64}}

The [[basal ganglia]], also called basal nuclei, are a set of structures deep within the hemispheres involved in behaviour and movement regulation.{{sfn|Purves|2012|p=399}} The largest component is the [[striatum]], others are the [[globus pallidus]], the [[substantia nigra]] and the [[subthalamic nucleus]].{{sfn|Purves|2012|p=399}} Part of the dorsal striatum, the [[putamen]], and the [[globus pallidus]], lie separated from the lateral ventricles and thalamus by the [[internal capsule]], whereas the [[caudate nucleus]] stretches around and abuts the lateral ventricles on their outer sides.{{sfn|Gray's Anatomy|2008|p=325-6}} At the deepest part of the [[lateral sulcus]] between the [[insular cortex]] and the striatum is a thin neuronal sheet called the [[claustrum]].<ref name="Goll">{{cite journal |last1=Goll |first1=Y. |last2=Atlan |first2=G. |last3=Citri |first3=A. |title=Attention: the claustrum |journal=Trends in Neurosciences |date=August 2015 |volume=38 |issue=8 |pages=486–95 |doi=10.1016/j.tins.2015.05.006 |pmid=26116988}}</ref>

Below and in front of the striatum are a number of [[basal forebrain]] structures. These include the [[nucleus accumbens]], [[nucleus basalis]], [[diagonal band of Broca]], [[substantia innominata]], and the [[medial septal nucleus]]. These structures are important in producing the [[neurotransmitter]], [[acetylcholine]], which is then distributed widely throughout the brain. The basal forebrain, in particular the nucleus basalis, is considered to be the major [[cholinergic]] output of the central nervous system to the striatum and neocortex.<ref name="Goard">{{cite journal |last1=Goard |first1=M. |last2=Dan |first2=Y. |title=Basal forebrain activation enhances cortical coding of natural scenes |journal=Nature Neuroscience |date=October 4, 2009 |volume=12 |issue=11 |pages=1444–1449 |doi=10.1038/nn.2402|pmid=19801988 |pmc=3576925 }}</ref>

====Cerebellum====
{{main|Cerebellum}}
[[File:Sobo 1909 623.png|thumb|upright|Human brain viewed from below, showing cerebellum and brainstem]]

The cerebellum is divided into an [[anterior lobe of cerebellum|anterior lobe]], a [[posterior lobe of cerebellum|posterior lobe]], and the [[flocculonodular lobe]].{{sfn|Guyton & Hall|2011|p=699}} The anterior and posterior lobes are connected in the middle by the [[cerebellar vermis|vermis]].{{sfn|Gray's Anatomy|2008|p=298}} The cerebellum has a much thinner outer cortex that is narrowly furrowed horizontally.{{sfn|Gray's Anatomy|2008|p=298}}
Viewed from underneath between the two lobes is the third lobe the flocculonodular lobe.<ref>{{cite book |last1=Netter |first1=F. |title=Atlas of Human Anatomy Including Student Consult Interactive Ancillaries and Guides. |date=2014 |publisher=W B Saunders Co |location=Philadelphia, Penn. |isbn=978-1-4557-0418-7 |page=114 |edition=6th}}</ref> The cerebellum rests at the back of the [[posterior cranial fossa|cranial cavity]], lying beneath the occipital lobes, and is separated from these by the [[cerebellar tentorium]], a sheet of fibre.{{sfn|Gray's Anatomy|2008|p=297}}

It is connected to the midbrain of the brainstem by the [[superior cerebellar peduncle]]s, to the pons by the [[middle cerebellar peduncle]]s, and to the medulla by the [[inferior cerebellar peduncle]]s.{{sfn|Gray's Anatomy|2008|p=298}} The cerebellum consists of an inner medulla of white matter and an outer cortex of richly folded grey matter.{{sfn|Gray's Anatomy|2008|p=297}} The cerebellum's anterior and posterior lobes appear to play a role in the coordination and smoothing of complex motor movements, and the flocculonodular lobe in the maintenance of [[Equilibrioception|balance]]{{sfn|Guyton & Hall|2011|pp=698–9}} although debate exists as to its cognitive, behavioural and motor functions.{{sfn|Squire|2013|pp=761–763}}

====Brainstem====
{{main|Brainstem}}
The brainstem lies beneath the cerebrum and consists of the [[midbrain]], [[pons]] and [[medulla oblongata|medulla]]. It lies in the [[posterior cranial fossa|back part of the skull]], resting on the part of the [[base of the skull|base]] known as the [[clivus (anatomy)|clivus]], and ends at the [[foramen magnum]], a large [[:wikt:foramen|opening]] in the [[occipital bone]]. The brainstem continues below this as the [[spinal cord]],{{sfn|Gray's Anatomy|2008|p=275}} protected by the [[vertebral column]].

Ten of the twelve pairs of [[cranial nerve]]s{{efn|Specifically the [[oculomotor]], [[trochlear nerve]], [[trigeminal nerve]], [[abducens nerve]], [[facial nerve]], [[vestibulocochlear nerve]], [[glossopharyngeal nerve]], [[vagus nerve]], [[accessory nerve]] and [[hypoglossal nerve]]s.{{sfn|Gray's Anatomy|2008|p=275}}}} emerge directly from the brainstem.{{sfn|Gray's Anatomy|2008|p=275}} The brainstem also contains many [[cranial nerve nucleus|cranial nerve nuclei]] and [[nucleus (neuroanatomy)|nuclei]] of [[nerve|peripheral nerves]], as well as nuclei involved in the regulation of many essential processes including [[breathing]], control of eye movements and balance.{{sfn|Guyton & Hall|2011|p=691}}{{sfn|Gray's Anatomy|2008|p=275}} The [[reticular formation]], a network of nuclei of ill-defined formation, is present within and along the length of the brainstem.{{sfn|Gray's Anatomy|2008|p=275}} Many [[nerve tract]]s, which transmit information to and from the cerebral cortex to the rest of the body, pass through the brainstem.{{sfn|Gray's Anatomy|2008|p=275}}

===Microanatomy===
The human brain is primarily composed of [[neuron]]s, [[glial cell]]s, [[neural stem cell]]s, and [[blood vessel]]s. Types of neuron include [[interneuron]]s, [[pyramidal cell]]s including [[Betz cell]]s, [[motor neuron]]s ([[upper motor neuron|upper]] and [[lower motor neuron]]s), and cerebellar [[Purkinje cell]]s. Betz cells are the largest cells (by size of cell body) in the nervous system.{{sfn|Purves|2012|p=377}} The adult human brain is estimated to contain 86±8 billion neurons, with a roughly equal number (85±10 billion) of non-neuronal cells.<ref name=":1" /> Out of these neurons, 16 billion (19%) are located in the cerebral cortex, and 69 billion (80%) are in the cerebellum.<ref name="Bigos"/><ref name=":1">{{cite journal |last1=Azevedo |first1=F. |display-authors=etal |title=Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain |journal=The Journal of Comparative Neurology |date=April 10, 2009 |volume=513 |issue=5 |pages=532–541 |doi=10.1002/cne.21974 |quote=despite the widespread quotes that the human brain contains 100 billion neurons and ten times more glial cells, the absolute number of neurons and glial cells in the human brain remains unknown. Here we determine these numbers by using the isotropic fractionator and compare them with the expected values for a human-sized primate. We find that the adult male human brain contains on average 86.1 ± 8.1 billion NeuN-positive cells (“neurons”) and 84.6 ± 9.8 billion NeuN-negative (“nonneuronal”) cells. |pmid=19226510}}</ref>

Types of glial cell are [[astrocyte]]s (including [[Bergmann glia]]), [[oligodendrocyte]]s, [[ependymal cell]]s (including [[tanycyte]]s), [[radial glial cell]]s, [[microglia]], and a subtype of [[oligodendrocyte progenitor cell]]s. Astrocytes are the largest of the glial cells. They are [[stellate cell]]s with many processes radiating from their [[soma (biology)|cell bodies]]. Some of these processes end as perivascular end-feet on [[capillary]] walls.<ref>{{Cite book |last1=Pavel |first1=Fiala |last2=Jiří |first2=Valenta |title=Central Nervous System |url=https://books.google.com/?id=LPlSBAAAQBAJ&pg=PA79 |publisher=Karolinum Press |page=79 |date=January 1, 2013|isbn=9788024620671 }}</ref> The [[glia limitans]] of the cortex is made up of astrocyte foot processes that serve in part to contain the cells of the brain.<ref name="Anatomy and Ultrastructure"/>

[[Mast cell]]s are [[white blood cell]]s that interact in the [[neuroimmune system]] in the brain.<ref name="Mast cell neuroimmmune system">{{cite journal | last1=Polyzoidis |first1=S. |last2=Koletsa |first2=T. |last3=Panagiotidou |first3=S. |last4=Ashkan |first4=K. |last5=Theoharides |first5=T.C. | title=Mast cells in meningiomas and brain inflammation | journal=Journal of Neuroinflammation | volume=12 | issue=1 | pages=170 | year=2015 | pmid=26377554 | pmc=4573939 | doi=10.1186/s12974-015-0388-3}}</ref> Mast cells in the central nervous system are present in the meninges;<ref name="Mast cell neuroimmmune system" /> they mediate neuroimmune responses in inflammatory conditions and help to maintain the blood–brain barrier, particularly in brain regions where the barrier is absent.<ref name="Mast cell neuroimmmune system" />{{sfn|Guyton & Hall|2011|pp=748–749}} Across systems, mast cells serve as the main [[effector cell]] through which pathogens can affect the [[gut–brain axis]].<ref name="pmid24833851">{{cite journal | last1=Budzyński |first1=J |last2=Kłopocka |first2=M. | title=Brain-gut axis in the pathogenesis of Helicobacter pylori infection | journal=World J. Gastroenterol. | volume=20 | issue=18 | pages=5212–25 | year=2014 | pmid=24833851 | pmc=4017036 | doi=10.3748/wjg.v20.i18.5212}}</ref><ref name="Microbiome-CNS-ENS">{{cite journal | last1=Carabotti |first1=M. |last2=Scirocco |first2=A. |last3=Maselli |first3=M.A. |last4=Severi |first4=C. | title=The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems | journal=Ann Gastroenterol | volume=28 | issue=2 | pages=203–209 | year=2015 | pmid=25830558 | pmc=4367209}}</ref>

Some 400 [[gene]]s are shown to be brain-specific. In all neurons, [[ELAVL3]] is expressed, and in pyramidal neurons, [[NRGN]] and [[REEP2]] are also expressed. [[GAD1]] – essential for the biosynthesis of the neurotransmitter [[GABA]] – is expressed in interneurons. Proteins expressed in glial cells are astrocyte markers GFAP, and [[S100B]]. [[Myelin basic protein]], and the transcription factor, [[OLIG2]] are expressed in oligodendrocytes.<ref>{{Cite journal|last=Sjöstedt|first=Evelina|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Häggmark|first4=Anna|last5=Mitsios|first5=Nicholas|last6=Nilsson|first6=Peter|last7=Pontén|first7=Fredrik|last8=Hökfelt|first8=Tomas|last9=Uhlén|first9=Mathias|date=June 15, 2015|title=Defining the human brain proteome using transcriptomics and antibody-based profiling with a focus on the cerebral cortex|journal=PLOS ONE |volume=10|issue=6|pages=e0130028 |doi=10.1371/journal.pone.0130028|pmid=26076492 |pmc=4468152|issn=1932-6203}}</ref>

===Cerebrospinal fluid===
[[Image:Blausen 0216 CerebrospinalSystem.png|thumb|[[Cerebrospinal fluid]] circulates in spaces around and within the brain]]
{{main|Cerebrospinal fluid}}
Cerebrospinal fluid is a clear, colourless [[transcellular fluid]] that circulates around the brain in the [[subarachnoid space]], in the [[ventricular system]], and in the [[central canal]] of the spinal cord. It also fills some gaps in the subarachnoid space, known as [[subarachnoid cisterns]].{{sfn|Gray's Anatomy|2008|pp=242–244}} The four ventricles, two [[lateral ventricle|lateral]], a [[third ventricle|third]], and a [[fourth ventricle]], all contain [[choroid plexus]] that produces cerebrospinal fluid.{{sfn|Purves|2012|p=742}} The third ventricle lies in the midline and [[Interventricular foramina (neuroanatomy)|is connected]] to the lateral ventricles.{{sfn|Gray's Anatomy|2008|pp=242–244}} A single [[duct (anatomy)|duct]], the [[cerebral aqueduct]] between the pons and the cerebellum, connects the third ventricle to the fourth ventricle.{{sfn|Gray's Anatomy|2008|p=243}} Three separate openings, the [[Medial aperture|middle]] and two [[lateral aperture]]s, drain the cerebrospinal fluid from the fourth ventricle to the [[cisterna magna]] one of the major cisterns. From here, cerebrospinal fluid circulates around the brain and spinal cord in the subarachnoid space, between the arachnoid mater and pia mater.{{sfn|Gray's Anatomy|2008|pp=242–244}}
At any one time, there is about 150mL of cerebrospinal fluid – most within the subarachnoid space. It is constantly being regenerated and absorbed, and replaces about once every 5–6 hours.{{sfn|Gray's Anatomy|2008|pp=242–244}}

A [[glymphatic system]] has been described<ref name="lliff">{{cite journal |last1=Iliff |first1=JJ |last2=Nedergaard |first2=M |title=Is there a cerebral lymphatic system? |journal=Stroke |date=June 2013 |volume=44 |issue=6 Suppl 1 |pages=S93-5 |doi=10.1161/STROKEAHA.112.678698 |pmid=23709744}}</ref><ref>{{cite web |last1=Gaillard |first1=F. |title=Glymphatic pathway |url=https://radiopaedia.org/articles/glymphatic-pathway |website=radiopaedia.org |deadurl=no |archiveurl=https://web.archive.org/web/20171030002906/https://radiopaedia.org/articles/glymphatic-pathway |archivedate=October 30, 2017}}</ref><ref name="Glymphatic system and brain waste clearance 2017 review" /> as the lymphatic drainage system of the brain. The brain-wide glymphatic pathway includes drainage routes from the cerebrospinal fluid, and from the [[meningeal lymphatic vessels]] that are associated with the dural sinuses, and run alongside the cerebral blood vessels.<ref name="D-O">{{cite journal|last1=Dissing-Olesen|first1=L.|last2=Hong|first2=S. |last3=Stevens|first3=B. |title=New brain lymphatic vessels drain old concepts |journal=EBioMedicine |date=August 2015|volume=2|issue=8|pages=776–7|doi=10.1016/j.ebiom.2015.08.019|pmid=26425672|pmc=4563157}}</ref><ref name="Sun">{{cite journal |last1=Sun |first1=BL |last2=Wang |first2=LH |last3=Yang |first3=T |last4=Sun |first4=JY |last5=Mao |first5=LL |last6=Yang |first6=MF |last7=Yuan |first7=H |last8=Colvin |first8=RA |last9=Yang |first9=XY |title=Lymphatic drainage system of the brain: A novel target for intervention of neurological diseases. |journal=Progress in neurobiology |date=April 2018 |volume=163-164 |pages=118–143 |doi=10.1016/j.pneurobio.2017.08.007 |pmid=28903061}}</ref> The pathway drains [[interstitial fluid]] from the tissue of the brain.<ref name="Sun"/>

===Blood supply===
{{main|Cerebral circulation}}
[[File: Circle of Willis en.svg|thumb|upright|Two circulations joining at the circle of Willis]]
[[File:Gray769-en.svg|thumb|Diagram showing features of cerebral [[meninges|outer membranes]] and supply of blood vessels]]
The [[internal carotid arteries]] supply [[Blood#Oxygen transport|oxygenated blood]] to the front of the brain and the [[vertebral arteries]] supply blood to the back of the brain.{{sfn|Gray's Anatomy|2008|p=247}} These two circulations [[anastomosis|join together]] in the [[circle of Willis]], a ring of connected arteries that lies in the [[interpeduncular cistern]] between the midbrain and pons.{{sfn|Gray's Anatomy|2008|p=251-2}}

The internal carotid arteries are branches of the [[common carotid arteries]]. They enter the [[cranium]] through the [[carotid canal]], travel through the [[cavernous sinus]] and enter the [[subarachnoid space]].{{sfn|Gray's Anatomy|2008|p=250}} They then enter the [[circle of Willis]], with two branches, the [[anterior cerebral arteries]] emerging. These branches travel forward and then upward along the [[longitudinal fissure]], and supply the front and midline parts of the brain.{{sfn|Gray's Anatomy|2008|p=248}} One or more small [[anterior communicating artery|anterior communicating arteries]] join the two anterior cerebral arteries shortly after they emerge as branches.{{sfn|Gray's Anatomy|2008|p=248}} The internal carotid arteries continue forward as the [[middle cerebral arteries]]. They travel sideways along the [[sphenoid bone]] of the [[orbit (anatomy)|eye socket]], then upwards through the [[insula cortex]], where final branches arise. The middle cerebral arteries send branches along their length.{{sfn|Gray's Anatomy|2008|p=250}}

The vertebral arteries emerge as branches of the left and right [[subclavian arteries]]. They travel upward through [[Vertebra#Cervical vertebrae|transverse foramina]] – spaces in the [[cervical vertebrae]] and then emerge as two vessels, one on the left and one on the right of the medulla.{{sfn|Gray's Anatomy|2008|p=250}} They give off [[Posterior inferior cerebellar artery|one of the three cerebellar branches]]. The vertebral arteries join in front of the middle part of the medulla to form the larger [[basilar artery]], which sends multiple branches to supply the medulla and pons, and the two other [[Anterior inferior cerebellar artery|anterior]] and [[Superior cerebellar artery|superior cerebellar branches]].{{sfn|Gray's Anatomy|2008|p=251}} Finally, the basilar artery divides into two [[posterior cerebral arteries]]. These travel outwards, around the superior cerebellar peduncles, and along the top of the cerebellar tentorium, where it sends branches to supply the temporal and occipital lobes.{{sfn|Gray's Anatomy|2008|p=251}} Each posterior cerebral artery sends a small [[posterior communicating artery]] to join with the internal carotid arteries.

====Blood drainage====

[[Cerebral veins]] drain [[Blood#Oxygen transport|deoxygenated blood]] from the brain. The brain has two main networks of [[vein]]s: an exterior or [[Superior cerebral veins|superficial network]], on the surface of the cerebrum that has three branches, and an [[Internal cerebral veins|interior network]]. These two networks communicate via [[anastomosis|anastomosing]] (joining) veins.{{sfn|Gray's Anatomy|2008|p=254-6}} The veins of the brain drain into larger cavities the [[dural venous sinuses]] usually situated between the dura mater and the covering of the skull.{{sfn|Elsevier's|2007|pp=311–4}} Blood from the cerebellum and midbrain drains into the [[great cerebral vein]]. Blood from the medulla and pons of the brainstem have a variable pattern of drainage, either into the [[spinal veins]] or into adjacent cerebral veins.{{sfn|Gray's Anatomy|2008|p=254-6}}

The blood in the [[Anatomical terms of location#deep|deep]] part of the brain drains, through a [[venous plexus]] into the [[cavernous sinus]] at the front, and the [[superior petrosal sinus|superior]] and [[inferior petrosal sinus]]es at the sides, and the [[inferior sagittal sinus]] at the back.{{sfn|Elsevier's|2007|pp=311–4}} Blood drains from the outer brain into the large [[superior sagittal sinus]], which rests in the midline on top of the brain. Blood from here joins with blood from the [[straight sinus]] at the [[confluence of sinuses]].{{sfn|Elsevier's|2007|pp=311–4}}

Blood from here drains into the left and right [[transverse sinus]]es.{{sfn|Elsevier's|2007|pp=311–4}} These then drain into the [[sigmoid sinus]]es, which receive blood from the cavernous sinus and superior and inferior petrosal sinuses. The sigmoid drains into the large [[internal jugular vein]]s.{{sfn|Elsevier's|2007|pp=311–4}}{{sfn|Gray's Anatomy|2008|p=254-6}}

====The blood–brain barrier====
The larger arteries throughout the brain supply blood to smaller [[capillaries]]. These smallest of [[blood vessel]]s in the brain, are lined with cells joined by [[tight junction]]s and so fluids do not seep in or leak out to the same degree as they do in other capillaries, thereby creating the [[blood–brain barrier]].{{sfn|Guyton & Hall|2011|pp=748–749}} [[Pericyte]]s play a major role in the formation of the tight junctions.<ref name="Daneman">{{cite journal |last1=Daneman |first1=R. |last2=Zhou |first2=L. |last3=Kebede |first3=A.A. |last4=Barres |first4=B.A. |title=Pericytes are required for blood-brain barrier integrity during embryogenesis |journal=Nature |date=November 25, 2010 |volume=468 |issue=7323 |pages=562–6 |pmid=20944625 |doi=10.1038/nature09513 |pmc=3241506}}</ref> The barrier is less permeable to larger molecules, but is still permeable to water, carbon dioxide, oxygen, and most fat-soluble substances (including [[anaesthetic]]s and alcohol).{{sfn|Guyton & Hall|2011|pp=748–749}} The blood–brain barrier is not present in the [[circumventricular organs]], structures in the brain that may need to respond to changes in body fluids, such as the [[pineal gland]], [[area postrema]], and some areas of the [[hypothalamus]].{{sfn|Guyton & Hall|2011|pp=748–749}} There is a similar [[Choroid plexus#Function|blood–cerebrospinal fluid barrier]], which serves the same purpose as the blood–brain barrier, but facilitates the transport of different substances into the brain due to the distinct structural characteristics between the two barrier systems.{{sfn|Guyton & Hall|2011|pp=748–749}}<ref name="BCSF">{{cite book |last1=Laterra |first1=J. |last2=Keep |first2=R. |last3=Betz |first3=L.A. |title=Basic neurochemistry: molecular, cellular and medical aspects |date=1999 |publisher=Lippincott-Raven |location=Philadelphia |edition=6th |section-url=https://www.ncbi.nlm.nih.gov/books/NBK27998/ |section=Blood–cerebrospinal fluid barrier |display-authors=etal}}</ref>

==Development==
{{Main |Development of the nervous system in humans}}
{{Further|Development of the human brain}}
[[File:Embryonic Development CNS.png|thumb|Neurulation and neural crest cells]]
[[File:1302 Brain Vesicle DevN.jpg|thumb|alt= Simple drawing of the lateral view of the three primary vesicle stage of the three to four week old embryo shown in different colors, and the five secondary vesicle stage of the five week old embryo shown in different colors and a lateral view of this |Primary and secondary [[brain vesicle|vesicle]] stages of development in the early embryo to the fifth week]]
[[File:6 week embryo brain.jpg|thumb|alt=Very simple drawing of the front end of a human embryo, showing each vesicle of the developing brain in a different color. |Brain of a human embryo in the sixth week of development]]

At the beginning of the third week of [[human embryonic development|development]], the [[embryo]]nic [[ectoderm]] forms a thickened strip called the [[neural plate]].<ref name="Sadler">{{cite book |last1=Sadler |first1=T. |title=Langman's medical embryology |date=2010 |publisher=Lippincott Williams & Wilkins |location=Philadelphia |isbn=978-07817-9069-7 |page=293 |edition=11th}}</ref> By the fourth week of development the neural plate has widened to give a broad [[cephalization|cephalic]] end, a less broad middle part and a narrow caudal end. These swellings are known as the [[Brain vesicle|primary brain vesicles]] and represent the beginnings of the [[forebrain]], [[midbrain]] and [[hindbrain]].{{sfn|Larsen|2001|p=419}}

[[Neural crest]] cells (derived from the ectoderm) populate the lateral edges of the plate at the [[neural fold]]s. In the fourth week in the [[neurulation |neurulation stage]] the [[Neural fold#Folding mechanism|neural folds close]] to form the [[neural tube]], bringing together the neural crest cells at the neural crest.{{sfn|Larsen|2001|pp=85–88}} The neural crest runs the length of the tube with cranial neural crest cells at the cephalic end and caudal neural crest cells at the tail. Cells detach from the crest and [[cell migration|migrate]] in a craniocaudal (head to tail) wave inside the tube.{{sfn|Larsen|2001|pp=85–88}} Cells at the cephalic end give rise to the brain, and cells at the caudal end give rise to the spinal cord.{{sfn|Purves|2012|pp=480–482}}

The tube flexes as it grows, forming the crescent-shaped cerebral hemispheres at the head. The cerebral hemispheres first appear on day 32.{{sfn|Larsen|2001|pp=445–446}}
Early in the fourth week the cephalic part bends sharply forward in a [[cephalic flexure]].{{sfn|Larsen|2001|pp=85–88}} This flexed part becomes the forebrain (prosencephalon); the adjoining curving part becomes the midbrain (mesencephalon) and the part caudal to the flexure becomes the hindbrain (rhombencephalon). These areas are formed as swellings known as the three primitive [[brain vesicle|vesicles]]. In the fifth week of development five [[brain vesicle]]s have formed.<ref>{{Cite web|title = OpenStax CNX|url = http://cnx.org/contents/b037bde2-ea37-43a5-9102-8d4fcbc623d1@3/The_Embryologic_Perspective|website = cnx.org|accessdate = May 5, 2015|deadurl = no|archiveurl = https://web.archive.org/web/20150505054856/http://cnx.org/contents/b037bde2-ea37-43a5-9102-8d4fcbc623d1@3/The_Embryologic_Perspective|archivedate = May 5, 2015|df = mdy-all}}</ref> The forebrain separates into two vesicles – an anterior telencephalon and a posterior [[diencephalon]]. The telencephalon gives rise to the cerebral cortex, basal ganglia, and related structures. The diencephalon gives rise to the thalamus and hypothalamus. The hindbrain also splits into two areas – the metencephalon and the myelencephalon. The metencephalon gives rise to the cerebellum and pons. The myelencephalon gives rise to the medulla oblongata.{{sfn|Larsen|2001|pp=85–87}} Also during the fifth week, the brain divides into [[segmentation (biology)|repeating segments]] called [[neuromere]]s.{{sfn|Larsen|2001|p=419}}{{sfn|Purves|2012|pp=481–484}} In the [[hindbrain]] these are known as [[rhombomere]]s.<ref name=Neuro>{{cite book |editor1-first=Dale |editor1-last=Purves |editor2-first=George J |editor2-last=Augustine |editor3-first=David |editor3-last=Fitzpatrick |editor4-first=Lawrence C |editor4-last=Katz |editor5-first=Anthony-Samuel |editor5-last=LaMantia |editor6-first=James O |editor6-last=McNamara |editor7-first=S Mark |editor7-last=Williams |year=2001 |chapter=Rhombomeres |chapterurl=https://www.ncbi.nlm.nih.gov/books/NBK10954/box/A1478/ |title=Neuroscience |edition=2nd |isbn=978-0-87893-742-4}}</ref>

A characteristic of the brain is the cortical folding known as [[gyrification]]. During [[prenatal development|fetal development]], the cortex starts off smooth. By the gestational age of 24 weeks, the wrinkled morphology showing the fissures that begin to mark out the lobes of the brain is evident.<ref name="Chen">{{cite book |url=https://books.google.com/books?id=94aPR_Oh40oC&pg=PA188 |title=Mechanical Self-Assembly: Science and Applications |publisher=[[Springer Science & Business Media]] |year=2012 |isbn=978-1461445623 |pages=188–189 |last=Chen |first=X.}}</ref> Scientists do not have a clear answer as to why the cortex wrinkles and folds, but they have linked gyrification with intelligence and [[neurological disorder]]s, and have proposed a [[Gyrification#Theories on causality in gyrification|number of gyrification theories]].<ref name="Chen"/> These theories include those based on [[Gyrification#Mechanical buckling|mechanical buckling]],<ref name="Ronan">{{cite journal |last1=Ronan |first1=L |last2=Voets |first2=N |last3=Rua |first3=C |last4=Alexander-Bloch |first4=A |last5=Hough |first5=M |last6=Mackay |first6=C |last7=Crow |first7=TJ |last8=James |first8=A |last9=Giedd |first9=JN |last10=Fletcher |first10=PC |title=Differential tangential expansion as a mechanism for cortical gyrification. |journal=Cerebral cortex (New York, N.Y. : 1991) |date=August 2014 |volume=24 |issue=8 |pages=2219–28 |doi=10.1093/cercor/bht082 |pmid=23542881}}</ref><ref name="Ackerman">{{cite book |last1=Ackerman |first1=S. |title=Discovering the brain |date=1992 |publisher=National Academy Press |location=Washington, D.C. |isbn=978-0-309-04529-2 |pages=22–25}}</ref> [[Gyrification#Axonal tension|axonal tension]],<ref name="Van Essen">{{cite journal |last1=Van Essen |first1=DC |title=A tension-based theory of morphogenesis and compact wiring in the central nervous system. |journal=Nature |date=23 January 1997 |volume=385 |issue=6614 |pages=313–8 |doi=10.1038/385313a0 |pmid=9002514}}</ref> and [[Gyrification#Differential tangential expansion|differential tangential expansion]].<ref name="Ronan"/>

The first cleft to appear in the fourth month is the lateral cerebral fossa.{{sfn|Larsen|2001|pp=445–446}} The expanding caudal end of the hemisphere has to curve over in a forward direction to fit into the restricted space. This covers the fossa and turns it into a much deeper ridge known as the [[lateral sulcus]] and this marks out the temporal lobe.{{sfn|Larsen|2001|pp=445–446}} By the sixth month other sulci have formed that demarcate the frontal, parietal, and occipital lobes.{{sfn|Larsen|2001|pp=445–446}} A gene present in the human genome ([[ArhGAP11B and human encephalisation|ArhGAP11B]]) may play a major role in gyrification and encephalisation.<ref>{{cite journal |last1=Florio |first1=M.|display-authors=etal |title=Human-specific gene ARHGAP11B promotes basal progenitor amplification and neocortex expansion |journal=Science |date=March 27, 2015 |volume=347 |issue=6229 |pages=1465–70 |pmid=25721503 |doi=10.1126/science.aaa1975}}</ref>
{{Gallery
| title=
| width=180
| height=180
| lines=3
|File:Gray651.png |Brain of human embryo at 4.5 weeks, showing interior of forebrain
|File:Gray653.png |Brain interior at 5 weeks
|File:Gray654.png |Brain viewed at midline at 3 months
}}

==Function==
[[File:Blausen 0103 Brain Sensory&Motor.png|thumb|Motor and sensory regions of the brain]]

===Motor control===
The [[motor system]] of the brain is responsible for the [[motor control|generation and control]] of movement.{{sfn|Guyton & Hall|2011|p=685}} Generated movements pass from the brain through nerves to [[motor neuron]]s in the body, which control the action of [[muscle]]s. The [[corticospinal tract]] carries movements from the brain, through the [[spinal cord]], to the torso and limbs.{{sfn|Guyton & Hall|2011|p=687}} The [[cranial nerves]] carry movements related to the eyes, mouth and face.

Gross movement – such as [[Animal locomotion|locomotion]] and the movement of arms and legs – is generated in the [[motor cortex]], divided into three parts: the [[primary motor cortex]], found in the [[prefrontal gyrus]] and has sections dedicated to the movement of different body parts. These movements are supported and regulated by two other areas, lying [[anterior]] to the primary motor cortex: the [[premotor area]] and the [[supplementary motor area]].{{sfn|Guyton & Hall|2011|p=686}} The hands and mouth have a much larger area dedicated to them than other body parts, allowing finer movement; this has been visualised in a [[Cortical homunculus#Types|motor homunculus]].{{sfn|Guyton & Hall|2011|p=686}} Impulses generated from the motor cortex travel along the [[corticospinal tract]] along the front of the medulla and cross over ([[decussate]]) at the [[medullary pyramids (brainstem)|medullary pyramids]]. These then travel down the [[spinal cord]], with most connecting to [[interneuron]]s, in turn connecting to lower [[motor neuron]]s within the [[grey matter]] that then transmit the impulse to move to muscles themselves.{{sfn|Guyton & Hall|2011|p=687}} The cerebellum and [[basal ganglia]], play a role in fine, complex and coordinated muscle movements.{{sfn|Guyton & Hall|2011|pp=698,708}} Connections between the cortex and the basal ganglia control muscle tone, posture and movement initiation, and are referred to as the [[extrapyramidal system]].{{sfn|Davidson's|2010|p=1139}}

===Sensory===
[[File:1604 Types of Cortical Areas-02.jpg|thumb|Cortical areas]]
[[File:Gray722.png|thumb|upright|Routing of neural signals from the two eyes to the brain]]
The [[sensory nervous system]] is involved with the reception and processing of [[sense|sensory information]]. This information is received through the cranial nerves, through tracts in the spinal cord, and directly at centres of the brain exposed to the blood.<ref name="Hellier">{{cite book |author=Hellier, J. |title=The Brain, the Nervous System, and Their Diseases [3 volumes] |publisher=[[ABC-CLIO]] |year=2014 |pages=300–303 |isbn=978-1610693387 |url=https://books.google.com/books?id=SDi2BQAAQBAJ&pg=PA300}}</ref> The brain also receives and interprets information from the [[special sense]]s of [[visual perception|vision]], [[Olfaction|smell]], [[hearing]], and [[taste]]. [[Sensory-motor coupling|Mixed motor and sensory signals]] are also integrated.<ref name="Hellier"/>

From the skin, the brain receives information about [[touch|fine touch]], [[pressure]], [[pain]], [[vibration]] and [[temperature]]. From the joints, the brain receives information about [[proprioception|joint position]].{{sfn|Guyton & Hall|2011|p=571–576}} The [[sensory cortex]] is found just near the motor cortex, and, like the motor cortex, has areas related to sensation from different body parts. Sensation collected by a [[sensory receptor]] on the skin is changed to a nerve signal, that is passed up a series of neurons through tracts in the spinal cord. The [[dorsal column–medial lemniscus pathway]] contains information about fine touch, vibration and position of joints. Neurons travel up the back part of the spinal cord to the back part of the medulla, where they connect with [[dorsal column–medial lemniscus pathway#Second-order neurons|second-order neurons]] that immediately swap sides. These neurons then travel upwards into the [[ventrobasal complex]] in the thalamus where they connect with [[dorsal column–medial lemniscus pathway#Third-order neurons|third-order neurons]] and travel up to the sensory cortex.{{sfn|Guyton & Hall|2011|p=571–576}}The [[spinothalamic tract]] carries information about pain, temperature, and gross touch. Neurons travel up the spinal cord and connect with second-order neurons in the [[reticular formation]] of the brainstem for pain and temperature, and also at the ventrobasal complex of the medulla for gross touch.{{sfn|Guyton & Hall|2011|pp=573–574}}

[[Visual perception|Vision]] is generated by light that hits the [[retina]] of the eye. [[Photoreceptor cell|Photoreceptors]] in the retina [[visual phototransduction|transduce]] the sensory stimulus of [[electromagnetic radiation|light]] into an electrical [[action potential|nerve signal]] that is sent to the [[visual cortex]] in the occipital lobe. Vision from the left visual field is received on the right side of each retina (and vice versa) and passes through the [[optic nerve]] until some information [[optic chiasm|changes sides]], so that all information about one side of the visual field passes through tracts in the opposite side of the brain. The nerves reach the brain at the [[lateral geniculate nucleus]], and travel through the [[optic radiation]] to reach the visual cortex.{{sfn|Guyton & Hall|2011|pp=623–631}}

[[Hearing]] and [[Equilibrioception|balance]] are both generated in the [[inner ear]]. The movement of [[Endolymph|liquids within the inner ear]] is generated by motion (for balance) and transmitted vibrations generated by the [[ossicles]] (for sound). This creates a nerve signal that passes through the [[vestibulocochlear nerve]]. From here, it passes through to the [[cochlear nuclei]], the [[superior olivary nucleus]], the [[medial geniculate nucleus]], and finally the [[auditory radiation]] to the [[auditory cortex]].{{sfn|Guyton & Hall|2011|pp=739–740}}

The sense of [[Olfaction|smell]] is generated by [[Olfactory receptor neuron|receptor cells]] in the [[olfactory epithelium|epithelium]] of the [[olfactory mucosa]] in the [[nasal cavity]]. This information passes through [[cribiform plate|a relatively permeable part]] of the skull to the [[olfactory nerve]]. This nerve transmits to the neural circuitry of the [[olfactory bulb]] from where information is passed to the [[olfactory system|olfactory cortex]].{{sfn|Pocock|2006|pp=138–139}}{{sfn|Squire|2013|pp=525–526}}
[[Taste]] is generated from [[Taste receptor|receptors on the tongue]] and passed along the [[facial]] and [[glossopharyngeal nerve]]s into the [[solitary tract]] in the brainstem. Some taste information is also passed from the pharynx into this area via the [[vagus nerve]]. Information is then passed from here through the thalamus into the [[gustatory cortex]].{{sfn|Guyton & Hall|2011|pp=647–648}}

===Regulation===
[[Autonomic nervous system|Autonomic]] functions of the brain include the regulation, or [[Neuroscience of rhythm|rhythmic control]] of the [[heart rate]] and [[respiratory rate|rate of breathing]], and maintaining [[homeostasis]].

[[Blood pressure]] and [[heart rate]] are influenced by the [[vasomotor center|vasomotor centre]] of the medulla, which causes arteries and veins to be somewhat constricted at rest. It does this by influencing the [[sympathetic nervous system|sympathetic]] and [[parasympathetic nervous system]]s via the [[vagus nerve]].{{sfn|Guyton & Hall|2011|pp=202–203}} Information about blood pressure is generated by [[baroreceptor]]s in [[aortic body|aortic bodies]] in the [[aortic arch]], and passed to the brain along the [[general visceral afferent fibers|afferent fibres]] of the vagus nerve. Information about the pressure changes in the [[carotid sinus]] comes from [[carotid body|carotid bodies]] located near the [[common carotid artery|carotid artery]] and this is passed via a [[Hering's nerve|nerve]] joining with the [[glossopharyngeal nerve]]. This information travels up to the [[solitary nucleus]] in the medulla. Signals from here influence the vasomotor centre to adjust vein and artery constriction accordingly.{{sfn|Guyton & Hall|2011|pp=205–208}}

The brain controls the [[respiratory rate|rate of breathing]], mainly by [[respiratory center|respiratory centre]]s in the medulla and pons.{{sfn|Guyton & Hall|2011|pp=505–509}} The respiratory centres control [[respiration (physiology)|respiration]], by generating motor signals that are passed down the spinal cord, along the [[phrenic nerve]] to the [[Thoracic diaphragm|diaphragm]] and other [[muscles of respiration]]. This is a [[spinal nerve|mixed nerve]] that carries sensory information back to the centres. There are four respiratory centres, three with a more clearly defined function, and an apneustic centre with a less clear function. In the medulla a dorsal respiratory group causes the desire to [[inhalation|breathe in]] and receives sensory information directly from the body. Also in the medulla, the ventral respiratory group influences [[exhalation|breathing out]] during exertion. In the pons the [[pneumotaxic center|pneumotaxic centre]] influences the duration of each breath,{{sfn|Guyton & Hall|2011|pp=505–509}} and the [[apneustic center|apneustic centre]] seems to have an influence on inhalation. The respiratory centres directly senses blood [[carbon dioxide]] and [[pH]]. Information about blood [[oxygen]], [[carbon dioxide]] and pH levels are also sensed on the walls of arteries in the [[peripheral chemoreceptor]]s of the aortic and carotid bodies. This information is passed via the vagus and glossopharyngeal nerves to the respiratory centres. High carbon dioxide, an acidic pH, or low oxygen stimulate the respiratory centres.{{sfn|Guyton & Hall|2011|pp=505–509}} The desire to breathe in is also affected by [[pulmonary stretch receptor]]s in the lungs which, when activated, prevent the lungs from overinflating by transmitting information to the respiratory centres via the vagus nerve.{{sfn|Guyton & Hall|2011|pp=505–509}}

The [[hypothalamus]] in the [[diencephalon]], is involved in regulating many functions of the body. Functions include [[neuroendocrine]] regulation, regulation of the [[circadian rhythm]], control of the [[autonomic nervous system]], and the regulation of fluid, and food intake. The circadian rhythm is controlled by two main cell groups in the hypothalamus. The anterior hypothalamus includes the [[suprachiasmatic nucleus]] and the [[ventrolateral preoptic nucleus]] which through gene expression cycles, generates a roughly 24 hour [[circadian clock]]. In the [[circadian clock|circadian day]] an [[ultradian rhythm]] takes control of the sleeping pattern. [[Sleep]] is an essential requirement for the body and brain and allows the closing down and resting of the body's systems. There are also findings that suggest that the daily build-up of toxins in the brain are removed during sleep.<ref name="sleep">{{cite web |title=Brain Basics: Understanding Sleep {{!}} National Institute of Neurological Disorders and Stroke |url=https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep |website=www.ninds.nih.gov |deadurl=no |archiveurl=https://web.archive.org/web/20171222044016/https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep |archivedate=December 22, 2017 }}</ref> Whilst awake the brain consumes a fifth of the body's total energy needs. [[Neuroscience of sleep|Sleep]] necessarily reduces this use and gives time for the restoration of energy-giving [[Adenosine triphosphate|ATP]]. The effects of [[sleep deprivation]] show the absolute need for sleep.{{sfn|Guyton & Hall|2011|p=723}}

The [[lateral hypothalamus]] contains [[orexin]]ergic neurons that control [[appetite]] and [[arousal]] through their projections to the [[ascending reticular activating system]].<ref name=Davis>{{ cite book | chapter=24. Orexigenic Hypothalamic Peptides Behavior and Feeding – 24.5 Orexin | chapter-url=https://books.google.com/books?id=KuAEPOPbW6MC&pg=PA361 | pages=361–362 |last1=Davis |first1=J.F. |last2=Choi |first2=D.L. |last3=Benoit |first3=S.C. | title=Handbook of Behavior, Food and Nutrition |editor1-last=Preedy |editor1-first= V.R. |editor2-last=Watson |editor2-first=R.R. |editor3-last=Martin |editor3-first=C.R. | publisher=Springer | year=2011 | isbn=9780387922713 }}</ref>{{sfn|Squire|2013|p=800}} The hypothalamus controls the [[pituitary gland]] through the release of peptides such as [[oxytocin]], and [[vasopressin]], as well as [[dopamine]] into the [[median eminence]]. Through the autonomic projections, the hypothalamus is involved in regulating functions such as blood pressure, heart rate, breathing, sweating, and other homeostatic mechanisms.{{sfn|Squire|2013|p=803}} The hypothalamus also plays a role in thermal regulation, and when stimulated by the immune system, is capable of generating a [[fever]]. The hypothalamus is influenced by the kidneys – when blood pressure falls, the [[renin]] released by the kidneys stimulates a need to drink. The hypothalamus also regulates food intake through autonomic signals, and hormone release by the digestive system.{{sfn|Squire|2013|p=805}}

===Language===
[[File:1605_Brocas_and_Wernickes_Areas-02.jpg|thumb|[[Broca's area]] and [[Wernicke's area]] are linked by the [[arcuate fasciculus]].]]
{{main |Language processing in the brain}}
{{See also|Two-streams hypothesis#Two auditory systems}}

While language functions were traditionally thought to be localized to [[Wernicke's area]] and [[Broca's area]],{{sfn|Guyton & Hall|2011|p=720-2}} it is now mostly accepted that a wider network of [[Cortex (anatomy)|cortical]] regions contributes to language functions.<ref>{{cite journal |last1=Poeppel |first1=D. |last2=Emmorey |first2=K. |last3=Hickok |first3=G. |last4=Pylkkänen |first4=L. |title=Towards a new neurobiology of language |journal=The Journal of Neuroscience |date=October 10, 2012 |volume=32 |issue=41 |pages=14125–14131 |doi=10.1523/JNEUROSCI.3244-12.2012 |pmid=23055482 |pmc=3495005}}</ref><ref>{{cite journal |last1=Hickok |first1=G |title=The functional neuroanatomy of language |journal=Physics of Life Reviews |date=September 2009 |volume=6 |issue=3 |pages=121–143 |doi=10.1016/j.plrev.2009.06.001|pmid=20161054 |pmc=2747108 }}</ref><ref>{{cite journal | last1=Fedorenko | first1=E. | last2=Kanwisher | first2=N. | journal=Language and Linguistics Compass | volume=3 | issue=4 | url=https://pdfs.semanticscholar.org/7bb1/d05e4e8842b1714fde9f8dd6cd8c86878039.pdf | title=Neuroimaging of language: why hasn't a clearer picture emerged? | pages=839–865 | doi=10.1111/j.1749-818x.2009.00143.x | year=2009 | deadurl=no | archiveurl=https://web.archive.org/web/20170422033827/https://pdfs.semanticscholar.org/7bb1/d05e4e8842b1714fde9f8dd6cd8c86878039.pdf | archivedate=April 22, 2017 | df=mdy-all }}</ref>

The study on how language is represented, processed, and [[language acquisition|acquired]] by the brain is called [[neurolinguistics]], which is a large multidisciplinary field drawing from [[cognitive neuroscience]], [[cognitive linguistics]], and [[psycholinguistics]].<ref>{{Cite book |title=Language intervention strategies in aphasia and related neurogenic communication disorders |last=Damasio |first=H. |date=2001 |publisher=Lippincott Williams & Wilkins |isbn=9780781721332 |editor-last=Chapey |editor-first=Roberta |edition=4th |pages=18–36 |chapter=Neural basis of language disorders |oclc=45952164}}</ref>

===Lateralisation===
{{Main |Lateralization of brain function}}
{{Further |Functional specialization (brain)}}
The cerebrum has a [[contralateral brain|contralateral organisation]] with each hemisphere of the brain interacting primarily with one half of the body: the left side of the brain interacts with the right side of the body, and vice versa. The developmental cause for this is uncertain.<ref name="Berntson">{{cite book |last1=Berntson |first1=G. |last2=Cacioppo |first2=J. |title=Handbook of Neuroscience for the Behavioral Sciences, Volume 1 |publisher=[[John Wiley & Sons]] |year=2009 |page=145 |isbn=978-0470083550 |url=https://books.google.com/books?id=LwdJhh8bOvwC&pg=PA145}}</ref> Motor connections from the brain to the spinal cord, and sensory connections from the spinal cord to the brain, both [[decussation|cross sides]] in the brainstem. Visual input follows a more complex rule: the optic nerves from the two eyes come together at a point called the [[optic chiasm]], and half of the fibres from each nerve split off to join the other.<ref>{{cite book |author=Hellier, J. |title=The Brain, the Nervous System, and Their Diseases [3 volumes] |isbn=978-1610693387 |publisher=[[ABC-CLIO]] |year=2014 |page=1135 |url=https://books.google.com/books?id=SDi2BQAAQBAJ&pg=PA1135}}</ref> The result is that connections from the left half of the retina, in both eyes, go to the left side of the brain, whereas connections from the right half of the retina go to the right side of the brain.<ref name="Kolb 2">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I.Q. |title=Introduction to Brain and Behavior |isbn=978-1464139604 |publisher=[[Macmillan Higher Education]] |year=2013 |page=296 |url=https://books.google.com/books?id=teUkAAAAQBAJ}}</ref> Because each half of the retina receives light coming from the opposite half of the visual field, the functional consequence is that visual input from the left side of the world goes to the right side of the brain, and vice versa.<ref name="Berntson"/> Thus, the right side of the brain receives somatosensory input from the left side of the body, and visual input from the left side of the visual field.<ref name="Sherwood">{{cite book |last1=Sherwood |first1=L. |title=Human Physiology: From Cells to Systems |isbn=978-1133708537 |publisher=[[Cengage Learning]] |year=2012 |page=181 |url=https://books.google.com/books?id=CZkJAAAAQBAJ&pg=PT181}}</ref><ref name="Kalat">{{cite book |author=Kalat, J |title=Biological Psychology |isbn=978-1305465299 |publisher=[[Cengage Learning]] |year=2015 |page=425 |url=https://books.google.com/books?id=EzZBBAAAQBAJ&pg=PA425}}</ref>

The left and right sides of the brain appear symmetrical, but they function asymmetrically.<ref name="Cowin">{{cite book |last1=Cowin |first1=S.C. |last2=Doty |first2=S.B. |title=Tissue Mechanics |isbn=978-0387499857 |publisher=[[Springer Science & Business Media]] |year=2007 |page=4 |url=https://books.google.com/books?id=8BJhRkat--YC&pg=PA4}}</ref> For example, the counterpart of the left-hemisphere motor area controlling the right hand is the right-hemisphere area controlling the left hand. There are, however, several important exceptions, involving language and spatial cognition. The left frontal lobe is dominant for language. If a key language area in the left hemisphere is damaged, it can leave the victim unable to speak or understand,<ref name="Cowin"/> whereas equivalent damage to the right hemisphere would cause only minor impairment to language skills.

A substantial part of current understanding of the interactions between the two hemispheres has come from the study of "[[split-brain]] patients"—people who underwent surgical transection of the corpus callosum in an attempt to reduce the severity of epileptic seizures.<ref name="Myers">{{cite book |last1=Morris |first1=C.G. |last2=Maisto |first2=A.A. |title=Understanding Psychology |isbn=978-0205769063 |publisher=[[Prentice Hall]] |year=2011 |page=56 |url=https://books.google.com/books?id=hoVWAAAAYAAJ}}</ref> These patients do not show unusual behaviour that is immediately obvious, but in some cases can behave almost like two different people in the same body, with the right hand taking an action and then the left hand undoing it.<ref name="Myers"/><ref name="Kolb 3">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I.Q. |title=Introduction to Brain and Behavior (Loose-Leaf) |isbn=978-1464139604 |publisher=[[Macmillan Higher Education]] |year=2013 |pages=524–549 |url=https://books.google.com/books?id=teUkAAAAQBAJ}}</ref> These patients, when briefly shown a picture on the right side of the point of visual fixation, are able to describe it verbally, but when the picture is shown on the left, are unable to describe it, but may be able to give an indication with the left hand of the nature of the object shown.<ref name="Kolb 3"/><ref name="Schacter">{{cite book |last1=Schacter |first1=D.L. |last2=Gilbert |first2=D.T. |last3=Wegner |first3=D.M. |title=Introducing Psychology |isbn=978-1429218214 |publisher=[[Macmillan Publishers|Macmillan]] |year=2009 |page=80 |url=https://books.google.com/books?id=gt8lpZylVmkC&pg=PA80}}</ref>

===Emotion===
{{main|Emotion}}
{{Further |Affective neuroscience}}
[[Emotion]]s are generally defined as two-step multicomponent processes involving [[Human intelligence (intelligence gathering)|elicitation]], followed by psychological feelings, appraisal, expression, autonomic responses, and action tendencies.<ref>{{cite book |last=Sander |first=David |editor1-last=Armony |editor1-first=J. |editor2-first=Patrik |editor2-last=Vuilleumier |title=The Cambridge handbook of human affective neuroscience |date=2013 |publisher=Cambridge Univ. Press |location=Cambridge |isbn=9780521171557 |pages=16 }}</ref> Attempts to localize basic emotions to certain brain regions have been controversial, with some research finding no evidence for specific locations corresponding to emotions, and instead circuitry involved in general emotional processes. The [[amygdala]], [[orbitofrontal cortex]], mid and anterior [[insula cortex]] and lateral [[prefrontal cortex]], appeared to be involved in generating the emotions, while weaker evidence was found for the [[ventral tegmental area]], [[ventral pallidum]] and [[nucleus accumbens]] in [[incentive salience]].<ref>{{cite journal |last1=Lindquist |first1=KA. |last2=Wager |first2=TD. |last3=Kober |first3=H |last4=Bliss-Moreau |first4=E |last5=Barrett |first5=LF |title=The brain basis of emotion: A meta-analytic review |journal=Behavioral and Brain Sciences |date=May 23, 2012 |volume=35 |issue=3 |pages=121–143 |doi=10.1017/S0140525X11000446|pmid=22617651 |pmc=4329228 }}</ref> Others, however, have found evidence of activation of specific regions, such as the [[basal ganglia]] in happiness, the [[corpus callosum|subcallosal]] [[cingulate cortex]] in sadness, and [[amygdala]] in fear.<ref>{{cite journal |last1=Phan |first1=KL |last2=Wager |first2=Tor |last3=Taylor |first3=SF. |last4=Liberzon |first4=l |title=Functional Neuroanatomy of Emotion: A Meta-Analysis of Emotion Activation Studies in PET and fMRI |journal=NeuroImage |date=June 1, 2002 |volume=16 |issue=2 |pages=331–348 |doi=10.1006/nimg.2002.1087 |url=http://europepmc.org/abstract/med/12030820 |pmid=12030820}}</ref>

===Cognition===
{{main|Cognition}} {{Further |Prefrontal cortex#Executive function}}

The brain is responsible for [[cognition]],<ref name="NHM preface - Cognition">{{cite book | last1=Malenka |first1=RC |last2=Nestler |first2=EJ |last3=Hyman |first3=SE | editor1-last=Sydor |editor1-first=A |editor2-last=Brown |editor2-first=RY | title=Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year=2009 | publisher=McGraw-Hill Medical | location=New York | isbn=9780071481274 | page=xiii | edition=2nd | chapter=Preface }}</ref><ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /> which functions through numerous [[cognitive process|processes]] and [[executive function]]s.<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter = Chapter 14: Higher Cognitive Function and Behavioral Control}}</ref><ref name="NHMH_3e – pathways">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter=Chapter 6: Widely Projecting Systems: Monoamines, Acetylcholine, and Orexin}}</ref><ref name="Executive functions">{{cite journal | last1=Diamond |first1=A |author1-link=Adele Diamond | title=Executive functions | journal=Annual Review of Psychology | volume=64 | issue= | pages=135–168 | year=2013 | pmid=23020641 | pmc=4084861 | doi=10.1146/annurev-psych-113011-143750 | quote=}} [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084861/figure/F4/ Figure 4: Executive functions and related terms] {{webarchive|url=https://web.archive.org/web/20180509181646/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084861/figure/F4/ |date=May 9, 2018 }}</ref> Executive functions include the ability to filter information and tune out irrelevant stimuli with [[attentional control]] and [[cognitive inhibition]], the ability to process and manipulate information held in [[working memory]], the ability to think about multiple concepts simultaneously and [[task switching (psychology)|switch tasks]] with [[cognitive flexibility]], the ability to inhibit [[impulse (psychology)|impulses]] and [[prepotent response]]s with [[inhibitory control]], and the ability to determine the relevance of information or appropriateness of an action.<ref name="NHMH_3e – pathways" /><ref name="Executive functions" /> Higher order executive functions require the simultaneous use of multiple basic executive functions, and include [[planning]] and [[fluid intelligence]] (i.e., [[reasoning]] and [[problem solving]]).<ref name="Executive functions" />

The [[prefrontal cortex]] plays a significant role in mediating executive functions.<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /><ref name="Executive functions" /><ref name="Goldstein">{{cite book | editor1-last=Goldstein |editor1-first=S. |editor2-last=Naglieri |editor2-first=J. | last1=Hyun |first1=J.C. |last2=Weyandt |first2=L.L. |last3=Swentosky |first3=A. | title=Handbook of Executive Functioning | date=2014 | publisher=Springer | location=New York | isbn=9781461481065 | pages=13–23 | chapter=Chapter 2: The Physiology of Executive Functioning | chapter-url=https://books.google.com/books?id=1e8VAgAAQBAJ&pg=PA13 }}</ref> Planning involves activation of the [[dorsolateral prefrontal cortex]] (DLPFC), [[anterior cingulate cortex]], angular prefrontal cortex, right prefrontal cortex, and [[supramarginal gyrus]].<ref name="Goldstein"/> Working memory manipulation involves the DLPFC, [[inferior frontal gyrus]], and areas of the [[parietal cortex]].<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /><ref name="Goldstein" /> [[Inhibitory control]] involves multiple areas of the prefrontal cortex, as well as the [[caudate nucleus]] and [[subthalamic nucleus]].<ref name="Executive functions" /><ref name="Goldstein" /><ref name="NHMH_3e – Addiction and ADHD" />

==Physiology==

===Neurotransmission===
{{main|Neurotransmission}}
{{Further | Summation (neurophysiology)}}
Brain activity is made possible by the interconnections of neurons that are linked together to reach their targets.{{sfn|Pocock|2006|p=68}} A neuron consists of a [[soma (biology)|cell body]], [[axon]], and [[dendrite]]s. Dendrites are often extensive branches that receive information in the form of signals from the axon terminals of other neurons. The signals received may cause the neuron to initiate an [[action potential]] (an electrochemical signal or nerve impulse) which is sent along its axon to the axon terminal, to connect with the dendrites or with the cell body of another neuron. An action potential is initiated at the [[Axon#Initial segment|initial segment]] of an axon, which contains a complex of proteins.<ref>{{cite journal |last=Clark |first=B.D. |author2=Goldberg, E.M. |author3=Rudy, B. |title=Electrogenic tuning of the axon initial segment. |journal=The Neuroscientist : A Review Journal Bringing Neurobiology, Neurology and Psychiatry |date=December 2009 |volume=15 |issue=6 |pages=651–68 |pmid=20007821 |doi=10.1177/1073858409341973 |pmc=2951114}}</ref> When an action potential, reaches the axon terminal it triggers the release of a [[neurotransmitter]] at a [[synapse]] that propagates a signal that acts on the target cell.{{sfn|Pocock|2006|pp=70–74}} These chemical neurotransmitters include [[dopamine]], [[serotonin]], [[gamma-Aminobutyric acid|GABA]], [[glutamate (neurotransmitter)|glutamate]], and [[acetylcholine]].<ref name=NIMH2017 /> GABA is the major inhibitory neurotransmitter in the brain, and glutamate is the major excitatory neurotransmitter.<ref>{{cite book|last1=Purves|first1=Dale|title=Neuroscience|date=2011|publisher=Sinauer|location=Sunderland, Mass.|isbn=978-0-87893-695-3|page=139|edition=5.}}</ref> Neurons link at synapses to form [[neural pathway]]s, [[neural circuit]]s, and large elaborate [[large scale brain networks|network systems]] such as the [[salience network]] and the [[default mode network]], and the activity between them is driven by the process of [[neurotransmission]].

===Metabolism===
[[File:PET-image.jpg|thumb|upright|alt=A flat oval object is surrounded by blue. The object is largely green-yellow, but contains a dark red patch at one end and a number of blue patches. |[[Positron emission tomography|PET]] image of the human brain showing energy consumption]]

The brain consumes up to 20% of the energy used by the human body, more than any other organ.<ref name="power-sciam">{{cite web |last=Swaminathan |first=N |title=Why Does the Brain Need So Much Power? |url=http://www.scientificamerican.com/article/why-does-the-brain-need-s/ |work=[[Scientific American]] |publisher=Scientific American, a Division of Nature America, Inc. |accessdate=November 19, 2010 |date=April 29, 2008 |deadurl=no |archiveurl=https://web.archive.org/web/20140127171142/http://www.scientificamerican.com/article/why-does-the-brain-need-s/ |archivedate=January 27, 2014 }}</ref> In humans, [[blood glucose]] is the primary [[food energy|source of energy]] for most cells and is critical for normal function in a number of tissues, including the brain.<ref name="Glucose-Glycogen storage review" /> The human brain consumes approximately 60% of blood glucose in fasted, sedentary individuals.<ref name="Glucose-Glycogen storage review">{{cite journal | vauthors = Wasserman DH | title = Four grams of glucose | journal = American Journal of Physiology. Endocrinology and Metabolism | volume = 296 | issue = 1 | pages = E11–21 | date = January 2009 | pmid = 18840763 | pmc = 2636990 | doi = 10.1152/ajpendo.90563.2008 | quote = Four grams of glucose circulates in the blood of a person weighing 70 kg. This glucose is critical for normal function in many cell types. In accordance with the importance of these 4 g of glucose, a sophisticated control system is in place to maintain blood glucose constant. Our focus has been on the mechanisms by which the flux of glucose from liver to blood and from blood to skeletal muscle is regulated. ... The brain consumes ∼60% of the blood glucose used in the sedentary, fasted person. ... The amount of glucose in the blood is preserved at the expense of glycogen reservoirs (Fig. 2). In postabsorptive humans, there are ∼100 g of glycogen in the liver and ∼400 g of glycogen in muscle. Carbohydrate oxidation by the working muscle can go up by ∼10-fold with exercise, and yet after 1 h, blood glucose is maintained at ∼4 g. ... It is now well established that both insulin and exercise cause translocation of GLUT4 to the plasma membrane. Except for the fundamental process of GLUT4 translocation, [muscle glucose uptake (MGU)] is controlled differently with exercise and insulin. Contraction-stimulated intracellular signaling (52, 80) and MGU (34, 75, 77, 88, 91, 98) are insulin independent. Moreover, the fate of glucose extracted from the blood is different in response to exercise and insulin (91, 105). For these reasons, barriers to glucose flux from blood to muscle must be defined independently for these two controllers of MGU.}}</ref> Brain [[metabolism]] normally relies upon blood [[glucose]] as an energy source, but during times of low glucose (such as [[fasting]], [[endurance exercise]], or limited [[carbohydrate]] intake), the brain uses [[ketone bodies]] for fuel with a smaller need for glucose. The brain can also utilize [[Lactic acid#Exercise and lactate|lactate during exercise]].<ref>{{cite journal |title=Lactate fuels the human brain during exercise |last1=Quistorff |first1=B |last2=Secher |first2=N |last3=Van Lieshout |first3=J |date=July 24, 2008 |journal=[[The FASEB Journal]] |doi=10.1096/fj.08-106104 |pmid=18653766 |volume=22 |issue=10 |pages=3443–3449 }}</ref> The brain stores glucose in the form of [[glycogen]], albeit in significantly smaller amounts than that found in the [[liver]] or [[skeletal muscle]].<ref>{{cite journal |last=Obel |first=L.F. |author2=Müller, M.S. |author3=Walls, A.B. |author4=Sickmann, H.M. |author5=Bak, L.K. |author6=Waagepetersen, H.S. |author7= Schousboe, A. |title=Brain glycogen-new perspectives on its metabolic function and regulation at the subcellular level. |journal=Frontiers in Neuroenergetics |date=2012 |volume=4 |pages=3 |pmid=22403540 |doi=10.3389/fnene.2012.00003 |pmc=3291878}}</ref> [[Fatty acid#Length of free fatty acid chains|Long-chain fatty acid]]s cannot cross the [[blood–brain barrier]], but the liver can break these down to produce ketone bodies. However, [[short-chain fatty acid]]s (e.g., [[butyric acid]], [[propionic acid]], and [[acetic acid]]) and the [[Fatty acid#Length of free fatty acid chains|medium-chain fatty acids]], [[octanoic acid]] and [[heptanoic acid]], can cross the blood–brain barrier and be metabolized by brain cells.<ref>{{cite journal |last1=Marin-Valencia |first1=I. |display-authors=etal |title=Heptanoate as a neural fuel: energetic and neurotransmitter precursors in normal and glucose transporter I-deficient (G1D) brain. |journal=Journal of Cerebral Blood Flow and Metabolism |date=February 2013 |volume=33 |issue=2 |pages=175–82 |pmid=23072752 |doi=10.1038/jcbfm.2012.151 |pmc=3564188}}</ref><ref name="SCFA MCT-mediated BBB passage - 2005 review">{{cite journal | author=Tsuji, A. | title=Small molecular drug transfer across the blood-brain barrier via carrier-mediated transport systems | journal=NeuroRx | volume=2 | issue=1 | pages=54–62 | year=2005 | pmid=15717057 | pmc=539320 | doi=10.1602/neurorx.2.1.54 | quote=Uptake of valproic acid was reduced in the presence of medium-chain fatty acids such as hexanoate, octanoate, and decanoate, but not propionate or butyrate, indicating that valproic acid is taken up into the brain via a transport system for medium-chain fatty acids, not short-chain fatty acids. ... Based on these reports, valproic acid is thought to be transported bidirectionally between blood and brain across the BBB via two distinct mechanisms, monocarboxylic acid-sensitive and medium-chain fatty acid-sensitive transporters, for efflux and uptake, respectively.}}</ref><ref name="SCFA MCT-mediated BBB passage - 2014 review">{{cite journal | last1=Vijay |first1=N. |last2=Morris |first2=M.E. | title=Role of monocarboxylate transporters in drug delivery to the brain | journal=Curr. Pharm. Des. | volume=20 | issue=10 | pages=1487–98 | year=2014 | pmid=23789956 | pmc=4084603 | doi=10.2174/13816128113199990462 | quote=Monocarboxylate transporters (MCTs) are known to mediate the transport of short chain monocarboxylates such as lactate, pyruvate and butyrate. ... MCT1 and MCT4 have also been associated with the transport of short chain fatty acids such as acetate and formate which are then metabolized in the astrocytes [78].}}</ref>

Although the human brain represents only 2% of the body weight, it receives 15% of the cardiac output, 20% of total body oxygen consumption, and 25% of total body [[glucose]] utilization.<ref>{{cite book |last=Clark |first=D.D. |author2=Sokoloff. L. |editor1=Siegel, G.J.|editor2=Agranoff, B.W.|editor3=Albers, R.W.|editor4=Fisher, S.K.|editor5=Uhler, M.D. |title=Basic Neurochemistry: Molecular, Cellular and Medical Aspects |publisher=Lippincott |location=Philadelphia |year=1999 |pages=637–670 |isbn=978-0-397-51820-3}}</ref> The brain mostly uses glucose for energy, and deprivation of glucose, as can happen in [[hypoglycemia]], can result in loss of consciousness.<ref name="Mrsulja">{{cite book |author=Mrsulja, B.B. |title=Pathophysiology of Cerebral Energy Metabolism |isbn=978-1468433487 |publisher=[[Springer Science & Business Media]] |year=2012 |pages=2–3 |url=https://books.google.com/books?id=8yzvBwAAQBAJ&pg=PA2}}</ref> The energy consumption of the brain does not vary greatly over time, but active regions of the cortex consume somewhat more energy than inactive regions: this fact forms the basis for the functional brain imaging methods [[Positron emission tomography|PET]] and [[fMRI]].<ref>{{cite journal |last=Raichle |first=M. |year=2002 |title=Appraising the brain's energy budget |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=99 |pages=10237–10239 |doi=10.1073/pnas.172399499 |pmid=12149485 |last2=Gusnard |first2=DA |pmc=124895 |issue=16}}</ref> These [[functional imaging]] techniques provide a three-dimensional image of metabolic activity.<ref name="Steptoe">{{cite book |editor-last=Steptoe |editor-first=A. |last1=Gianaros |first1=Peter J. |last2=Gray |first2=Marcus A. |last3=Onyewuenyi |first3=Ikechukwu |last4=Critchley |first4=Hugo D.|title=Handbook of Behavioral Medicine: Methods and Applications |chapter=Chapter 50. Neuroimaging methods in behavioral medicine |isbn=978-0387094885 |publisher=[[Springer Science & Business Media]] |year=2010 |page=770 |chapter-url=https://books.google.com/books?id=Si9TtI5AGIEC&pg=PA770 |doi=10.1007/978-0-387-09488-5_50}}</ref>

The function of [[sleep]] is not fully understood; however, there is evidence that sleep enhances the clearance of metabolic waste products, some of which are potentially [[neurotoxic]], from the brain and may also permit repair.<ref name="Glymphatic system and brain waste clearance 2017 review" /><ref>{{cite web |title=Brain may flush out toxins during sleep |url=http://www.ninds.nih.gov/news_and_events/news_articles/pressrelease_brain_sleep_10182013.htm |work=[[National Institutes of Health]] |accessdate=October 25, 2013 |deadurl=no |archiveurl=https://web.archive.org/web/20131020220815/http://www.ninds.nih.gov/news_and_events/news_articles/pressrelease_brain_sleep_10182013.htm |archivedate=October 20, 2013 }}</ref><ref name="Sleep – clearance of neurotoxic waste products">{{cite journal | vauthors = Xie L, Kang H, Xu Q, Chen MJ, Liao Y, Thiyagarajan M, O'Donnell J, Christensen DJ, Nicholson C, Iliff JJ, Takano T, Deane R, Nedergaard M | title = Sleep drives metabolite clearance from the adult brain | journal = Science | volume = 342 | issue = 6156 | pages = 373–377 | date = October 2013 | pmid = 24136970 | pmc = 3880190 | doi = 10.1126/science.1241224 | quote = Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.}}</ref> Evidence suggests that the increased clearance of metabolic waste during sleep occurs via increased functioning of the [[glymphatic system]].<ref name="Glymphatic system and brain waste clearance 2017 review">{{cite journal | vauthors = Bacyinski A, Xu M, Wang W, Hu J | title = The Paravascular Pathway for Brain Waste Clearance: Current Understanding, Significance and Controversy | journal = Frontiers in Neuroanatomy | volume = 11 | issue = | pages = 101 | date = November 2017 | pmid = 29163074 | pmc = 5681909 | doi = 10.3389/fnana.2017.00101 | quote = The paravascular pathway, also known as the “glymphatic” pathway, is a recently described system for waste clearance in the brain. According to this model, cerebrospinal fluid (CSF) enters the paravascular spaces surrounding penetrating arteries of the brain, mixes with interstitial fluid (ISF) and solutes in the parenchyma, and exits along paravascular spaces of draining veins.  ... In addition to Aβ clearance, the glymphatic system may be involved in the removal of other interstitial solutes and metabolites. By measuring the lactate concentration in the brains and cervical lymph nodes of awake and sleeping mice, Lundgaard et al. (2017) demonstrated that lactate can exit the CNS via the paravascular pathway. Their analysis took advantage of the substantiated hypothesis that glymphatic function is promoted during sleep (Xie et al., 2013; Lee et al., 2015; Liu et al., 2017).}}</ref> Sleep may also have an effect on cognitive function by weakening unnecessary connections.<ref>{{cite journal |url=https://pdfs.semanticscholar.org/6f9d/f7817534e55865bd1f6b7da6d2912bdbeaf3.pdf |last1=Tononi |first1=Guilio |last2=Cirelli |first2=Chiara |title=Perchance to Prune |journal=Scientific American |volume=309 |issue=2 |date=August 2013 |pages=34–39 |pmid=23923204|doi=10.1038/scientificamerican0813-34 }}</ref>

==Research==
The brain is not fully understood, and research is ongoing.<ref name=HCP2009 /> [[Neuroscience|Neuroscientists]], along with researchers from allied disciplines, study how the human brain works. The boundaries between the specialties of [[neuroscience]], [[neurology]] and other disciplines such as [[psychiatry]] have faded as they are all influenced by [[basic research]] in neuroscience.

Neuroscience research has expanded considerably in recent decades. The "[[Decade of the Brain]]", an initiative of the United States Government in the 1990s, is considered to have marked much of this increase in research,<ref>{{Cite journal |url=http://www.sciencemag.org/cgi/content/summary/284/5415/739 |first1=E.G. |last1=Jones |authorlink1=Edward G. Jones |first2=L.M. |last2=Mendell |title=Assessing the Decade of the Brain |journal=Science |doi=10.1126/science.284.5415.739 |date=April 30, 1999 |volume=284 |issue=5415 |page=739 |pmid=10336393 |deadurl=no |archiveurl=https://web.archive.org/web/20100614091805/http://www.sciencemag.org/cgi/content/summary/284/5415/739 |archivedate=June 14, 2010 }}</ref> and was followed in 2013 by the [[BRAIN Initiative]].<ref>{{cite web |title=A $4.5 Billion Price Tag for the BRAIN Initiative? |url=http://www.sciencemag.org/news/2014/06/45-billion-price-tag-brain-initiative |website=Science {{!}} AAAS |date=June 5, 2014 |deadurl=no |archiveurl=https://web.archive.org/web/20170618154752/http://www.sciencemag.org/news/2014/06/45-billion-price-tag-brain-initiative |archivedate=June 18, 2017 }}</ref> The [[Human Connectome Project]] was a five-year study launched in 2009 to analyse the anatomical and functional connections of parts of the brain, and has provided much data.<ref name=HCP2009>{{cite journal |last1=Van Essen |first1=D.C. |display-authors=etal |title=The Human Connectome Project: A data acquisition perspective |journal=NeuroImage |date=October 2012 |volume=62 |issue=4 |pages=2222–2231 |doi=10.1016/j.neuroimage.2012.02.018|pmid=22366334 |pmc=3606888 }}</ref>

===Methods===
Information about the structure and function of the human brain comes from a variety of experimental methods, including animals and humans. Information about brain trauma and stroke has provided information about the function of parts of the brain and the effects of [[brain damage]]. [[Neuroimaging]] is used to visualise the brain and record brain activity. [[Electrophysiology]] is used to measure, record and monitor the electrical activity of the cortex. Measurements may be of [[local field potential]]s of cortical areas, or of the activity of a single neuron. An [[electroencephalography|electroencephalogram]] can record the electrical activity of the cortex using [[electrode]]s placed non-invasively on the [[scalp]].<ref>{{cite journal | last1=Towle |first1=V.L. |display-authors=etal |title=The spatial location of EEG electrodes: locating the best-fitting sphere relative to cortical anatomy |journal=Electroencephalography and Clinical Neurophysiology |date=January 1993 |volume=86 |issue=1 |pages=1–6 |pmid=7678386 |doi=10.1016/0013-4694(93)90061-y}}</ref>{{sfn|Purves|2012|pp=632–633}}

Invasive measures include [[electrocorticography]], which uses electrodes placed directly on the exposed surface of the brain. This method is used in [[cortical stimulation mapping]], used in the study of the relationship between cortical areas and their systemic function.<ref>{{cite journal |last1=Silverstein |first1=J. |title=Mapping the Motor and Sensory Cortices: A Historical Look and a Current Case Study in Sensorimotor Localization and Direct Cortical Motor Stimulation |journal=The Neurodiagnostic Journal |pmid=22558647 |url=http://www.readperiodicals.com/201203/2662763741.html |year=2012 |volume=52 |issue=1 |pages=54–68 |deadurl=no |archiveurl=https://web.archive.org/web/20121117021132/http://www.readperiodicals.com/201203/2662763741.html |archivedate=November 17, 2012 }}</ref> By using much smaller [[microelectrode]]s, [[single-unit recording]]s can be made from a single neuron that give a high [[Angular resolution|spatial resolution]] and high [[temporal resolution]]. This has enabled the linking of brain activity to behaviour, and the creation of neuronal maps.<ref>{{cite journal |last1=Boraud |first1=T. |last2=Bezard |first2=E. | year=2002 | title=From single extracellular unit recording in experimental and human Parkinsonism to the development of a functional concept of the role played by the basal ganglia in motor control | journal=Progress in Neurobiology | volume=66 | issue=4 | pages=265–283 | doi=10.1016/s0301-0082(01)00033-8 |display-authors=etal}}</ref>

The development of [[cerebral organoid]]s has opened ways for studying the growth of the brain, and of the cortex, and for understanding disease development, offering further implications for therapeutic applications.<ref name="Lancaster">{{cite journal |last1=Lancaster |first1=MA |last2=Renner |first2=M |last3=Martin |first3=CA |last4=Wenzel |first4=D |last5=Bicknell |first5=LS |last6=Hurles |first6=ME |last7=Homfray |first7=T |last8=Penninger |first8=JM |last9=Jackson |first9=AP |last10=Knoblich |first10=JA |title=Cerebral organoids model human brain development and microcephaly. |journal=Nature |date=19 September 2013 |volume=501 |issue=7467 |pages=373-9 |doi=10.1038/nature12517 |pmid=23995685}}</ref><ref name="Lee">{{cite journal |last1=Lee |first1=CT |last2=Bendriem |first2=RM |last3=Wu |first3=WW |last4=Shen |first4=RF |title=3D brain Organoids derived from pluripotent stem cells: promising experimental models for brain development and neurodegenerative disorders. |journal=Journal of biomedical science |date=20 August 2017 |volume=24 |issue=1 |pages=59 |doi=10.1186/s12929-017-0362-8 |pmid=28822354}}</ref>

===Imaging===
{{Further |Magnetic resonance imaging of the brain}}

[[Functional neuroimaging]] techniques show changes in brain activity that relate to the function of specific brain areas. One technique is [[functional magnetic resonance imaging]] (fMRI) which has the advantages over earlier methods of [[SPECT]] and [[positron emission tomography|PET]] of not needing the use of [[Nuclear medicine|radioactive materials]] and of offering a higher resolution.<ref>{{cite web |title=Magnetic Resonance, a critical peer-reviewed introduction; functional MRI |publisher=European Magnetic Resonance Forum |accessdate=June 30, 2017 |url=http://www.magnetic-resonance.org/ch/11-03.html |deadurl=no |archiveurl=https://web.archive.org/web/20170602035337/http://www.magnetic-resonance.org/ch/11-03.html |archivedate=June 2, 2017 }}</ref> Another technique is [[functional near-infrared spectroscopy]]. These methods rely on the [[haemodynamic response]] that shows changes in brain activity in relation to changes in [[cerebral circulation|blood flow]], useful in [[brain mapping|mapping functions to brain areas]].<ref>{{cite journal |last1=Buxton |first1=R. |last2=Uludag |first2=K. |last3=Liu |first3=T. | year= 2004| title=Modeling the haemodynamic response to brain activation | journal=NeuroImage | volume= 23 | issue= | pages=S220–S233 | doi=10.1016/j.neuroimage.2004.07.013|pmid=15501093 |citeseerx=10.1.1.329.29 }}</ref> [[Resting state fMRI]]
looks at the interaction of brain regions whilst the brain is not performing a specific task.<ref>{{cite journal |last1=Biswal |first1=B.B. |title=Resting state fMRI: a personal history |journal=NeuroImage|date=August 15, 2012|volume=62|issue=2|pages=938–44|pmid=22326802|doi=10.1016/j.neuroimage.2012.01.090}}</ref> This is also used to show the [[default mode network]].

Any electrical current generates a magnetic field; [[neural oscillation]]s induce weak magnetic fields, and in functional [[magnetoencephalography]] the current produced can show localised brain function in high resolution.{{sfn|Purves|2012|p=20}} [[Tractography]] uses [[MRI]] and [[image analysis]] to create [[3D modeling|3D images]] of the [[nerve tract]]s of the brain. [[Connectogram]]s give a graphical representation of the [[connectome|neural connections]] of the brain.<ref name="Kane">{{cite book |last1=Kane |first1=R.L. |last2=Parsons |first2=T.D. |title=The Role of Technology in Clinical Neuropsychology |isbn=978-0190234737 |publisher=[[Oxford University Press]] |year=2017 |page=399 |url=https://books.google.com/books?id=iuAwDgAAQBAJ |quote=Irimia, Chambers, Torgerson, and Van Horn (2012) provide a first-step graphic on how best to display connectivity findings, as is presented in Figure 13.15. This is referred to as a connectogram.}}</ref>

Differences in [[brain morphometry|brain structure can be measured]] in some disorders, notably [[schizophrenia]] and [[dementia]]. Different biological approaches using imaging have given more insight for example into the disorders of [[biology of depression|depression]] and [[biology of obsessive-compulsive disorder|obsessive-compulsive disorder]]. A key source of information about the function of brain regions is the effects of damage to them.<ref>{{cite book | url=https://books.google.com/?id=kiCtU8wBTfwC | title=Neuropsychology | last=Andrews | first=D.G. | publisher=Psychology Press | year=2001 | isbn=978-1-84169-103-9}}</ref>

Advances in [[neuroimaging]] have enabled objective insights into mental disorders, leading to faster diagnosis, more accurate prognosis, and better monitoring.<ref>{{cite web |author=Lepage, M. |date=2010 |title=Research at the Brain Imaging Centre |work=Douglas Mental Health University Institute |url=http://www.douglas.qc.ca/page/imagerie-cerebrale?locale=en |deadurl=yes |archiveurl=https://web.archive.org/web/20120305042011/http://www.douglas.qc.ca/page/imagerie-cerebrale?locale=en |archivedate=March 5, 2012 }}</ref>

===Gene and protein expression===
{{Main|Bioinformatics}}
{{See also |List of neuroscience databases}}
[[Bioinformatics]] is a field of study that includes the creation and advancement of databases, and computational and statistical techniques, that can be used in studies of the human brain, particularly in the areas of [[Bioinformatics#Gene and protein expression|gene and protein expression]]. Bioinformatics and studies in [[genomics]], and [[functional genomics]], generated the need for [[DNA annotation]], a [[Transcriptomics technologies|transcriptome technology]], identifying [[gene]]s, and their and location and function.<ref name="Steward">{{cite journal | title=Genome annotation for clinical genomic diagnostics: strengths and weaknesses | author=Steward, C.A. |display-authors=etal | pmid=28558813 | doi=10.1186/s13073-017-0441-1 | volume=9 | issue=1 | pmc=5448149 | year=2017 | journal=Genome Med | page=49}}</ref><ref>{{cite journal | title=GENCODE: the reference human genome annotation for The ENCODE Project. | author=Harrow, J. |display-authors=etal | pmid=22955987 | doi=10.1101/gr.135350.111 | pmc=3431492 | volume=22 | issue=9 | date=September 2012 | journal=Genome Res. | pages=1760–74}}</ref><ref name="Gibson and Muse">{{cite book |vauthors=Gibson G, Muse SV |title=A primer of genome science |edition=3rd |publisher=Sinauer Associates |location=Sunderland, MA}}</ref> [[GeneCards]] is a major database.

As of 2017, just under 20,000 [[Human genome#Coding sequences (protein-coding genes)|protein-coding genes]] are seen to be expressed in the human,<ref name="Steward"/> and some 400 of these genes are brain-specific.<ref>{{Cite web|url=https://www.proteinatlas.org/humanproteome/brain|title=The human proteome in brain – The Human Protein Atlas|website=www.proteinatlas.org|access-date=September 29, 2017|deadurl=no|archiveurl=https://web.archive.org/web/20170929231550/https://www.proteinatlas.org/humanproteome/brain|archivedate=September 29, 2017}}</ref><ref>{{Cite journal|last=Uhlén|first=Mathias|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Lindskog|first4=Cecilia|last5=Oksvold|first5=Per|last6=Mardinoglu|first6=Adil|last7=Sivertsson|first7=Åsa|last8=Kampf|first8=Caroline|last9=Sjöstedt|first9=Evelina|date=January 23, 2015|title=Tissue-based map of the human proteome|url=http://science.sciencemag.org/content/347/6220/1260419|journal=Science|language=en|volume=347|issue=6220|pages=1260419|doi=10.1126/science.1260419|issn=0036-8075|pmid=25613900|deadurl=no|archiveurl=https://web.archive.org/web/20170716202510/http://science.sciencemag.org/content/347/6220/1260419|archivedate=July 16, 2017}}</ref> The data that has been provided on [[gene expression]] in the brain has fuelled further research into a number of disorders. The long term use of alcohol for example, has shown altered gene expression in the brain, and cell-type specific changes that may relate to [[alcoholism|alcohol use disorder]].<ref>{{cite journal|last=Warden|first=A|year=2017|title=Gene expression profiling in the human alcoholic brain.|journal=Neuropharmacology|volume=122|pages=161–174|pmid=28254370|via=|doi=10.1016/j.neuropharm.2017.02.017|pmc=5479716}}</ref> These changes have been noted in the [[Synapse|synaptic]] [[transcriptome]] in the prefrontal cortex, and are seen as a factor causing the drive to alcohol dependence, and also to other [[substance abuse]]s.<ref>{{cite journal | title=Applying the new genomics to alcohol dependence. | author=Farris, S.P. |display-authors=etal | journal=Alcohol | year=2015 | pmid=25896098 | doi=10.1016/j.alcohol.2015.03.001 | volume=49 | issue=8 | pmc=4586299 | pages=825–36}}</ref>

Other related studies have also shown evidence of synaptic alterations and their loss, in the [[ageing brain]]. Changes in gene expression alter the levels of proteins in various pathways and this has been shown to be evident in synaptic contact dysfunction or loss. This dysfunction has been seen to affect many structures of the brain and has a marked effect on inhibitory neurons resulting in a decreased level of neurotransmission, and subsequent cognitive decline and disease.<ref name="Rozycka">{{cite journal|last1=Rozycka|first1=A|last2=Liguz-Lecznar|first2=M|title=The space where aging acts: focus on the GABAergic synapse.|journal=Aging Cell|date=August 2017|volume=16|issue=4|pages=634–643|doi=10.1111/acel.12605|pmid=28497576|pmc=5506442}}</ref><ref>{{cite journal|last1=Flores|first1=CE|last2=Méndez|first2=P|title=Shaping inhibition: activity dependent structural plasticity of GABAergic synapses.|journal=Frontiers in Cellular Neuroscience|date=2014|volume=8|pages=327|doi=10.3389/fncel.2014.00327|pmid=25386117|pmc=4209871}}</ref>

==Clinical significance==
===Injury===
[[Brain damage|Injury to the brain]] can manifest in many ways. [[Traumatic brain injury]], for example received in [[contact sport]], after a [[Falling (accident)|fall]], or a [[traffic collision|traffic]] or [[work accident]], can be associated with both immediate and longer-term problems. Immediate problems may include [[intracerebral haemorrhage|bleeding within the brain]], this may compress the brain tissue or damage its blood supply. [[Cerebral contusion|Bruising]] to the brain may occur. Bruising may cause widespread damage to the nerve tracts that can lead to a condition of [[diffuse axonal injury]].<ref name="GE Health">{{cite web|url=http://www.medcyclopaedia.com/library/topics/volume_vi_1/b/BRAIN_INJURY_TRAUMATIC.aspx|archive-url=https://archive.is/20110526162429/http://www.medcyclopaedia.com/library/topics/volume_vi_1/b/BRAIN_INJURY_TRAUMATIC.aspx|dead-url=yes|archive-date=May 26, 2011|title=Brain Injury, Traumatic|publisher=[[General Electric|GE]]|work=Medcyclopaedia}}</ref> A [[skull fracture|fractured skull]], injury to a particular area, [[deafness]], and [[concussion]] are also possible immediate developments. In addition to the site of injury, the opposite side of the brain may be affected, termed a [[Coup contrecoup injury|contrecoup]] injury. Longer-term issues that may develop include [[posttraumatic stress disorder]], and [[hydrocephalus]]. [[Chronic traumatic encephalopathy]] can develop following multiple [[head injury|head injuries]].<ref>{{Cite journal |last1=Dawodu |first1=S.T. |title=Traumatic Brain Injury (TBI) – Definition and Pathophysiology: Overview, Epidemiology, Primary Injury |url=http://emedicine.medscape.com/article/326510-overview#a3 |website=Medscape |date=March 9, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170409021001/http://emedicine.medscape.com/article/326510-overview#a3 |archivedate=April 9, 2017 }}</ref>

===Disease===
[[Neurodegenerative disease]]s result in progressive damage to different parts of the brain's function, and [[Aging brain|worsen with age]]. Common examples include [[dementia]] such as [[Alzheimer's disease]], [[alcoholic dementia]] or [[vascular dementia]]; [[Parkinson's disease]]; and other rarer infectious, genetic, or metabolic causes such as [[Huntington's disease]], [[motor neuron disease]]s, [[HIV dementia]], [[Neurosyphilis|syphilis-related dementia]] and [[Wilson's disease]]. Neurodegenerative diseases can affect different parts of the brain, and can affect movement, [[memory]], and cognition.{{sfn|Davidson's|2010|p=1196-7}}

The brain, although protected by the blood–brain barrier, can be affected by infections including [[virus]]es, [[bacteria]] and [[fungi]]. Infection may be of the [[meninges]] ([[meningitis]]), the brain matter ([[encephalitis]]), or within the brain matter (such as a [[cerebral abscess]]).{{sfn|Davidson's|2010|p=1205-15}} Rare [[prion disease]]s including [[Creutzfeldt–Jakob disease]] and its [[Variant Creutzfeldt–Jakob disease|variant]], and [[Kuru (disease)|kuru]] may also affect the brain.{{sfn|Davidson's|2010|p=1205-15}}

===Tumours===
[[Brain tumor|Brain tumours]] can be either [[benign]] or [[malignant|cancerous]]. Most malignant tumours [[metastasis|arise from another part of the body]], most commonly from the [[lung cancer|lung]], [[breast cancer|breast]] and [[melanoma|skin]].{{sfn|Davidson's|2010|p=1216-7}} Cancers of brain tissue can also occur, and originate from any tissue in and around the brain. [[Meningioma]], cancer of the meninges around the brain, is more common than cancers of brain tissue.{{sfn|Davidson's|2010|p=1216-7}} Cancers within the brain may cause symptoms related to their size or position, with symptoms including headache and nausea, or the gradual development of focal symptoms such as gradual difficulty seeing, swallowing, talking, or as a change of mood.{{sfn|Davidson's|2010|p=1216-7}} Cancers are in general investigated through the use of CT scans and MRI scans. A variety of other tests including blood tests and lumbar puncture may be used to investigate for the cause of the cancer and evaluate the type and [[cancer staging|stage]] of the cancer.{{sfn|Davidson's|2010|p=1216-7}} The [[corticosteroid]] [[dexamethasone]] is often given to decrease the [[oedema|swelling]] of brain tissue around a tumour. Surgery may be considered, however given the complex nature of many tumours or based on tumour stage or type, [[radiotherapy]] or [[chemotherapy]] may be considered more suitable.{{sfn|Davidson's|2010|p=1216-7}}

===Mental disorders===
[[Mental disorder]]s, such as [[major depressive disorder|depression]], [[schizophrenia]], [[bipolar disorder]], [[posttraumatic stress disorder]], [[attention deficit hyperactivity disorder]], [[obsessive-compulsive disorder]], [[Tourette syndrome]], and [[addiction]], are known to relate to the functioning of the brain.<ref name="NHMH_3e – Addiction and ADHD">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter = Chapter 14: Higher Cognitive Function and Behavioral Control | quote =In conditions in which prepotent responses tend to dominate behavior, such as in drug addiction, where drug cues can elicit drug seeking (Chapter 16), or in attention deficit hyperactivity disorder (ADHD; described below), significant negative consequences can result. ... ADHD can be conceptualized as a disorder of executive function; specifically, ADHD is characterized by reduced ability to exert and maintain cognitive control of behavior. Compared with healthy individuals, those with ADHD have diminished ability to suppress inappropriate prepotent responses to stimuli (impaired response inhibition) and diminished ability to inhibit responses to irrelevant stimuli (impaired interference suppression). ... Functional neuroimaging in humans demonstrates activation of the prefrontal cortex and caudate nucleus (part of the dorsal striatum) in tasks that demand inhibitory control of behavior. ... Early results with structural MRI show a thinner cerebral cortex, across much of the cerebrum, in ADHD subjects compared with age-matched controls, including areas of [the] prefrontal cortex involved in working memory and attention.}}</ref><ref name=NIMH2017>{{cite web |title=NIMH » Brain Basics |url=https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml |website=www.nimh.nih.gov |accessdate=March 26, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170326230311/https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml |archivedate=March 26, 2017 }}</ref><ref name="Addiction - brain disease review">{{cite journal | last1=Volkow |first1=N.D. |last2=Koob |first2=G.F. |last3=McLellan |first3=A.T. | title=Neurobiologic advances from the brain disease model of addiction | journal=[[The New England Journal of Medicine]] | volume=374 | issue=4 | pages=363–371 | date=January 2016 | pmid=26816013 | pmc=6135257 | doi=10.1056/NEJMra1511480}}</ref> Treatment for mental disorders may include [[psychotherapy]], [[psychiatry]], [[social interventionism|social intervention]] and personal [[Recovery model|recovery]] work or [[cognitive behavioural therapy]]; the underlying issues and associated prognoses vary significantly between individuals.<ref name="Simpson">{{cite book |last1=Simpson |first1=J.M. |last2=Moriarty |first2=G.L. |title=Multimodal Treatment of Acute Psychiatric Illness: A Guide for Hospital Diversion |publisher=[[Columbia University Press]] |year=2013 |pages=22–24 |isbn=978-0231536097 |url=https://books.google.com/books?id=MbtkAgAAQBAJ&pg=PA22}}</ref>

===Epilepsy===
[[Epileptic seizure]]s are thought to relate to abnormal electrical activity.{{sfn|Davidson's|2010|p=1172-9}} Seizure activity can manifest as [[absence seizure|absence of consciousness]], [[focal seizure|focal]] effects such as limb movement or impediments of speech, or be [[generalised seizure|generalized]] in nature.{{sfn|Davidson's|2010|p=1172-9}} [[Status epilepticus]] refers to a seizure or series of seizures that have not terminated within 5 minutes.<ref name="foundation">{{cite web |title=Status Epilepticus |url=https://www.epilepsy.com/learn/challenges-epilepsy/seizure-emergencies/status-epilepticus |website=Epilepsy Foundation |language=en}}</ref> Seizures have a large number of causes, however many seizures occur without a definitive cause being found. In a person with [[epilepsy]], risk factors for further seizures may include sleeplessness, drug and alcohol intake, and stress. Seizures may be assessed using [[blood test]]s, [[EEG]] and various [[medical imaging]] techniques based on the [[medical history]] and [[medical examination|exam]] findings.{{sfn|Davidson's|2010|p=1172-9}} In addition to treating an underlying cause and reducing exposure to risk factors, [[anticonvulsant]] medications can play a role in preventing further seizures.{{sfn|Davidson's|2010|p=1172-9}}

===Congenital===
Some brain disorders such as [[Tay–Sachs disease]]<ref name="Moore">{{cite book |last=Moore |first=S.P. |title=The Definitive Neurological Surgery Board Review |publisher=[[Lippincott Williams & Wilkins]] |isbn=978-1405104593 |page=112 |year=2005 |url=https://books.google.com/books?id=mkK1a4mEx3IC&pg=PA112}}</ref> are [[congenital disorder|congenital]],<ref name="Pennington">{{cite book |last=Pennington |first=B.F. |title=Diagnosing Learning Disorders, Second Edition: A Neuropsychological Framework |publisher=[[Guilford Press]] |isbn=978-1606237861 |pages=3–10 |year=2008 |url=https://books.google.com/books?id=LVV10L62z6kC&pg=PA3}}</ref> and linked to [[Mutation|genetic]] and [[chromosome abnormality|chromosomal]] mutations.<ref name="Pennington"/> A rare group of congenital [[cephalic disorder]]s known as [[lissencephaly]] is characterised by the lack of, or inadequacy of, cortical folding.<ref name="Govaert">{{cite book |last1=Govaert |first1=P. |last2=de Vries |first2=L.S. |title=An Atlas of Neonatal Brain Sonography: (CDM 182–183) |publisher=[[John Wiley & Sons]] |isbn=978-1898683568 |pages=89–92 |year=2010 |url=https://books.google.com/books?id=FzcaxpvV1JUC&pg=PA89}}</ref> Normal [[prenatal development|development]] of the brain can be affected during [[pregnancy]] by [[nutritional deficiencies]],<ref name="Perese">{{cite book |last=Perese |first=E.F. |title=Psychiatric Advanced Practice Nursing: A Biopsychsocial Foundation for Practice |publisher=[[F.A. Davis]] |isbn=978-0803629998 |pages=82–88 |year=2012 |url=https://books.google.com/books?id=6X_2AAAAQBAJ&pg=PA82}}</ref> [[teratology|teratogen]]s,<ref name="Kearney">{{cite book |last1=Kearney |first1=C. |last2=Trull |first2=T.J. |title=Abnormal Psychology and Life: A Dimensional Approach |publisher=[[Cengage Learning]] |isbn=978-1337098106 |page=395 |year=2016 |url=https://books.google.com/books?id=B9q5DQAAQBAJ&pg=PA395}}</ref> [[infectious diseases]],<ref name="Stevenson">{{cite book |last1=Stevenson |first1=D.K. |last2=Sunshine |first2=P. |last3=Benitz |first3=W.E. |title=Fetal and Neonatal Brain Injury: Mechanisms, Management and the Risks of Practice |publisher=[[Cambridge University Press]] |isbn=978-0521806916 |page=191 |year=2003 |url=https://books.google.com/books?id=RuekFAj_tIAC&pg=PA191}}</ref> and by the use of [[Recreational drug use|recreational drugs]] and [[Fetal alcohol spectrum disorders|alcohol]].<ref name="Perese"/><ref name="Dewhurst">{{cite book |last=Dewhurst |first=John |title=Dewhurst's Textbook of Obstetrics and Gynaecology |publisher=[[John Wiley & Sons]] |isbn=978-0470654576 |page=43 |year=2012 |url=https://books.google.com/books?id=HfakBRceodcC&pg=PA43}}</ref>

===Stroke===
{{main|Stroke}}
[[File:Parachemableedwithedema.png|thumb|upright|[[CT scan]] of a [[cerebral hemorrhage]], showing an intraparenchymal bleed (bottom arrow) with surrounding edema (top arrow)]]

A [[stroke]] is a [[ischemia|decrease in blood supply]] to an area of the brain causing [[cell death]] and [[Brain damage#Causes|brain injury]]. This can lead to a wide range of [[Stroke#Signs and symptoms|symptoms]], including the "[[FAST (stroke)|FAST]]" symptoms of facial droop, arm weakness, and speech difficulties (including [[dysarthria|with speaking]] and [[dysphasia|finding words or forming sentences]]).<ref>{{cite journal |last1=Harbison |first1=J. |last2=Massey |first2=A. |last3=Barnett |first3=L. |last4=Hodge |first4=D. |last5=Ford |first5=G.A. | title=Rapid ambulance protocol for acute stroke | journal=Lancet | volume=353 | issue=9168 | pages=1935 | date=June 1999 | pmid=10371574 | doi=10.1016/S0140-6736(99)00966-6 }}</ref> Symptoms relate to the function of the affected area of the brain and can point to the likely site and cause of the stroke. Difficulties with movement, speech, or sight usually relate to the cerebrum, whereas [[ataxia|imbalance]], [[diplopia|double vision]], [[vertigo]] and symptoms affecting more than one side of the body usually relate to the brainstem or cerebellum.{{sfn|Davidson's|2010|p=1183}}

Most strokes result from loss of blood supply, typically because of an [[embolus]], rupture of a [[atheroma|fatty plaque]] or [[arteriosclerotic|narrowing of small arteries]]. Strokes can also result from [[Stroke#Hemorrhagic|bleeding within the brain]].{{sfn|Davidson's|2010|p=1180-1}} [[Transient ischemic attack|Transient ischaemic attack]]s (TIAs) are strokes in which symptoms resolve within 24 hours.{{sfn|Davidson's|2010|p=1180-1}} Investigation into the stroke will involve a [[medical examination]] (including a [[neurological examination]]) and the taking of a [[medical history]], focusing on the duration of the symptoms and risk factors (including [[Hypertension|high blood pressure]], [[atrial fibrillation]], and [[tobacco smoking|smoking]]).{{sfn|Davidson's|2010|p=1183-1185}}{{sfn|Davidson's|2010|p=1181}} Further investigation is needed in younger patients.{{sfn|Davidson's|2010|p=1183-1185}} An [[ECG]] and [[biotelemetry]] may be conducted to identify [[atrial fibrillation]]; an [[ultrasound]] can investigate [[carotid stenosis|narrowing]] of the [[Common carotid artery|carotid arteries]]; an [[echocardiogram]] can be used to look for clots within the heart, [[Valvular heart disease|diseases of the heart valves]] or the presence of a [[patent foramen ovale]].{{sfn|Davidson's|2010|p=1183-1185}} [[Blood test]]s are routinely done as part of the [[Medical diagnosis#Other diagnostic procedure methods|workup]] including [[Diabetes mellitus#Diagnosis|diabetes tests]] and a [[lipid profile]].{{sfn|Davidson's|2010|p=1183-1185}}

Some treatments for stroke are time-critical. These include [[thrombolysis|clot dissolution]] or [[embolectomy|surgical removal of a clot]] for [[Brain ischemia|ischaemic strokes]], and [[decompression (surgery)|decompression]] for [[Intracranial hemorrhage|haemorrhagic strokes]].{{sfn|Davidson's|2010|p=1185-1189}}<ref>{{cite journal |last1=Goyal |first1=M. |display-authors=etal |title=Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials |journal=The Lancet |date=April 2016 |volume=387 |issue=10029 |pages=1723–1731 |doi=10.1016/S0140-6736(16)00163-X |pmid=26898852 }}</ref> As stroke is time critical,<ref>{{cite journal |last1=Saver |first1=J. L. |title=Time is brain—quantified |journal=Stroke |date=December 8, 2005 |volume=37 |issue=1 |pages=263–266 |doi=10.1161/01.STR.0000196957.55928.ab|pmid=16339467 }}</ref> hospitals and even pre-hospital care of stroke involves expedited investigations – usually a [[CT scan]] to investigate for a haemorrhagic stroke and a [[CT angiogram|CT]] or [[MR angiogram]] to evaluate arteries that supply the brain.{{sfn|Davidson's|2010|p=1183-1185}} [[MRI scan]]s, not as widely available, may be able to demonstrate the affected area of the brain more accurately, particularly with ischaemic stroke.{{sfn|Davidson's|2010|p=1183-1185}}

Having experienced a stroke, a person may be admitted to a [[stroke unit]], and treatments may be directed as [[secondary prevention|preventing]] future strokes, including ongoing [[anticoagulation]] (such as [[aspirin]] or [[clopidogrel]]), [[Antihypertensive drug|antihypertensives]], and [[lipid-lowering agent|lipid-lowering drugs]].{{sfn|Davidson's|2010|p=1185-1189}} A [[multidisciplinary team]] including [[speech pathologist]]s, [[physiotherapists]], [[occupational therapist]]s, and [[psychologist]]s plays a large role in supporting a person affected by a stroke and their [[physical medicine and rehabilitation|rehabilitation]].<ref>{{cite journal |last1=Winstein |first1=C.J. |display-authors=etal |title=Guidelines for adult stroke rehabilitation and recovery |journal=Stroke |date=June 2016 |volume=47 |issue=6 |pages=e98–e169 |doi=10.1161/STR.0000000000000098|pmid=27145936 }}</ref>{{sfn|Davidson's|2010|p=1183-1185}} A history of stroke increases the risk of developing dementia by around 70%, and recent stroke increases the risk by around 120%.<ref>{{Cite journal|last=Kuźma|first=Elżbieta|last2=Lourida|first2=Ilianna|last3=Moore|first3=Sarah F.|last4=Levine|first4=Deborah A.|last5=Ukoumunne|first5=Obioha C.|last6=Llewellyn|first6=David J.|date=November 2018 |title=Stroke and dementia risk: A systematic review and meta-analysis|journal=Alzheimer's & Dementia |volume=14 |issue=11 |pages=1416–1426 |doi=10.1016/j.jalz.2018.06.3061 |pmid=30177276|pmc=6231970|issn=1552-5260}}</ref>

===Brain death===
{{main|Brain death}}
Brain death refers to an irreversible total loss of brain function.<ref name="GOILA2009">{{cite journal |last1=Goila |first1=AK |last2=Pawar |first2=M |title=The diagnosis of brain death |journal=Indian Journal of Critical Care Medicine |date=2009 |volume=13 |issue=1 |pages=7–11 |doi=10.4103/0972-5229.53108|pmid=19881172 |pmc=2772257 }}</ref><ref name=":0">{{Cite journal |last=Wijdicks |first=EFM |date=January 8, 2002 |title=Brain death worldwide: accepted fact but no global consensus in diagnostic criteria |journal=Neurology |volume=58 |issue=1 |pages=20–25 |pmid=11781400 |doi=10.1212/wnl.58.1.20}}</ref> This is characterised by [[coma]], loss of [[reflex]]es, and [[apnoea]],<ref name=GOILA2009/> however, the declaration of brain death varies geographically and is not always accepted.<ref name=":0" /> In some countries there is also a defined syndrome of [[brainstem death]].<ref>{{cite journal |last1=Dhanwate |first1=AD |title=Brainstem death: A comprehensive review in Indian perspective. |journal=Indian Journal of Critical Care Medicine |date=September 2014 |volume=18 |issue=9 |pages=596–605 |pmid=25249744 |doi=10.4103/0972-5229.140151 |pmc=4166875}}</ref> Declaration of brain death can have profound implications as the declaration, under the principle of [[Futile medical care|medical futility]], will be associated with the withdrawal of life support,{{sfn|Davidson's|2010|p=1158}} and as those with brain death often have organs suitable for [[organ donation]].<ref name=":0" />{{sfn|Davidson's|2010|p=200}} The process is often made more difficult by poor communication with patients' families.<ref name="Urden">{{cite book |last1=Urden |first1=L.D. |last2=Stacy |first2=K.M. |last3=Lough |first3=M.E. |title=Priorities in Critical Care Nursing – E-Book |publisher=[[Elsevier Health Sciences]] |isbn=978-0323294140 |pages=112–113 |year=2013 |url=https://books.google.com/books?id=lLvwAwAAQBAJ&pg=PA112}}</ref>

When brain death is suspected, reversible [[differential diagnosis|differential diagnoses]] such as, electrolyte, neurological and drug-related cognitive suppression need to be excluded.<ref name="GOILA2009" />{{sfn|Davidson's|2010|p=1158}} Testing for reflexes{{efn|Including the [[vestibulo-ocular reflex]], [[corneal reflex]], [[gag reflex]] and dilation of the pupils in response to light ,{{sfn|Davidson's|2010|p=1158}}}} can be of help in the decision, as can the absence of response and breathing.{{sfn|Davidson's|2010|p=1158}} Clinical observations, including a total lack of responsiveness, a known diagnosis, and [[neural imaging]] evidence, may all play a role in the decision to pronounce brain death.<ref name="GOILA2009" />

==Society and culture==
[[Neuroanthropology]] is the study of the relationship between culture and the brain. It explores how the brain gives rise to culture, and how culture influences brain development.<ref>{{Cite book |last1=Domínguez |first1=J.F. |last2=Lewis |first2=E.D. |last3=Turner |first3=R. |last4=Egan |first4=G.F. |editor1-last=Chiao |editor1-first=J.Y. |title=The Brain in Culture and Culture in the Brain: A Review of Core Issues in Neuroanthropology |journal=Progress in Brain Research |date=2009 |volume=178 |pages=43–6 |doi=10.1016/S0079-6123(09)17804-4 |pmid=19874961 |series=Special issue: Cultural Neuroscience: Cultural Influences on Brain Function |isbn=9780444533616 }}</ref> Cultural differences and their relation to brain development and structure are researched in different fields.<ref name="Cultural">{{cite web |title=Cultural Environment Influences Brain Function {{!}} Psych Central News |url=https://psychcentral.com/news/2010/08/04/cultural-environment-influences-brain-function/16380.html |website=Psych Central News |date=August 4, 2010 |deadurl=no |archiveurl=https://web.archive.org/web/20170117094114/http://psychcentral.com/news/2010/08/04/cultural-environment-influences-brain-function/16380.html |archivedate=January 17, 2017 }}</ref>

===The mind===
{{Main |Cognition |Mind}}
[[File:Phineas gage - 1868 skull diagram.jpg|thumb|right|upright|The skull of [[Phineas Gage]], with the path of the iron rod that passed through it without killing him, but altering his cognition. The case helped to convince people that mental functions were localized in the brain.<ref name=Macmillan/>]]

The [[philosophy of mind|philosophy of the mind]] studies such issues as the problem of understanding [[consciousness]] and the [[mind–body problem]]. The relationship between the brain and the [[mind]] is a significant challenge both philosophically and scientifically. This is because of the difficulty in explaining how mental activities, such as thoughts and emotions, can be implemented by physical structures such as neurons and [[synapse]]s, or by any other type of physical mechanism. This difficulty was expressed by [[Gottfried Leibniz]] in the analogy known as ''Leibniz's Mill'':

{{quote |One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception.

::— Leibniz, [[Monadology]]<ref>{{cite book |author=Rescher, N. |title=G. W. Leibniz's Monadology |year=1992 |publisher=Psychology Press |isbn=978-0-415-07284-7 |page=83}}</ref>}}

Doubt about the possibility of a mechanistic explanation of thought drove [[René Descartes]], and most other philosophers along with him, to [[Dualism (philosophy of mind)|dualism]]: the belief that the mind is to some degree independent of the brain.<ref>{{cite book |last=Hart |first=WD |year=1996 |editor=Guttenplan S |title=A Companion to the Philosophy of Mind |publisher=Blackwell |pages=265–267}}</ref> There has always, however, been a strong argument in the opposite direction. There is clear empirical evidence that physical manipulations of, or injuries to, the brain (for example by drugs or by lesions, respectively) can affect the mind in potent and intimate ways.<ref name=Churchland>{{cite book |last=Churchland |first=P.S. |title=Neurophilosophy |publisher=MIT Press |year=1989 |isbn=978-0-262-53085-9 |chapter-url=https://books.google.com/?id=hAeFMFW3rDUC |chapter=Ch. 8}}</ref><ref>{{cite journal |last1=Selimbeyoglu |first1=Aslihan |last2=Parvizi |first2=J |title=Electrical stimulation of the human brain: perceptual and behavioral phenomena reported in the old and new literature |journal=Frontiers in Human Neuroscience |date=2010 |volume=4 |page=46 |doi=10.3389/fnhum.2010.00046 |pmid=20577584 |pmc=2889679}}</ref> In the 19th century, the case of [[Phineas Gage]], a railway worker who was injured by a stout iron rod passing through his brain, convinced both researchers and the public that cognitive functions were localised in the brain.<ref name=Macmillan>{{cite book |last=Macmillan |first=Malcolm B. |year=2000 |title=An Odd Kind of Fame: Stories of Phineas Gage |publisher=[[MIT Press]] |url=https://books.google.com/?id=Qx4fMsTqGFYC |isbn=978-0-262-13363-0}}</ref> Following this line of thinking, a large body of empirical evidence for a close relationship between brain activity and mental activity has led most neuroscientists and contemporary philosophers to be [[Materialism|materialists]], believing that mental phenomena are ultimately the result of, or reducible to, physical phenomena.<ref>Schwartz, J.H. '' Appendix D: Consciousness and the Neurobiology of the Twenty-First Century''. In Kandel, E.R.; Schwartz, J.H.; Jessell, T.M. (2000). ''Principles of Neural Science, 4th Edition''.</ref>

===Brain size===
{{main|Brain size}}
The size of the brain and a person's [[intelligence]] are not strongly related.<ref>{{Cite book |url=https://books.google.com/?id=8DlS0gfO_QUC&pg=PT89 |title=50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior |last=Lilienfeld |first=S.O. |last2=Lynn |first2=S.J. |last3=Ruscio |first3=J. |last4=Beyerstein |first4=B.L. |date=2011 |publisher=John Wiley & Sons |isbn=9781444360745 |page=89}}</ref> Studies tend to indicate small to moderate [[correlations]] (averaging around 0.3 to 0.4) between brain volume and [[Intelligence quotient|IQ]].<ref>{{cite journal |last=McDaniel |first=M. |journal=Intelligence |volume=33 |issue=4 |pages=337–346 |year=2005 |url=http://www.people.vcu.edu/~mamcdani/Big-Brained%20article.pdf |title=Big-brained people are smarter |ref=harv |doi=10.1016/j.intell.2004.11.005 |deadurl=no |archiveurl=https://web.archive.org/web/20140906221726/http://www.people.vcu.edu/~mamcdani/Big-Brained%20article.pdf |archivedate=September 6, 2014 }}</ref> The most consistent associations are observed within the frontal, temporal, and parietal lobes, the hippocampi, and the cerebellum, but these only account for a relatively small amount of variance in IQ, which itself has only a partial relationship to general intelligence and real-world performance.<ref>{{cite journal |last1=Luders |first1=E. |display-authors=etal |title=Mapping the relationship between cortical convolution and intelligence: effects of gender |journal=Cerebral Cortex |date=September 2008 |volume=18 |issue=9 |pages=2019–26 |pmid=18089578 |doi=10.1093/cercor/bhm227 |pmc=2517107}}</ref><ref>{{Cite journal |last=Hoppe |first=C |last2=Stojanovic |first2=J |year=2008 |title=High-Aptitude Minds |journal=Scientific American Mind |volume=19 |issue=4 |pages=60–67 |doi=10.1038/scientificamericanmind0808-60}}</ref>

Other animals, including whales and elephants have larger brains than humans. However, when the [[brain-to-body mass ratio]] is taken into account, the human brain is almost twice as large as that of a [[bottlenose dolphin]], and three times as large as that of a [[Common chimpanzee|chimpanzee]]. However, a high ratio does not of itself demonstrate intelligence: very small animals have high ratios and the [[treeshrew]] has the largest quotient of any mammal.<ref>{{Cite web |url=http://genome.wustl.edu/genomes/view/tupaia_belangeri |title=Tupaia belangeri |publisher=The Genome Institute, Washington University |accessdate=January 22, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20100601201841/http://genome.wustl.edu/genomes/view/tupaia_belangeri/ |archivedate=June 1, 2010 }}</ref>

===In popular culture===
[[File:PhrenologyPix.jpg|thumb|upright|[[Phrenology]] summarized in an 1883 chart]]
Research has disproved some common [[List of common misconceptions#Brain|misconceptions about the brain]]. These include both ancient and modern myths. It is not true that neurons are not replaced after the age of two; nor that only [[Ten percent of the brain myth|ten per cent of the brain]] is used.<ref>{{cite book |last1=Jarrett |first1=C. |title=Great Myths of the Brain |publisher=John Wiley & Sons |isbn=9781118312711 |url=https://books.google.com/?id=fBPyBQAAQBAJ |date=2014-11-17 }}</ref> Popular culture has also oversimplified the [[Lateralization of brain function|lateralisation of the brain]], suggesting that functions are completely specific to one side of the brain or the other. [[Akio Mori]] coined the term [[game brain]] for the unreliably supported theory that spending long periods playing [[video game]]s harmed the brain's pre-frontal region and the expression of emotion and creativity.<ref>{{cite magazine|url=https://www.newscientist.com/article/dn2538-video-game-brain-damage-claim-criticised.html|title=Video game "brain damage" claim criticised|accessdate=February 6, 2008|first=Helen |last=Phillips|date=July 11, 2002|magazine=[[New Scientist]] |deadurl=no|archiveurl=https://web.archive.org/web/20090111065557/http://www.newscientist.com/article/dn2538-video-game-brain-damage-claim-criticised.html|archivedate=January 11, 2009}}</ref>

Historically, the brain featured in popular culture through [[phrenology]], a [[pseudoscience]] that assigned personality attributes to different regions of the cortex. The cortex remains important in popular culture as covered in books and satire.<ref>{{cite news |last1=Popova |first1=Maria |title='Brain Culture': How Neuroscience Became a Pop Culture Fixation |url=https://www.theatlantic.com/health/archive/2011/08/brain-culture-how-neuroscience-became-a-pop-culture-fixation/243810/ |work=The Atlantic |date=August 18, 2011 |deadurl=no |archiveurl=https://web.archive.org/web/20170728165041/https://www.theatlantic.com/health/archive/2011/08/brain-culture-how-neuroscience-became-a-pop-culture-fixation/243810/ |archivedate=July 28, 2017 }}</ref><ref>{{cite book |last1=Thornton |first1=Davi Johnson |title=Brain Culture. Neuroscience and Popular Media |date=2011 |publisher=Rutgers University Press |isbn=978-0813550138}}</ref> [[Brain in science fiction|The brain features in science fiction]], with themes such as [[brain transplant]]s and [[Cyborgs in fiction|cyborgs]] (beings with features like partly [[artificial brain]]s).<ref>[http://web.mit.edu/digitalapollo/Documents/Chapter1/cyborgs.pdf Cyborgs and Space] {{webarchive|url=https://web.archive.org/web/20111006190955/http://web.mit.edu/digitalapollo/Documents/Chapter1/cyborgs.pdf |date=October 6, 2011 }}, in ''Astronautics'' (September 1960), by Manfred E. Clynes and Nathan S. Kline.</ref> The 1942 science fiction book (adapted three times for cinema) ''[[Donovan's Brain]]'' tells the tale of an [[isolated brain]] kept alive ''in vitro'', gradually taken over by a malign intelligence.<ref>{{cite book |author=Bergfelder, Tim |title=International Adventures: German Popular Cinema and European Co-productions in the 1960s |url=https://books.google.com/books?id=B1Nj41yxvZkC&pg=PA129 |year=2005 |publisher=Berghahn Books |isbn=978-1-57181-538-5 |page=129}}</ref>


==History==
{{Main |History of neuroscience}}

=== Early history===
[[File:Hieroglyph brain.svg|thumb|right|upright=1.0|[[Hieroglyph]] for the word "brain" (c.1700 BC)]]
The [[Edwin Smith Papyrus]], an [[ancient Egypt]]ian [[medical literature|medical treatise]] written in the 17th century BC, contains the earliest recorded reference to the brain. The [[hieroglyph]] for brain, occurring eight times in this papyrus, describes the symptoms, diagnosis, and prognosis of two traumatic injuries to the head. The papyrus mentions the external surface of the brain, the effects of injury (including seizures and [[aphasia]]), the meninges, and cerebrospinal fluid.<ref name=Kandel>{{cite book | authorlink=Eric R. Kandel | last=Kandel | first=ER |author2=Schwartz JH |author3=Jessell TM | title=Principles of Neural Science | edition=4th | publisher=McGraw-Hill | location=New York | year=2000 | isbn=978-0-8385-7701-1| title-link=Principles of Neural Science }}</ref><ref name="Adelman">{{cite book |last1=Gross|first1=Charles G. |editor-first=George |editor-last=Adelman |title=Encyclopedia of neuroscience |date=1987 |publisher=Birkhäeuser |location=Boston |isbn=978-0817633356 |pages=843–847 |edition=2. |url=http://www.princeton.edu/~cggross/Hist_Neurosci_Ency_neurosci.pdf |deadurl=no |archiveurl=https://web.archive.org/web/20130505044949/http://www.princeton.edu/~cggross/Hist_Neurosci_Ency_neurosci.pdf |archivedate=May 5, 2013 }}</ref>

In the fifth century BC, [[Alcmaeon of Croton]] in [[Magna Grecia]], first considered the brain to be the [[Sensorium|seat of the mind]].<ref name="Adelman"/> Also in the [[Fifth-century Athens|fifth century BC in Athens]], the unknown author of ''[[On the Sacred Disease]]'', a medical treatise which is part of the [[Hippocratic Corpus]] and traditionally attributed to [[Hippocrates]], believed the brain to be the seat of intelligence. [[Aristotle]], in his [[Aristotle's biology|biology]] initially believed the heart to be the seat of [[intelligence]], and saw the brain as a cooling mechanism for the blood. He reasoned that humans are more rational than the beasts because, among other reasons, they have a larger brain to cool their hot-bloodedness.<ref name=Bear>{{cite book | last=Bear | first=M.F. |author2=B.W. Connors |author3=M.A. Paradiso | title=Neuroscience: Exploring the Brain | location=Baltimore | publisher=Lippincott | year=2001 | isbn=978-0-7817-3944-3}}</ref> Aristotle did describe the meninges and distinguished between the cerebrum and cerebellum.<ref>von Staden, p.157</ref> [[Herophilus]] of [[Chalcedon]] in the fourth and third centuries BC distinguished the cerebrum and the cerebellum, and provided the first clear description of the [[Ventricular system|ventricles]]; and with [[Erasistratus]] of [[Kea (island)|Ceos]] experimented on living brains. Their works are now mostly lost, and we know about their achievements due mostly to secondary sources. Some of their discoveries had to be re-discovered a millennium after their deaths.<ref name="Adelman"/> Anatomist physician [[Galen]] in the second century AD, during the time of the [[Roman Empire]], dissected the brains of sheep, monkeys, dogs, and pigs. He concluded that, as the cerebellum was denser than the brain, it must control the [[muscle]]s, while as the cerebrum was soft, it must be where the senses were processed. Galen further theorized that the brain functioned by movement of animal spirits through the ventricles.<ref name="Adelman"/><ref name=Bear/>

===Renaissance===

In 1316, [[Mondino de Luzzi]]'s ''Anathomia'' began the modern study of brain anatomy.<ref>{{cite book |last1=Swanson |first1=Larry W. |title=Neuroanatomical Terminology: A Lexicon of Classical Origins and Historical Foundations |publisher=Oxford University Press |isbn=9780195340624 |url=https://books.google.com/?id=--PRAwAAQBAJ&pg=PA7&lpg=PA7&dq=nervous+system+anatomy+stagnation+galen+to+vesalius#v=onepage|date=2014-08-12 }}</ref>
[[Niccolò Massa]] discovered in 1536 that the ventricles were filled with fluid.<ref name=LOKHORST2016/> [[Archangelo Piccolomini]] of [[Rome]] was the first to distinguish between the cerebrum and cerebral cortex.<ref name="Gross1999" /> In 1543 [[Andreas Vesalius]] published his seven-volume ''[[De humani corporis fabrica]]''.<ref name="Gross1999" /><ref name="MARSHALL">{{cite book |last1=Marshall |first1=Louise H. |last2=Magoun |first2=Horace W. |title=Discoveries in the Human Brain: Neuroscience Prehistory, Brain Structure, and Function |publisher=Springer Science & Business Media |isbn=978-1-475-74997-7 |page=44 |url=https://books.google.com/?id=guncBwAAQBAJ&pg=PR5&dq=vesalius+and+the+human+brain#v=onepage&q=vesalius&f=false|date=2013-03-09 }}</ref><ref>{{cite book |last1=Holtz |first1=Anders |last2=Levi |first2=Richard |title=Spinal Cord Injury |publisher=Oxford University Press |isbn=9780199706815 |url=https://books.google.com/?id=ZvCqdwWwGRsC&pg=PA5&lpg=PA5#v=onepage|date=2010-07-20 }}</ref> The seventh book covered the brain and eye, with detailed images of the ventricles, cranial nerves, [[pituitary gland]], meninges, structures of the [[human eye|eye]], the vascular supply to the brain and spinal cord, and an image of the peripheral nerves.<ref name="tessman">{{cite journal | author=Tessman, Patrick A. | author2=Suarez, Jose I. | year=2002 | title=Influence of early printmaking on the development of neuroanatomy and neurology | journal=Archives of Neurology | volume=59 | issue=12 | pages=1964–1969 | pmid=12470188 | doi=10.1001/archneur.59.12.1964 }}</ref> Vesalius rejected the common belief that the ventricles were responsible for brain function, arguing that many animals have a similar ventricular system to humans, but no true intelligence.<ref name="Gross1999">{{cite book |last1=Gross |first1=Charles G. |title=Brain, vision, memory : tales in the history of neuroscience. |date=1999 |publisher=MIT |location=Cambridge, Mass. |isbn=978-0262571357 |pages=37–51 |edition=1st MIT Press pbk.}}</ref>

[[René Descartes]] proposed the theory of [[Mind-body dualism|dualism]] to tackle the issue of the brain's relation to the mind. He suggested that the [[pineal gland]] was where the mind interacted with the body after recording the brain mechanisms responsible for circulating cerebrospinal fluid.<ref name=LOKHORST2016>{{cite web |last1=Lokhorst |first1=Gert-Jan |title=Descartes and the Pineal Gland |url=https://plato.stanford.edu/entries/pineal-gland/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |accessdate=March 11, 2017 |date=January 1, 2016}}</ref> This dualism likely provided impetus for later anatomists to further explore the relationship between the anatomical and functional aspects of brain anatomy.<ref name=OCONNOR2003>{{cite journal |last1=O'Connor |first1=James |title=Thomas Willis and the background to Cerebri Anatome |journal=Journal of the Royal Society of Medicine |date=2003 |volume=96 |issue=3 |pages=139–143 |pmc=539424 |pmid=12612118 |doi=10.1258/jrsm.96.3.139}}</ref>

[[Thomas Willis]] is considered a second pioneer in the study of neurology and brain science. In 1664 in ''Cerebri Anatome'' ({{lang-la |Anatomy of the brain}}),{{efn|Illustrated by architect [[Christopher Wren]]<ref name="Gross1999" />}} followed by ''Cerebral Pathology'' in 1667. In these he described the structure of the cerebellum, the ventricles, the cerebral hemispheres, the brainstem, and the cranial nerves, studied its blood supply; and proposed functions associated with different areas of the brain.<ref name="Gross1999" /> The circle of Willis was named after his investigations into the blood supply of the brain, and he was the first to use the word "neurology."<ref name="Emery2000">{{cite journal |last1=EMERY |first1=ALAN |title=A Short History of Neurology: The British Contribution 1660–1910. Edited by F. CLIFFORD ROSE. (Pp. 282; illustrated; £25 Paperback; ISBN 07506 4165 7.) Oxford: Butterworth-Heinemann |journal=Journal of Anatomy |date=October 2000 |volume=197 |issue=3 |pages=513–518 |doi=10.1046/j.1469-7580.2000.197305131.x|pmc=1468164 }}</ref> Willis removed the brain from the body when examining it, and rejected the commonly held view that the cortex only consisted of blood vessels and the view of the last two millennia that the cortex was only incidentally important.<ref name="Gross1999" />

In the late 19th century, [[Emil du Bois-Reymond]] and [[Hermann von Helmholtz]], following the work of their teacher [[Johannes Peter Müller]] showed the electrical inpulses which pass along nerves; but unlike Müller's views, that such impulses were able to be observed.<ref>{{cite web |last1=Sabbatini |first1=Renato M.E. |title=Sabbatini, R.M.E.: The Discovery of Bioelectricity. Nerve Conduction |url=http://www.cerebromente.org.br/n06/historia/bioelectr3_i.htm |website=www.cerebromente.org.br |accessdate=June 10, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170626011707/http://www.cerebromente.org.br/n06/historia/bioelectr3_i.htm |archivedate=June 26, 2017 }}</ref> [[Richard Caton]] in 1875 demonstrated electrical impulses in the cerebral hemispheres of rabbits and monkeys.<ref>{{cite journal |last1=Karbowski |first1=Kazimierz |title=Sixty Years of Clinical Electroencephalography |journal=European Neurology |date=February 14, 2008 |volume=30 |issue=3 |pages=170–175 |doi=10.1159/000117338|pmid=2192889 }}</ref> In the 1820s, [[Jean Pierre Flourens]] pioneered the experimental method of damaging specific parts of animal brains describing the effects on movement and behavior.<ref>{{cite journal |last1=Pearce |first1=J.M.S. |title=Marie-Jean-Pierre Flourens (1794–1867) and Cortical Localization |journal=European Neurology |date=March 17, 2009 |volume=61 |issue=5 |pages=311–314 |doi=10.1159/000206858|pmid=19295220 }}</ref>
{{multiple image

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| image1 = 1543,AndreasVesalius'Fabrica,BaseOfTheBrain.png
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| caption1 = Drawing of the base of the brain, from [[Andreas Vesalius]]'s 1543 work ''[[De humani corporis fabrica]]''
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| image2 = View of a Skull.jpg
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| caption2 = One of [[Leonardo da Vinci]]'s sketches of the human skull
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===Modern period===
{{Further |Neuropsychiatry}}
{{multiple image

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| image1 = Golgi 1885 Plate XXII.JPG
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| alt1 =
| caption1 = Drawing by [[Camillo Golgi]] of vertical section of rabbit [[hippocampus]], from his "Sulla fina anatomia degli organi centrali del sistema nervoso", 1885


| image2 = CajalCerebellum.jpg
| width2 =
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| caption2 = Drawing of cells in chick [[cerebellum]] by [[Santiago Ramón y Cajal]], from "Estructura de los centros nerviosos de las aves", Madrid, 1905
}}
Studies of the brain became more sophisticated with the use of the [[microscope]] and the development of a [[silver stain]]ing [[Golgi method|method]] by [[Camillo Golgi]] during the 1880s. This was able to show the intricate structures of single neurons.<ref name="DECARLOS2007">{{cite journal |last1=De Carlos |first1=Juan A. |last2=Borrell |first2=José |title=A historical reflection of the contributions of Cajal and Golgi to the foundations of neuroscience |journal=Brain Research Reviews |date=August 2007 |volume=55 |issue=1 |pages=8–16 |doi=10.1016/j.brainresrev.2007.03.010|pmid=17490748 |hdl=10261/62299 }}</ref> This was used by [[Santiago Ramón y Cajal]] and led to the formation of the [[neuron doctrine]], the then revolutionary hypothesis that the neuron is the functional unit of the brain. He used microscopy to uncover many cell types, and proposed functions for the cells he saw.<ref name="DECARLOS2007" /> For this, Golgi and Cajal are considered the founders of [[History of neuroscience|twentieth century neuroscience]], both sharing the [[Nobel prize]] in 1906 for their studies and discoveries in this field.<ref name="DECARLOS2007" />

[[Charles Scott Sherrington|Charles Sherrington]] published his influential 1906 work ''The Integrative Action of the Nervous System'' examining the function of reflexes, evolutionary development of the nervous system, functional specialisation of the brain, and layout and cellular function of the central nervous system.<ref>{{cite journal | last1=Burke | first1=R.E. | title=Sir Charles Sherrington's The integrative action of the nervous system: a centenary appreciation | url=http://brain.oxfordjournals.org/content/130/4/887 | journal=Brain | volume=130 | issue= Pt 4| pages=887–894 | doi=10.1093/brain/awm022 | pmid=17438014 | date=April 2007 | deadurl=no | archiveurl=http://archive.wikiwix.com/cache/20150527230739/http://brain.oxfordjournals.org/content/130/4/887 | archivedate=May 27, 2015 | df=mdy-all }}</ref> [[John Farquhar Fulton]], founded the ''Journal of Neurophysiology'' and published the first comprehensive textbook on the physiology of the nervous system during 1938.<ref name="SQUIRE1996">{{cite book |editor1-last=Squire |editor1-first=Larry R. |title=The history of neuroscience in autobiography |date=1996 |publisher=Society for Neuroscience |location=Washington DC |isbn=978-0126603057 |pages=475–97}}</ref> [[History of neuroscience#Twentieth century|Neuroscience during the twentieth century]] began to be recognised as a distinct unified academic discipline, with [[David Rioch]], [[Francis O. Schmitt]], and [[Stephen Kuffler]] playing critical roles in establishing the field.<ref name="COWAN2000">{{Cite journal |last1=Cowan |first1=W.M. |last2=Harter |first2=D.H. |last3=Kandel |first3=E.R. |date=2000 |title=The emergence of modern neuroscience: Some implications for neurology and psychiatry |journal=Annual Review of Neuroscience |volume=23 |pages=345–346 |doi=10.1146/annurev.neuro.23.1.343 |pmid=10845068}}</ref> Rioch originated the integration of basic anatomical and physiological research with clinical psychiatry at the [[Walter Reed Army Institute of Research]], starting in the 1950s.<ref>{{cite book |last1=Brady |first1=Joseph V. |last2=Nauta |first2=Walle J. H. |title=Principles, Practices, and Positions in Neuropsychiatric Research: Proceedings of a Conference Held in June 1970 at the Walter Reed Army Institute of Research, Washington, D.C., in Tribute to Dr. David Mckenzie Rioch upon His Retirement as Director of the Neuropsychiatry Division of That Institute |publisher=Elsevier |isbn=9781483154534 |page=vii |url=https://books.google.com/?id=AK4aAwAAQBAJ&pg=PR7&lpg=PR7 |date=2013-10-22 }}</ref> During the same period, Schmitt established the [[Neuroscience Research Program]], an inter-university and international organisation, bringing together biology, medicine, psychological and behavioural sciences. The word neuroscience itself arises from this program.<ref>{{cite journal |last1=Adelman |first1=George |title=The Neurosciences Research Program at MIT and the Beginning of the Modern Field of Neuroscience |journal=Journal of the History of the Neurosciences |date=January 15, 2010 |volume=19 |issue=1 |pages=15–23 |doi=10.1080/09647040902720651|pmid=20391098 }}</ref>

[[Paul Broca]] associated regions of the brain with specific functions, in particular language in [[Broca's area]], following work on brain-damaged patients.<ref name="Neural Science 2000">Principles of Neural Science, 4th ed. Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, eds. McGraw-Hill:New York, NY. 2000.</ref> [[John Hughlings Jackson]] described the function of the [[motor cortex]] by watching the progression of [[epileptic seizure]]s through the body. [[Carl Wernicke]] described [[Wernicke's area|a region]] associated with language comprehension and production. [[Korbinian Brodmann]] divided regions of the brain based on the appearance of cells.<ref name="Neural Science 2000" /> By 1950, Sherrington, [[James Papez|Papez]], and [[Paul D. MacLean|MacLean]] had identified many of the brainstem and limbic system functions.<ref name="Papez">{{cite journal |last1=Papez |first1=J.W. |title=A proposed mechanism of emotion. 1937. |journal=The Journal of Neuropsychiatry and Clinical Neurosciences |date=February 1995 |volume=7 |issue=1 |pages=103–12 |pmid=7711480 |doi=10.1176/jnp.7.1.103}}</ref><ref>{{Cite journal |title=A proposed mechanism of emotion. 1937 [classical article] |journal=The Journal of Neuropsychiatry and Clinical Neurosciences |volume=7 |issue=1 |pages=103–112 |doi=10.1176/jnp.7.1.103 |pmid=7711480 |date=February 1, 1995|last1=Papez |first1=J. W. }}</ref><ref>{{cite journal |last1=Lambert |first1=Kelly G. |title=The life and career of Paul MacLean |journal=Physiology & Behavior |date=August 2003 |volume=79 |issue=3 |pages=343–349 |doi=10.1016/S0031-9384(03)00147-1}}</ref> The capacity of the brain to re-organise and change with age, and a recognised critical development period, were attributed to [[neuroplasticity]], pioneered by [[Margaret Kennard]], who experimented on monkeys during the 1930-40s.<ref>{{cite book |last1=Chatterjee |first1=Anjan |last2=Coslett |first2=H. Branch |title=The Roots of Cognitive Neuroscience: Behavioral Neurology and Neuropsychology |publisher=OUP USA |isbn=9780195395549 |pages=337–8 |url=https://books.google.com/?id=f9dMAgAAQBAJ&pg=PA338&dq=neuroscience+20th+century#v=onepage|date=December 2013 }}</ref>

[[Harvey Cushing]] (1869–1939) is recognised as the first proficient [[neurosurgery|brain surgeon]] in the world.<ref name="M.Bliss">{{cite book |url=https://books.google.com/?id=EzbjVnjwjPYC |last=Bliss |first=Michael |title=Harvey Cushing : A Life in Surgery: A Life in Surgery |pages=ix–x |publisher=Oxford University Press |location=USA |date=October 1, 2005|isbn=9780195346954 }}</ref> In 1937, [[Walter Dandy]] began the practice of vascular [[neurosurgery]] by performing the first surgical clipping of an [[intracranial aneurysm]].<ref>{{cite journal | last1=Kretzer | first1=RM | last2=Coon | first2=AL | last3=Tamargo | first3=RJ | date=June 2010 | title=Walter E. Dandy's contributions to vascular neurosurgery | journal=Journal of Neurosurgery | volume=112 | issue=6 | pages=1182–91 | doi=10.3171/2009.7.JNS09737 | pmid=20515365 }}</ref>

==Comparative anatomy==
{{See also|Evolution of the brain}}
The human brain has many properties that are common to all [[vertebrate]] brains.<ref>{{cite book |last1=Glees |first1=Paul |title=The Human Brain |date=2005 |publisher=Cambridge University Press |isbn=9780521017817 |page=1 |url=https://books.google.com/?id=kWgeOPGdl_MC&pg=PA1#v=onepage}}</ref> Many of its features are common to all [[mammal]]ian brains,<ref name="Simpkins">{{cite book |first1=C. Alexander |last1=Simpkins |first2=Annellen M. |last2=Simpkins |title=Neuroscience for Clinicians: Evidence, Models, and Practice |isbn=978-1461448426 |publisher=[[Springer Science & Business Media]] |year=2012 |page=143 |url=https://books.google.com/books?id=QG4LC-d2sm8C&pg=PA143}}</ref> most notably a six-layered cerebral cortex and a set of associated structures,<ref name="Bornstein">{{cite book |first1=Marc H. |last1=Bornstein |first2=Michael E. |last2=Lamb |title=Developmental Science: An Advanced Textbook |isbn=978-1136282201 |publisher=[[Psychology Press]] |year=2015 |page=220 |url=https://books.google.com/books?id=XhA-CgAAQBAJ&pg=PA220}}</ref> including the hippocampus and [[amygdala]].<ref name="Bernstein">{{cite book |first=Douglas |last=Bernstein |title=Essentials of Psychology |isbn=978-0495906933 |publisher=[[Cengage Learning]] |year=2010 |page=64 |url=https://books.google.com/books?id=rd77N0KsLVkC&pg=PA64}}</ref> The cortex is proportionally larger in greater mammals and humans than many other mammals.<ref name="HOFMAN2014">{{cite journal |last1=Hofman |first1=Michel A. |title=Evolution of the human brain: when bigger is better |journal=Frontiers in Neuroanatomy |date=March 27, 2014 |volume=8 |pages=15 |doi=10.3389/fnana.2014.00015|pmid=24723857 |pmc=3973910 }}</ref> Humans have more association cortex, sensory and motor parts than smaller mammals such as the rat and the cat.<ref>{{Cite book |title=Psychology |last=Gray |first=Peter |publisher=Worth Publishers |year=2002 |isbn=978-0716751625 |edition=4th |pages= |oclc=46640860}}</ref>

As a [[primate]] brain, the human brain has a much larger cerebral cortex, in proportion to body size, than most mammals,<ref name="Bernstein" /> and a highly developed visual system.<ref name="Lu">{{cite book |url=https://books.google.com/books?id=nYr6AQAAQBAJ&pg=PA3 |title=Visual Psychophysics: From Laboratory to Theory |publisher=[[MIT Press]] |year=2013 |isbn=978-0262019453 |page=3 |last1=Lu |first1=Zhong-Lin |last2=Dosher |first2=Barbara }}</ref><ref name="Sharwood Smith">{{cite book |url=https://books.google.com/books?id=fe-SDQAAQBAJ&pg=PA206 |title=Introducing Language and Cognition |publisher=[[Cambridge University Press]] |year=2017 |isbn=978-1107152892 |page=206 |first=Mike |last=Sharwood Smith}}</ref>

As a [[hominidae|hominid]] brain, the human brain is substantially enlarged even in comparison to the brain of a typical monkey. The sequence of [[human evolution]] from ''[[Australopithecus]]'' (four million years ago) to [[human|''Homo sapiens'']] (modern humans) was marked by a steady increase in brain size.<ref name="Kolb and Whishaw">{{cite book |last1=Kolb |first1=Bryan |last2=Whishaw |first2=Ian Q. |title=Introduction to Brain and Behavior |publisher=[[Macmillan Higher Education]] |isbn=978-1464139604 |page=21 |year=2013 |url=https://books.google.com/books?id=teUkAAAAQBAJ&q}}</ref><ref name="Nieuwenhuys">{{cite book |last1=Nieuwenhuys |first1=Rudolf |last2=ten Donkelaar |first2=Hans J. |last3=Nicholson |first3=Charles |title=The Central Nervous System of Vertebrates |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-3642182624 |page=2127 |year=2014 |url=https://books.google.com/books?id=gsDqCAAAQBAJ&pg=PA2127}}</ref> As brain size increased, this altered the size and shape of the skull,<ref name="Lee Lerner">{{cite book |last1=Lerner |first1=Lee |last2=Lerner |first2=Brenda Wilmoth |title=The Gale Encyclopedia of Science: Pheasants-Star |isbn=978-0787675592 |publisher=[[Gale (publisher)|Gale]] |year=2004 |page=3759 |url=https://books.google.com/books?id=mp7kcdK6SekC&q |quote=As human's position changed and the manner in which the skull balanced on the spinal column pivoted, the brain expanded, altering the shape of the cranium.}}</ref> from about 600 [[Cubic centimetre|cm3]] in ''[[Homo habilis]]'' to an average of about 1520 cm3 in ''[[Homo neanderthalensis]]''.<ref>{{cite book |last1=Begun |first1=David R. |title=A Companion to Paleoanthropology |date=2012 |publisher=John Wiley & Sons |isbn=9781118332375 |page=388 |url=https://books.google.com/books?id=oIoT1RcFeCwC&pg=PT388}}</ref> Differences in [[DNA]], [[gene expression]], and [[gene–environment interaction]]s help explain the differences between the function of the human brain and other primates.<ref>{{cite journal |author=Jones, R. |title=Neurogenetics: What makes a human brain? |journal=Nature Reviews Neuroscience |volume=13 |page=655 |year=2012 |pmid=22992645 |doi=10.1038/nrn3355 |issue=10}}</ref>

== See also==
{{Portal |Neuroscience |Thinking}}
* [[Cerebral atrophy]]
* [[Cortical spreading depression]]
* [[Enchanted loom]]
* [[Large scale brain networks]]

==References==
{{Reflist}}

==Bibliography==
* {{cite book |editor1-first=Nicki R. |editor1-last=Colledge |editor2-first=Brian R. |editor2-last=Walker |editor3-first=Stuart H. |editor3-last=Ralston |editor4-last=Ralston |title=Davidson's Principles and Practice of Medicine |date=2010 |publisher=Churchill Livingstone/Elsevier |location=Edinburgh |isbn=978-0-7020-3085-7 |edition=21st |ref={{harvid |Davidson's|2010}}}}
* {{cite book |last1=Hall |first=John |title=Guyton and Hall Textbook of Medical Physiology |year=2011 |publisher=Saunders/Elsevier |location=Philadelphia, PA |isbn=978-1-4160-4574-8 |edition=12th |ref={{harvid |Guyton & Hall|2011}}}}
* {{cite book |last1=Larsen |first1=William J. |title=Human Embryology |date=2001 |publisher=Churchill Livingstone |location=Philadelphia, PA |isbn=978-0-443-06583-5 |edition=3rd |ref={{harvid |Larsen|2001}}}}
* {{cite book |last2=Ort |first1=Bruce Ian |last1=Bogart |first2=Victoria |title=Elsevier's Integrated Anatomy and Embryology |date=2007 |publisher=Elsevier Saunders |location=Philadelphia, PA |isbn=978-1-4160-3165-9 |ref={{harvid |Elsevier's|2007}}}}
* {{cite book |last1=Pocock |first1=G. |last2=Richards |first2=C. |title=Human Physiology: The Basis of Medicine |date=2006 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-856878-0 |edition=3rd |ref={{harvid |Pocock|2006}}}}
* {{cite book |last1=Purves |first1=Dale |title=Neuroscience |date=2012 |publisher=Sinauer associates |location=Sunderland, MA |isbn=978-0-87893-695-3 |edition=5th |ref={{harvid |Purves|2012}}}}
* {{cite book |last1=Squire |first1=Larry |title=Fundamental Neuroscience |date=2013 |publisher=Elsevier |location=Waltham, MA |isbn=978-0-12-385-870-2 |ref={{harvid |Squire|2013}}}}
* {{cite book |editor1-last=Standring |editor1-first=Susan |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |date=2008 |publisher=Churchill Livingstone |location=London |isbn=978-0-8089-2371-8 |edition=40th |ref={{harvid |Gray's Anatomy|2008}}}}

==Notes==
{{notelist}}

==External links==
{{Commons category | Brain}}
* [https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml Brain basics by NIMH]
* [http://www.thehumanbrain.info/ Atlas of the human brain]
* [http://faculty.washington.edu/chudler/facts.html Brain facts and figures]
* [http://www.benbest.com/science/anatmind/anatmind.html The Anatomical Basis of Mind]

{{navboxes
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{{Medulla}}
{{Pons}}
{{Mesencephalon}}
{{Cerebellum}}
{{Diencephalon}}
{{Cerebral cortex}}
{{Basal ganglia}}
{{Meninges}}
{{Ventricular system}}
{{Commissural fibers and septum}}
{{Cranial nerves}}
{{Arteries of head and neck}}
{{Veins of the head and neck}}
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{{Human systems and organs}}
{{Nervous system}}
{{Nervous system physiology}}
{{Nervous tissue}}
{{Neural tracts}}
{{Neuroscience}}
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{{Good article}}
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{{DEFAULTSORT:Human Brain}}
[[Category:Brain]]
[[Category:Human anatomy by organ|Brain]]
[[Category:Articles with images not understandable by color blind users]]
[[Category:Brain anatomy]]

Benutzer:Robin16324/

2019-04-11T13:54:12Z

176.228.51.29: /* External links */

{{About |the human brain |information about brains in general|Brain}}
{{pp-pc1}}
{{Use British English |date=April 2017}}
{{Use mdy dates|date=June 2018}}
{{Infobox anatomy
| Name = Human brain
| Latin = Cerebrum<ref>{{cite web |url=http://dictionary.reference.com/browse/cerebrum |title=''Cerebrum'' Etymology |publisher=''[[dictionary.com]]'' |accessdate=October 24, 2015 |deadurl=no |archiveurl=https://web.archive.org/web/20151024035732/http://dictionary.reference.com/browse/cerebrum |archivedate=October 24, 2015 }}</ref>
| Greek = ἐγκέφαλος (enképhalos)<ref>{{cite web |url=http://etymonline.com/index.php?allowed_in_frame=0&search=encephalo- |title=''Encephalo-'' Etymology |publisher=''[[Online Etymology Dictionary]]'' |accessdate=October 24, 2015 |deadurl=no |archiveurl=https://web.archive.org/web/20171002022623/http://etymonline.com/index.php?allowed_in_frame=0&search=encephalo- |archivedate=October 2, 2017 }}</ref>
| Image = Skull and brain normal human.svg
| Caption = Human brain and skull
| Width =
| Image2 = Cerebral lobes.png
| Caption2 = Cerebral lobes: the [[frontal lobe]] (pink), [[parietal lobe]] (green) and [[occipital lobe]] (blue)
| Precursor = [[Neural tube]]
| System = [[Central nervous system]] [[Neuroimmune system]]
| Artery = [[Internal carotid artery|Internal carotid arteries]], [[Vertebral artery|vertebral arteries]]
| Vein = [[Internal jugular vein]], [[internal cerebral veins]]; external veins: ([[superior cerebral veins|superior]], [[middle cerebral veins|middle]], and [[inferior cerebral veins|inferior]] [[cerebral veins]]), [[basal vein]], and [[cerebellar veins]]
| Nerve =
| Lymph =
}}
The '''human brain''' is the central [[organ (anatomy)|organ]] of the human [[nervous system]], and with the [[spinal cord]] makes up the [[central nervous system]]. The brain consists of the [[cerebrum]], the [[brainstem]] and the [[cerebellum]]. It controls most of the activities of the [[human body|body]], processing, integrating, and coordinating the information it receives from the [[Sensory nervous system|sense organs]], and making decisions as to the instructions sent to the rest of the body. The brain is contained in, and protected by, the [[neurocranium|skull bones]] of the [[human head|head]].

The cerebrum is the largest part of the human brain. It is divided into two [[cerebral hemisphere]]s. The [[cerebral cortex]] is an outer layer of [[grey matter]], covering the core of [[white matter]]. The cortex is split into the [[neocortex]] and the much smaller [[allocortex]]. The neocortex is made up of six [[Cerebral cortex#Layers|neuronal layers]], while the allocortex has three or four. Each hemisphere is conventionally divided into four [[lobes of the brain|lobes]] – the [[frontal lobe|frontal]], [[temporal lobe|temporal]], [[parietal lobe|parietal]], and [[occipital lobe]]s. The frontal lobe is associated with [[executive functions]] including [[self-control]], [[planning]], [[reason]]ing, and [[abstraction|abstract thought]], while the occipital lobe is dedicated to vision. Within each lobe, cortical areas are associated with specific functions, such as the [[sensory cortex|sensory]], [[motor cortex|motor]] and [[Cerebral cortex#Association areas|association]] regions. Although the left and right hemispheres are broadly similar in shape and function, some functions are [[lateralization of brain function|associated with one side]], such as [[language]] in the left and [[spatial visualization ability|visual-spatial ability]] in the right. The hemispheres are connected by [[Commissural fiber|commissural nerve tracts]], the largest being the [[corpus callosum]].

The cerebrum is connected by the brainstem to the spinal cord. The brainstem consists of the [[midbrain]], the [[pons]], and the [[medulla oblongata]]. The [[cerebellum]] is connected to the brainstem by [[cerebellar peduncle|pairs of tracts]]. Within the cerebrum is the [[ventricular system]], consisting of four interconnected [[Ventricular system#Structure|ventricles]] in which [[cerebrospinal fluid]] is produced and circulated. Underneath the cerebral cortex are several important structures, including the [[thalamus]], the [[epithalamus]], the [[pineal gland]], the [[hypothalamus]], the [[pituitary gland]], and the [[subthalamus]]; the [[limbic system|limbic structures]], including the [[amygdala]] and the [[hippocampus]]; the [[claustrum]], the various [[Nucleus (neuroanatomy)|nuclei]] of the [[basal ganglia]]; the [[basal forebrain]] structures, and the three [[circumventricular organ]]s. The [[Cell (biology)|cells]] of the brain include [[neuron]]s and supportive [[neuroglia|glial cells]]. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of [[neurotransmitter]]s in response to [[action potential|nerve impulses]]. Neurons connect to form [[neural pathway]]s, [[neural circuit]]s, and elaborate [[Large scale brain networks|network systems]]. The whole circuitry is driven by the process of [[neurotransmission]].

The brain is protected by the [[skull]], suspended in [[cerebrospinal fluid]], and isolated from the [[circulatory system|bloodstream]] by the [[blood–brain barrier]]. However, the brain is still susceptible to [[brain damage|damage]], [[Central nervous system disease|disease]], and [[infection]]. Damage can be caused by [[closed head injury|trauma]], or a loss of blood supply known as a [[stroke]]. The brain is susceptible to [[neurodegeneration|degenerative disorders]], such as [[Parkinson's disease]], [[dementia]]s including [[Alzheimer's disease]], and [[multiple sclerosis]]. [[Psychiatric condition]]s, including [[schizophrenia]] and [[major depressive disorder|clinical depression]], are thought to be associated with brain dysfunctions. The brain can also be the site of [[brain tumors|tumours]], both [[benign tumour|benign]] and [[cancer|malignant]]; these mostly [[metastasis|originate from other sites in the body]].

The study of the anatomy of the brain is [[neuroanatomy]], while the study of its function is [[neuroscience]]. A number of techniques are used to study the brain. [[Biological specimen|Specimens]] from other animals, which may be [[histology|examined microscopically]], have traditionally provided much information. [[Medical imaging]] technologies such as [[functional neuroimaging]], and [[electroencephalography]] (EEG) recordings are important in studying the brain. The [[medical history]] of people with [[brain damage|brain injury]] has provided insight into the function of each part of the brain.

In culture, the [[philosophy of mind]] has for centuries attempted to address the question of the nature of [[consciousness]] and the [[mind-body problem]]. The [[pseudoscience]] of [[phrenology]] attempted to localise personality attributes to regions of the cortex in the 19th century. [[Brain transplant#In science fiction|In science fiction, brain transplants]] are imagined in tales such as the 1942 ''[[Donovan's Brain]]''.
{{TOC limit |3}}

==Structure==
{{See also|List of regions in the human brain |Outline of the human brain}}

===Gross anatomy===
{{Further|Neuroscience of sex differences}}
The adult human brain weighs on average about {{convert|1.2-1.4|kg|abbr=on}} which is about 2% of the total body weight,<ref name=CarpenterCh1>{{cite book |title=Carpenter's Human Neuroanatomy |last1=Parent |first1=A. |last2=Carpenter |first2=M.B. |publisher=Williams & Wilkins |year=1995 |isbn=978-0-683-06752-1 |chapter=Ch. 1}}</ref><ref name="Bigos">{{cite book |last1=Bigos |first1=K.L. |last2=Hariri |first2=A. |last3=Weinberger |first3=D. |title=Neuroimaging Genetics: Principles and Practices |publisher=[[Oxford University Press]] |isbn=978-0199920228 |year=2015 |page=157 |url=https://books.google.com/books?id=TF_iCgAAQBAJ&pg=PA157}}</ref> with a volume of around 1260 [[cubic centimetre|cm3]] in men and 1130 cm3 in women, although there is substantial individual variation.<ref>{{cite journal |last1=Cosgrove |first1=K.P. |last2=Mazure |first2=C.M. |last3=Staley |first3=J.K. |title=Evolving knowledge of sex differences in brain structure, function, and chemistry |year=2007 |journal=Biol Psychiatry |volume=62 |pages=847–855 |pmid=17544382 |pmc=2711771 |doi=10.1016/j.biopsych.2007.03.001 |issue=8}}</ref> Neurological [[sex differences in intelligence|differences between the sexes]] have not been shown to correlate in any simple way with [[intelligence quotient|IQ]] or other measures of cognitive performance.<ref name="pmid10234034">{{cite journal |last1=Gur |first1=R.C. |last2=Turetsky |first2=B.I. |last3=Matsui |first3=M. |last4=Yan |first4=M. |last5=Bilker |first5=W. |last6=Hughett |first6=P. |last7=Gur |first7=R.E. |title=Sex differences in brain gray and white matter in healthy young adults: correlations with cognitive performance |journal=[[The Journal of Neuroscience]] |volume=19 |pages=4065–4072 |year=1999 |pmid=10234034 |issue=10|doi=10.1523/JNEUROSCI.19-10-04065.1999 }}</ref>

The [[cerebrum]], consisting of the [[cerebral hemisphere]]s, forms the largest part of the brain and overlies the other brain structures.{{sfn|Gray's Anatomy|2008|p=227-9}} The outer region of the hemispheres, the [[cerebral cortex]], is [[grey matter]], consisting of [[Cerebral cortex#Layers|cortical layers]] of [[neuron]]s. Each hemisphere is divided into four main [[lobes of the brain|lobes]] – the [[frontal lobe]], [[parietal lobe]], [[temporal lobe]], and [[occipital lobe]].{{sfn|Gray's Anatomy|2008|p=335-7}} Three other lobes are included by some sources which are a ''central lobe'', a [[limbic lobe]], and an [[Insular cortex|insular lobe]].<ref name="Ribas">{{cite journal |page=7 |pmid=20121437|year=2010|last1=Ribas|first1=G. C.|title=The cerebral sulci and gyri|journal=Neurosurgical Focus|volume=28|issue=2|doi=10.3171/2009.11.FOCUS09245}}</ref> The central lobe comprises the [[precentral gyrus]] and the [[postcentral gyrus]] and is included since it forms a distinct functional role.<ref name="Ribas"/><ref name="Frigeri">{{cite journal |pmid=25555079|year=2015|last1=Frigeri|first1=T.|title=Microsurgical anatomy of the central lobe|journal=Journal of Neurosurgery|volume=122|issue=3|pages=483–98|last2=Paglioli|first2=E.|last3=De Oliveira|first3=E.|last4=Rhoton Jr|first4=A. L.|doi=10.3171/2014.11.JNS14315}}</ref>

The [[brainstem]], resembling a stalk, attaches to and leaves the cerebrum at the start of the [[midbrain]] area. The brainstem includes the midbrain, the [[pons]], and the [[medulla oblongata]]. Behind the brainstem is the [[cerebellum]] ({{lang-la |little brain}}).{{sfn|Gray's Anatomy|2008|p=227-9}}

The cerebrum, brainstem, cerebellum, and spinal cord are covered by three membranes called [[meninges]]. The membranes are the tough [[dura mater]]; the middle [[arachnoid mater]] and the more delicate inner [[pia mater]]. Between the arachnoid mater and the pia mater is the [[Meninges#Subarachnoid spaces|subarachnoid space]] and [[subarachnoid cisterns]], which contain the [[cerebrospinal fluid]].{{sfn|Purves|2012|p=724}} The outermost membrane of the cerebral cortex is the basement membrane of the pia mater called the [[glia limitans]] and is an important part of the [[blood–brain barrier]].<ref name="Anatomy and Ultrastructure">{{Cite book |last1=Cipolla |first1=M.J. |title=Anatomy and Ultrastructure |url=https://www.ncbi.nlm.nih.gov/books/NBK53086/#s2.2 |publisher=Morgan & Claypool Life Sciences |date=January 1, 2009 |deadurl=no |archiveurl=https://web.archive.org/web/20171001170945/https://www.ncbi.nlm.nih.gov/books/NBK53086/#s2.2 |archivedate=October 1, 2017 }}</ref>
The living brain is very soft, having a gel-like consistency similar to soft tofu.<ref name="NPR">{{cite web |title=A Surgeon's-Eye View of the Brain |url=https://www.npr.org/templates/story/story.php?storyId=5396115 |website=NPR.org |deadurl=no |archiveurl=https://web.archive.org/web/20171107023155/http://www.npr.org/templates/story/story.php?storyId=5396115 |archivedate=November 7, 2017 }}</ref> The cortical layers of neurons constitute much of the cerebral [[grey matter]], while the deeper subcortical regions of [[myelin]]ated [[axon]]s, make up the [[white matter]].{{sfn|Gray's Anatomy|2008|p=227-229}} The white matter of the brain makes up about half of the total brain volume.<ref name="Neuron">{{cite journal |last1=Sampaio-Baptista |first1=C |last2=Johansen-Berg |first2=H |title=White Matter Plasticity in the Adult Brain. |journal=Neuron |date=20 December 2017 |volume=96 |issue=6 |pages=1239–1251 |doi=10.1016/j.neuron.2017.11.026 |pmid=29268094}}</ref>
{{multiple image

| align =center
| direction =horizontal
| total_width =700


| header_align =center
| header =Structural and functional areas of the human brain


| image1 =Sobo 1909 624.png
| width1 =3060
| height1 =2247
| alt1 =A diagram showing various structures within the human brain
| caption1 =Human brain bisected in the [[sagittal plane]], showing the white matter of the corpus callosum


| image2 =Blausen 0102 Brain Motor&Sensory (flipped).png
| width2 =1425
| height2 =951
| alt2 =A diagram of the functional areas of the human brain
| caption2 =Functional areas of the human brain. Dashed areas shown are commonly left hemisphere dominant

}}

====Cerebrum====
{{main|Cerebrum|Cerebral cortex}}
[[File:Gray726.png|thumb|Major gyri and sulci on the lateral surface of the cortex]]
[[File:Gehirn, medial - Lobi en.svg|thumb|Lobes of the brain]]

The cerebrum is the largest part of the brain, and is divided into nearly [[Symmetry in biology#Bilateral symmetry|symmetrical]] left and right [[cerebral hemisphere|hemisphere]]s by a deep groove, the [[longitudinal fissure]].<ref name="Davey">{{cite book |author=Davey, G. |title=Applied Psychology |isbn=978-1444331219 |publisher=[[John Wiley & Sons]] |year=2011 |page=153 |url=https://books.google.com/books?id=K1qq1SsgoxUC&pg=PA153}}</ref> The hemispheres are connected by five [[Commissural fiber#Structure|commissures]] that span the longitudinal fissure, the largest of these is the [[corpus callosum]].{{sfn|Gray's Anatomy|2008|p=227-9}}
Each hemisphere is conventionally divided into four main [[lobes of the brain|lobes]]; the [[frontal lobe]], [[parietal lobe]], [[temporal lobe]], and [[occipital lobe]], named according to the [[skull |skull bones]] that overlie them.{{sfn|Gray's Anatomy|2008|p=335-7}} Each lobe is associated with one or two specialised functions though there is some functional overlap between them.<ref name=Ackerman/> The surface of the brain is [[gyrification|folded]] into ridges ([[gyrus|gyri]]) and grooves ([[sulcus (neuroanatomy)|sulci]]), many of which are named, usually according to their position, such as the [[frontal gyrus]] of the frontal lobe or the [[central sulcus]] separating the central regions of the hemispheres. There are many small variations in the secondary and tertiary folds.{{sfn|Larsen|2001|pp=455–456}}

The outer part of the cerebrum is the [[cerebral cortex]], made up of [[grey matter]] arranged in layers. It is {{convert|2 |to |4 |mm}} thick, and deeply folded to give a convoluted appearance.<ref>{{cite book |last=Kandel |first=E.R. |author2=Schwartz, J.H. |author3=Jessel T.M. |title=Principles of Neural Science |year=2000 |publisher=McGraw-Hill Professional |isbn=978-0-8385-7701-1 |page=324}}</ref> Beneath the cortex is the cerebral [[white matter]]. The largest part of the cerebral cortex is the [[neocortex]], which has six neuronal layers. The rest of the cortex is of [[allocortex]], which has three or four layers.{{sfn|Gray's Anatomy|2008|pp=227–229}}

The cortex is [[brain mapping|mapped]] by divisions into about fifty different functional areas known as [[Brodmann's areas]]. These areas are distinctly different when [[Histology|seen under a microscope]].{{sfn|Guyton & Hall|2011|p=574}} The cortex is divided into two main functional areas – a [[motor cortex]] and a [[sensory cortex]].{{sfn|Guyton & Hall|2011|p=667}} The [[primary motor cortex]], which sends axons down to [[motor neuron]]s in the brainstem and spinal cord, occupies the rear portion of the frontal lobe, directly in front of the somatosensory area. The [[primary sensory areas]] receive signals from the [[sensory nerve]]s and [[nerve tract|tracts]] by way of [[Thalamus#Thalamic nuclei|relay nuclei]] in the [[thalamus]]. Primary sensory areas include the [[visual cortex]] of the [[occipital lobe]], the [[auditory cortex]] in parts of the [[temporal lobe]] and [[insular cortex]], and the [[somatosensory cortex]] in the [[parietal lobe]]. The remaining parts of the cortex, are called the [[association areas]]. These areas receive input from the sensory areas and lower parts of the brain and are involved in the complex [[cognition|cognitive processes]] of [[perception]], [[thought]], and [[decision-making]].<ref>Principles of Anatomy and Physiology 12th Edition – Tortora, Page 519.</ref> The main functions of the frontal lobe are to [[Attentional control|control attention]], abstract thinking, behaviour, problem solving tasks, and physical reactions and personality.<ref name="Freberg">{{cite book |author=Freberg, L. |title=Discovering Biological Psychology |publisher=[[Cengage Learning]] |year=2009 |pages=44–46 |isbn=978-0547177793 |url=https://books.google.com/books?id=-zyTMXAjzQsC&pg=PA44}}</ref><ref name="Kolb">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I. |title=Fundamentals of Human Neuropsychology |publisher=[[Macmillan Publishers|Macmillan]] |year=2009 |pages=73–75 |isbn=978-0716795865 |url=https://books.google.com/books?id=z0DThNQqdL4C&pg=PA73}}</ref> The occipital lobe is the smallest lobe; its main functions are visual reception, visual-spatial processing, movement, and [[Color vision#Color in the human brain|colour recognition]].<ref name="Freberg"/><ref name="Kolb"/> There is a smaller occipital lobule in the lobe known as the [[cuneus]]. The temporal lobe controls [[Echoic memory|auditory]] and [[visual memory|visual memories]], [[Language processing in the brain|language]], and some hearing and speech.<ref name="Freberg"/>

[[File:Visible Human head slice.jpg|thumb|upright|Cortical folds and white matter in horizontal bisection of head]]

The cerebrum contains the [[ventricular system|ventricles]] where the cerebrospinal fluid is produced and circulated. Below the corpus callosum is the [[septum pellucidum]], a membrane that separates the [[lateral ventricles]]. Beneath the lateral ventricles is the [[thalamus]] and to the front and below this is the [[hypothalamus]]. The hypothalamus leads on to the [[pituitary gland]]. At the back of the thalamus is the brainstem.{{sfn|Pocock|2006|p=64}}

The [[basal ganglia]], also called basal nuclei, are a set of structures deep within the hemispheres involved in behaviour and movement regulation.{{sfn|Purves|2012|p=399}} The largest component is the [[striatum]], others are the [[globus pallidus]], the [[substantia nigra]] and the [[subthalamic nucleus]].{{sfn|Purves|2012|p=399}} Part of the dorsal striatum, the [[putamen]], and the [[globus pallidus]], lie separated from the lateral ventricles and thalamus by the [[internal capsule]], whereas the [[caudate nucleus]] stretches around and abuts the lateral ventricles on their outer sides.{{sfn|Gray's Anatomy|2008|p=325-6}} At the deepest part of the [[lateral sulcus]] between the [[insular cortex]] and the striatum is a thin neuronal sheet called the [[claustrum]].<ref name="Goll">{{cite journal |last1=Goll |first1=Y. |last2=Atlan |first2=G. |last3=Citri |first3=A. |title=Attention: the claustrum |journal=Trends in Neurosciences |date=August 2015 |volume=38 |issue=8 |pages=486–95 |doi=10.1016/j.tins.2015.05.006 |pmid=26116988}}</ref>

Below and in front of the striatum are a number of [[basal forebrain]] structures. These include the [[nucleus accumbens]], [[nucleus basalis]], [[diagonal band of Broca]], [[substantia innominata]], and the [[medial septal nucleus]]. These structures are important in producing the [[neurotransmitter]], [[acetylcholine]], which is then distributed widely throughout the brain. The basal forebrain, in particular the nucleus basalis, is considered to be the major [[cholinergic]] output of the central nervous system to the striatum and neocortex.<ref name="Goard">{{cite journal |last1=Goard |first1=M. |last2=Dan |first2=Y. |title=Basal forebrain activation enhances cortical coding of natural scenes |journal=Nature Neuroscience |date=October 4, 2009 |volume=12 |issue=11 |pages=1444–1449 |doi=10.1038/nn.2402|pmid=19801988 |pmc=3576925 }}</ref>

====Cerebellum====
{{main|Cerebellum}}
[[File:Sobo 1909 623.png|thumb|upright|Human brain viewed from below, showing cerebellum and brainstem]]

The cerebellum is divided into an [[anterior lobe of cerebellum|anterior lobe]], a [[posterior lobe of cerebellum|posterior lobe]], and the [[flocculonodular lobe]].{{sfn|Guyton & Hall|2011|p=699}} The anterior and posterior lobes are connected in the middle by the [[cerebellar vermis|vermis]].{{sfn|Gray's Anatomy|2008|p=298}} The cerebellum has a much thinner outer cortex that is narrowly furrowed horizontally.{{sfn|Gray's Anatomy|2008|p=298}}
Viewed from underneath between the two lobes is the third lobe the flocculonodular lobe.<ref>{{cite book |last1=Netter |first1=F. |title=Atlas of Human Anatomy Including Student Consult Interactive Ancillaries and Guides. |date=2014 |publisher=W B Saunders Co |location=Philadelphia, Penn. |isbn=978-1-4557-0418-7 |page=114 |edition=6th}}</ref> The cerebellum rests at the back of the [[posterior cranial fossa|cranial cavity]], lying beneath the occipital lobes, and is separated from these by the [[cerebellar tentorium]], a sheet of fibre.{{sfn|Gray's Anatomy|2008|p=297}}

It is connected to the midbrain of the brainstem by the [[superior cerebellar peduncle]]s, to the pons by the [[middle cerebellar peduncle]]s, and to the medulla by the [[inferior cerebellar peduncle]]s.{{sfn|Gray's Anatomy|2008|p=298}} The cerebellum consists of an inner medulla of white matter and an outer cortex of richly folded grey matter.{{sfn|Gray's Anatomy|2008|p=297}} The cerebellum's anterior and posterior lobes appear to play a role in the coordination and smoothing of complex motor movements, and the flocculonodular lobe in the maintenance of [[Equilibrioception|balance]]{{sfn|Guyton & Hall|2011|pp=698–9}} although debate exists as to its cognitive, behavioural and motor functions.{{sfn|Squire|2013|pp=761–763}}

====Brainstem====
{{main|Brainstem}}
The brainstem lies beneath the cerebrum and consists of the [[midbrain]], [[pons]] and [[medulla oblongata|medulla]]. It lies in the [[posterior cranial fossa|back part of the skull]], resting on the part of the [[base of the skull|base]] known as the [[clivus (anatomy)|clivus]], and ends at the [[foramen magnum]], a large [[:wikt:foramen|opening]] in the [[occipital bone]]. The brainstem continues below this as the [[spinal cord]],{{sfn|Gray's Anatomy|2008|p=275}} protected by the [[vertebral column]].

Ten of the twelve pairs of [[cranial nerve]]s{{efn|Specifically the [[oculomotor]], [[trochlear nerve]], [[trigeminal nerve]], [[abducens nerve]], [[facial nerve]], [[vestibulocochlear nerve]], [[glossopharyngeal nerve]], [[vagus nerve]], [[accessory nerve]] and [[hypoglossal nerve]]s.{{sfn|Gray's Anatomy|2008|p=275}}}} emerge directly from the brainstem.{{sfn|Gray's Anatomy|2008|p=275}} The brainstem also contains many [[cranial nerve nucleus|cranial nerve nuclei]] and [[nucleus (neuroanatomy)|nuclei]] of [[nerve|peripheral nerves]], as well as nuclei involved in the regulation of many essential processes including [[breathing]], control of eye movements and balance.{{sfn|Guyton & Hall|2011|p=691}}{{sfn|Gray's Anatomy|2008|p=275}} The [[reticular formation]], a network of nuclei of ill-defined formation, is present within and along the length of the brainstem.{{sfn|Gray's Anatomy|2008|p=275}} Many [[nerve tract]]s, which transmit information to and from the cerebral cortex to the rest of the body, pass through the brainstem.{{sfn|Gray's Anatomy|2008|p=275}}

===Microanatomy===
The human brain is primarily composed of [[neuron]]s, [[glial cell]]s, [[neural stem cell]]s, and [[blood vessel]]s. Types of neuron include [[interneuron]]s, [[pyramidal cell]]s including [[Betz cell]]s, [[motor neuron]]s ([[upper motor neuron|upper]] and [[lower motor neuron]]s), and cerebellar [[Purkinje cell]]s. Betz cells are the largest cells (by size of cell body) in the nervous system.{{sfn|Purves|2012|p=377}} The adult human brain is estimated to contain 86±8 billion neurons, with a roughly equal number (85±10 billion) of non-neuronal cells.<ref name=":1" /> Out of these neurons, 16 billion (19%) are located in the cerebral cortex, and 69 billion (80%) are in the cerebellum.<ref name="Bigos"/><ref name=":1">{{cite journal |last1=Azevedo |first1=F. |display-authors=etal |title=Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain |journal=The Journal of Comparative Neurology |date=April 10, 2009 |volume=513 |issue=5 |pages=532–541 |doi=10.1002/cne.21974 |quote=despite the widespread quotes that the human brain contains 100 billion neurons and ten times more glial cells, the absolute number of neurons and glial cells in the human brain remains unknown. Here we determine these numbers by using the isotropic fractionator and compare them with the expected values for a human-sized primate. We find that the adult male human brain contains on average 86.1 ± 8.1 billion NeuN-positive cells (“neurons”) and 84.6 ± 9.8 billion NeuN-negative (“nonneuronal”) cells. |pmid=19226510}}</ref>

Types of glial cell are [[astrocyte]]s (including [[Bergmann glia]]), [[oligodendrocyte]]s, [[ependymal cell]]s (including [[tanycyte]]s), [[radial glial cell]]s, [[microglia]], and a subtype of [[oligodendrocyte progenitor cell]]s. Astrocytes are the largest of the glial cells. They are [[stellate cell]]s with many processes radiating from their [[soma (biology)|cell bodies]]. Some of these processes end as perivascular end-feet on [[capillary]] walls.<ref>{{Cite book |last1=Pavel |first1=Fiala |last2=Jiří |first2=Valenta |title=Central Nervous System |url=https://books.google.com/?id=LPlSBAAAQBAJ&pg=PA79 |publisher=Karolinum Press |page=79 |date=January 1, 2013|isbn=9788024620671 }}</ref> The [[glia limitans]] of the cortex is made up of astrocyte foot processes that serve in part to contain the cells of the brain.<ref name="Anatomy and Ultrastructure"/>

[[Mast cell]]s are [[white blood cell]]s that interact in the [[neuroimmune system]] in the brain.<ref name="Mast cell neuroimmmune system">{{cite journal | last1=Polyzoidis |first1=S. |last2=Koletsa |first2=T. |last3=Panagiotidou |first3=S. |last4=Ashkan |first4=K. |last5=Theoharides |first5=T.C. | title=Mast cells in meningiomas and brain inflammation | journal=Journal of Neuroinflammation | volume=12 | issue=1 | pages=170 | year=2015 | pmid=26377554 | pmc=4573939 | doi=10.1186/s12974-015-0388-3}}</ref> Mast cells in the central nervous system are present in the meninges;<ref name="Mast cell neuroimmmune system" /> they mediate neuroimmune responses in inflammatory conditions and help to maintain the blood–brain barrier, particularly in brain regions where the barrier is absent.<ref name="Mast cell neuroimmmune system" />{{sfn|Guyton & Hall|2011|pp=748–749}} Across systems, mast cells serve as the main [[effector cell]] through which pathogens can affect the [[gut–brain axis]].<ref name="pmid24833851">{{cite journal | last1=Budzyński |first1=J |last2=Kłopocka |first2=M. | title=Brain-gut axis in the pathogenesis of Helicobacter pylori infection | journal=World J. Gastroenterol. | volume=20 | issue=18 | pages=5212–25 | year=2014 | pmid=24833851 | pmc=4017036 | doi=10.3748/wjg.v20.i18.5212}}</ref><ref name="Microbiome-CNS-ENS">{{cite journal | last1=Carabotti |first1=M. |last2=Scirocco |first2=A. |last3=Maselli |first3=M.A. |last4=Severi |first4=C. | title=The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems | journal=Ann Gastroenterol | volume=28 | issue=2 | pages=203–209 | year=2015 | pmid=25830558 | pmc=4367209}}</ref>

Some 400 [[gene]]s are shown to be brain-specific. In all neurons, [[ELAVL3]] is expressed, and in pyramidal neurons, [[NRGN]] and [[REEP2]] are also expressed. [[GAD1]] – essential for the biosynthesis of the neurotransmitter [[GABA]] – is expressed in interneurons. Proteins expressed in glial cells are astrocyte markers GFAP, and [[S100B]]. [[Myelin basic protein]], and the transcription factor, [[OLIG2]] are expressed in oligodendrocytes.<ref>{{Cite journal|last=Sjöstedt|first=Evelina|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Häggmark|first4=Anna|last5=Mitsios|first5=Nicholas|last6=Nilsson|first6=Peter|last7=Pontén|first7=Fredrik|last8=Hökfelt|first8=Tomas|last9=Uhlén|first9=Mathias|date=June 15, 2015|title=Defining the human brain proteome using transcriptomics and antibody-based profiling with a focus on the cerebral cortex|journal=PLOS ONE |volume=10|issue=6|pages=e0130028 |doi=10.1371/journal.pone.0130028|pmid=26076492 |pmc=4468152|issn=1932-6203}}</ref>

===Cerebrospinal fluid===
[[Image:Blausen 0216 CerebrospinalSystem.png|thumb|[[Cerebrospinal fluid]] circulates in spaces around and within the brain]]
{{main|Cerebrospinal fluid}}
Cerebrospinal fluid is a clear, colourless [[transcellular fluid]] that circulates around the brain in the [[subarachnoid space]], in the [[ventricular system]], and in the [[central canal]] of the spinal cord. It also fills some gaps in the subarachnoid space, known as [[subarachnoid cisterns]].{{sfn|Gray's Anatomy|2008|pp=242–244}} The four ventricles, two [[lateral ventricle|lateral]], a [[third ventricle|third]], and a [[fourth ventricle]], all contain [[choroid plexus]] that produces cerebrospinal fluid.{{sfn|Purves|2012|p=742}} The third ventricle lies in the midline and [[Interventricular foramina (neuroanatomy)|is connected]] to the lateral ventricles.{{sfn|Gray's Anatomy|2008|pp=242–244}} A single [[duct (anatomy)|duct]], the [[cerebral aqueduct]] between the pons and the cerebellum, connects the third ventricle to the fourth ventricle.{{sfn|Gray's Anatomy|2008|p=243}} Three separate openings, the [[Medial aperture|middle]] and two [[lateral aperture]]s, drain the cerebrospinal fluid from the fourth ventricle to the [[cisterna magna]] one of the major cisterns. From here, cerebrospinal fluid circulates around the brain and spinal cord in the subarachnoid space, between the arachnoid mater and pia mater.{{sfn|Gray's Anatomy|2008|pp=242–244}}
At any one time, there is about 150mL of cerebrospinal fluid – most within the subarachnoid space. It is constantly being regenerated and absorbed, and replaces about once every 5–6 hours.{{sfn|Gray's Anatomy|2008|pp=242–244}}

A [[glymphatic system]] has been described<ref name="lliff">{{cite journal |last1=Iliff |first1=JJ |last2=Nedergaard |first2=M |title=Is there a cerebral lymphatic system? |journal=Stroke |date=June 2013 |volume=44 |issue=6 Suppl 1 |pages=S93-5 |doi=10.1161/STROKEAHA.112.678698 |pmid=23709744}}</ref><ref>{{cite web |last1=Gaillard |first1=F. |title=Glymphatic pathway |url=https://radiopaedia.org/articles/glymphatic-pathway |website=radiopaedia.org |deadurl=no |archiveurl=https://web.archive.org/web/20171030002906/https://radiopaedia.org/articles/glymphatic-pathway |archivedate=October 30, 2017}}</ref><ref name="Glymphatic system and brain waste clearance 2017 review" /> as the lymphatic drainage system of the brain. The brain-wide glymphatic pathway includes drainage routes from the cerebrospinal fluid, and from the [[meningeal lymphatic vessels]] that are associated with the dural sinuses, and run alongside the cerebral blood vessels.<ref name="D-O">{{cite journal|last1=Dissing-Olesen|first1=L.|last2=Hong|first2=S. |last3=Stevens|first3=B. |title=New brain lymphatic vessels drain old concepts |journal=EBioMedicine |date=August 2015|volume=2|issue=8|pages=776–7|doi=10.1016/j.ebiom.2015.08.019|pmid=26425672|pmc=4563157}}</ref><ref name="Sun">{{cite journal |last1=Sun |first1=BL |last2=Wang |first2=LH |last3=Yang |first3=T |last4=Sun |first4=JY |last5=Mao |first5=LL |last6=Yang |first6=MF |last7=Yuan |first7=H |last8=Colvin |first8=RA |last9=Yang |first9=XY |title=Lymphatic drainage system of the brain: A novel target for intervention of neurological diseases. |journal=Progress in neurobiology |date=April 2018 |volume=163-164 |pages=118–143 |doi=10.1016/j.pneurobio.2017.08.007 |pmid=28903061}}</ref> The pathway drains [[interstitial fluid]] from the tissue of the brain.<ref name="Sun"/>

===Blood supply===
{{main|Cerebral circulation}}
[[File: Circle of Willis en.svg|thumb|upright|Two circulations joining at the circle of Willis]]
[[File:Gray769-en.svg|thumb|Diagram showing features of cerebral [[meninges|outer membranes]] and supply of blood vessels]]
The [[internal carotid arteries]] supply [[Blood#Oxygen transport|oxygenated blood]] to the front of the brain and the [[vertebral arteries]] supply blood to the back of the brain.{{sfn|Gray's Anatomy|2008|p=247}} These two circulations [[anastomosis|join together]] in the [[circle of Willis]], a ring of connected arteries that lies in the [[interpeduncular cistern]] between the midbrain and pons.{{sfn|Gray's Anatomy|2008|p=251-2}}

The internal carotid arteries are branches of the [[common carotid arteries]]. They enter the [[cranium]] through the [[carotid canal]], travel through the [[cavernous sinus]] and enter the [[subarachnoid space]].{{sfn|Gray's Anatomy|2008|p=250}} They then enter the [[circle of Willis]], with two branches, the [[anterior cerebral arteries]] emerging. These branches travel forward and then upward along the [[longitudinal fissure]], and supply the front and midline parts of the brain.{{sfn|Gray's Anatomy|2008|p=248}} One or more small [[anterior communicating artery|anterior communicating arteries]] join the two anterior cerebral arteries shortly after they emerge as branches.{{sfn|Gray's Anatomy|2008|p=248}} The internal carotid arteries continue forward as the [[middle cerebral arteries]]. They travel sideways along the [[sphenoid bone]] of the [[orbit (anatomy)|eye socket]], then upwards through the [[insula cortex]], where final branches arise. The middle cerebral arteries send branches along their length.{{sfn|Gray's Anatomy|2008|p=250}}

The vertebral arteries emerge as branches of the left and right [[subclavian arteries]]. They travel upward through [[Vertebra#Cervical vertebrae|transverse foramina]] – spaces in the [[cervical vertebrae]] and then emerge as two vessels, one on the left and one on the right of the medulla.{{sfn|Gray's Anatomy|2008|p=250}} They give off [[Posterior inferior cerebellar artery|one of the three cerebellar branches]]. The vertebral arteries join in front of the middle part of the medulla to form the larger [[basilar artery]], which sends multiple branches to supply the medulla and pons, and the two other [[Anterior inferior cerebellar artery|anterior]] and [[Superior cerebellar artery|superior cerebellar branches]].{{sfn|Gray's Anatomy|2008|p=251}} Finally, the basilar artery divides into two [[posterior cerebral arteries]]. These travel outwards, around the superior cerebellar peduncles, and along the top of the cerebellar tentorium, where it sends branches to supply the temporal and occipital lobes.{{sfn|Gray's Anatomy|2008|p=251}} Each posterior cerebral artery sends a small [[posterior communicating artery]] to join with the internal carotid arteries.

====Blood drainage====

[[Cerebral veins]] drain [[Blood#Oxygen transport|deoxygenated blood]] from the brain. The brain has two main networks of [[vein]]s: an exterior or [[Superior cerebral veins|superficial network]], on the surface of the cerebrum that has three branches, and an [[Internal cerebral veins|interior network]]. These two networks communicate via [[anastomosis|anastomosing]] (joining) veins.{{sfn|Gray's Anatomy|2008|p=254-6}} The veins of the brain drain into larger cavities the [[dural venous sinuses]] usually situated between the dura mater and the covering of the skull.{{sfn|Elsevier's|2007|pp=311–4}} Blood from the cerebellum and midbrain drains into the [[great cerebral vein]]. Blood from the medulla and pons of the brainstem have a variable pattern of drainage, either into the [[spinal veins]] or into adjacent cerebral veins.{{sfn|Gray's Anatomy|2008|p=254-6}}

The blood in the [[Anatomical terms of location#deep|deep]] part of the brain drains, through a [[venous plexus]] into the [[cavernous sinus]] at the front, and the [[superior petrosal sinus|superior]] and [[inferior petrosal sinus]]es at the sides, and the [[inferior sagittal sinus]] at the back.{{sfn|Elsevier's|2007|pp=311–4}} Blood drains from the outer brain into the large [[superior sagittal sinus]], which rests in the midline on top of the brain. Blood from here joins with blood from the [[straight sinus]] at the [[confluence of sinuses]].{{sfn|Elsevier's|2007|pp=311–4}}

Blood from here drains into the left and right [[transverse sinus]]es.{{sfn|Elsevier's|2007|pp=311–4}} These then drain into the [[sigmoid sinus]]es, which receive blood from the cavernous sinus and superior and inferior petrosal sinuses. The sigmoid drains into the large [[internal jugular vein]]s.{{sfn|Elsevier's|2007|pp=311–4}}{{sfn|Gray's Anatomy|2008|p=254-6}}

====The blood–brain barrier====
The larger arteries throughout the brain supply blood to smaller [[capillaries]]. These smallest of [[blood vessel]]s in the brain, are lined with cells joined by [[tight junction]]s and so fluids do not seep in or leak out to the same degree as they do in other capillaries, thereby creating the [[blood–brain barrier]].{{sfn|Guyton & Hall|2011|pp=748–749}} [[Pericyte]]s play a major role in the formation of the tight junctions.<ref name="Daneman">{{cite journal |last1=Daneman |first1=R. |last2=Zhou |first2=L. |last3=Kebede |first3=A.A. |last4=Barres |first4=B.A. |title=Pericytes are required for blood-brain barrier integrity during embryogenesis |journal=Nature |date=November 25, 2010 |volume=468 |issue=7323 |pages=562–6 |pmid=20944625 |doi=10.1038/nature09513 |pmc=3241506}}</ref> The barrier is less permeable to larger molecules, but is still permeable to water, carbon dioxide, oxygen, and most fat-soluble substances (including [[anaesthetic]]s and alcohol).{{sfn|Guyton & Hall|2011|pp=748–749}} The blood–brain barrier is not present in the [[circumventricular organs]], structures in the brain that may need to respond to changes in body fluids, such as the [[pineal gland]], [[area postrema]], and some areas of the [[hypothalamus]].{{sfn|Guyton & Hall|2011|pp=748–749}} There is a similar [[Choroid plexus#Function|blood–cerebrospinal fluid barrier]], which serves the same purpose as the blood–brain barrier, but facilitates the transport of different substances into the brain due to the distinct structural characteristics between the two barrier systems.{{sfn|Guyton & Hall|2011|pp=748–749}}<ref name="BCSF">{{cite book |last1=Laterra |first1=J. |last2=Keep |first2=R. |last3=Betz |first3=L.A. |title=Basic neurochemistry: molecular, cellular and medical aspects |date=1999 |publisher=Lippincott-Raven |location=Philadelphia |edition=6th |section-url=https://www.ncbi.nlm.nih.gov/books/NBK27998/ |section=Blood–cerebrospinal fluid barrier |display-authors=etal}}</ref>

==Development==
{{Main |Development of the nervous system in humans}}
{{Further|Development of the human brain}}
[[File:Embryonic Development CNS.png|thumb|Neurulation and neural crest cells]]
[[File:1302 Brain Vesicle DevN.jpg|thumb|alt= Simple drawing of the lateral view of the three primary vesicle stage of the three to four week old embryo shown in different colors, and the five secondary vesicle stage of the five week old embryo shown in different colors and a lateral view of this |Primary and secondary [[brain vesicle|vesicle]] stages of development in the early embryo to the fifth week]]
[[File:6 week embryo brain.jpg|thumb|alt=Very simple drawing of the front end of a human embryo, showing each vesicle of the developing brain in a different color. |Brain of a human embryo in the sixth week of development]]

At the beginning of the third week of [[human embryonic development|development]], the [[embryo]]nic [[ectoderm]] forms a thickened strip called the [[neural plate]].<ref name="Sadler">{{cite book |last1=Sadler |first1=T. |title=Langman's medical embryology |date=2010 |publisher=Lippincott Williams & Wilkins |location=Philadelphia |isbn=978-07817-9069-7 |page=293 |edition=11th}}</ref> By the fourth week of development the neural plate has widened to give a broad [[cephalization|cephalic]] end, a less broad middle part and a narrow caudal end. These swellings are known as the [[Brain vesicle|primary brain vesicles]] and represent the beginnings of the [[forebrain]], [[midbrain]] and [[hindbrain]].{{sfn|Larsen|2001|p=419}}

[[Neural crest]] cells (derived from the ectoderm) populate the lateral edges of the plate at the [[neural fold]]s. In the fourth week in the [[neurulation |neurulation stage]] the [[Neural fold#Folding mechanism|neural folds close]] to form the [[neural tube]], bringing together the neural crest cells at the neural crest.{{sfn|Larsen|2001|pp=85–88}} The neural crest runs the length of the tube with cranial neural crest cells at the cephalic end and caudal neural crest cells at the tail. Cells detach from the crest and [[cell migration|migrate]] in a craniocaudal (head to tail) wave inside the tube.{{sfn|Larsen|2001|pp=85–88}} Cells at the cephalic end give rise to the brain, and cells at the caudal end give rise to the spinal cord.{{sfn|Purves|2012|pp=480–482}}

The tube flexes as it grows, forming the crescent-shaped cerebral hemispheres at the head. The cerebral hemispheres first appear on day 32.{{sfn|Larsen|2001|pp=445–446}}
Early in the fourth week the cephalic part bends sharply forward in a [[cephalic flexure]].{{sfn|Larsen|2001|pp=85–88}} This flexed part becomes the forebrain (prosencephalon); the adjoining curving part becomes the midbrain (mesencephalon) and the part caudal to the flexure becomes the hindbrain (rhombencephalon). These areas are formed as swellings known as the three primitive [[brain vesicle|vesicles]]. In the fifth week of development five [[brain vesicle]]s have formed.<ref>{{Cite web|title = OpenStax CNX|url = http://cnx.org/contents/b037bde2-ea37-43a5-9102-8d4fcbc623d1@3/The_Embryologic_Perspective|website = cnx.org|accessdate = May 5, 2015|deadurl = no|archiveurl = https://web.archive.org/web/20150505054856/http://cnx.org/contents/b037bde2-ea37-43a5-9102-8d4fcbc623d1@3/The_Embryologic_Perspective|archivedate = May 5, 2015|df = mdy-all}}</ref> The forebrain separates into two vesicles – an anterior telencephalon and a posterior [[diencephalon]]. The telencephalon gives rise to the cerebral cortex, basal ganglia, and related structures. The diencephalon gives rise to the thalamus and hypothalamus. The hindbrain also splits into two areas – the metencephalon and the myelencephalon. The metencephalon gives rise to the cerebellum and pons. The myelencephalon gives rise to the medulla oblongata.{{sfn|Larsen|2001|pp=85–87}} Also during the fifth week, the brain divides into [[segmentation (biology)|repeating segments]] called [[neuromere]]s.{{sfn|Larsen|2001|p=419}}{{sfn|Purves|2012|pp=481–484}} In the [[hindbrain]] these are known as [[rhombomere]]s.<ref name=Neuro>{{cite book |editor1-first=Dale |editor1-last=Purves |editor2-first=George J |editor2-last=Augustine |editor3-first=David |editor3-last=Fitzpatrick |editor4-first=Lawrence C |editor4-last=Katz |editor5-first=Anthony-Samuel |editor5-last=LaMantia |editor6-first=James O |editor6-last=McNamara |editor7-first=S Mark |editor7-last=Williams |year=2001 |chapter=Rhombomeres |chapterurl=https://www.ncbi.nlm.nih.gov/books/NBK10954/box/A1478/ |title=Neuroscience |edition=2nd |isbn=978-0-87893-742-4}}</ref>

A characteristic of the brain is the cortical folding known as [[gyrification]]. During [[prenatal development|fetal development]], the cortex starts off smooth. By the gestational age of 24 weeks, the wrinkled morphology showing the fissures that begin to mark out the lobes of the brain is evident.<ref name="Chen">{{cite book |url=https://books.google.com/books?id=94aPR_Oh40oC&pg=PA188 |title=Mechanical Self-Assembly: Science and Applications |publisher=[[Springer Science & Business Media]] |year=2012 |isbn=978-1461445623 |pages=188–189 |last=Chen |first=X.}}</ref> Scientists do not have a clear answer as to why the cortex wrinkles and folds, but they have linked gyrification with intelligence and [[neurological disorder]]s, and have proposed a [[Gyrification#Theories on causality in gyrification|number of gyrification theories]].<ref name="Chen"/> These theories include those based on [[Gyrification#Mechanical buckling|mechanical buckling]],<ref name="Ronan">{{cite journal |last1=Ronan |first1=L |last2=Voets |first2=N |last3=Rua |first3=C |last4=Alexander-Bloch |first4=A |last5=Hough |first5=M |last6=Mackay |first6=C |last7=Crow |first7=TJ |last8=James |first8=A |last9=Giedd |first9=JN |last10=Fletcher |first10=PC |title=Differential tangential expansion as a mechanism for cortical gyrification. |journal=Cerebral cortex (New York, N.Y. : 1991) |date=August 2014 |volume=24 |issue=8 |pages=2219–28 |doi=10.1093/cercor/bht082 |pmid=23542881}}</ref><ref name="Ackerman">{{cite book |last1=Ackerman |first1=S. |title=Discovering the brain |date=1992 |publisher=National Academy Press |location=Washington, D.C. |isbn=978-0-309-04529-2 |pages=22–25}}</ref> [[Gyrification#Axonal tension|axonal tension]],<ref name="Van Essen">{{cite journal |last1=Van Essen |first1=DC |title=A tension-based theory of morphogenesis and compact wiring in the central nervous system. |journal=Nature |date=23 January 1997 |volume=385 |issue=6614 |pages=313–8 |doi=10.1038/385313a0 |pmid=9002514}}</ref> and [[Gyrification#Differential tangential expansion|differential tangential expansion]].<ref name="Ronan"/>

The first cleft to appear in the fourth month is the lateral cerebral fossa.{{sfn|Larsen|2001|pp=445–446}} The expanding caudal end of the hemisphere has to curve over in a forward direction to fit into the restricted space. This covers the fossa and turns it into a much deeper ridge known as the [[lateral sulcus]] and this marks out the temporal lobe.{{sfn|Larsen|2001|pp=445–446}} By the sixth month other sulci have formed that demarcate the frontal, parietal, and occipital lobes.{{sfn|Larsen|2001|pp=445–446}} A gene present in the human genome ([[ArhGAP11B and human encephalisation|ArhGAP11B]]) may play a major role in gyrification and encephalisation.<ref>{{cite journal |last1=Florio |first1=M.|display-authors=etal |title=Human-specific gene ARHGAP11B promotes basal progenitor amplification and neocortex expansion |journal=Science |date=March 27, 2015 |volume=347 |issue=6229 |pages=1465–70 |pmid=25721503 |doi=10.1126/science.aaa1975}}</ref>
{{Gallery
| title=
| width=180
| height=180
| lines=3
|File:Gray651.png |Brain of human embryo at 4.5 weeks, showing interior of forebrain
|File:Gray653.png |Brain interior at 5 weeks
|File:Gray654.png |Brain viewed at midline at 3 months
}}

==Function==
[[File:Blausen 0103 Brain Sensory&Motor.png|thumb|Motor and sensory regions of the brain]]

===Motor control===
The [[motor system]] of the brain is responsible for the [[motor control|generation and control]] of movement.{{sfn|Guyton & Hall|2011|p=685}} Generated movements pass from the brain through nerves to [[motor neuron]]s in the body, which control the action of [[muscle]]s. The [[corticospinal tract]] carries movements from the brain, through the [[spinal cord]], to the torso and limbs.{{sfn|Guyton & Hall|2011|p=687}} The [[cranial nerves]] carry movements related to the eyes, mouth and face.

Gross movement – such as [[Animal locomotion|locomotion]] and the movement of arms and legs – is generated in the [[motor cortex]], divided into three parts: the [[primary motor cortex]], found in the [[prefrontal gyrus]] and has sections dedicated to the movement of different body parts. These movements are supported and regulated by two other areas, lying [[anterior]] to the primary motor cortex: the [[premotor area]] and the [[supplementary motor area]].{{sfn|Guyton & Hall|2011|p=686}} The hands and mouth have a much larger area dedicated to them than other body parts, allowing finer movement; this has been visualised in a [[Cortical homunculus#Types|motor homunculus]].{{sfn|Guyton & Hall|2011|p=686}} Impulses generated from the motor cortex travel along the [[corticospinal tract]] along the front of the medulla and cross over ([[decussate]]) at the [[medullary pyramids (brainstem)|medullary pyramids]]. These then travel down the [[spinal cord]], with most connecting to [[interneuron]]s, in turn connecting to lower [[motor neuron]]s within the [[grey matter]] that then transmit the impulse to move to muscles themselves.{{sfn|Guyton & Hall|2011|p=687}} The cerebellum and [[basal ganglia]], play a role in fine, complex and coordinated muscle movements.{{sfn|Guyton & Hall|2011|pp=698,708}} Connections between the cortex and the basal ganglia control muscle tone, posture and movement initiation, and are referred to as the [[extrapyramidal system]].{{sfn|Davidson's|2010|p=1139}}

===Sensory===
[[File:1604 Types of Cortical Areas-02.jpg|thumb|Cortical areas]]
[[File:Gray722.png|thumb|upright|Routing of neural signals from the two eyes to the brain]]
The [[sensory nervous system]] is involved with the reception and processing of [[sense|sensory information]]. This information is received through the cranial nerves, through tracts in the spinal cord, and directly at centres of the brain exposed to the blood.<ref name="Hellier">{{cite book |author=Hellier, J. |title=The Brain, the Nervous System, and Their Diseases [3 volumes] |publisher=[[ABC-CLIO]] |year=2014 |pages=300–303 |isbn=978-1610693387 |url=https://books.google.com/books?id=SDi2BQAAQBAJ&pg=PA300}}</ref> The brain also receives and interprets information from the [[special sense]]s of [[visual perception|vision]], [[Olfaction|smell]], [[hearing]], and [[taste]]. [[Sensory-motor coupling|Mixed motor and sensory signals]] are also integrated.<ref name="Hellier"/>

From the skin, the brain receives information about [[touch|fine touch]], [[pressure]], [[pain]], [[vibration]] and [[temperature]]. From the joints, the brain receives information about [[proprioception|joint position]].{{sfn|Guyton & Hall|2011|p=571–576}} The [[sensory cortex]] is found just near the motor cortex, and, like the motor cortex, has areas related to sensation from different body parts. Sensation collected by a [[sensory receptor]] on the skin is changed to a nerve signal, that is passed up a series of neurons through tracts in the spinal cord. The [[dorsal column–medial lemniscus pathway]] contains information about fine touch, vibration and position of joints. Neurons travel up the back part of the spinal cord to the back part of the medulla, where they connect with [[dorsal column–medial lemniscus pathway#Second-order neurons|second-order neurons]] that immediately swap sides. These neurons then travel upwards into the [[ventrobasal complex]] in the thalamus where they connect with [[dorsal column–medial lemniscus pathway#Third-order neurons|third-order neurons]] and travel up to the sensory cortex.{{sfn|Guyton & Hall|2011|p=571–576}}The [[spinothalamic tract]] carries information about pain, temperature, and gross touch. Neurons travel up the spinal cord and connect with second-order neurons in the [[reticular formation]] of the brainstem for pain and temperature, and also at the ventrobasal complex of the medulla for gross touch.{{sfn|Guyton & Hall|2011|pp=573–574}}

[[Visual perception|Vision]] is generated by light that hits the [[retina]] of the eye. [[Photoreceptor cell|Photoreceptors]] in the retina [[visual phototransduction|transduce]] the sensory stimulus of [[electromagnetic radiation|light]] into an electrical [[action potential|nerve signal]] that is sent to the [[visual cortex]] in the occipital lobe. Vision from the left visual field is received on the right side of each retina (and vice versa) and passes through the [[optic nerve]] until some information [[optic chiasm|changes sides]], so that all information about one side of the visual field passes through tracts in the opposite side of the brain. The nerves reach the brain at the [[lateral geniculate nucleus]], and travel through the [[optic radiation]] to reach the visual cortex.{{sfn|Guyton & Hall|2011|pp=623–631}}

[[Hearing]] and [[Equilibrioception|balance]] are both generated in the [[inner ear]]. The movement of [[Endolymph|liquids within the inner ear]] is generated by motion (for balance) and transmitted vibrations generated by the [[ossicles]] (for sound). This creates a nerve signal that passes through the [[vestibulocochlear nerve]]. From here, it passes through to the [[cochlear nuclei]], the [[superior olivary nucleus]], the [[medial geniculate nucleus]], and finally the [[auditory radiation]] to the [[auditory cortex]].{{sfn|Guyton & Hall|2011|pp=739–740}}

The sense of [[Olfaction|smell]] is generated by [[Olfactory receptor neuron|receptor cells]] in the [[olfactory epithelium|epithelium]] of the [[olfactory mucosa]] in the [[nasal cavity]]. This information passes through [[cribiform plate|a relatively permeable part]] of the skull to the [[olfactory nerve]]. This nerve transmits to the neural circuitry of the [[olfactory bulb]] from where information is passed to the [[olfactory system|olfactory cortex]].{{sfn|Pocock|2006|pp=138–139}}{{sfn|Squire|2013|pp=525–526}}
[[Taste]] is generated from [[Taste receptor|receptors on the tongue]] and passed along the [[facial]] and [[glossopharyngeal nerve]]s into the [[solitary tract]] in the brainstem. Some taste information is also passed from the pharynx into this area via the [[vagus nerve]]. Information is then passed from here through the thalamus into the [[gustatory cortex]].{{sfn|Guyton & Hall|2011|pp=647–648}}

===Regulation===
[[Autonomic nervous system|Autonomic]] functions of the brain include the regulation, or [[Neuroscience of rhythm|rhythmic control]] of the [[heart rate]] and [[respiratory rate|rate of breathing]], and maintaining [[homeostasis]].

[[Blood pressure]] and [[heart rate]] are influenced by the [[vasomotor center|vasomotor centre]] of the medulla, which causes arteries and veins to be somewhat constricted at rest. It does this by influencing the [[sympathetic nervous system|sympathetic]] and [[parasympathetic nervous system]]s via the [[vagus nerve]].{{sfn|Guyton & Hall|2011|pp=202–203}} Information about blood pressure is generated by [[baroreceptor]]s in [[aortic body|aortic bodies]] in the [[aortic arch]], and passed to the brain along the [[general visceral afferent fibers|afferent fibres]] of the vagus nerve. Information about the pressure changes in the [[carotid sinus]] comes from [[carotid body|carotid bodies]] located near the [[common carotid artery|carotid artery]] and this is passed via a [[Hering's nerve|nerve]] joining with the [[glossopharyngeal nerve]]. This information travels up to the [[solitary nucleus]] in the medulla. Signals from here influence the vasomotor centre to adjust vein and artery constriction accordingly.{{sfn|Guyton & Hall|2011|pp=205–208}}

The brain controls the [[respiratory rate|rate of breathing]], mainly by [[respiratory center|respiratory centre]]s in the medulla and pons.{{sfn|Guyton & Hall|2011|pp=505–509}} The respiratory centres control [[respiration (physiology)|respiration]], by generating motor signals that are passed down the spinal cord, along the [[phrenic nerve]] to the [[Thoracic diaphragm|diaphragm]] and other [[muscles of respiration]]. This is a [[spinal nerve|mixed nerve]] that carries sensory information back to the centres. There are four respiratory centres, three with a more clearly defined function, and an apneustic centre with a less clear function. In the medulla a dorsal respiratory group causes the desire to [[inhalation|breathe in]] and receives sensory information directly from the body. Also in the medulla, the ventral respiratory group influences [[exhalation|breathing out]] during exertion. In the pons the [[pneumotaxic center|pneumotaxic centre]] influences the duration of each breath,{{sfn|Guyton & Hall|2011|pp=505–509}} and the [[apneustic center|apneustic centre]] seems to have an influence on inhalation. The respiratory centres directly senses blood [[carbon dioxide]] and [[pH]]. Information about blood [[oxygen]], [[carbon dioxide]] and pH levels are also sensed on the walls of arteries in the [[peripheral chemoreceptor]]s of the aortic and carotid bodies. This information is passed via the vagus and glossopharyngeal nerves to the respiratory centres. High carbon dioxide, an acidic pH, or low oxygen stimulate the respiratory centres.{{sfn|Guyton & Hall|2011|pp=505–509}} The desire to breathe in is also affected by [[pulmonary stretch receptor]]s in the lungs which, when activated, prevent the lungs from overinflating by transmitting information to the respiratory centres via the vagus nerve.{{sfn|Guyton & Hall|2011|pp=505–509}}

The [[hypothalamus]] in the [[diencephalon]], is involved in regulating many functions of the body. Functions include [[neuroendocrine]] regulation, regulation of the [[circadian rhythm]], control of the [[autonomic nervous system]], and the regulation of fluid, and food intake. The circadian rhythm is controlled by two main cell groups in the hypothalamus. The anterior hypothalamus includes the [[suprachiasmatic nucleus]] and the [[ventrolateral preoptic nucleus]] which through gene expression cycles, generates a roughly 24 hour [[circadian clock]]. In the [[circadian clock|circadian day]] an [[ultradian rhythm]] takes control of the sleeping pattern. [[Sleep]] is an essential requirement for the body and brain and allows the closing down and resting of the body's systems. There are also findings that suggest that the daily build-up of toxins in the brain are removed during sleep.<ref name="sleep">{{cite web |title=Brain Basics: Understanding Sleep {{!}} National Institute of Neurological Disorders and Stroke |url=https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep |website=www.ninds.nih.gov |deadurl=no |archiveurl=https://web.archive.org/web/20171222044016/https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep |archivedate=December 22, 2017 }}</ref> Whilst awake the brain consumes a fifth of the body's total energy needs. [[Neuroscience of sleep|Sleep]] necessarily reduces this use and gives time for the restoration of energy-giving [[Adenosine triphosphate|ATP]]. The effects of [[sleep deprivation]] show the absolute need for sleep.{{sfn|Guyton & Hall|2011|p=723}}

The [[lateral hypothalamus]] contains [[orexin]]ergic neurons that control [[appetite]] and [[arousal]] through their projections to the [[ascending reticular activating system]].<ref name=Davis>{{ cite book | chapter=24. Orexigenic Hypothalamic Peptides Behavior and Feeding – 24.5 Orexin | chapter-url=https://books.google.com/books?id=KuAEPOPbW6MC&pg=PA361 | pages=361–362 |last1=Davis |first1=J.F. |last2=Choi |first2=D.L. |last3=Benoit |first3=S.C. | title=Handbook of Behavior, Food and Nutrition |editor1-last=Preedy |editor1-first= V.R. |editor2-last=Watson |editor2-first=R.R. |editor3-last=Martin |editor3-first=C.R. | publisher=Springer | year=2011 | isbn=9780387922713 }}</ref>{{sfn|Squire|2013|p=800}} The hypothalamus controls the [[pituitary gland]] through the release of peptides such as [[oxytocin]], and [[vasopressin]], as well as [[dopamine]] into the [[median eminence]]. Through the autonomic projections, the hypothalamus is involved in regulating functions such as blood pressure, heart rate, breathing, sweating, and other homeostatic mechanisms.{{sfn|Squire|2013|p=803}} The hypothalamus also plays a role in thermal regulation, and when stimulated by the immune system, is capable of generating a [[fever]]. The hypothalamus is influenced by the kidneys – when blood pressure falls, the [[renin]] released by the kidneys stimulates a need to drink. The hypothalamus also regulates food intake through autonomic signals, and hormone release by the digestive system.{{sfn|Squire|2013|p=805}}

===Language===
[[File:1605_Brocas_and_Wernickes_Areas-02.jpg|thumb|[[Broca's area]] and [[Wernicke's area]] are linked by the [[arcuate fasciculus]].]]
{{main |Language processing in the brain}}
{{See also|Two-streams hypothesis#Two auditory systems}}

While language functions were traditionally thought to be localized to [[Wernicke's area]] and [[Broca's area]],{{sfn|Guyton & Hall|2011|p=720-2}} it is now mostly accepted that a wider network of [[Cortex (anatomy)|cortical]] regions contributes to language functions.<ref>{{cite journal |last1=Poeppel |first1=D. |last2=Emmorey |first2=K. |last3=Hickok |first3=G. |last4=Pylkkänen |first4=L. |title=Towards a new neurobiology of language |journal=The Journal of Neuroscience |date=October 10, 2012 |volume=32 |issue=41 |pages=14125–14131 |doi=10.1523/JNEUROSCI.3244-12.2012 |pmid=23055482 |pmc=3495005}}</ref><ref>{{cite journal |last1=Hickok |first1=G |title=The functional neuroanatomy of language |journal=Physics of Life Reviews |date=September 2009 |volume=6 |issue=3 |pages=121–143 |doi=10.1016/j.plrev.2009.06.001|pmid=20161054 |pmc=2747108 }}</ref><ref>{{cite journal | last1=Fedorenko | first1=E. | last2=Kanwisher | first2=N. | journal=Language and Linguistics Compass | volume=3 | issue=4 | url=https://pdfs.semanticscholar.org/7bb1/d05e4e8842b1714fde9f8dd6cd8c86878039.pdf | title=Neuroimaging of language: why hasn't a clearer picture emerged? | pages=839–865 | doi=10.1111/j.1749-818x.2009.00143.x | year=2009 | deadurl=no | archiveurl=https://web.archive.org/web/20170422033827/https://pdfs.semanticscholar.org/7bb1/d05e4e8842b1714fde9f8dd6cd8c86878039.pdf | archivedate=April 22, 2017 | df=mdy-all }}</ref>

The study on how language is represented, processed, and [[language acquisition|acquired]] by the brain is called [[neurolinguistics]], which is a large multidisciplinary field drawing from [[cognitive neuroscience]], [[cognitive linguistics]], and [[psycholinguistics]].<ref>{{Cite book |title=Language intervention strategies in aphasia and related neurogenic communication disorders |last=Damasio |first=H. |date=2001 |publisher=Lippincott Williams & Wilkins |isbn=9780781721332 |editor-last=Chapey |editor-first=Roberta |edition=4th |pages=18–36 |chapter=Neural basis of language disorders |oclc=45952164}}</ref>

===Lateralisation===
{{Main |Lateralization of brain function}}
{{Further |Functional specialization (brain)}}
The cerebrum has a [[contralateral brain|contralateral organisation]] with each hemisphere of the brain interacting primarily with one half of the body: the left side of the brain interacts with the right side of the body, and vice versa. The developmental cause for this is uncertain.<ref name="Berntson">{{cite book |last1=Berntson |first1=G. |last2=Cacioppo |first2=J. |title=Handbook of Neuroscience for the Behavioral Sciences, Volume 1 |publisher=[[John Wiley & Sons]] |year=2009 |page=145 |isbn=978-0470083550 |url=https://books.google.com/books?id=LwdJhh8bOvwC&pg=PA145}}</ref> Motor connections from the brain to the spinal cord, and sensory connections from the spinal cord to the brain, both [[decussation|cross sides]] in the brainstem. Visual input follows a more complex rule: the optic nerves from the two eyes come together at a point called the [[optic chiasm]], and half of the fibres from each nerve split off to join the other.<ref>{{cite book |author=Hellier, J. |title=The Brain, the Nervous System, and Their Diseases [3 volumes] |isbn=978-1610693387 |publisher=[[ABC-CLIO]] |year=2014 |page=1135 |url=https://books.google.com/books?id=SDi2BQAAQBAJ&pg=PA1135}}</ref> The result is that connections from the left half of the retina, in both eyes, go to the left side of the brain, whereas connections from the right half of the retina go to the right side of the brain.<ref name="Kolb 2">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I.Q. |title=Introduction to Brain and Behavior |isbn=978-1464139604 |publisher=[[Macmillan Higher Education]] |year=2013 |page=296 |url=https://books.google.com/books?id=teUkAAAAQBAJ}}</ref> Because each half of the retina receives light coming from the opposite half of the visual field, the functional consequence is that visual input from the left side of the world goes to the right side of the brain, and vice versa.<ref name="Berntson"/> Thus, the right side of the brain receives somatosensory input from the left side of the body, and visual input from the left side of the visual field.<ref name="Sherwood">{{cite book |last1=Sherwood |first1=L. |title=Human Physiology: From Cells to Systems |isbn=978-1133708537 |publisher=[[Cengage Learning]] |year=2012 |page=181 |url=https://books.google.com/books?id=CZkJAAAAQBAJ&pg=PT181}}</ref><ref name="Kalat">{{cite book |author=Kalat, J |title=Biological Psychology |isbn=978-1305465299 |publisher=[[Cengage Learning]] |year=2015 |page=425 |url=https://books.google.com/books?id=EzZBBAAAQBAJ&pg=PA425}}</ref>

The left and right sides of the brain appear symmetrical, but they function asymmetrically.<ref name="Cowin">{{cite book |last1=Cowin |first1=S.C. |last2=Doty |first2=S.B. |title=Tissue Mechanics |isbn=978-0387499857 |publisher=[[Springer Science & Business Media]] |year=2007 |page=4 |url=https://books.google.com/books?id=8BJhRkat--YC&pg=PA4}}</ref> For example, the counterpart of the left-hemisphere motor area controlling the right hand is the right-hemisphere area controlling the left hand. There are, however, several important exceptions, involving language and spatial cognition. The left frontal lobe is dominant for language. If a key language area in the left hemisphere is damaged, it can leave the victim unable to speak or understand,<ref name="Cowin"/> whereas equivalent damage to the right hemisphere would cause only minor impairment to language skills.

A substantial part of current understanding of the interactions between the two hemispheres has come from the study of "[[split-brain]] patients"—people who underwent surgical transection of the corpus callosum in an attempt to reduce the severity of epileptic seizures.<ref name="Myers">{{cite book |last1=Morris |first1=C.G. |last2=Maisto |first2=A.A. |title=Understanding Psychology |isbn=978-0205769063 |publisher=[[Prentice Hall]] |year=2011 |page=56 |url=https://books.google.com/books?id=hoVWAAAAYAAJ}}</ref> These patients do not show unusual behaviour that is immediately obvious, but in some cases can behave almost like two different people in the same body, with the right hand taking an action and then the left hand undoing it.<ref name="Myers"/><ref name="Kolb 3">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I.Q. |title=Introduction to Brain and Behavior (Loose-Leaf) |isbn=978-1464139604 |publisher=[[Macmillan Higher Education]] |year=2013 |pages=524–549 |url=https://books.google.com/books?id=teUkAAAAQBAJ}}</ref> These patients, when briefly shown a picture on the right side of the point of visual fixation, are able to describe it verbally, but when the picture is shown on the left, are unable to describe it, but may be able to give an indication with the left hand of the nature of the object shown.<ref name="Kolb 3"/><ref name="Schacter">{{cite book |last1=Schacter |first1=D.L. |last2=Gilbert |first2=D.T. |last3=Wegner |first3=D.M. |title=Introducing Psychology |isbn=978-1429218214 |publisher=[[Macmillan Publishers|Macmillan]] |year=2009 |page=80 |url=https://books.google.com/books?id=gt8lpZylVmkC&pg=PA80}}</ref>

===Emotion===
{{main|Emotion}}
{{Further |Affective neuroscience}}
[[Emotion]]s are generally defined as two-step multicomponent processes involving [[Human intelligence (intelligence gathering)|elicitation]], followed by psychological feelings, appraisal, expression, autonomic responses, and action tendencies.<ref>{{cite book |last=Sander |first=David |editor1-last=Armony |editor1-first=J. |editor2-first=Patrik |editor2-last=Vuilleumier |title=The Cambridge handbook of human affective neuroscience |date=2013 |publisher=Cambridge Univ. Press |location=Cambridge |isbn=9780521171557 |pages=16 }}</ref> Attempts to localize basic emotions to certain brain regions have been controversial, with some research finding no evidence for specific locations corresponding to emotions, and instead circuitry involved in general emotional processes. The [[amygdala]], [[orbitofrontal cortex]], mid and anterior [[insula cortex]] and lateral [[prefrontal cortex]], appeared to be involved in generating the emotions, while weaker evidence was found for the [[ventral tegmental area]], [[ventral pallidum]] and [[nucleus accumbens]] in [[incentive salience]].<ref>{{cite journal |last1=Lindquist |first1=KA. |last2=Wager |first2=TD. |last3=Kober |first3=H |last4=Bliss-Moreau |first4=E |last5=Barrett |first5=LF |title=The brain basis of emotion: A meta-analytic review |journal=Behavioral and Brain Sciences |date=May 23, 2012 |volume=35 |issue=3 |pages=121–143 |doi=10.1017/S0140525X11000446|pmid=22617651 |pmc=4329228 }}</ref> Others, however, have found evidence of activation of specific regions, such as the [[basal ganglia]] in happiness, the [[corpus callosum|subcallosal]] [[cingulate cortex]] in sadness, and [[amygdala]] in fear.<ref>{{cite journal |last1=Phan |first1=KL |last2=Wager |first2=Tor |last3=Taylor |first3=SF. |last4=Liberzon |first4=l |title=Functional Neuroanatomy of Emotion: A Meta-Analysis of Emotion Activation Studies in PET and fMRI |journal=NeuroImage |date=June 1, 2002 |volume=16 |issue=2 |pages=331–348 |doi=10.1006/nimg.2002.1087 |url=http://europepmc.org/abstract/med/12030820 |pmid=12030820}}</ref>

===Cognition===
{{main|Cognition}} {{Further |Prefrontal cortex#Executive function}}

The brain is responsible for [[cognition]],<ref name="NHM preface - Cognition">{{cite book | last1=Malenka |first1=RC |last2=Nestler |first2=EJ |last3=Hyman |first3=SE | editor1-last=Sydor |editor1-first=A |editor2-last=Brown |editor2-first=RY | title=Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year=2009 | publisher=McGraw-Hill Medical | location=New York | isbn=9780071481274 | page=xiii | edition=2nd | chapter=Preface }}</ref><ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /> which functions through numerous [[cognitive process|processes]] and [[executive function]]s.<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter = Chapter 14: Higher Cognitive Function and Behavioral Control}}</ref><ref name="NHMH_3e – pathways">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter=Chapter 6: Widely Projecting Systems: Monoamines, Acetylcholine, and Orexin}}</ref><ref name="Executive functions">{{cite journal | last1=Diamond |first1=A |author1-link=Adele Diamond | title=Executive functions | journal=Annual Review of Psychology | volume=64 | issue= | pages=135–168 | year=2013 | pmid=23020641 | pmc=4084861 | doi=10.1146/annurev-psych-113011-143750 | quote=}} [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084861/figure/F4/ Figure 4: Executive functions and related terms] {{webarchive|url=https://web.archive.org/web/20180509181646/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084861/figure/F4/ |date=May 9, 2018 }}</ref> Executive functions include the ability to filter information and tune out irrelevant stimuli with [[attentional control]] and [[cognitive inhibition]], the ability to process and manipulate information held in [[working memory]], the ability to think about multiple concepts simultaneously and [[task switching (psychology)|switch tasks]] with [[cognitive flexibility]], the ability to inhibit [[impulse (psychology)|impulses]] and [[prepotent response]]s with [[inhibitory control]], and the ability to determine the relevance of information or appropriateness of an action.<ref name="NHMH_3e – pathways" /><ref name="Executive functions" /> Higher order executive functions require the simultaneous use of multiple basic executive functions, and include [[planning]] and [[fluid intelligence]] (i.e., [[reasoning]] and [[problem solving]]).<ref name="Executive functions" />

The [[prefrontal cortex]] plays a significant role in mediating executive functions.<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /><ref name="Executive functions" /><ref name="Goldstein">{{cite book | editor1-last=Goldstein |editor1-first=S. |editor2-last=Naglieri |editor2-first=J. | last1=Hyun |first1=J.C. |last2=Weyandt |first2=L.L. |last3=Swentosky |first3=A. | title=Handbook of Executive Functioning | date=2014 | publisher=Springer | location=New York | isbn=9781461481065 | pages=13–23 | chapter=Chapter 2: The Physiology of Executive Functioning | chapter-url=https://books.google.com/books?id=1e8VAgAAQBAJ&pg=PA13 }}</ref> Planning involves activation of the [[dorsolateral prefrontal cortex]] (DLPFC), [[anterior cingulate cortex]], angular prefrontal cortex, right prefrontal cortex, and [[supramarginal gyrus]].<ref name="Goldstein"/> Working memory manipulation involves the DLPFC, [[inferior frontal gyrus]], and areas of the [[parietal cortex]].<ref name="NHMH_3e – Higher Cognitive Function and Behavioral Control" /><ref name="Goldstein" /> [[Inhibitory control]] involves multiple areas of the prefrontal cortex, as well as the [[caudate nucleus]] and [[subthalamic nucleus]].<ref name="Executive functions" /><ref name="Goldstein" /><ref name="NHMH_3e – Addiction and ADHD" />

==Physiology==

===Neurotransmission===
{{main|Neurotransmission}}
{{Further | Summation (neurophysiology)}}
Brain activity is made possible by the interconnections of neurons that are linked together to reach their targets.{{sfn|Pocock|2006|p=68}} A neuron consists of a [[soma (biology)|cell body]], [[axon]], and [[dendrite]]s. Dendrites are often extensive branches that receive information in the form of signals from the axon terminals of other neurons. The signals received may cause the neuron to initiate an [[action potential]] (an electrochemical signal or nerve impulse) which is sent along its axon to the axon terminal, to connect with the dendrites or with the cell body of another neuron. An action potential is initiated at the [[Axon#Initial segment|initial segment]] of an axon, which contains a complex of proteins.<ref>{{cite journal |last=Clark |first=B.D. |author2=Goldberg, E.M. |author3=Rudy, B. |title=Electrogenic tuning of the axon initial segment. |journal=The Neuroscientist : A Review Journal Bringing Neurobiology, Neurology and Psychiatry |date=December 2009 |volume=15 |issue=6 |pages=651–68 |pmid=20007821 |doi=10.1177/1073858409341973 |pmc=2951114}}</ref> When an action potential, reaches the axon terminal it triggers the release of a [[neurotransmitter]] at a [[synapse]] that propagates a signal that acts on the target cell.{{sfn|Pocock|2006|pp=70–74}} These chemical neurotransmitters include [[dopamine]], [[serotonin]], [[gamma-Aminobutyric acid|GABA]], [[glutamate (neurotransmitter)|glutamate]], and [[acetylcholine]].<ref name=NIMH2017 /> GABA is the major inhibitory neurotransmitter in the brain, and glutamate is the major excitatory neurotransmitter.<ref>{{cite book|last1=Purves|first1=Dale|title=Neuroscience|date=2011|publisher=Sinauer|location=Sunderland, Mass.|isbn=978-0-87893-695-3|page=139|edition=5.}}</ref> Neurons link at synapses to form [[neural pathway]]s, [[neural circuit]]s, and large elaborate [[large scale brain networks|network systems]] such as the [[salience network]] and the [[default mode network]], and the activity between them is driven by the process of [[neurotransmission]].

===Metabolism===
[[File:PET-image.jpg|thumb|upright|alt=A flat oval object is surrounded by blue. The object is largely green-yellow, but contains a dark red patch at one end and a number of blue patches. |[[Positron emission tomography|PET]] image of the human brain showing energy consumption]]

The brain consumes up to 20% of the energy used by the human body, more than any other organ.<ref name="power-sciam">{{cite web |last=Swaminathan |first=N |title=Why Does the Brain Need So Much Power? |url=http://www.scientificamerican.com/article/why-does-the-brain-need-s/ |work=[[Scientific American]] |publisher=Scientific American, a Division of Nature America, Inc. |accessdate=November 19, 2010 |date=April 29, 2008 |deadurl=no |archiveurl=https://web.archive.org/web/20140127171142/http://www.scientificamerican.com/article/why-does-the-brain-need-s/ |archivedate=January 27, 2014 }}</ref> In humans, [[blood glucose]] is the primary [[food energy|source of energy]] for most cells and is critical for normal function in a number of tissues, including the brain.<ref name="Glucose-Glycogen storage review" /> The human brain consumes approximately 60% of blood glucose in fasted, sedentary individuals.<ref name="Glucose-Glycogen storage review">{{cite journal | vauthors = Wasserman DH | title = Four grams of glucose | journal = American Journal of Physiology. Endocrinology and Metabolism | volume = 296 | issue = 1 | pages = E11–21 | date = January 2009 | pmid = 18840763 | pmc = 2636990 | doi = 10.1152/ajpendo.90563.2008 | quote = Four grams of glucose circulates in the blood of a person weighing 70 kg. This glucose is critical for normal function in many cell types. In accordance with the importance of these 4 g of glucose, a sophisticated control system is in place to maintain blood glucose constant. Our focus has been on the mechanisms by which the flux of glucose from liver to blood and from blood to skeletal muscle is regulated. ... The brain consumes ∼60% of the blood glucose used in the sedentary, fasted person. ... The amount of glucose in the blood is preserved at the expense of glycogen reservoirs (Fig. 2). In postabsorptive humans, there are ∼100 g of glycogen in the liver and ∼400 g of glycogen in muscle. Carbohydrate oxidation by the working muscle can go up by ∼10-fold with exercise, and yet after 1 h, blood glucose is maintained at ∼4 g. ... It is now well established that both insulin and exercise cause translocation of GLUT4 to the plasma membrane. Except for the fundamental process of GLUT4 translocation, [muscle glucose uptake (MGU)] is controlled differently with exercise and insulin. Contraction-stimulated intracellular signaling (52, 80) and MGU (34, 75, 77, 88, 91, 98) are insulin independent. Moreover, the fate of glucose extracted from the blood is different in response to exercise and insulin (91, 105). For these reasons, barriers to glucose flux from blood to muscle must be defined independently for these two controllers of MGU.}}</ref> Brain [[metabolism]] normally relies upon blood [[glucose]] as an energy source, but during times of low glucose (such as [[fasting]], [[endurance exercise]], or limited [[carbohydrate]] intake), the brain uses [[ketone bodies]] for fuel with a smaller need for glucose. The brain can also utilize [[Lactic acid#Exercise and lactate|lactate during exercise]].<ref>{{cite journal |title=Lactate fuels the human brain during exercise |last1=Quistorff |first1=B |last2=Secher |first2=N |last3=Van Lieshout |first3=J |date=July 24, 2008 |journal=[[The FASEB Journal]] |doi=10.1096/fj.08-106104 |pmid=18653766 |volume=22 |issue=10 |pages=3443–3449 }}</ref> The brain stores glucose in the form of [[glycogen]], albeit in significantly smaller amounts than that found in the [[liver]] or [[skeletal muscle]].<ref>{{cite journal |last=Obel |first=L.F. |author2=Müller, M.S. |author3=Walls, A.B. |author4=Sickmann, H.M. |author5=Bak, L.K. |author6=Waagepetersen, H.S. |author7= Schousboe, A. |title=Brain glycogen-new perspectives on its metabolic function and regulation at the subcellular level. |journal=Frontiers in Neuroenergetics |date=2012 |volume=4 |pages=3 |pmid=22403540 |doi=10.3389/fnene.2012.00003 |pmc=3291878}}</ref> [[Fatty acid#Length of free fatty acid chains|Long-chain fatty acid]]s cannot cross the [[blood–brain barrier]], but the liver can break these down to produce ketone bodies. However, [[short-chain fatty acid]]s (e.g., [[butyric acid]], [[propionic acid]], and [[acetic acid]]) and the [[Fatty acid#Length of free fatty acid chains|medium-chain fatty acids]], [[octanoic acid]] and [[heptanoic acid]], can cross the blood–brain barrier and be metabolized by brain cells.<ref>{{cite journal |last1=Marin-Valencia |first1=I. |display-authors=etal |title=Heptanoate as a neural fuel: energetic and neurotransmitter precursors in normal and glucose transporter I-deficient (G1D) brain. |journal=Journal of Cerebral Blood Flow and Metabolism |date=February 2013 |volume=33 |issue=2 |pages=175–82 |pmid=23072752 |doi=10.1038/jcbfm.2012.151 |pmc=3564188}}</ref><ref name="SCFA MCT-mediated BBB passage - 2005 review">{{cite journal | author=Tsuji, A. | title=Small molecular drug transfer across the blood-brain barrier via carrier-mediated transport systems | journal=NeuroRx | volume=2 | issue=1 | pages=54–62 | year=2005 | pmid=15717057 | pmc=539320 | doi=10.1602/neurorx.2.1.54 | quote=Uptake of valproic acid was reduced in the presence of medium-chain fatty acids such as hexanoate, octanoate, and decanoate, but not propionate or butyrate, indicating that valproic acid is taken up into the brain via a transport system for medium-chain fatty acids, not short-chain fatty acids. ... Based on these reports, valproic acid is thought to be transported bidirectionally between blood and brain across the BBB via two distinct mechanisms, monocarboxylic acid-sensitive and medium-chain fatty acid-sensitive transporters, for efflux and uptake, respectively.}}</ref><ref name="SCFA MCT-mediated BBB passage - 2014 review">{{cite journal | last1=Vijay |first1=N. |last2=Morris |first2=M.E. | title=Role of monocarboxylate transporters in drug delivery to the brain | journal=Curr. Pharm. Des. | volume=20 | issue=10 | pages=1487–98 | year=2014 | pmid=23789956 | pmc=4084603 | doi=10.2174/13816128113199990462 | quote=Monocarboxylate transporters (MCTs) are known to mediate the transport of short chain monocarboxylates such as lactate, pyruvate and butyrate. ... MCT1 and MCT4 have also been associated with the transport of short chain fatty acids such as acetate and formate which are then metabolized in the astrocytes [78].}}</ref>

Although the human brain represents only 2% of the body weight, it receives 15% of the cardiac output, 20% of total body oxygen consumption, and 25% of total body [[glucose]] utilization.<ref>{{cite book |last=Clark |first=D.D. |author2=Sokoloff. L. |editor1=Siegel, G.J.|editor2=Agranoff, B.W.|editor3=Albers, R.W.|editor4=Fisher, S.K.|editor5=Uhler, M.D. |title=Basic Neurochemistry: Molecular, Cellular and Medical Aspects |publisher=Lippincott |location=Philadelphia |year=1999 |pages=637–670 |isbn=978-0-397-51820-3}}</ref> The brain mostly uses glucose for energy, and deprivation of glucose, as can happen in [[hypoglycemia]], can result in loss of consciousness.<ref name="Mrsulja">{{cite book |author=Mrsulja, B.B. |title=Pathophysiology of Cerebral Energy Metabolism |isbn=978-1468433487 |publisher=[[Springer Science & Business Media]] |year=2012 |pages=2–3 |url=https://books.google.com/books?id=8yzvBwAAQBAJ&pg=PA2}}</ref> The energy consumption of the brain does not vary greatly over time, but active regions of the cortex consume somewhat more energy than inactive regions: this fact forms the basis for the functional brain imaging methods [[Positron emission tomography|PET]] and [[fMRI]].<ref>{{cite journal |last=Raichle |first=M. |year=2002 |title=Appraising the brain's energy budget |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=99 |pages=10237–10239 |doi=10.1073/pnas.172399499 |pmid=12149485 |last2=Gusnard |first2=DA |pmc=124895 |issue=16}}</ref> These [[functional imaging]] techniques provide a three-dimensional image of metabolic activity.<ref name="Steptoe">{{cite book |editor-last=Steptoe |editor-first=A. |last1=Gianaros |first1=Peter J. |last2=Gray |first2=Marcus A. |last3=Onyewuenyi |first3=Ikechukwu |last4=Critchley |first4=Hugo D.|title=Handbook of Behavioral Medicine: Methods and Applications |chapter=Chapter 50. Neuroimaging methods in behavioral medicine |isbn=978-0387094885 |publisher=[[Springer Science & Business Media]] |year=2010 |page=770 |chapter-url=https://books.google.com/books?id=Si9TtI5AGIEC&pg=PA770 |doi=10.1007/978-0-387-09488-5_50}}</ref>

The function of [[sleep]] is not fully understood; however, there is evidence that sleep enhances the clearance of metabolic waste products, some of which are potentially [[neurotoxic]], from the brain and may also permit repair.<ref name="Glymphatic system and brain waste clearance 2017 review" /><ref>{{cite web |title=Brain may flush out toxins during sleep |url=http://www.ninds.nih.gov/news_and_events/news_articles/pressrelease_brain_sleep_10182013.htm |work=[[National Institutes of Health]] |accessdate=October 25, 2013 |deadurl=no |archiveurl=https://web.archive.org/web/20131020220815/http://www.ninds.nih.gov/news_and_events/news_articles/pressrelease_brain_sleep_10182013.htm |archivedate=October 20, 2013 }}</ref><ref name="Sleep – clearance of neurotoxic waste products">{{cite journal | vauthors = Xie L, Kang H, Xu Q, Chen MJ, Liao Y, Thiyagarajan M, O'Donnell J, Christensen DJ, Nicholson C, Iliff JJ, Takano T, Deane R, Nedergaard M | title = Sleep drives metabolite clearance from the adult brain | journal = Science | volume = 342 | issue = 6156 | pages = 373–377 | date = October 2013 | pmid = 24136970 | pmc = 3880190 | doi = 10.1126/science.1241224 | quote = Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.}}</ref> Evidence suggests that the increased clearance of metabolic waste during sleep occurs via increased functioning of the [[glymphatic system]].<ref name="Glymphatic system and brain waste clearance 2017 review">{{cite journal | vauthors = Bacyinski A, Xu M, Wang W, Hu J | title = The Paravascular Pathway for Brain Waste Clearance: Current Understanding, Significance and Controversy | journal = Frontiers in Neuroanatomy | volume = 11 | issue = | pages = 101 | date = November 2017 | pmid = 29163074 | pmc = 5681909 | doi = 10.3389/fnana.2017.00101 | quote = The paravascular pathway, also known as the “glymphatic” pathway, is a recently described system for waste clearance in the brain. According to this model, cerebrospinal fluid (CSF) enters the paravascular spaces surrounding penetrating arteries of the brain, mixes with interstitial fluid (ISF) and solutes in the parenchyma, and exits along paravascular spaces of draining veins.  ... In addition to Aβ clearance, the glymphatic system may be involved in the removal of other interstitial solutes and metabolites. By measuring the lactate concentration in the brains and cervical lymph nodes of awake and sleeping mice, Lundgaard et al. (2017) demonstrated that lactate can exit the CNS via the paravascular pathway. Their analysis took advantage of the substantiated hypothesis that glymphatic function is promoted during sleep (Xie et al., 2013; Lee et al., 2015; Liu et al., 2017).}}</ref> Sleep may also have an effect on cognitive function by weakening unnecessary connections.<ref>{{cite journal |url=https://pdfs.semanticscholar.org/6f9d/f7817534e55865bd1f6b7da6d2912bdbeaf3.pdf |last1=Tononi |first1=Guilio |last2=Cirelli |first2=Chiara |title=Perchance to Prune |journal=Scientific American |volume=309 |issue=2 |date=August 2013 |pages=34–39 |pmid=23923204|doi=10.1038/scientificamerican0813-34 }}</ref>

==Research==
The brain is not fully understood, and research is ongoing.<ref name=HCP2009 /> [[Neuroscience|Neuroscientists]], along with researchers from allied disciplines, study how the human brain works. The boundaries between the specialties of [[neuroscience]], [[neurology]] and other disciplines such as [[psychiatry]] have faded as they are all influenced by [[basic research]] in neuroscience.

Neuroscience research has expanded considerably in recent decades. The "[[Decade of the Brain]]", an initiative of the United States Government in the 1990s, is considered to have marked much of this increase in research,<ref>{{Cite journal |url=http://www.sciencemag.org/cgi/content/summary/284/5415/739 |first1=E.G. |last1=Jones |authorlink1=Edward G. Jones |first2=L.M. |last2=Mendell |title=Assessing the Decade of the Brain |journal=Science |doi=10.1126/science.284.5415.739 |date=April 30, 1999 |volume=284 |issue=5415 |page=739 |pmid=10336393 |deadurl=no |archiveurl=https://web.archive.org/web/20100614091805/http://www.sciencemag.org/cgi/content/summary/284/5415/739 |archivedate=June 14, 2010 }}</ref> and was followed in 2013 by the [[BRAIN Initiative]].<ref>{{cite web |title=A $4.5 Billion Price Tag for the BRAIN Initiative? |url=http://www.sciencemag.org/news/2014/06/45-billion-price-tag-brain-initiative |website=Science {{!}} AAAS |date=June 5, 2014 |deadurl=no |archiveurl=https://web.archive.org/web/20170618154752/http://www.sciencemag.org/news/2014/06/45-billion-price-tag-brain-initiative |archivedate=June 18, 2017 }}</ref> The [[Human Connectome Project]] was a five-year study launched in 2009 to analyse the anatomical and functional connections of parts of the brain, and has provided much data.<ref name=HCP2009>{{cite journal |last1=Van Essen |first1=D.C. |display-authors=etal |title=The Human Connectome Project: A data acquisition perspective |journal=NeuroImage |date=October 2012 |volume=62 |issue=4 |pages=2222–2231 |doi=10.1016/j.neuroimage.2012.02.018|pmid=22366334 |pmc=3606888 }}</ref>

===Methods===
Information about the structure and function of the human brain comes from a variety of experimental methods, including animals and humans. Information about brain trauma and stroke has provided information about the function of parts of the brain and the effects of [[brain damage]]. [[Neuroimaging]] is used to visualise the brain and record brain activity. [[Electrophysiology]] is used to measure, record and monitor the electrical activity of the cortex. Measurements may be of [[local field potential]]s of cortical areas, or of the activity of a single neuron. An [[electroencephalography|electroencephalogram]] can record the electrical activity of the cortex using [[electrode]]s placed non-invasively on the [[scalp]].<ref>{{cite journal | last1=Towle |first1=V.L. |display-authors=etal |title=The spatial location of EEG electrodes: locating the best-fitting sphere relative to cortical anatomy |journal=Electroencephalography and Clinical Neurophysiology |date=January 1993 |volume=86 |issue=1 |pages=1–6 |pmid=7678386 |doi=10.1016/0013-4694(93)90061-y}}</ref>{{sfn|Purves|2012|pp=632–633}}

Invasive measures include [[electrocorticography]], which uses electrodes placed directly on the exposed surface of the brain. This method is used in [[cortical stimulation mapping]], used in the study of the relationship between cortical areas and their systemic function.<ref>{{cite journal |last1=Silverstein |first1=J. |title=Mapping the Motor and Sensory Cortices: A Historical Look and a Current Case Study in Sensorimotor Localization and Direct Cortical Motor Stimulation |journal=The Neurodiagnostic Journal |pmid=22558647 |url=http://www.readperiodicals.com/201203/2662763741.html |year=2012 |volume=52 |issue=1 |pages=54–68 |deadurl=no |archiveurl=https://web.archive.org/web/20121117021132/http://www.readperiodicals.com/201203/2662763741.html |archivedate=November 17, 2012 }}</ref> By using much smaller [[microelectrode]]s, [[single-unit recording]]s can be made from a single neuron that give a high [[Angular resolution|spatial resolution]] and high [[temporal resolution]]. This has enabled the linking of brain activity to behaviour, and the creation of neuronal maps.<ref>{{cite journal |last1=Boraud |first1=T. |last2=Bezard |first2=E. | year=2002 | title=From single extracellular unit recording in experimental and human Parkinsonism to the development of a functional concept of the role played by the basal ganglia in motor control | journal=Progress in Neurobiology | volume=66 | issue=4 | pages=265–283 | doi=10.1016/s0301-0082(01)00033-8 |display-authors=etal}}</ref>

The development of [[cerebral organoid]]s has opened ways for studying the growth of the brain, and of the cortex, and for understanding disease development, offering further implications for therapeutic applications.<ref name="Lancaster">{{cite journal |last1=Lancaster |first1=MA |last2=Renner |first2=M |last3=Martin |first3=CA |last4=Wenzel |first4=D |last5=Bicknell |first5=LS |last6=Hurles |first6=ME |last7=Homfray |first7=T |last8=Penninger |first8=JM |last9=Jackson |first9=AP |last10=Knoblich |first10=JA |title=Cerebral organoids model human brain development and microcephaly. |journal=Nature |date=19 September 2013 |volume=501 |issue=7467 |pages=373-9 |doi=10.1038/nature12517 |pmid=23995685}}</ref><ref name="Lee">{{cite journal |last1=Lee |first1=CT |last2=Bendriem |first2=RM |last3=Wu |first3=WW |last4=Shen |first4=RF |title=3D brain Organoids derived from pluripotent stem cells: promising experimental models for brain development and neurodegenerative disorders. |journal=Journal of biomedical science |date=20 August 2017 |volume=24 |issue=1 |pages=59 |doi=10.1186/s12929-017-0362-8 |pmid=28822354}}</ref>

===Imaging===
{{Further |Magnetic resonance imaging of the brain}}

[[Functional neuroimaging]] techniques show changes in brain activity that relate to the function of specific brain areas. One technique is [[functional magnetic resonance imaging]] (fMRI) which has the advantages over earlier methods of [[SPECT]] and [[positron emission tomography|PET]] of not needing the use of [[Nuclear medicine|radioactive materials]] and of offering a higher resolution.<ref>{{cite web |title=Magnetic Resonance, a critical peer-reviewed introduction; functional MRI |publisher=European Magnetic Resonance Forum |accessdate=June 30, 2017 |url=http://www.magnetic-resonance.org/ch/11-03.html |deadurl=no |archiveurl=https://web.archive.org/web/20170602035337/http://www.magnetic-resonance.org/ch/11-03.html |archivedate=June 2, 2017 }}</ref> Another technique is [[functional near-infrared spectroscopy]]. These methods rely on the [[haemodynamic response]] that shows changes in brain activity in relation to changes in [[cerebral circulation|blood flow]], useful in [[brain mapping|mapping functions to brain areas]].<ref>{{cite journal |last1=Buxton |first1=R. |last2=Uludag |first2=K. |last3=Liu |first3=T. | year= 2004| title=Modeling the haemodynamic response to brain activation | journal=NeuroImage | volume= 23 | issue= | pages=S220–S233 | doi=10.1016/j.neuroimage.2004.07.013|pmid=15501093 |citeseerx=10.1.1.329.29 }}</ref> [[Resting state fMRI]]
looks at the interaction of brain regions whilst the brain is not performing a specific task.<ref>{{cite journal |last1=Biswal |first1=B.B. |title=Resting state fMRI: a personal history |journal=NeuroImage|date=August 15, 2012|volume=62|issue=2|pages=938–44|pmid=22326802|doi=10.1016/j.neuroimage.2012.01.090}}</ref> This is also used to show the [[default mode network]].

Any electrical current generates a magnetic field; [[neural oscillation]]s induce weak magnetic fields, and in functional [[magnetoencephalography]] the current produced can show localised brain function in high resolution.{{sfn|Purves|2012|p=20}} [[Tractography]] uses [[MRI]] and [[image analysis]] to create [[3D modeling|3D images]] of the [[nerve tract]]s of the brain. [[Connectogram]]s give a graphical representation of the [[connectome|neural connections]] of the brain.<ref name="Kane">{{cite book |last1=Kane |first1=R.L. |last2=Parsons |first2=T.D. |title=The Role of Technology in Clinical Neuropsychology |isbn=978-0190234737 |publisher=[[Oxford University Press]] |year=2017 |page=399 |url=https://books.google.com/books?id=iuAwDgAAQBAJ |quote=Irimia, Chambers, Torgerson, and Van Horn (2012) provide a first-step graphic on how best to display connectivity findings, as is presented in Figure 13.15. This is referred to as a connectogram.}}</ref>

Differences in [[brain morphometry|brain structure can be measured]] in some disorders, notably [[schizophrenia]] and [[dementia]]. Different biological approaches using imaging have given more insight for example into the disorders of [[biology of depression|depression]] and [[biology of obsessive-compulsive disorder|obsessive-compulsive disorder]]. A key source of information about the function of brain regions is the effects of damage to them.<ref>{{cite book | url=https://books.google.com/?id=kiCtU8wBTfwC | title=Neuropsychology | last=Andrews | first=D.G. | publisher=Psychology Press | year=2001 | isbn=978-1-84169-103-9}}</ref>

Advances in [[neuroimaging]] have enabled objective insights into mental disorders, leading to faster diagnosis, more accurate prognosis, and better monitoring.<ref>{{cite web |author=Lepage, M. |date=2010 |title=Research at the Brain Imaging Centre |work=Douglas Mental Health University Institute |url=http://www.douglas.qc.ca/page/imagerie-cerebrale?locale=en |deadurl=yes |archiveurl=https://web.archive.org/web/20120305042011/http://www.douglas.qc.ca/page/imagerie-cerebrale?locale=en |archivedate=March 5, 2012 }}</ref>

===Gene and protein expression===
{{Main|Bioinformatics}}
{{See also |List of neuroscience databases}}
[[Bioinformatics]] is a field of study that includes the creation and advancement of databases, and computational and statistical techniques, that can be used in studies of the human brain, particularly in the areas of [[Bioinformatics#Gene and protein expression|gene and protein expression]]. Bioinformatics and studies in [[genomics]], and [[functional genomics]], generated the need for [[DNA annotation]], a [[Transcriptomics technologies|transcriptome technology]], identifying [[gene]]s, and their and location and function.<ref name="Steward">{{cite journal | title=Genome annotation for clinical genomic diagnostics: strengths and weaknesses | author=Steward, C.A. |display-authors=etal | pmid=28558813 | doi=10.1186/s13073-017-0441-1 | volume=9 | issue=1 | pmc=5448149 | year=2017 | journal=Genome Med | page=49}}</ref><ref>{{cite journal | title=GENCODE: the reference human genome annotation for The ENCODE Project. | author=Harrow, J. |display-authors=etal | pmid=22955987 | doi=10.1101/gr.135350.111 | pmc=3431492 | volume=22 | issue=9 | date=September 2012 | journal=Genome Res. | pages=1760–74}}</ref><ref name="Gibson and Muse">{{cite book |vauthors=Gibson G, Muse SV |title=A primer of genome science |edition=3rd |publisher=Sinauer Associates |location=Sunderland, MA}}</ref> [[GeneCards]] is a major database.

As of 2017, just under 20,000 [[Human genome#Coding sequences (protein-coding genes)|protein-coding genes]] are seen to be expressed in the human,<ref name="Steward"/> and some 400 of these genes are brain-specific.<ref>{{Cite web|url=https://www.proteinatlas.org/humanproteome/brain|title=The human proteome in brain – The Human Protein Atlas|website=www.proteinatlas.org|access-date=September 29, 2017|deadurl=no|archiveurl=https://web.archive.org/web/20170929231550/https://www.proteinatlas.org/humanproteome/brain|archivedate=September 29, 2017}}</ref><ref>{{Cite journal|last=Uhlén|first=Mathias|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Lindskog|first4=Cecilia|last5=Oksvold|first5=Per|last6=Mardinoglu|first6=Adil|last7=Sivertsson|first7=Åsa|last8=Kampf|first8=Caroline|last9=Sjöstedt|first9=Evelina|date=January 23, 2015|title=Tissue-based map of the human proteome|url=http://science.sciencemag.org/content/347/6220/1260419|journal=Science|language=en|volume=347|issue=6220|pages=1260419|doi=10.1126/science.1260419|issn=0036-8075|pmid=25613900|deadurl=no|archiveurl=https://web.archive.org/web/20170716202510/http://science.sciencemag.org/content/347/6220/1260419|archivedate=July 16, 2017}}</ref> The data that has been provided on [[gene expression]] in the brain has fuelled further research into a number of disorders. The long term use of alcohol for example, has shown altered gene expression in the brain, and cell-type specific changes that may relate to [[alcoholism|alcohol use disorder]].<ref>{{cite journal|last=Warden|first=A|year=2017|title=Gene expression profiling in the human alcoholic brain.|journal=Neuropharmacology|volume=122|pages=161–174|pmid=28254370|via=|doi=10.1016/j.neuropharm.2017.02.017|pmc=5479716}}</ref> These changes have been noted in the [[Synapse|synaptic]] [[transcriptome]] in the prefrontal cortex, and are seen as a factor causing the drive to alcohol dependence, and also to other [[substance abuse]]s.<ref>{{cite journal | title=Applying the new genomics to alcohol dependence. | author=Farris, S.P. |display-authors=etal | journal=Alcohol | year=2015 | pmid=25896098 | doi=10.1016/j.alcohol.2015.03.001 | volume=49 | issue=8 | pmc=4586299 | pages=825–36}}</ref>

Other related studies have also shown evidence of synaptic alterations and their loss, in the [[ageing brain]]. Changes in gene expression alter the levels of proteins in various pathways and this has been shown to be evident in synaptic contact dysfunction or loss. This dysfunction has been seen to affect many structures of the brain and has a marked effect on inhibitory neurons resulting in a decreased level of neurotransmission, and subsequent cognitive decline and disease.<ref name="Rozycka">{{cite journal|last1=Rozycka|first1=A|last2=Liguz-Lecznar|first2=M|title=The space where aging acts: focus on the GABAergic synapse.|journal=Aging Cell|date=August 2017|volume=16|issue=4|pages=634–643|doi=10.1111/acel.12605|pmid=28497576|pmc=5506442}}</ref><ref>{{cite journal|last1=Flores|first1=CE|last2=Méndez|first2=P|title=Shaping inhibition: activity dependent structural plasticity of GABAergic synapses.|journal=Frontiers in Cellular Neuroscience|date=2014|volume=8|pages=327|doi=10.3389/fncel.2014.00327|pmid=25386117|pmc=4209871}}</ref>

==Clinical significance==
===Injury===
[[Brain damage|Injury to the brain]] can manifest in many ways. [[Traumatic brain injury]], for example received in [[contact sport]], after a [[Falling (accident)|fall]], or a [[traffic collision|traffic]] or [[work accident]], can be associated with both immediate and longer-term problems. Immediate problems may include [[intracerebral haemorrhage|bleeding within the brain]], this may compress the brain tissue or damage its blood supply. [[Cerebral contusion|Bruising]] to the brain may occur. Bruising may cause widespread damage to the nerve tracts that can lead to a condition of [[diffuse axonal injury]].<ref name="GE Health">{{cite web|url=http://www.medcyclopaedia.com/library/topics/volume_vi_1/b/BRAIN_INJURY_TRAUMATIC.aspx|archive-url=https://archive.is/20110526162429/http://www.medcyclopaedia.com/library/topics/volume_vi_1/b/BRAIN_INJURY_TRAUMATIC.aspx|dead-url=yes|archive-date=May 26, 2011|title=Brain Injury, Traumatic|publisher=[[General Electric|GE]]|work=Medcyclopaedia}}</ref> A [[skull fracture|fractured skull]], injury to a particular area, [[deafness]], and [[concussion]] are also possible immediate developments. In addition to the site of injury, the opposite side of the brain may be affected, termed a [[Coup contrecoup injury|contrecoup]] injury. Longer-term issues that may develop include [[posttraumatic stress disorder]], and [[hydrocephalus]]. [[Chronic traumatic encephalopathy]] can develop following multiple [[head injury|head injuries]].<ref>{{Cite journal |last1=Dawodu |first1=S.T. |title=Traumatic Brain Injury (TBI) – Definition and Pathophysiology: Overview, Epidemiology, Primary Injury |url=http://emedicine.medscape.com/article/326510-overview#a3 |website=Medscape |date=March 9, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170409021001/http://emedicine.medscape.com/article/326510-overview#a3 |archivedate=April 9, 2017 }}</ref>

===Disease===
[[Neurodegenerative disease]]s result in progressive damage to different parts of the brain's function, and [[Aging brain|worsen with age]]. Common examples include [[dementia]] such as [[Alzheimer's disease]], [[alcoholic dementia]] or [[vascular dementia]]; [[Parkinson's disease]]; and other rarer infectious, genetic, or metabolic causes such as [[Huntington's disease]], [[motor neuron disease]]s, [[HIV dementia]], [[Neurosyphilis|syphilis-related dementia]] and [[Wilson's disease]]. Neurodegenerative diseases can affect different parts of the brain, and can affect movement, [[memory]], and cognition.{{sfn|Davidson's|2010|p=1196-7}}

The brain, although protected by the blood–brain barrier, can be affected by infections including [[virus]]es, [[bacteria]] and [[fungi]]. Infection may be of the [[meninges]] ([[meningitis]]), the brain matter ([[encephalitis]]), or within the brain matter (such as a [[cerebral abscess]]).{{sfn|Davidson's|2010|p=1205-15}} Rare [[prion disease]]s including [[Creutzfeldt–Jakob disease]] and its [[Variant Creutzfeldt–Jakob disease|variant]], and [[Kuru (disease)|kuru]] may also affect the brain.{{sfn|Davidson's|2010|p=1205-15}}

===Tumours===
[[Brain tumor|Brain tumours]] can be either [[benign]] or [[malignant|cancerous]]. Most malignant tumours [[metastasis|arise from another part of the body]], most commonly from the [[lung cancer|lung]], [[breast cancer|breast]] and [[melanoma|skin]].{{sfn|Davidson's|2010|p=1216-7}} Cancers of brain tissue can also occur, and originate from any tissue in and around the brain. [[Meningioma]], cancer of the meninges around the brain, is more common than cancers of brain tissue.{{sfn|Davidson's|2010|p=1216-7}} Cancers within the brain may cause symptoms related to their size or position, with symptoms including headache and nausea, or the gradual development of focal symptoms such as gradual difficulty seeing, swallowing, talking, or as a change of mood.{{sfn|Davidson's|2010|p=1216-7}} Cancers are in general investigated through the use of CT scans and MRI scans. A variety of other tests including blood tests and lumbar puncture may be used to investigate for the cause of the cancer and evaluate the type and [[cancer staging|stage]] of the cancer.{{sfn|Davidson's|2010|p=1216-7}} The [[corticosteroid]] [[dexamethasone]] is often given to decrease the [[oedema|swelling]] of brain tissue around a tumour. Surgery may be considered, however given the complex nature of many tumours or based on tumour stage or type, [[radiotherapy]] or [[chemotherapy]] may be considered more suitable.{{sfn|Davidson's|2010|p=1216-7}}

===Mental disorders===
[[Mental disorder]]s, such as [[major depressive disorder|depression]], [[schizophrenia]], [[bipolar disorder]], [[posttraumatic stress disorder]], [[attention deficit hyperactivity disorder]], [[obsessive-compulsive disorder]], [[Tourette syndrome]], and [[addiction]], are known to relate to the functioning of the brain.<ref name="NHMH_3e – Addiction and ADHD">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE, Holtzman DM | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2015 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071827706 | edition = 3rd | chapter = Chapter 14: Higher Cognitive Function and Behavioral Control | quote =In conditions in which prepotent responses tend to dominate behavior, such as in drug addiction, where drug cues can elicit drug seeking (Chapter 16), or in attention deficit hyperactivity disorder (ADHD; described below), significant negative consequences can result. ... ADHD can be conceptualized as a disorder of executive function; specifically, ADHD is characterized by reduced ability to exert and maintain cognitive control of behavior. Compared with healthy individuals, those with ADHD have diminished ability to suppress inappropriate prepotent responses to stimuli (impaired response inhibition) and diminished ability to inhibit responses to irrelevant stimuli (impaired interference suppression). ... Functional neuroimaging in humans demonstrates activation of the prefrontal cortex and caudate nucleus (part of the dorsal striatum) in tasks that demand inhibitory control of behavior. ... Early results with structural MRI show a thinner cerebral cortex, across much of the cerebrum, in ADHD subjects compared with age-matched controls, including areas of [the] prefrontal cortex involved in working memory and attention.}}</ref><ref name=NIMH2017>{{cite web |title=NIMH » Brain Basics |url=https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml |website=www.nimh.nih.gov |accessdate=March 26, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170326230311/https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml |archivedate=March 26, 2017 }}</ref><ref name="Addiction - brain disease review">{{cite journal | last1=Volkow |first1=N.D. |last2=Koob |first2=G.F. |last3=McLellan |first3=A.T. | title=Neurobiologic advances from the brain disease model of addiction | journal=[[The New England Journal of Medicine]] | volume=374 | issue=4 | pages=363–371 | date=January 2016 | pmid=26816013 | pmc=6135257 | doi=10.1056/NEJMra1511480}}</ref> Treatment for mental disorders may include [[psychotherapy]], [[psychiatry]], [[social interventionism|social intervention]] and personal [[Recovery model|recovery]] work or [[cognitive behavioural therapy]]; the underlying issues and associated prognoses vary significantly between individuals.<ref name="Simpson">{{cite book |last1=Simpson |first1=J.M. |last2=Moriarty |first2=G.L. |title=Multimodal Treatment of Acute Psychiatric Illness: A Guide for Hospital Diversion |publisher=[[Columbia University Press]] |year=2013 |pages=22–24 |isbn=978-0231536097 |url=https://books.google.com/books?id=MbtkAgAAQBAJ&pg=PA22}}</ref>

===Epilepsy===
[[Epileptic seizure]]s are thought to relate to abnormal electrical activity.{{sfn|Davidson's|2010|p=1172-9}} Seizure activity can manifest as [[absence seizure|absence of consciousness]], [[focal seizure|focal]] effects such as limb movement or impediments of speech, or be [[generalised seizure|generalized]] in nature.{{sfn|Davidson's|2010|p=1172-9}} [[Status epilepticus]] refers to a seizure or series of seizures that have not terminated within 5 minutes.<ref name="foundation">{{cite web |title=Status Epilepticus |url=https://www.epilepsy.com/learn/challenges-epilepsy/seizure-emergencies/status-epilepticus |website=Epilepsy Foundation |language=en}}</ref> Seizures have a large number of causes, however many seizures occur without a definitive cause being found. In a person with [[epilepsy]], risk factors for further seizures may include sleeplessness, drug and alcohol intake, and stress. Seizures may be assessed using [[blood test]]s, [[EEG]] and various [[medical imaging]] techniques based on the [[medical history]] and [[medical examination|exam]] findings.{{sfn|Davidson's|2010|p=1172-9}} In addition to treating an underlying cause and reducing exposure to risk factors, [[anticonvulsant]] medications can play a role in preventing further seizures.{{sfn|Davidson's|2010|p=1172-9}}

===Congenital===
Some brain disorders such as [[Tay–Sachs disease]]<ref name="Moore">{{cite book |last=Moore |first=S.P. |title=The Definitive Neurological Surgery Board Review |publisher=[[Lippincott Williams & Wilkins]] |isbn=978-1405104593 |page=112 |year=2005 |url=https://books.google.com/books?id=mkK1a4mEx3IC&pg=PA112}}</ref> are [[congenital disorder|congenital]],<ref name="Pennington">{{cite book |last=Pennington |first=B.F. |title=Diagnosing Learning Disorders, Second Edition: A Neuropsychological Framework |publisher=[[Guilford Press]] |isbn=978-1606237861 |pages=3–10 |year=2008 |url=https://books.google.com/books?id=LVV10L62z6kC&pg=PA3}}</ref> and linked to [[Mutation|genetic]] and [[chromosome abnormality|chromosomal]] mutations.<ref name="Pennington"/> A rare group of congenital [[cephalic disorder]]s known as [[lissencephaly]] is characterised by the lack of, or inadequacy of, cortical folding.<ref name="Govaert">{{cite book |last1=Govaert |first1=P. |last2=de Vries |first2=L.S. |title=An Atlas of Neonatal Brain Sonography: (CDM 182–183) |publisher=[[John Wiley & Sons]] |isbn=978-1898683568 |pages=89–92 |year=2010 |url=https://books.google.com/books?id=FzcaxpvV1JUC&pg=PA89}}</ref> Normal [[prenatal development|development]] of the brain can be affected during [[pregnancy]] by [[nutritional deficiencies]],<ref name="Perese">{{cite book |last=Perese |first=E.F. |title=Psychiatric Advanced Practice Nursing: A Biopsychsocial Foundation for Practice |publisher=[[F.A. Davis]] |isbn=978-0803629998 |pages=82–88 |year=2012 |url=https://books.google.com/books?id=6X_2AAAAQBAJ&pg=PA82}}</ref> [[teratology|teratogen]]s,<ref name="Kearney">{{cite book |last1=Kearney |first1=C. |last2=Trull |first2=T.J. |title=Abnormal Psychology and Life: A Dimensional Approach |publisher=[[Cengage Learning]] |isbn=978-1337098106 |page=395 |year=2016 |url=https://books.google.com/books?id=B9q5DQAAQBAJ&pg=PA395}}</ref> [[infectious diseases]],<ref name="Stevenson">{{cite book |last1=Stevenson |first1=D.K. |last2=Sunshine |first2=P. |last3=Benitz |first3=W.E. |title=Fetal and Neonatal Brain Injury: Mechanisms, Management and the Risks of Practice |publisher=[[Cambridge University Press]] |isbn=978-0521806916 |page=191 |year=2003 |url=https://books.google.com/books?id=RuekFAj_tIAC&pg=PA191}}</ref> and by the use of [[Recreational drug use|recreational drugs]] and [[Fetal alcohol spectrum disorders|alcohol]].<ref name="Perese"/><ref name="Dewhurst">{{cite book |last=Dewhurst |first=John |title=Dewhurst's Textbook of Obstetrics and Gynaecology |publisher=[[John Wiley & Sons]] |isbn=978-0470654576 |page=43 |year=2012 |url=https://books.google.com/books?id=HfakBRceodcC&pg=PA43}}</ref>

===Stroke===
{{main|Stroke}}
[[File:Parachemableedwithedema.png|thumb|upright|[[CT scan]] of a [[cerebral hemorrhage]], showing an intraparenchymal bleed (bottom arrow) with surrounding edema (top arrow)]]

A [[stroke]] is a [[ischemia|decrease in blood supply]] to an area of the brain causing [[cell death]] and [[Brain damage#Causes|brain injury]]. This can lead to a wide range of [[Stroke#Signs and symptoms|symptoms]], including the "[[FAST (stroke)|FAST]]" symptoms of facial droop, arm weakness, and speech difficulties (including [[dysarthria|with speaking]] and [[dysphasia|finding words or forming sentences]]).<ref>{{cite journal |last1=Harbison |first1=J. |last2=Massey |first2=A. |last3=Barnett |first3=L. |last4=Hodge |first4=D. |last5=Ford |first5=G.A. | title=Rapid ambulance protocol for acute stroke | journal=Lancet | volume=353 | issue=9168 | pages=1935 | date=June 1999 | pmid=10371574 | doi=10.1016/S0140-6736(99)00966-6 }}</ref> Symptoms relate to the function of the affected area of the brain and can point to the likely site and cause of the stroke. Difficulties with movement, speech, or sight usually relate to the cerebrum, whereas [[ataxia|imbalance]], [[diplopia|double vision]], [[vertigo]] and symptoms affecting more than one side of the body usually relate to the brainstem or cerebellum.{{sfn|Davidson's|2010|p=1183}}

Most strokes result from loss of blood supply, typically because of an [[embolus]], rupture of a [[atheroma|fatty plaque]] or [[arteriosclerotic|narrowing of small arteries]]. Strokes can also result from [[Stroke#Hemorrhagic|bleeding within the brain]].{{sfn|Davidson's|2010|p=1180-1}} [[Transient ischemic attack|Transient ischaemic attack]]s (TIAs) are strokes in which symptoms resolve within 24 hours.{{sfn|Davidson's|2010|p=1180-1}} Investigation into the stroke will involve a [[medical examination]] (including a [[neurological examination]]) and the taking of a [[medical history]], focusing on the duration of the symptoms and risk factors (including [[Hypertension|high blood pressure]], [[atrial fibrillation]], and [[tobacco smoking|smoking]]).{{sfn|Davidson's|2010|p=1183-1185}}{{sfn|Davidson's|2010|p=1181}} Further investigation is needed in younger patients.{{sfn|Davidson's|2010|p=1183-1185}} An [[ECG]] and [[biotelemetry]] may be conducted to identify [[atrial fibrillation]]; an [[ultrasound]] can investigate [[carotid stenosis|narrowing]] of the [[Common carotid artery|carotid arteries]]; an [[echocardiogram]] can be used to look for clots within the heart, [[Valvular heart disease|diseases of the heart valves]] or the presence of a [[patent foramen ovale]].{{sfn|Davidson's|2010|p=1183-1185}} [[Blood test]]s are routinely done as part of the [[Medical diagnosis#Other diagnostic procedure methods|workup]] including [[Diabetes mellitus#Diagnosis|diabetes tests]] and a [[lipid profile]].{{sfn|Davidson's|2010|p=1183-1185}}

Some treatments for stroke are time-critical. These include [[thrombolysis|clot dissolution]] or [[embolectomy|surgical removal of a clot]] for [[Brain ischemia|ischaemic strokes]], and [[decompression (surgery)|decompression]] for [[Intracranial hemorrhage|haemorrhagic strokes]].{{sfn|Davidson's|2010|p=1185-1189}}<ref>{{cite journal |last1=Goyal |first1=M. |display-authors=etal |title=Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials |journal=The Lancet |date=April 2016 |volume=387 |issue=10029 |pages=1723–1731 |doi=10.1016/S0140-6736(16)00163-X |pmid=26898852 }}</ref> As stroke is time critical,<ref>{{cite journal |last1=Saver |first1=J. L. |title=Time is brain—quantified |journal=Stroke |date=December 8, 2005 |volume=37 |issue=1 |pages=263–266 |doi=10.1161/01.STR.0000196957.55928.ab|pmid=16339467 }}</ref> hospitals and even pre-hospital care of stroke involves expedited investigations – usually a [[CT scan]] to investigate for a haemorrhagic stroke and a [[CT angiogram|CT]] or [[MR angiogram]] to evaluate arteries that supply the brain.{{sfn|Davidson's|2010|p=1183-1185}} [[MRI scan]]s, not as widely available, may be able to demonstrate the affected area of the brain more accurately, particularly with ischaemic stroke.{{sfn|Davidson's|2010|p=1183-1185}}

Having experienced a stroke, a person may be admitted to a [[stroke unit]], and treatments may be directed as [[secondary prevention|preventing]] future strokes, including ongoing [[anticoagulation]] (such as [[aspirin]] or [[clopidogrel]]), [[Antihypertensive drug|antihypertensives]], and [[lipid-lowering agent|lipid-lowering drugs]].{{sfn|Davidson's|2010|p=1185-1189}} A [[multidisciplinary team]] including [[speech pathologist]]s, [[physiotherapists]], [[occupational therapist]]s, and [[psychologist]]s plays a large role in supporting a person affected by a stroke and their [[physical medicine and rehabilitation|rehabilitation]].<ref>{{cite journal |last1=Winstein |first1=C.J. |display-authors=etal |title=Guidelines for adult stroke rehabilitation and recovery |journal=Stroke |date=June 2016 |volume=47 |issue=6 |pages=e98–e169 |doi=10.1161/STR.0000000000000098|pmid=27145936 }}</ref>{{sfn|Davidson's|2010|p=1183-1185}} A history of stroke increases the risk of developing dementia by around 70%, and recent stroke increases the risk by around 120%.<ref>{{Cite journal|last=Kuźma|first=Elżbieta|last2=Lourida|first2=Ilianna|last3=Moore|first3=Sarah F.|last4=Levine|first4=Deborah A.|last5=Ukoumunne|first5=Obioha C.|last6=Llewellyn|first6=David J.|date=November 2018 |title=Stroke and dementia risk: A systematic review and meta-analysis|journal=Alzheimer's & Dementia |volume=14 |issue=11 |pages=1416–1426 |doi=10.1016/j.jalz.2018.06.3061 |pmid=30177276|pmc=6231970|issn=1552-5260}}</ref>

===Brain death===
{{main|Brain death}}
Brain death refers to an irreversible total loss of brain function.<ref name="GOILA2009">{{cite journal |last1=Goila |first1=AK |last2=Pawar |first2=M |title=The diagnosis of brain death |journal=Indian Journal of Critical Care Medicine |date=2009 |volume=13 |issue=1 |pages=7–11 |doi=10.4103/0972-5229.53108|pmid=19881172 |pmc=2772257 }}</ref><ref name=":0">{{Cite journal |last=Wijdicks |first=EFM |date=January 8, 2002 |title=Brain death worldwide: accepted fact but no global consensus in diagnostic criteria |journal=Neurology |volume=58 |issue=1 |pages=20–25 |pmid=11781400 |doi=10.1212/wnl.58.1.20}}</ref> This is characterised by [[coma]], loss of [[reflex]]es, and [[apnoea]],<ref name=GOILA2009/> however, the declaration of brain death varies geographically and is not always accepted.<ref name=":0" /> In some countries there is also a defined syndrome of [[brainstem death]].<ref>{{cite journal |last1=Dhanwate |first1=AD |title=Brainstem death: A comprehensive review in Indian perspective. |journal=Indian Journal of Critical Care Medicine |date=September 2014 |volume=18 |issue=9 |pages=596–605 |pmid=25249744 |doi=10.4103/0972-5229.140151 |pmc=4166875}}</ref> Declaration of brain death can have profound implications as the declaration, under the principle of [[Futile medical care|medical futility]], will be associated with the withdrawal of life support,{{sfn|Davidson's|2010|p=1158}} and as those with brain death often have organs suitable for [[organ donation]].<ref name=":0" />{{sfn|Davidson's|2010|p=200}} The process is often made more difficult by poor communication with patients' families.<ref name="Urden">{{cite book |last1=Urden |first1=L.D. |last2=Stacy |first2=K.M. |last3=Lough |first3=M.E. |title=Priorities in Critical Care Nursing – E-Book |publisher=[[Elsevier Health Sciences]] |isbn=978-0323294140 |pages=112–113 |year=2013 |url=https://books.google.com/books?id=lLvwAwAAQBAJ&pg=PA112}}</ref>

When brain death is suspected, reversible [[differential diagnosis|differential diagnoses]] such as, electrolyte, neurological and drug-related cognitive suppression need to be excluded.<ref name="GOILA2009" />{{sfn|Davidson's|2010|p=1158}} Testing for reflexes{{efn|Including the [[vestibulo-ocular reflex]], [[corneal reflex]], [[gag reflex]] and dilation of the pupils in response to light ,{{sfn|Davidson's|2010|p=1158}}}} can be of help in the decision, as can the absence of response and breathing.{{sfn|Davidson's|2010|p=1158}} Clinical observations, including a total lack of responsiveness, a known diagnosis, and [[neural imaging]] evidence, may all play a role in the decision to pronounce brain death.<ref name="GOILA2009" />

==Society and culture==
[[Neuroanthropology]] is the study of the relationship between culture and the brain. It explores how the brain gives rise to culture, and how culture influences brain development.<ref>{{Cite book |last1=Domínguez |first1=J.F. |last2=Lewis |first2=E.D. |last3=Turner |first3=R. |last4=Egan |first4=G.F. |editor1-last=Chiao |editor1-first=J.Y. |title=The Brain in Culture and Culture in the Brain: A Review of Core Issues in Neuroanthropology |journal=Progress in Brain Research |date=2009 |volume=178 |pages=43–6 |doi=10.1016/S0079-6123(09)17804-4 |pmid=19874961 |series=Special issue: Cultural Neuroscience: Cultural Influences on Brain Function |isbn=9780444533616 }}</ref> Cultural differences and their relation to brain development and structure are researched in different fields.<ref name="Cultural">{{cite web |title=Cultural Environment Influences Brain Function {{!}} Psych Central News |url=https://psychcentral.com/news/2010/08/04/cultural-environment-influences-brain-function/16380.html |website=Psych Central News |date=August 4, 2010 |deadurl=no |archiveurl=https://web.archive.org/web/20170117094114/http://psychcentral.com/news/2010/08/04/cultural-environment-influences-brain-function/16380.html |archivedate=January 17, 2017 }}</ref>

===The mind===
{{Main |Cognition |Mind}}
[[File:Phineas gage - 1868 skull diagram.jpg|thumb|right|upright|The skull of [[Phineas Gage]], with the path of the iron rod that passed through it without killing him, but altering his cognition. The case helped to convince people that mental functions were localized in the brain.<ref name=Macmillan/>]]

The [[philosophy of mind|philosophy of the mind]] studies such issues as the problem of understanding [[consciousness]] and the [[mind–body problem]]. The relationship between the brain and the [[mind]] is a significant challenge both philosophically and scientifically. This is because of the difficulty in explaining how mental activities, such as thoughts and emotions, can be implemented by physical structures such as neurons and [[synapse]]s, or by any other type of physical mechanism. This difficulty was expressed by [[Gottfried Leibniz]] in the analogy known as ''Leibniz's Mill'':

{{quote |One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception.

::— Leibniz, [[Monadology]]<ref>{{cite book |author=Rescher, N. |title=G. W. Leibniz's Monadology |year=1992 |publisher=Psychology Press |isbn=978-0-415-07284-7 |page=83}}</ref>}}

Doubt about the possibility of a mechanistic explanation of thought drove [[René Descartes]], and most other philosophers along with him, to [[Dualism (philosophy of mind)|dualism]]: the belief that the mind is to some degree independent of the brain.<ref>{{cite book |last=Hart |first=WD |year=1996 |editor=Guttenplan S |title=A Companion to the Philosophy of Mind |publisher=Blackwell |pages=265–267}}</ref> There has always, however, been a strong argument in the opposite direction. There is clear empirical evidence that physical manipulations of, or injuries to, the brain (for example by drugs or by lesions, respectively) can affect the mind in potent and intimate ways.<ref name=Churchland>{{cite book |last=Churchland |first=P.S. |title=Neurophilosophy |publisher=MIT Press |year=1989 |isbn=978-0-262-53085-9 |chapter-url=https://books.google.com/?id=hAeFMFW3rDUC |chapter=Ch. 8}}</ref><ref>{{cite journal |last1=Selimbeyoglu |first1=Aslihan |last2=Parvizi |first2=J |title=Electrical stimulation of the human brain: perceptual and behavioral phenomena reported in the old and new literature |journal=Frontiers in Human Neuroscience |date=2010 |volume=4 |page=46 |doi=10.3389/fnhum.2010.00046 |pmid=20577584 |pmc=2889679}}</ref> In the 19th century, the case of [[Phineas Gage]], a railway worker who was injured by a stout iron rod passing through his brain, convinced both researchers and the public that cognitive functions were localised in the brain.<ref name=Macmillan>{{cite book |last=Macmillan |first=Malcolm B. |year=2000 |title=An Odd Kind of Fame: Stories of Phineas Gage |publisher=[[MIT Press]] |url=https://books.google.com/?id=Qx4fMsTqGFYC |isbn=978-0-262-13363-0}}</ref> Following this line of thinking, a large body of empirical evidence for a close relationship between brain activity and mental activity has led most neuroscientists and contemporary philosophers to be [[Materialism|materialists]], believing that mental phenomena are ultimately the result of, or reducible to, physical phenomena.<ref>Schwartz, J.H. '' Appendix D: Consciousness and the Neurobiology of the Twenty-First Century''. In Kandel, E.R.; Schwartz, J.H.; Jessell, T.M. (2000). ''Principles of Neural Science, 4th Edition''.</ref>

===Brain size===
{{main|Brain size}}
The size of the brain and a person's [[intelligence]] are not strongly related.<ref>{{Cite book |url=https://books.google.com/?id=8DlS0gfO_QUC&pg=PT89 |title=50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior |last=Lilienfeld |first=S.O. |last2=Lynn |first2=S.J. |last3=Ruscio |first3=J. |last4=Beyerstein |first4=B.L. |date=2011 |publisher=John Wiley & Sons |isbn=9781444360745 |page=89}}</ref> Studies tend to indicate small to moderate [[correlations]] (averaging around 0.3 to 0.4) between brain volume and [[Intelligence quotient|IQ]].<ref>{{cite journal |last=McDaniel |first=M. |journal=Intelligence |volume=33 |issue=4 |pages=337–346 |year=2005 |url=http://www.people.vcu.edu/~mamcdani/Big-Brained%20article.pdf |title=Big-brained people are smarter |ref=harv |doi=10.1016/j.intell.2004.11.005 |deadurl=no |archiveurl=https://web.archive.org/web/20140906221726/http://www.people.vcu.edu/~mamcdani/Big-Brained%20article.pdf |archivedate=September 6, 2014 }}</ref> The most consistent associations are observed within the frontal, temporal, and parietal lobes, the hippocampi, and the cerebellum, but these only account for a relatively small amount of variance in IQ, which itself has only a partial relationship to general intelligence and real-world performance.<ref>{{cite journal |last1=Luders |first1=E. |display-authors=etal |title=Mapping the relationship between cortical convolution and intelligence: effects of gender |journal=Cerebral Cortex |date=September 2008 |volume=18 |issue=9 |pages=2019–26 |pmid=18089578 |doi=10.1093/cercor/bhm227 |pmc=2517107}}</ref><ref>{{Cite journal |last=Hoppe |first=C |last2=Stojanovic |first2=J |year=2008 |title=High-Aptitude Minds |journal=Scientific American Mind |volume=19 |issue=4 |pages=60–67 |doi=10.1038/scientificamericanmind0808-60}}</ref>

Other animals, including whales and elephants have larger brains than humans. However, when the [[brain-to-body mass ratio]] is taken into account, the human brain is almost twice as large as that of a [[bottlenose dolphin]], and three times as large as that of a [[Common chimpanzee|chimpanzee]]. However, a high ratio does not of itself demonstrate intelligence: very small animals have high ratios and the [[treeshrew]] has the largest quotient of any mammal.<ref>{{Cite web |url=http://genome.wustl.edu/genomes/view/tupaia_belangeri |title=Tupaia belangeri |publisher=The Genome Institute, Washington University |accessdate=January 22, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20100601201841/http://genome.wustl.edu/genomes/view/tupaia_belangeri/ |archivedate=June 1, 2010 }}</ref>

===In popular culture===
[[File:PhrenologyPix.jpg|thumb|upright|[[Phrenology]] summarized in an 1883 chart]]
Research has disproved some common [[List of common misconceptions#Brain|misconceptions about the brain]]. These include both ancient and modern myths. It is not true that neurons are not replaced after the age of two; nor that only [[Ten percent of the brain myth|ten per cent of the brain]] is used.<ref>{{cite book |last1=Jarrett |first1=C. |title=Great Myths of the Brain |publisher=John Wiley & Sons |isbn=9781118312711 |url=https://books.google.com/?id=fBPyBQAAQBAJ |date=2014-11-17 }}</ref> Popular culture has also oversimplified the [[Lateralization of brain function|lateralisation of the brain]], suggesting that functions are completely specific to one side of the brain or the other. [[Akio Mori]] coined the term [[game brain]] for the unreliably supported theory that spending long periods playing [[video game]]s harmed the brain's pre-frontal region and the expression of emotion and creativity.<ref>{{cite magazine|url=https://www.newscientist.com/article/dn2538-video-game-brain-damage-claim-criticised.html|title=Video game "brain damage" claim criticised|accessdate=February 6, 2008|first=Helen |last=Phillips|date=July 11, 2002|magazine=[[New Scientist]] |deadurl=no|archiveurl=https://web.archive.org/web/20090111065557/http://www.newscientist.com/article/dn2538-video-game-brain-damage-claim-criticised.html|archivedate=January 11, 2009}}</ref>

Historically, the brain featured in popular culture through [[phrenology]], a [[pseudoscience]] that assigned personality attributes to different regions of the cortex. The cortex remains important in popular culture as covered in books and satire.<ref>{{cite news |last1=Popova |first1=Maria |title='Brain Culture': How Neuroscience Became a Pop Culture Fixation |url=https://www.theatlantic.com/health/archive/2011/08/brain-culture-how-neuroscience-became-a-pop-culture-fixation/243810/ |work=The Atlantic |date=August 18, 2011 |deadurl=no |archiveurl=https://web.archive.org/web/20170728165041/https://www.theatlantic.com/health/archive/2011/08/brain-culture-how-neuroscience-became-a-pop-culture-fixation/243810/ |archivedate=July 28, 2017 }}</ref><ref>{{cite book |last1=Thornton |first1=Davi Johnson |title=Brain Culture. Neuroscience and Popular Media |date=2011 |publisher=Rutgers University Press |isbn=978-0813550138}}</ref> [[Brain in science fiction|The brain features in science fiction]], with themes such as [[brain transplant]]s and [[Cyborgs in fiction|cyborgs]] (beings with features like partly [[artificial brain]]s).<ref>[http://web.mit.edu/digitalapollo/Documents/Chapter1/cyborgs.pdf Cyborgs and Space] {{webarchive|url=https://web.archive.org/web/20111006190955/http://web.mit.edu/digitalapollo/Documents/Chapter1/cyborgs.pdf |date=October 6, 2011 }}, in ''Astronautics'' (September 1960), by Manfred E. Clynes and Nathan S. Kline.</ref> The 1942 science fiction book (adapted three times for cinema) ''[[Donovan's Brain]]'' tells the tale of an [[isolated brain]] kept alive ''in vitro'', gradually taken over by a malign intelligence.<ref>{{cite book |author=Bergfelder, Tim |title=International Adventures: German Popular Cinema and European Co-productions in the 1960s |url=https://books.google.com/books?id=B1Nj41yxvZkC&pg=PA129 |year=2005 |publisher=Berghahn Books |isbn=978-1-57181-538-5 |page=129}}</ref>


==History==
{{Main |History of neuroscience}}

=== Early history===
[[File:Hieroglyph brain.svg|thumb|right|upright=1.0|[[Hieroglyph]] for the word "brain" (c.1700 BC)]]
The [[Edwin Smith Papyrus]], an [[ancient Egypt]]ian [[medical literature|medical treatise]] written in the 17th century BC, contains the earliest recorded reference to the brain. The [[hieroglyph]] for brain, occurring eight times in this papyrus, describes the symptoms, diagnosis, and prognosis of two traumatic injuries to the head. The papyrus mentions the external surface of the brain, the effects of injury (including seizures and [[aphasia]]), the meninges, and cerebrospinal fluid.<ref name=Kandel>{{cite book | authorlink=Eric R. Kandel | last=Kandel | first=ER |author2=Schwartz JH |author3=Jessell TM | title=Principles of Neural Science | edition=4th | publisher=McGraw-Hill | location=New York | year=2000 | isbn=978-0-8385-7701-1| title-link=Principles of Neural Science }}</ref><ref name="Adelman">{{cite book |last1=Gross|first1=Charles G. |editor-first=George |editor-last=Adelman |title=Encyclopedia of neuroscience |date=1987 |publisher=Birkhäeuser |location=Boston |isbn=978-0817633356 |pages=843–847 |edition=2. |url=http://www.princeton.edu/~cggross/Hist_Neurosci_Ency_neurosci.pdf |deadurl=no |archiveurl=https://web.archive.org/web/20130505044949/http://www.princeton.edu/~cggross/Hist_Neurosci_Ency_neurosci.pdf |archivedate=May 5, 2013 }}</ref>

In the fifth century BC, [[Alcmaeon of Croton]] in [[Magna Grecia]], first considered the brain to be the [[Sensorium|seat of the mind]].<ref name="Adelman"/> Also in the [[Fifth-century Athens|fifth century BC in Athens]], the unknown author of ''[[On the Sacred Disease]]'', a medical treatise which is part of the [[Hippocratic Corpus]] and traditionally attributed to [[Hippocrates]], believed the brain to be the seat of intelligence. [[Aristotle]], in his [[Aristotle's biology|biology]] initially believed the heart to be the seat of [[intelligence]], and saw the brain as a cooling mechanism for the blood. He reasoned that humans are more rational than the beasts because, among other reasons, they have a larger brain to cool their hot-bloodedness.<ref name=Bear>{{cite book | last=Bear | first=M.F. |author2=B.W. Connors |author3=M.A. Paradiso | title=Neuroscience: Exploring the Brain | location=Baltimore | publisher=Lippincott | year=2001 | isbn=978-0-7817-3944-3}}</ref> Aristotle did describe the meninges and distinguished between the cerebrum and cerebellum.<ref>von Staden, p.157</ref> [[Herophilus]] of [[Chalcedon]] in the fourth and third centuries BC distinguished the cerebrum and the cerebellum, and provided the first clear description of the [[Ventricular system|ventricles]]; and with [[Erasistratus]] of [[Kea (island)|Ceos]] experimented on living brains. Their works are now mostly lost, and we know about their achievements due mostly to secondary sources. Some of their discoveries had to be re-discovered a millennium after their deaths.<ref name="Adelman"/> Anatomist physician [[Galen]] in the second century AD, during the time of the [[Roman Empire]], dissected the brains of sheep, monkeys, dogs, and pigs. He concluded that, as the cerebellum was denser than the brain, it must control the [[muscle]]s, while as the cerebrum was soft, it must be where the senses were processed. Galen further theorized that the brain functioned by movement of animal spirits through the ventricles.<ref name="Adelman"/><ref name=Bear/>

===Renaissance===

In 1316, [[Mondino de Luzzi]]'s ''Anathomia'' began the modern study of brain anatomy.<ref>{{cite book |last1=Swanson |first1=Larry W. |title=Neuroanatomical Terminology: A Lexicon of Classical Origins and Historical Foundations |publisher=Oxford University Press |isbn=9780195340624 |url=https://books.google.com/?id=--PRAwAAQBAJ&pg=PA7&lpg=PA7&dq=nervous+system+anatomy+stagnation+galen+to+vesalius#v=onepage|date=2014-08-12 }}</ref>
[[Niccolò Massa]] discovered in 1536 that the ventricles were filled with fluid.<ref name=LOKHORST2016/> [[Archangelo Piccolomini]] of [[Rome]] was the first to distinguish between the cerebrum and cerebral cortex.<ref name="Gross1999" /> In 1543 [[Andreas Vesalius]] published his seven-volume ''[[De humani corporis fabrica]]''.<ref name="Gross1999" /><ref name="MARSHALL">{{cite book |last1=Marshall |first1=Louise H. |last2=Magoun |first2=Horace W. |title=Discoveries in the Human Brain: Neuroscience Prehistory, Brain Structure, and Function |publisher=Springer Science & Business Media |isbn=978-1-475-74997-7 |page=44 |url=https://books.google.com/?id=guncBwAAQBAJ&pg=PR5&dq=vesalius+and+the+human+brain#v=onepage&q=vesalius&f=false|date=2013-03-09 }}</ref><ref>{{cite book |last1=Holtz |first1=Anders |last2=Levi |first2=Richard |title=Spinal Cord Injury |publisher=Oxford University Press |isbn=9780199706815 |url=https://books.google.com/?id=ZvCqdwWwGRsC&pg=PA5&lpg=PA5#v=onepage|date=2010-07-20 }}</ref> The seventh book covered the brain and eye, with detailed images of the ventricles, cranial nerves, [[pituitary gland]], meninges, structures of the [[human eye|eye]], the vascular supply to the brain and spinal cord, and an image of the peripheral nerves.<ref name="tessman">{{cite journal | author=Tessman, Patrick A. | author2=Suarez, Jose I. | year=2002 | title=Influence of early printmaking on the development of neuroanatomy and neurology | journal=Archives of Neurology | volume=59 | issue=12 | pages=1964–1969 | pmid=12470188 | doi=10.1001/archneur.59.12.1964 }}</ref> Vesalius rejected the common belief that the ventricles were responsible for brain function, arguing that many animals have a similar ventricular system to humans, but no true intelligence.<ref name="Gross1999">{{cite book |last1=Gross |first1=Charles G. |title=Brain, vision, memory : tales in the history of neuroscience. |date=1999 |publisher=MIT |location=Cambridge, Mass. |isbn=978-0262571357 |pages=37–51 |edition=1st MIT Press pbk.}}</ref>

[[René Descartes]] proposed the theory of [[Mind-body dualism|dualism]] to tackle the issue of the brain's relation to the mind. He suggested that the [[pineal gland]] was where the mind interacted with the body after recording the brain mechanisms responsible for circulating cerebrospinal fluid.<ref name=LOKHORST2016>{{cite web |last1=Lokhorst |first1=Gert-Jan |title=Descartes and the Pineal Gland |url=https://plato.stanford.edu/entries/pineal-gland/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |accessdate=March 11, 2017 |date=January 1, 2016}}</ref> This dualism likely provided impetus for later anatomists to further explore the relationship between the anatomical and functional aspects of brain anatomy.<ref name=OCONNOR2003>{{cite journal |last1=O'Connor |first1=James |title=Thomas Willis and the background to Cerebri Anatome |journal=Journal of the Royal Society of Medicine |date=2003 |volume=96 |issue=3 |pages=139–143 |pmc=539424 |pmid=12612118 |doi=10.1258/jrsm.96.3.139}}</ref>

[[Thomas Willis]] is considered a second pioneer in the study of neurology and brain science. In 1664 in ''Cerebri Anatome'' ({{lang-la |Anatomy of the brain}}),{{efn|Illustrated by architect [[Christopher Wren]]<ref name="Gross1999" />}} followed by ''Cerebral Pathology'' in 1667. In these he described the structure of the cerebellum, the ventricles, the cerebral hemispheres, the brainstem, and the cranial nerves, studied its blood supply; and proposed functions associated with different areas of the brain.<ref name="Gross1999" /> The circle of Willis was named after his investigations into the blood supply of the brain, and he was the first to use the word "neurology."<ref name="Emery2000">{{cite journal |last1=EMERY |first1=ALAN |title=A Short History of Neurology: The British Contribution 1660–1910. Edited by F. CLIFFORD ROSE. (Pp. 282; illustrated; £25 Paperback; ISBN 07506 4165 7.) Oxford: Butterworth-Heinemann |journal=Journal of Anatomy |date=October 2000 |volume=197 |issue=3 |pages=513–518 |doi=10.1046/j.1469-7580.2000.197305131.x|pmc=1468164 }}</ref> Willis removed the brain from the body when examining it, and rejected the commonly held view that the cortex only consisted of blood vessels and the view of the last two millennia that the cortex was only incidentally important.<ref name="Gross1999" />

In the late 19th century, [[Emil du Bois-Reymond]] and [[Hermann von Helmholtz]], following the work of their teacher [[Johannes Peter Müller]] showed the electrical inpulses which pass along nerves; but unlike Müller's views, that such impulses were able to be observed.<ref>{{cite web |last1=Sabbatini |first1=Renato M.E. |title=Sabbatini, R.M.E.: The Discovery of Bioelectricity. Nerve Conduction |url=http://www.cerebromente.org.br/n06/historia/bioelectr3_i.htm |website=www.cerebromente.org.br |accessdate=June 10, 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170626011707/http://www.cerebromente.org.br/n06/historia/bioelectr3_i.htm |archivedate=June 26, 2017 }}</ref> [[Richard Caton]] in 1875 demonstrated electrical impulses in the cerebral hemispheres of rabbits and monkeys.<ref>{{cite journal |last1=Karbowski |first1=Kazimierz |title=Sixty Years of Clinical Electroencephalography |journal=European Neurology |date=February 14, 2008 |volume=30 |issue=3 |pages=170–175 |doi=10.1159/000117338|pmid=2192889 }}</ref> In the 1820s, [[Jean Pierre Flourens]] pioneered the experimental method of damaging specific parts of animal brains describing the effects on movement and behavior.<ref>{{cite journal |last1=Pearce |first1=J.M.S. |title=Marie-Jean-Pierre Flourens (1794–1867) and Cortical Localization |journal=European Neurology |date=March 17, 2009 |volume=61 |issue=5 |pages=311–314 |doi=10.1159/000206858|pmid=19295220 }}</ref>
{{multiple image

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| image1 = 1543,AndreasVesalius'Fabrica,BaseOfTheBrain.png
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| caption1 = Drawing of the base of the brain, from [[Andreas Vesalius]]'s 1543 work ''[[De humani corporis fabrica]]''
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| image2 = View of a Skull.jpg
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| caption2 = One of [[Leonardo da Vinci]]'s sketches of the human skull
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===Modern period===
{{Further |Neuropsychiatry}}
{{multiple image

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| image1 = Golgi 1885 Plate XXII.JPG
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| alt1 =
| caption1 = Drawing by [[Camillo Golgi]] of vertical section of rabbit [[hippocampus]], from his "Sulla fina anatomia degli organi centrali del sistema nervoso", 1885


| image2 = CajalCerebellum.jpg
| width2 =
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| caption2 = Drawing of cells in chick [[cerebellum]] by [[Santiago Ramón y Cajal]], from "Estructura de los centros nerviosos de las aves", Madrid, 1905
}}
Studies of the brain became more sophisticated with the use of the [[microscope]] and the development of a [[silver stain]]ing [[Golgi method|method]] by [[Camillo Golgi]] during the 1880s. This was able to show the intricate structures of single neurons.<ref name="DECARLOS2007">{{cite journal |last1=De Carlos |first1=Juan A. |last2=Borrell |first2=José |title=A historical reflection of the contributions of Cajal and Golgi to the foundations of neuroscience |journal=Brain Research Reviews |date=August 2007 |volume=55 |issue=1 |pages=8–16 |doi=10.1016/j.brainresrev.2007.03.010|pmid=17490748 |hdl=10261/62299 }}</ref> This was used by [[Santiago Ramón y Cajal]] and led to the formation of the [[neuron doctrine]], the then revolutionary hypothesis that the neuron is the functional unit of the brain. He used microscopy to uncover many cell types, and proposed functions for the cells he saw.<ref name="DECARLOS2007" /> For this, Golgi and Cajal are considered the founders of [[History of neuroscience|twentieth century neuroscience]], both sharing the [[Nobel prize]] in 1906 for their studies and discoveries in this field.<ref name="DECARLOS2007" />

[[Charles Scott Sherrington|Charles Sherrington]] published his influential 1906 work ''The Integrative Action of the Nervous System'' examining the function of reflexes, evolutionary development of the nervous system, functional specialisation of the brain, and layout and cellular function of the central nervous system.<ref>{{cite journal | last1=Burke | first1=R.E. | title=Sir Charles Sherrington's The integrative action of the nervous system: a centenary appreciation | url=http://brain.oxfordjournals.org/content/130/4/887 | journal=Brain | volume=130 | issue= Pt 4| pages=887–894 | doi=10.1093/brain/awm022 | pmid=17438014 | date=April 2007 | deadurl=no | archiveurl=http://archive.wikiwix.com/cache/20150527230739/http://brain.oxfordjournals.org/content/130/4/887 | archivedate=May 27, 2015 | df=mdy-all }}</ref> [[John Farquhar Fulton]], founded the ''Journal of Neurophysiology'' and published the first comprehensive textbook on the physiology of the nervous system during 1938.<ref name="SQUIRE1996">{{cite book |editor1-last=Squire |editor1-first=Larry R. |title=The history of neuroscience in autobiography |date=1996 |publisher=Society for Neuroscience |location=Washington DC |isbn=978-0126603057 |pages=475–97}}</ref> [[History of neuroscience#Twentieth century|Neuroscience during the twentieth century]] began to be recognised as a distinct unified academic discipline, with [[David Rioch]], [[Francis O. Schmitt]], and [[Stephen Kuffler]] playing critical roles in establishing the field.<ref name="COWAN2000">{{Cite journal |last1=Cowan |first1=W.M. |last2=Harter |first2=D.H. |last3=Kandel |first3=E.R. |date=2000 |title=The emergence of modern neuroscience: Some implications for neurology and psychiatry |journal=Annual Review of Neuroscience |volume=23 |pages=345–346 |doi=10.1146/annurev.neuro.23.1.343 |pmid=10845068}}</ref> Rioch originated the integration of basic anatomical and physiological research with clinical psychiatry at the [[Walter Reed Army Institute of Research]], starting in the 1950s.<ref>{{cite book |last1=Brady |first1=Joseph V. |last2=Nauta |first2=Walle J. H. |title=Principles, Practices, and Positions in Neuropsychiatric Research: Proceedings of a Conference Held in June 1970 at the Walter Reed Army Institute of Research, Washington, D.C., in Tribute to Dr. David Mckenzie Rioch upon His Retirement as Director of the Neuropsychiatry Division of That Institute |publisher=Elsevier |isbn=9781483154534 |page=vii |url=https://books.google.com/?id=AK4aAwAAQBAJ&pg=PR7&lpg=PR7 |date=2013-10-22 }}</ref> During the same period, Schmitt established the [[Neuroscience Research Program]], an inter-university and international organisation, bringing together biology, medicine, psychological and behavioural sciences. The word neuroscience itself arises from this program.<ref>{{cite journal |last1=Adelman |first1=George |title=The Neurosciences Research Program at MIT and the Beginning of the Modern Field of Neuroscience |journal=Journal of the History of the Neurosciences |date=January 15, 2010 |volume=19 |issue=1 |pages=15–23 |doi=10.1080/09647040902720651|pmid=20391098 }}</ref>

[[Paul Broca]] associated regions of the brain with specific functions, in particular language in [[Broca's area]], following work on brain-damaged patients.<ref name="Neural Science 2000">Principles of Neural Science, 4th ed. Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, eds. McGraw-Hill:New York, NY. 2000.</ref> [[John Hughlings Jackson]] described the function of the [[motor cortex]] by watching the progression of [[epileptic seizure]]s through the body. [[Carl Wernicke]] described [[Wernicke's area|a region]] associated with language comprehension and production. [[Korbinian Brodmann]] divided regions of the brain based on the appearance of cells.<ref name="Neural Science 2000" /> By 1950, Sherrington, [[James Papez|Papez]], and [[Paul D. MacLean|MacLean]] had identified many of the brainstem and limbic system functions.<ref name="Papez">{{cite journal |last1=Papez |first1=J.W. |title=A proposed mechanism of emotion. 1937. |journal=The Journal of Neuropsychiatry and Clinical Neurosciences |date=February 1995 |volume=7 |issue=1 |pages=103–12 |pmid=7711480 |doi=10.1176/jnp.7.1.103}}</ref><ref>{{Cite journal |title=A proposed mechanism of emotion. 1937 [classical article] |journal=The Journal of Neuropsychiatry and Clinical Neurosciences |volume=7 |issue=1 |pages=103–112 |doi=10.1176/jnp.7.1.103 |pmid=7711480 |date=February 1, 1995|last1=Papez |first1=J. W. }}</ref><ref>{{cite journal |last1=Lambert |first1=Kelly G. |title=The life and career of Paul MacLean |journal=Physiology & Behavior |date=August 2003 |volume=79 |issue=3 |pages=343–349 |doi=10.1016/S0031-9384(03)00147-1}}</ref> The capacity of the brain to re-organise and change with age, and a recognised critical development period, were attributed to [[neuroplasticity]], pioneered by [[Margaret Kennard]], who experimented on monkeys during the 1930-40s.<ref>{{cite book |last1=Chatterjee |first1=Anjan |last2=Coslett |first2=H. Branch |title=The Roots of Cognitive Neuroscience: Behavioral Neurology and Neuropsychology |publisher=OUP USA |isbn=9780195395549 |pages=337–8 |url=https://books.google.com/?id=f9dMAgAAQBAJ&pg=PA338&dq=neuroscience+20th+century#v=onepage|date=December 2013 }}</ref>

[[Harvey Cushing]] (1869–1939) is recognised as the first proficient [[neurosurgery|brain surgeon]] in the world.<ref name="M.Bliss">{{cite book |url=https://books.google.com/?id=EzbjVnjwjPYC |last=Bliss |first=Michael |title=Harvey Cushing : A Life in Surgery: A Life in Surgery |pages=ix–x |publisher=Oxford University Press |location=USA |date=October 1, 2005|isbn=9780195346954 }}</ref> In 1937, [[Walter Dandy]] began the practice of vascular [[neurosurgery]] by performing the first surgical clipping of an [[intracranial aneurysm]].<ref>{{cite journal | last1=Kretzer | first1=RM | last2=Coon | first2=AL | last3=Tamargo | first3=RJ | date=June 2010 | title=Walter E. Dandy's contributions to vascular neurosurgery | journal=Journal of Neurosurgery | volume=112 | issue=6 | pages=1182–91 | doi=10.3171/2009.7.JNS09737 | pmid=20515365 }}</ref>

==Comparative anatomy==
{{See also|Evolution of the brain}}
The human brain has many properties that are common to all [[vertebrate]] brains.<ref>{{cite book |last1=Glees |first1=Paul |title=The Human Brain |date=2005 |publisher=Cambridge University Press |isbn=9780521017817 |page=1 |url=https://books.google.com/?id=kWgeOPGdl_MC&pg=PA1#v=onepage}}</ref> Many of its features are common to all [[mammal]]ian brains,<ref name="Simpkins">{{cite book |first1=C. Alexander |last1=Simpkins |first2=Annellen M. |last2=Simpkins |title=Neuroscience for Clinicians: Evidence, Models, and Practice |isbn=978-1461448426 |publisher=[[Springer Science & Business Media]] |year=2012 |page=143 |url=https://books.google.com/books?id=QG4LC-d2sm8C&pg=PA143}}</ref> most notably a six-layered cerebral cortex and a set of associated structures,<ref name="Bornstein">{{cite book |first1=Marc H. |last1=Bornstein |first2=Michael E. |last2=Lamb |title=Developmental Science: An Advanced Textbook |isbn=978-1136282201 |publisher=[[Psychology Press]] |year=2015 |page=220 |url=https://books.google.com/books?id=XhA-CgAAQBAJ&pg=PA220}}</ref> including the hippocampus and [[amygdala]].<ref name="Bernstein">{{cite book |first=Douglas |last=Bernstein |title=Essentials of Psychology |isbn=978-0495906933 |publisher=[[Cengage Learning]] |year=2010 |page=64 |url=https://books.google.com/books?id=rd77N0KsLVkC&pg=PA64}}</ref> The cortex is proportionally larger in greater mammals and humans than many other mammals.<ref name="HOFMAN2014">{{cite journal |last1=Hofman |first1=Michel A. |title=Evolution of the human brain: when bigger is better |journal=Frontiers in Neuroanatomy |date=March 27, 2014 |volume=8 |pages=15 |doi=10.3389/fnana.2014.00015|pmid=24723857 |pmc=3973910 }}</ref> Humans have more association cortex, sensory and motor parts than smaller mammals such as the rat and the cat.<ref>{{Cite book |title=Psychology |last=Gray |first=Peter |publisher=Worth Publishers |year=2002 |isbn=978-0716751625 |edition=4th |pages= |oclc=46640860}}</ref>

As a [[primate]] brain, the human brain has a much larger cerebral cortex, in proportion to body size, than most mammals,<ref name="Bernstein" /> and a highly developed visual system.<ref name="Lu">{{cite book |url=https://books.google.com/books?id=nYr6AQAAQBAJ&pg=PA3 |title=Visual Psychophysics: From Laboratory to Theory |publisher=[[MIT Press]] |year=2013 |isbn=978-0262019453 |page=3 |last1=Lu |first1=Zhong-Lin |last2=Dosher |first2=Barbara }}</ref><ref name="Sharwood Smith">{{cite book |url=https://books.google.com/books?id=fe-SDQAAQBAJ&pg=PA206 |title=Introducing Language and Cognition |publisher=[[Cambridge University Press]] |year=2017 |isbn=978-1107152892 |page=206 |first=Mike |last=Sharwood Smith}}</ref>

As a [[hominidae|hominid]] brain, the human brain is substantially enlarged even in comparison to the brain of a typical monkey. The sequence of [[human evolution]] from ''[[Australopithecus]]'' (four million years ago) to [[human|''Homo sapiens'']] (modern humans) was marked by a steady increase in brain size.<ref name="Kolb and Whishaw">{{cite book |last1=Kolb |first1=Bryan |last2=Whishaw |first2=Ian Q. |title=Introduction to Brain and Behavior |publisher=[[Macmillan Higher Education]] |isbn=978-1464139604 |page=21 |year=2013 |url=https://books.google.com/books?id=teUkAAAAQBAJ&q}}</ref><ref name="Nieuwenhuys">{{cite book |last1=Nieuwenhuys |first1=Rudolf |last2=ten Donkelaar |first2=Hans J. |last3=Nicholson |first3=Charles |title=The Central Nervous System of Vertebrates |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-3642182624 |page=2127 |year=2014 |url=https://books.google.com/books?id=gsDqCAAAQBAJ&pg=PA2127}}</ref> As brain size increased, this altered the size and shape of the skull,<ref name="Lee Lerner">{{cite book |last1=Lerner |first1=Lee |last2=Lerner |first2=Brenda Wilmoth |title=The Gale Encyclopedia of Science: Pheasants-Star |isbn=978-0787675592 |publisher=[[Gale (publisher)|Gale]] |year=2004 |page=3759 |url=https://books.google.com/books?id=mp7kcdK6SekC&q |quote=As human's position changed and the manner in which the skull balanced on the spinal column pivoted, the brain expanded, altering the shape of the cranium.}}</ref> from about 600 [[Cubic centimetre|cm3]] in ''[[Homo habilis]]'' to an average of about 1520 cm3 in ''[[Homo neanderthalensis]]''.<ref>{{cite book |last1=Begun |first1=David R. |title=A Companion to Paleoanthropology |date=2012 |publisher=John Wiley & Sons |isbn=9781118332375 |page=388 |url=https://books.google.com/books?id=oIoT1RcFeCwC&pg=PT388}}</ref> Differences in [[DNA]], [[gene expression]], and [[gene–environment interaction]]s help explain the differences between the function of the human brain and other primates.<ref>{{cite journal |author=Jones, R. |title=Neurogenetics: What makes a human brain? |journal=Nature Reviews Neuroscience |volume=13 |page=655 |year=2012 |pmid=22992645 |doi=10.1038/nrn3355 |issue=10}}</ref>

== See also==
{{Portal |Neuroscience |Thinking}}
* [[Cerebral atrophy]]
* [[Cortical spreading depression]]
* [[Enchanted loom]]
* [[Large scale brain networks]]

==References==
{{Reflist}}

==Bibliography==
* {{cite book |editor1-first=Nicki R. |editor1-last=Colledge |editor2-first=Brian R. |editor2-last=Walker |editor3-first=Stuart H. |editor3-last=Ralston |editor4-last=Ralston |title=Davidson's Principles and Practice of Medicine |date=2010 |publisher=Churchill Livingstone/Elsevier |location=Edinburgh |isbn=978-0-7020-3085-7 |edition=21st |ref={{harvid |Davidson's|2010}}}}
* {{cite book |last1=Hall |first=John |title=Guyton and Hall Textbook of Medical Physiology |year=2011 |publisher=Saunders/Elsevier |location=Philadelphia, PA |isbn=978-1-4160-4574-8 |edition=12th |ref={{harvid |Guyton & Hall|2011}}}}
* {{cite book |last1=Larsen |first1=William J. |title=Human Embryology |date=2001 |publisher=Churchill Livingstone |location=Philadelphia, PA |isbn=978-0-443-06583-5 |edition=3rd |ref={{harvid |Larsen|2001}}}}
* {{cite book |last2=Ort |first1=Bruce Ian |last1=Bogart |first2=Victoria |title=Elsevier's Integrated Anatomy and Embryology |date=2007 |publisher=Elsevier Saunders |location=Philadelphia, PA |isbn=978-1-4160-3165-9 |ref={{harvid |Elsevier's|2007}}}}
* {{cite book |last1=Pocock |first1=G. |last2=Richards |first2=C. |title=Human Physiology: The Basis of Medicine |date=2006 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-856878-0 |edition=3rd |ref={{harvid |Pocock|2006}}}}
* {{cite book |last1=Purves |first1=Dale |title=Neuroscience |date=2012 |publisher=Sinauer associates |location=Sunderland, MA |isbn=978-0-87893-695-3 |edition=5th |ref={{harvid |Purves|2012}}}}
* {{cite book |last1=Squire |first1=Larry |title=Fundamental Neuroscience |date=2013 |publisher=Elsevier |location=Waltham, MA |isbn=978-0-12-385-870-2 |ref={{harvid |Squire|2013}}}}
* {{cite book |editor1-last=Standring |editor1-first=Susan |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |date=2008 |publisher=Churchill Livingstone |location=London |isbn=978-0-8089-2371-8 |edition=40th |ref={{harvid |Gray's Anatomy|2008}}}}

==Notes==
{{notelist}}

==External links==
{{Commons category | Brain}}
* [https://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml Brain basics by NIMH]
* [http://www.thehumanbrain.info/ Atlas of the Human Brain]
* [http://faculty.washington.edu/chudler/facts.html Brain Facts and Figures]
* [http://www.brain-maps.com/index.html Brain Maps: Brain Anatomy, Functions and Disorders]
* [http://dai.fmph.uniba.sk/courses/CCN/lectures/CCN-06-areas.pdf Brain Areas]

{{navboxes
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{{Meninges}}
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{{Commissural fibers and septum}}
{{Cranial nerves}}
{{Arteries of head and neck}}
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}}
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Der Herr der Karawane

2018-08-20T01:20:38Z

176.228.51.29: /* Music */

{{unreferenced|date=June 2012}}
{{Infobox film
| name = Caravans
| image = Caravans_(1978).jpg
| image size =
| caption =
| alt =
| director = [[James Fargo]]
| producer = [[Elmo Williams]]
| based on = {{based on|''[[Caravans (novel)|Caravans]]''|[[James A. Michener]]}}
| screenplay = [[Nancy Voyles Crawford]], [[Thomas A. McMahon]] and [[Lorraine Williams]]
| starring = [[Anthony Quinn]] [[Behrouz Vossoughi]] [[Michael Sarrazin]] [[Christopher Lee]]
| music = [[Mike Batt]]
| cinematography = [[Douglas Slocombe]]
| studio = [[FIDCI]]
| editing = [[Richard Marden]]
| distributor = [[Universal Pictures]]
| released = {{film date|1978|11|2}}
| runtime = 127 minutes
| country = United States Iran
| language = English Persian
| budget =
| gross =
}}

'''Caravans''' is a 1978 Iranian-American film directed by [[James Fargo]] based on [[Caravans (novel)|the novel]] by [[James A. Michener]]. Nancy Voyles Crawford wrote the screenplay. The movie was shot in [[Iran]] and starred [[Anthony Quinn]], [[Jennifer O'Neill]], and [[Michael Sarrazin]].

==Plot==
The story is set in the fictional Middle Eastern country of Zadestan in 1948. Mark Miller is stationed at the U.S. Embassy in the fictional city of Kashkhan and is assigned to investigate the disappearance of and locate a young woman, Ellen Jasper, the daughter of a United States Senator, who vanished after her marriage to Colonel Nazrullah several months previously. Nazrullah is desperate to find her and becomes defensive when Miller asks about her. By law, Ellen has given up her rights as an American by becoming his wife. Miller traces her to a band of nomads who are running illegal guns. She doesn't want to leave, being estranged from both her parents and her husband. Miller doesn't want to return without proof she's alive and OK, which she refuses to give. Nazrullah lures the gun-runners into a trap. He separates Miller from the nomads and asks his wife to return to him but she refuses. Ellen at last gives Miller a note for her family. As the nomads leave, Nazrullah orders his troops to fire on them and Ellen is killed trying to rescue a child. A heart-broken Nazrullah carries away the body of his dead wife.

==Changes from the source novel==
The film was not well received by James Michener as it strayed wildly from the plot of his book, even eradicating its main character, a Nazi war criminal on the run who falls in love with the female lead character. This omission and other story changes caused Michener to take legal action.

==Music==
[[Mike Batt]] wrote the score, which has been the most successful element of the film, remaining a bestseller for many years after the film's release. The song "Caravan Song" was written by Mike Batt and sung by the Scottish singer [[Barbara Dickson]]. It peaked at No. 41 in UK charts and featured on the album ''[[All for a Song]]''.

==Cast==
*[[Anthony Quinn]] as Zulffiqar
*[[Michael Sarrazin]] as Mark Miller
*[[Christopher Lee]] as Sardar Khan
*[[Jennifer O'Neill]] as Ellen Jasper
*[[Joseph Cotten]] as Crandall
*[[Behrouz Vossoughi]] as Nasrollah
*[[Barry Sullivan (actor)|Barry Sullivan]] as Richardson
*[[Jeremy Kemp]] as Dr. Smythe
*Duncan Quinn as Moheb
*Behrouz Gramian as Peasant Boy (Behrooz Gueramian)
*[[Mohamad Ali Keshavarz]] as Shakkur
*[[Parviz Gharib-Afshar]] as Nur Mohammad
*Fahimeh Amouzandeh as Mira
*Mohammad Kahnemoui as Maftoon (Mohammad Taghi Kahnemoui)
*Khosrow Tabatabai as Dancing Boy

==External links==
*{{IMDb title|id=0077296|title=Caravans}}

{{James Fargo}}

[[Category:English-language films]]
[[Category:1978 films]]
[[Category:Films set in the Middle East]]
[[Category:Films set in a fictional Asian country]]
[[Category:Films set in 1948]]
[[Category:Universal Pictures films]]
[[Category:American adventure drama films]]
[[Category:American films]]
[[Category:Films shot in Iran]]

Der Herr der Karawane

2018-08-20T01:18:53Z

176.228.51.29:

{{unreferenced|date=June 2012}}
{{Infobox film
| name = Caravans
| image = Caravans_(1978).jpg
| image size =
| caption =
| alt =
| director = [[James Fargo]]
| producer = [[Elmo Williams]]
| based on = {{based on|''[[Caravans (novel)|Caravans]]''|[[James A. Michener]]}}
| screenplay = [[Nancy Voyles Crawford]], [[Thomas A. McMahon]] and [[Lorraine Williams]]
| starring = [[Anthony Quinn]] [[Behrouz Vossoughi]] [[Michael Sarrazin]] [[Christopher Lee]]
| music = [[Mike Batt]]
| cinematography = [[Douglas Slocombe]]
| studio = [[FIDCI]]
| editing = [[Richard Marden]]
| distributor = [[Universal Pictures]]
| released = {{film date|1978|11|2}}
| runtime = 127 minutes
| country = United States Iran
| language = English Persian
| budget =
| gross =
}}

'''Caravans''' is a 1978 Iranian-American film directed by [[James Fargo]] based on [[Caravans (novel)|the novel]] by [[James A. Michener]]. Nancy Voyles Crawford wrote the screenplay. The movie was shot in [[Iran]] and starred [[Anthony Quinn]], [[Jennifer O'Neill]], and [[Michael Sarrazin]].

==Plot==
The story is set in the fictional Middle Eastern country of Zadestan in 1948. Mark Miller is stationed at the U.S. Embassy in the fictional city of Kashkhan and is assigned to investigate the disappearance of and locate a young woman, Ellen Jasper, the daughter of a United States Senator, who vanished after her marriage to Colonel Nazrullah several months previously. Nazrullah is desperate to find her and becomes defensive when Miller asks about her. By law, Ellen has given up her rights as an American by becoming his wife. Miller traces her to a band of nomads who are running illegal guns. She doesn't want to leave, being estranged from both her parents and her husband. Miller doesn't want to return without proof she's alive and OK, which she refuses to give. Nazrullah lures the gun-runners into a trap. He separates Miller from the nomads and asks his wife to return to him but she refuses. Ellen at last gives Miller a note for her family. As the nomads leave, Nazrullah orders his troops to fire on them and Ellen is killed trying to rescue a child. A heart-broken Nazrullah carries away the body of his dead wife.

==Changes from the source novel==
The film was not well received by James Michener as it strayed wildly from the plot of his book, even eradicating its main character, a Nazi war criminal on the run who falls in love with the female lead character. This omission and other story changes caused Michener to take legal action.

==Music==
Mike Batt wrote the score, which has been the most successful element of the film, remaining a bestseller for many years after the film's release. The song "Caravan Song" was written by Mike Batt and sung by the Scottish singer [[Barbara Dickson]]. It peaked at No. 41 in UK charts and featured on the album ''[[All for a Song]]''.

==Cast==
*[[Anthony Quinn]] as Zulffiqar
*[[Michael Sarrazin]] as Mark Miller
*[[Christopher Lee]] as Sardar Khan
*[[Jennifer O'Neill]] as Ellen Jasper
*[[Joseph Cotten]] as Crandall
*[[Behrouz Vossoughi]] as Nasrollah
*[[Barry Sullivan (actor)|Barry Sullivan]] as Richardson
*[[Jeremy Kemp]] as Dr. Smythe
*Duncan Quinn as Moheb
*Behrouz Gramian as Peasant Boy (Behrooz Gueramian)
*[[Mohamad Ali Keshavarz]] as Shakkur
*[[Parviz Gharib-Afshar]] as Nur Mohammad
*Fahimeh Amouzandeh as Mira
*Mohammad Kahnemoui as Maftoon (Mohammad Taghi Kahnemoui)
*Khosrow Tabatabai as Dancing Boy

==External links==
*{{IMDb title|id=0077296|title=Caravans}}

{{James Fargo}}

[[Category:English-language films]]
[[Category:1978 films]]
[[Category:Films set in the Middle East]]
[[Category:Films set in a fictional Asian country]]
[[Category:Films set in 1948]]
[[Category:Universal Pictures films]]
[[Category:American adventure drama films]]
[[Category:American films]]
[[Category:Films shot in Iran]]

Monolingualismus

2018-06-14T03:54:39Z

176.228.51.29: /* Predominance of English */

'''Monoglottism''' ([[Greek language|Greek]] μόνοσ ''monos'', "alone, solitary", + γλώττα ''glotta'', "tongue, language") or, more commonly, '''monolingualism''' or '''unilingualism''', is the condition of being able to speak only a single language, as opposed to [[multilingualism]]. In a different context, "unilingualism" may refer to a [[language policy]] which [[forced language|enforces]] an official or [[national language]] over others.

Being '''monolingual''' or '''unilingual''' is also said of a text, [[dictionary]], or conversation written or conducted in only one language, and of an [[entity]] in which a single language is either used or officially recognized (in particular when being compared with bilingual or multilingual entities or in the presence of individuals speaking different languages). Note that mono''glottism'' can only refer to lacking the ''ability'' to speak several languages. Multilingual speakers outnumber monolingual speakers in the world's population.<ref>G. Richard Tucker (1999)[http://www.cal.org/resources/Digest/digestglobal.html A Global Perspective on Bilingualism and Bilingual Education] {{webarchive|url=https://web.archive.org/web/20120822104004/http://www.cal.org/resources/Digest/digestglobal.html |date=2012-08-22 }} Carnegie Mellon University CALL Digest EDO-FL-99-04</ref>

Suzzane Romaine pointed out, in her 1995 book ''Bilingualism'', that it would be weird to find a book titled ''Monolingualism''.<ref>{{cite book |last=Romaine |first=Suzzane |year=1995 |publisher=Wiley-Blackwell |title=Bilingualism |pages=1 |isbn=978-0-631-19539-9}}</ref> This statement reflects the traditional assumption that linguistic theories often take on: that monolingualism is the norm.<ref>{{cite journal |last=Pavlenko |first=Aneta |title=L2 influence on L1 in late bilingualism. |journal=Issues in Applied Linguistics. |year=2000 |volume=11 |issue=2 |pages=175–206 }}</ref> Monolingualism is thus rarely the subject of scholarly publications, as it is viewed to be an unmarked or prototypical concept where it has the sense of being normal and [[multilingualism]] is the exception.<ref name="ellis">{{cite journal |last=Ellis |first=Elizabeth |title=Monolingualism: The unmarked case |journal=Estudios de Sociolingüística. |year=2006 |volume=7 |issue=2 |pages=173–196}}</ref>

The assumption of normative monolingualism is also often the view of monolinguals who speak a [[world language|global language]], like the [[English language]]. Crystal (1987) said that this assumption is adopted by many in Western society.<ref>{{cite book |last=Crystal |first=David |year=1987 |publisher=Cambridge University Press |title=The Cambridge Encyclopaedia of Language |isbn=978-0-521-55967-6}}</ref> One explanation is provided by Edwards, who in 2004 claimed that evidence of the "monolingual mindset" can be traced back to 19th century [[Europe]], when the nation was rising and a dominant group had control{{what|date=December 2013}}, and European mindsets on language were carried forth to its [[colonies]], further perpetuating the monolingual mindset.<ref>{{cite book |last1=Edwards |first1=Viv |title=Multilingualism in the English-speaking world. |publisher=Wiley-Blackwell |year=2004 |isbn=978-0-631-23613-9 |pages=3–5}}</ref>

Another explanation is that the nations who speak the [[English language]] are both “the producers and beneficiaries of English as a [[world language|global language]]” and the populations within these countries tend to be monolingual.<ref name="ellis"/>

==Comparison with multilingualism==
===Vocabulary size and verbal fluency===
According to a study on lexical access,<ref>{{cite journal |last1=Bialystok |first1=Ellen |last2=Craik |first2=Fergus I.M |last3=Luk |first3=Gigi. |title=Lexical access in bilinguals: Effects of vocabulary size and executive control |journal=Journal of Neurolinguistics |volume=21 |issue=6 |pages=522–538 |year=2008 |doi=10.1016/j.jneuroling.2007.07.001}}</ref> monolinguals often maintain a wider [[vocabulary]] in a target language relative to a comparable [[bilingual]], and that increases the efficiency of word retrieval in monolinguals. Monolinguals also access words more often than bilinguals in a target language.

In letter fluency tasks, monolinguals in the study were also able to respond with more words to the letter cue than bilinguals, but such an effect was not seen in bilinguals with a high [[vocabulary]] score.

Also, monolinguals performed better than bilinguals on verbal fluency in the study. If the [[vocabulary abilities]] were made to be more comparable, however, many of the differences would disappear, indicating that [[vocabulary]] size may be a factor that moderated a person's performance in verbal fluency and naming tasks. The same study also found that bilinguals, in a version of the letter fluency task that placed more demand on executive control, performed better than monolinguals. Thus, once [[vocabulary]] abilities were controlled, bilinguals performed better on letter fluency possibilities by the enhanced frontal executive processes in the [[brain]].

It is important to note here that bilinguals' overall vocabulary size in both languages combined was equivalent to monolinguals' in one language. While monolinguals may excel in vocabulary size for the one language they speak, their vocabulary content is not greater. Bilinguals may have smaller vocabularies in each individual language, but when their vocabularies were combined, the content size was approximately similar to that of the monolingual. Monolingual children demonstrated larger vocabulary scored than their bilingual peers, but bilingual children's vocabulary scores still increased with age, just like the monolingual children's vocabulary scores (Core et al., 2011). Despite a variation in vocabulary scores, there was absolutely no difference between monolingual and bilingual children in terms of total vocabulary size and total vocabulary gains (Core et al., 2011). Bilingual children and monolingual children have the same vocabulary size and gain the same vocabulary knowledge.

===Creative functioning===
In a study testing for creative functioning that involved monolingual and bilingual children in [[Singapore]],<ref>{{cite journal |last1=Torrance |first1=E. Paul |last2=Gowan |first2=John.C. |last3=Wu |first3=Jing-Jyi |last4=Aliotti |first4=Nicholas C. |title=Creative functioning of monolingual and bilingual children in Singapore |journal=Journal of Educational Psychology |volume=61 |issue=1 |pages=72–75 |year=1970 |doi=10.1037/h0028767}}</ref> researchers found that monolinguals performed better on fluency and flexibility than bilinguals. The trend was reversed, however, on tests for originality and elaboration.

===Mental well-being===
In another recent study in [[Canada]], it has been shown that monolinguals were worse at the onset of [[senility]] than bilinguals.<ref>{{cite news|url=http://www.biologynews.net/archives/2007/01/11/canadian_study_shows_bilingualism_has_protective_effect_in_delaying_onset_of_dementia_by_four_years.html|title=Canadian study shows bilingualism has protective effect in delaying onset of dementia by 4 years|work= Biology News Net|date=January 11, 2007}}</ref> In the study, it seems that being [[bilingual]] is associated with a delay of [[dementia]] by four years as compared to monolinguals. Bialystok's most recent work also shows that lifelong bilingualism can delay symptoms of [[dementia]].<ref name="university affairs">{{cite web|url=http://www.universityaffairs.ca/the-rise-of-the-monoglots.aspx |title=The rise of the monoglots |publisher=University Affairs.ca |date=August 5, 2008 |accessdate=11 March 2012}}</ref>

It is believed that bilingualism contributes to cognitive reserve by preventing effects of cognitive delay and prolonging the onset of sicknesses such as dementia. Cognitive reserve refers to the idea that engaging in stimulating physical or mental activity maintains cognitive functioning (Bialystok et al., 2012). In that case, knowing more than one language is similar to stimulating mental activity. To test whether or not bilingualism contributes to cognitive reserve, Bialystok et al. (2012) looked at hospital records among monolingual and bilingual adults who have dementia. The researchers found that elderly bilingual adults were diagnosed with dementia about three to four years later than elderly monolingual adults. The results have been replicated and validated, with outside factors being controlled. In fact, outside factors such as socioeconomic status and cultural differences always helped monolinguals, making the argument the bilingualism contributes to cognitive reserve even stronger (Bialystok et al., 2012). That finding enhances the fact that bilinguals are at an advantage because of their ability to speak two languages, not because of outside factors. A probable explanation for this phenomenon is that knowledge of multiple languages keeps the brain alert and therefore more mentally aware for a longer period of time.

===Emotion and behaviour===
A study conducted with children in their early school years suggested that there are emotional and behavioural benefits to being bilingual.<ref>{{cite journal |last1=Han |first1=Wen-Jui |last2=Huang |first2=Chien-Chung |title=The forgotten treasure: Bilingualism and Asian children's emotional and behavioural health |journal=American Journal of Public Health |year=2010 |volume=100 |issue=5 |pages=831–838 |doi=10.2105/ajph.2009.174219|pmc=2853634 }}</ref> In the same study, the findings show that monolingual children, in particular non-English monolingual children, display more poor behavioural and emotional outcomes in their school years. The non-English monolingual children had the highest level of externalizing and internalizing behaviourial problems by fifth grade(around 10–11 years of age), even though the children were all measured to have similar levels of internalizing and externalizing behaviourial problems at the start{{what|date=December 2013}}. In contrast, the fluent [[bilingual]] and non-English dominant bilingual children were found to have the lowest level of these behaviourial problems. The authors suggest that monolingualism seems to be a risk factor. However, if there is a supportive school environment with teachers who are experienced in [[ESL]] (English as a Second Language), children seem to have better emotional constitution.

===Memory performance===
In a study conducted at the [[University of Florida]], which compared Native-English [[bilingual]]s to English monolinguals, although there was no difference in accuracy between the two groups, there was an evident slower response rate from bilinguals on tasks that involve latency of recognition of a list of abstract words and [[lexical decision task]]s.<ref>{{cite journal |last1=Ransdell |first1=Sarah Ellen |last2=Fischler |first2=Ira |title=Memory in a monolingual mode:When are bilinguals at a disadvantage? |journal=Journal of Memory and Language |year=1987 |volume=26 |pages=392–405 |doi=10.1016/0749-596x(87)90098-2}}</ref> For these two tasks, language-specific and data driven processes were more prevalent, that is, the tasks were driven by the dominant language and the data (the words used in the task). The study differed from prior research that there is more balance in familiarity of the [[dominant language]]. Magiste's (1980) hypothesis that it could have been due to differential familiarity with the [[dominant language]] is suggested to be a possible reason for the bilingual disadvantage.<ref>{{cite journal |last=Magiste |first=Edith |year=1980 |title=Memory for numbers in monolinguals and bilinguals |journal=Acta Psychologica |volume=46 |pages=63–68 |doi=10.1016/0001-6918(80)90059-1}}</ref> They explained that for bilinguals, it could be because the acquiring and using of the [[second language]] meant that there was less time to process English, as compared to the monolingual participants in the study.

However, evidence from a research study shows that bilinguals have a faster reaction time in most working memory tasks. While a lot of research asserts that monolingual children outperform bilingual children, other research asserts the opposite. Research by Bialystok et al., as reported by Kapa and Colombo (2013, p. 233) shows that bilingual individuals perform better than monolingual individuals on a wide variety of cognitive tests, thus demonstrating cognitive control advantages. Two different concepts, attentional inhibition and attentional monitoring, are used to measure attentional control. In terms of attentional control, early bilingual learners showed the greatest advantage, compared to monolingual speakers and late bilingual speakers. In terms of overall performance on ATN, the three groups performed equally, but when age and verbal ability variables were controlled, there was a difference in reaction time. The early bilingual children's reaction time was tremendously faster than the monolingual children, and only slightly faster than the late bilingual children (Kapa & Colombo, 2013). Early bilingual learners showed that they simply responded most efficiently to the task at hand. The results from this study demonstrate the advantages bilingual children have with attentional control. This is likely because bilingual children are used to balancing more than one language at time, and are therefore used to focusing on which language is necessary at a certain time. By constantly being aware of what language to use and being able to successfully switch between languages, it makes sense that bilingual children would be better at directing and focusing their attention.

===Verbal and non-verbal cognitive development===
A 2012 study by the [[University of York]] published in ''Child Development'' journal<ref>{{cite web |url=http://www.dushi.ca/tor/education/bencandy.php/fid18/aid1819 |title=最新研究：双语儿童比单语小孩更聪慧 |publisher=加拿大都市网 |date=10 February 2012 |accessdate=23 March 2013}}</ref> reviewed the effects of the development of a child's verbal and non-verbal language, matched between monolinguals and bilinguals in a particular language. Researchers compared about 100 6-year-old monolingual and [[bilingual]] children (monolingual in English; bilingual in English and Mandarin, bilingual in French and English, bilingual in Spanish and English), to test their verbal and [[non-verbal communication]] [[cognitive development]]. The research takes into consideration factors like the similarity of the language, the cultural background and education experience. These students mostly come from public schools from various areas, having similar social and economic background.

Results show that in the child's early stage, multilingual kids are very different from one another in their language and [[cognitive]] skills development, and also when compared to monolingual children. When compared to monolinguals, multilingual children are slower in building up their [[vocabulary]] in every language. However, their metalinguistic development allowed them to understand better the structure of the language. They also performed better in non-verbal control tests. A non-verbal control test refers to the ability to focus and then able to divert their attention when being instructed to.

==Reasons for persistence==
===Convergence principle===
According to the convergence principle,<ref name="snow">{{cite book|title=Language Loyalties: A Source Book on the Official English Controversy. |chapter=The Costs of Monolingualism |last1=Snow |first1=Catherine E.|last2=Hakuta |first2=Kenji |editor=Crawford, J.|publisher=The University of Chicago |year=1992 |pages=384–394 |url=http://www.stanford.edu/~hakuta/Publications/(1992)%20-%20THE%20COST%20OF%20MONOLINGUALISM.pdf |accessdate=9 March 2012}}</ref> language style tends to change to that of people who are liked and admired. Conversations in which one party speaks a language different from the other persons both are hard to maintain and have reduced intimacy. Thus, speech is usually adapted and accommodated for convenience, lack of misunderstanding and conflict and the maintenance of intimacy. In intermarriages, one partner tends to become monolingual, which also usually applies to the children.

===Predominance of English===
{{see also|English-only movement}}
The predominance of [[English language|English]] in many sectors, such as world trade, [[technology]] and [[science]], has contributed to English-speaking societies being persistently monolingual, as there is no relevant need to learn a [[second language]] if all dealings can be done in their [[native language]];<ref>{{cite journal |last=Peel |first=Quentin |title=The monotony of monoglots |journal=Language Learning Journal |volume=23 |issue=1 |pages=13–14 |year=2001 |doi=10.1080/09571730185200041}}</ref> that is especially the case for English-speakers in the [[United States]], particularly the [[Northeastern United States|Northeastern]], [[Midwestern United States|Midwestern]], and most of the [[Southern United States]], where everyday contact with other languages, such as [[Spanish language|Spanish]] and [[French language|French]] is usually limited. The country's large area and the most populous regions' distance from large non-English-speaking areas, such as [[Mexico]] and [[Quebec]], increase the geographic and economic barriers to foreign travel.<ref>{{cite news|url=http://news.gallup.com/poll/1825/about-one-four-americans-can-hold-conversation-second-language.aspx|title=About One in Four Americans Can Hold a Conversation in a Second Language}}</ref> Although the country is economically interdependent with trade partners such as [[China]], American corporations and heavily-Americanized subsidiaries of foreign corporations both mediate and control most citizens' contact with most other nations' products. There is a popular joke: "What do you call a person who speaks three languages? A trilingual. What do you call a person who speaks two languages? A bilingual. What do you call a person who speaks one language? An American."<ref>{{cite book|last1=Gramling|first1=David|title=The Invention of Monolingualism|date= 6 October 2016|publisher=Bloomsbury Publishing|isbn=1501318055|pages=60-61}}</ref>

There is also increasing pressure on [[multilingualism|bilingual]] [[immigrants]] to renounce their [[mother tongue]] and to adopt their host country's language. As a result, even though there may be immigrants from a wide variety of nationalities and cultures, the main language spoken in the country does not reflect them.{{Citation needed|date=February 2015}}<ref>[https://www.quora.com/Why-dont-most-Americans-learn-a-second-language Why don't most Americans learn a second language?]</ref>

==Costs==
Snow and Hakuta<ref name="snow" /> write that in a cost-benefit analysis, the choosing of English as the official and national language often comes with additional costs on the society, as the alternative choice of multilingualism has its own benefits.

===Education===
Some of the education budget is allocated for foreign-language training, but [[fluency]] of foreign-language students is lower than those who learned it at home.<ref name="snow" />

===Economic===
[[International business]] may be impeded by a lack of people competent in other languages.<ref name="snow" />

===National security===
Money has to be spent to train foreign-service personnel in foreign languages.<ref name="snow" />

===Time and effort===
Compared to the maintenance of a language that is learned at home, more time, effort and hard work are required to learn it in school.<ref name="snow" />

===Job opportunities===
Kirkpatrick asserts that monolinguals are at a disadvantage to bilinguals in the international job market.<ref>{{cite journal |last=Kirkpatrick |first=Andy |year=2000 |title=The disadvantaged monolingual: Why English alone is not enough. |journal=Australian Language Matters |volume=8 |issue=3 |pages=5–7 }}</ref>

==In the media==
[[Lawrence Summers]], in an article published in the ''[[New York Times]]'',<ref>{{cite news |url=https://www.nytimes.com/2012/01/22/education/edlife/the-21st-century-education.html?pagewanted=all |last=Summers |first=Lawrence H. |title=What You (Really) Need to Know |work=New York Times |date=20 January 2012}}</ref> discusses how to prepare for the future advancement of America. He also questioned the importance and necessity of learning foreign languages by remarking that "English's emergence as the [[global language]], along with the rapid progress in [[machine translation]] and the fragmentation of languages spoken around the world, makes it less clear that the substantial investment necessary to speak a foreign tongue is universally worthwhile."

Others have disagreed with Summers' view. A week later, the ''New York Times'' hosted a discussion among six panelists,<ref>{{cite news |url=https://www.nytimes.com/roomfordebate/2012/01/29/is-learning-a-language-other-than-english-worthwhile |date=29 January 2012 |title=English Is Global, So Why Learn Arabic? |work=New York Times |last1=Berdan |first1=Stacie Nevadomski |last2=Jackson |first2=Anthony |last3=Erard |first3=Michael |last4=Ho |first4=Melanie |last5=Suarez-Orozco |first5=Marcelo M. |last6=Lewis |first6=Clayton}}</ref> all of whom were for learning foreign languages and cited the benefits and advantages and the changing global landscape.

==See also==
*[[Multilingualism]]
*[[Languages of the United Kingdom]]
*[[Languages of the United States]]
*[[Linguistic imperialism]]
*[[List of multilingual countries and regions]]

==References==
{{Reflist}}

* Bialystok, E., Craik, F. & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Neuropsychology & Neurology, Linguistics & Language & Speech, 16(4), 240-250.
* Core, C., Hoff, E., Rumiche, R., & Senor, M. (2011). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637-1649.
* Kapa, L., & Colombo, J. (2013). Attentional control in early and later bilingual children.Cognitive Development, 28(3), 233-246.

==External links==
{{Wiktionary|monoglottism|monolingualism|unilingualism}}
*[https://litigation-essentials.lexisnexis.com/webcd/app?action=DocumentDisplay&crawlid=1&crawlid=1&doctype=cite&docid=14+Cardozo+L.+Rev.+1713&srctype=smi&srcid=3B15&key=30ce6efd643c7fdf6f394561a88d0a65 Monolingualism and Judaism] by Jose Faur, contrasting the Greek monolingualism with the polyglot culture of the Hebrews

[[Category:Monolingualism]]

Monolingualismus

2018-04-28T03:54:22Z

176.228.51.29: Undid revision 838611381 by 176.228.51.29 (talk)

'''Monoglottism''' ([[Greek language|Greek]] μόνοσ ''monos'', "alone, solitary", + γλώττα ''glotta'', "tongue, language") or, more commonly, '''monolingualism''' or '''unilingualism''', is the condition of being able to speak only a single language, as opposed to [[multilingualism]]. In a different context, "unilingualism" may refer to a [[language policy]] which [[forced language|enforces]] an official or [[national language]] over others.

Being '''monolingual''' or '''unilingual''' is also said of a text, [[dictionary]], or conversation written or conducted in only one language, and of an [[entity]] in which a single language is either used or officially recognized (in particular when being compared with bilingual or multilingual entities or in the presence of individuals speaking different languages). Note that mono''glottism'' can only refer to lacking the ''ability'' to speak several languages. Multilingual speakers outnumber monolingual speakers in the world's population.<ref>G. Richard Tucker (1999)[http://www.cal.org/resources/Digest/digestglobal.html A Global Perspective on Bilingualism and Bilingual Education] {{webarchive|url=https://web.archive.org/web/20120822104004/http://www.cal.org/resources/Digest/digestglobal.html |date=2012-08-22 }} Carnegie Mellon University CALL Digest EDO-FL-99-04</ref>

Suzzane Romaine pointed out, in her 1995 book ''Bilingualism'', that it would be weird to find a book titled ''Monolingualism''.<ref>{{cite book |last=Romaine |first=Suzzane |year=1995 |publisher=Wiley-Blackwell |title=Bilingualism |pages=1 |isbn=978-0-631-19539-9}}</ref> This statement reflects the traditional assumption that linguistic theories often take on: that monolingualism is the norm.<ref>{{cite journal |last=Pavlenko |first=Aneta |title=L2 influence on L1 in late bilingualism. |journal=Issues in Applied Linguistics. |year=2000 |volume=11 |issue=2 |pages=175–206 }}</ref> Monolingualism is thus rarely the subject of scholarly publications, as it is viewed to be an unmarked or prototypical concept where it has the sense of being normal and [[multilingualism]] is the exception.<ref name="ellis">{{cite journal |last=Ellis |first=Elizabeth |title=Monolingualism: The unmarked case |journal=Estudios de Sociolingüística. |year=2006 |volume=7 |issue=2 |pages=173–196}}</ref>

The assumption of normative monolingualism is also often the view of monolinguals who speak a [[world language|global language]], like the [[English language]]. Crystal (1987) said that this assumption is adopted by many in Western society.<ref>{{cite book |last=Crystal |first=David |year=1987 |publisher=Cambridge University Press |title=The Cambridge Encyclopaedia of Language |isbn=978-0-521-55967-6}}</ref> One explanation is provided by Edwards, who in 2004 claimed that evidence of the "monolingual mindset" can be traced back to 19th century [[Europe]], when the nation was rising and a dominant group had control{{what|date=December 2013}}, and European mindsets on language were carried forth to its [[colonies]], further perpetuating the monolingual mindset.<ref>{{cite book |last1=Edwards |first1=Viv |title=Multilingualism in the English-speaking world. |publisher=Wiley-Blackwell |year=2004 |isbn=978-0-631-23613-9 |pages=3–5}}</ref>

Another explanation is that the nations who speak the [[English language]] are both “the producers and beneficiaries of English as a [[world language|global language]]” and the populations within these countries tend to be monolingual.<ref name="ellis"/>

==Comparison with multilingualism==
===Vocabulary size and verbal fluency===
According to a study on lexical access,<ref>{{cite journal |last1=Bialystok |first1=Ellen |last2=Craik |first2=Fergus I.M |last3=Luk |first3=Gigi. |title=Lexical access in bilinguals: Effects of vocabulary size and executive control |journal=Journal of Neurolinguistics |volume=21 |issue=6 |pages=522–538 |year=2008 |doi=10.1016/j.jneuroling.2007.07.001}}</ref> monolinguals often maintain a wider [[vocabulary]] in a target language relative to a comparable [[bilingual]], and that increases the efficiency of word retrieval in monolinguals. Monolinguals also access words more often than bilinguals in a target language.

In letter fluency tasks, monolinguals in the study were also able to respond with more words to the letter cue than bilinguals, but such an effect was not seen in bilinguals with a high [[vocabulary]] score.

Also, monolinguals performed better than bilinguals on verbal fluency in the study. If the [[vocabulary abilities]] were made to be more comparable, however, many of the differences would disappear, indicating that [[vocabulary]] size may be a factor that moderated a person's performance in verbal fluency and naming tasks. The same study also found that bilinguals, in a version of the letter fluency task that placed more demand on executive control, performed better than monolinguals. Thus, once [[vocabulary]] abilities were controlled, bilinguals performed better on letter fluency possibilities by the enhanced frontal executive processes in the [[brain]].

It is important to note here that bilinguals' overall vocabulary size in both languages combined was equivalent to monolinguals' in one language. While monolinguals may excel in vocabulary size for the one language they speak, their vocabulary content is not greater. Bilinguals may have smaller vocabularies in each individual language, but when their vocabularies were combined, the content size was approximately similar to that of the monolingual. Monolingual children demonstrated larger vocabulary scored than their bilingual peers, but bilingual children's vocabulary scores still increased with age, just like the monolingual children's vocabulary scores (Core et al., 2011). Despite a variation in vocabulary scores, there was absolutely no difference between monolingual and bilingual children in terms of total vocabulary size and total vocabulary gains (Core et al., 2011). Bilingual children and monolingual children have the same vocabulary size and gain the same vocabulary knowledge.

===Creative functioning===
In a study testing for creative functioning that involved monolingual and bilingual children in [[Singapore]],<ref>{{cite journal |last1=Torrance |first1=E. Paul |last2=Gowan |first2=John.C. |last3=Wu |first3=Jing-Jyi |last4=Aliotti |first4=Nicholas C. |title=Creative functioning of monolingual and bilingual children in Singapore |journal=Journal of Educational Psychology |volume=61 |issue=1 |pages=72–75 |year=1970 |doi=10.1037/h0028767}}</ref> researchers found that monolinguals performed better on fluency and flexibility than bilinguals. The trend was reversed, however, on tests for originality and elaboration.

===Mental well-being===
In another recent study in [[Canada]], it has been shown that monolinguals were worse at the onset of [[senility]] than bilinguals.<ref>{{cite news|url=http://www.biologynews.net/archives/2007/01/11/canadian_study_shows_bilingualism_has_protective_effect_in_delaying_onset_of_dementia_by_four_years.html|title=Canadian study shows bilingualism has protective effect in delaying onset of dementia by 4 years|work= Biology News Net|date=January 11, 2007}}</ref> In the study, it seems that being [[bilingual]] is associated with a delay of [[dementia]] by four years as compared to monolinguals. Bialystok's most recent work also shows that lifelong bilingualism can delay symptoms of [[dementia]].<ref name="university affairs">{{cite web|url=http://www.universityaffairs.ca/the-rise-of-the-monoglots.aspx |title=The rise of the monoglots |publisher=University Affairs.ca |date=August 5, 2008 |accessdate=11 March 2012}}</ref>

It is believed that bilingualism contributes to cognitive reserve by preventing effects of cognitive delay and prolonging the onset of sicknesses such as dementia. Cognitive reserve refers to the idea that engaging in stimulating physical or mental activity maintains cognitive functioning (Bialystok et al., 2012). In that case, knowing more than one language is similar to stimulating mental activity. To test whether or not bilingualism contributes to cognitive reserve, Bialystok et al. (2012) looked at hospital records among monolingual and bilingual adults who have dementia. The researchers found that elderly bilingual adults were diagnosed with dementia about three to four years later than elderly monolingual adults. The results have been replicated and validated, with outside factors being controlled. In fact, outside factors such as socioeconomic status and cultural differences always helped monolinguals, making the argument the bilingualism contributes to cognitive reserve even stronger (Bialystok et al., 2012). That finding enhances the fact that bilinguals are at an advantage because of their ability to speak two languages, not because of outside factors. A probable explanation for this phenomenon is that knowledge of multiple languages keeps the brain alert and therefore more mentally aware for a longer period of time.

===Emotion and behaviour===
A study conducted with children in their early school years suggested that there are emotional and behavioural benefits to being bilingual.<ref>{{cite journal |last1=Han |first1=Wen-Jui |last2=Huang |first2=Chien-Chung |title=The forgotten treasure: Bilingualism and Asian children's emotional and behavioural health |journal=American Journal of Public Health |year=2010 |volume=100 |issue=5 |pages=831–838 |doi=10.2105/ajph.2009.174219}}</ref> In the same study, the findings show that monolingual children, in particular non-English monolingual children, display more poor behavioural and emotional outcomes in their school years. The non-English monolingual children had the highest level of externalizing and internalizing behaviourial problems by fifth grade(around 10–11 years of age), even though the children were all measured to have similar levels of internalizing and externalizing behaviourial problems at the start{{what|date=December 2013}}. In contrast, the fluent [[bilingual]] and non-English dominant bilingual children were found to have the lowest level of these behaviourial problems. The authors suggest that monolingualism seems to be a risk factor. However, if there is a supportive school environment with teachers who are experienced in [[ESL]] (English as a Second Language), children seem to have better emotional constitution.

===Memory performance===
In a study conducted at the [[University of Florida]], which compared Native-English [[bilingual]]s to English monolinguals, although there was no difference in accuracy between the two groups, there was an evident slower response rate from bilinguals on tasks that involve latency of recognition of a list of abstract words and [[lexical decision task]]s.<ref>{{cite journal |last1=Ransdell |first1=Sarah Ellen |last2=Fischler |first2=Ira |title=Memory in a monolingual mode:When are bilinguals at a disadvantage? |journal=Journal of Memory and Language |year=1987 |volume=26 |pages=392–405 |doi=10.1016/0749-596x(87)90098-2}}</ref> For these two tasks, language-specific and data driven processes were more prevalent, that is, the tasks were driven by the dominant language and the data (the words used in the task). The study differed from prior research that there is more balance in familiarity of the [[dominant language]]. Magiste's (1980) hypothesis that it could have been due to differential familiarity with the [[dominant language]] is suggested to be a possible reason for the bilingual disadvantage.<ref>{{cite journal |last=Magiste |first=Edith |year=1980 |title=Memory for numbers in monolinguals and bilinguals |journal=Acta Psychologica |volume=46 |pages=63–68 |doi=10.1016/0001-6918(80)90059-1}}</ref> They explained that for bilinguals, it could be because the acquiring and using of the [[second language]] meant that there was less time to process English, as compared to the monolingual participants in the study.

However, evidence from a research study shows that bilinguals have a faster reaction time in most working memory tasks. While a lot of research asserts that monolingual children outperform bilingual children, other research asserts the opposite. Research by Bialystok et al., as reported by Kapa and Colombo (2013, p. 233) shows that bilingual individuals perform better than monolingual individuals on a wide variety of cognitive tests, thus demonstrating cognitive control advantages. Two different concepts, attentional inhibition and attentional monitoring, are used to measure attentional control. In terms of attentional control, early bilingual learners showed the greatest advantage, compared to monolingual speakers and late bilingual speakers. In terms of overall performance on ATN, the three groups performed equally, but when age and verbal ability variables were controlled, there was a difference in reaction time. The early bilingual children's reaction time was tremendously faster than the monolingual children, and only slightly faster than the late bilingual children (Kapa & Colombo, 2013). Early bilingual learners showed that they simply responded most efficiently to the task at hand. The results from this study demonstrate the advantages bilingual children have with attentional control. This is likely because bilingual children are used to balancing more than one language at time, and are therefore used to focusing on which language is necessary at a certain time. By constantly being aware of what language to use and being able to successfully switch between languages, it makes sense that bilingual children would be better at directing and focusing their attention.

===Verbal and non-verbal cognitive development===
A 2012 study by the [[University of York]] published in ''Child Development'' journal<ref>{{cite web |url=http://www.dushi.ca/tor/education/bencandy.php/fid18/aid1819 |title=最新研究：双语儿童比单语小孩更聪慧 |publisher=加拿大都市网 |date=10 February 2012 |accessdate=23 March 2013}}</ref> reviewed the effects of the development of a child's verbal and non-verbal language, matched between monolinguals and bilinguals in a particular language. Researchers compared about 100 6-year-old monolingual and [[bilingual]] children (monolingual in English; bilingual in English and Mandarin, bilingual in French and English, bilingual in Spanish and English), to test their verbal and [[non-verbal communication]] [[cognitive development]]. The research takes into consideration factors like the similarity of the language, the cultural background and education experience. These students mostly come from public schools from various areas, having similar social and economic background.

Results show that in the child's early stage, multilingual kids are very different from one another in their language and [[cognitive]] skills development, and also when compared to monolingual children. When compared to monolinguals, multilingual children are slower in building up their [[vocabulary]] in every language. However, their metalinguistic development allowed them to understand better the structure of the language. They also performed better in non-verbal control tests. A non-verbal control test refers to the ability to focus and then able to divert their attention when being instructed to.

==Reasons for persistence==
===Convergence principle===
According to the convergence principle,<ref name="snow">{{cite book|title=Language Loyalties: A Source Book on the Official English Controversy. |chapter=The Costs of Monolingualism |last1=Snow |first1=Catherine E.|last2=Hakuta |first2=Kenji |editor=Crawford, J.|publisher=The University of Chicago |year=1992 |pages=384–394 |url=http://www.stanford.edu/~hakuta/Publications/(1992)%20-%20THE%20COST%20OF%20MONOLINGUALISM.pdf |accessdate=9 March 2012}}</ref> language style tends to change to that of people who are liked and admired. Conversations in which one party speaks a language different from the other persons both are hard to maintain and have reduced intimacy. Thus, speech is usually adapted and accommodated for convenience, lack of misunderstanding and conflict and the maintenance of intimacy. In intermarriages, one partner tends to become monolingual, which also usually applies to the children.

===Predominance of English===
{{see also|English-only movement}}
The predominance of [[English language|English]] in many sectors, such as world trade, [[technology]] and [[science]], has contributed to English-speaking societies being persistently monolingual, as there is no relevant need to learn a [[second language]] if all dealings can be done in their [[native language]];<ref>{{cite journal |last=Peel |first=Quentin |title=The monotony of monoglots |journal=Language Learning Journal |volume=23 |issue=1 |pages=13–14 |year=2001 |doi=10.1080/09571730185200041}}</ref> that is especially the case for English-speakers in the [[United States]], particularly the [[Northeastern United States|Northeastern]], [[Midwestern United States|Midwestern]], and most of the [[Southern United States]], where everyday contact with other languages, such as [[Spanish language|Spanish]] and [[French language|French]] is usually limited. The country's large area and the most populous regions' distance from large non-English-speaking areas, such as [[Mexico]] and [[Quebec]], increase the geographic and economic barriers to foreign travel.<ref>{{cite news|url=http://news.gallup.com/poll/1825/about-one-four-americans-can-hold-conversation-second-language.aspx|title=About One in Four Americans Can Hold a Conversation in a Second Language}}</ref> Although the country is economically interdependent with trade partners such as [[China]], American corporations and heavily-Americanized subsidiaries of foreign corporations both mediate and control most citizens' contact with most other nations' products. There is a popular joke: "What do you call a person who speaks three languages? A trilingual. What do you call a person who speaks two languages? A bilingual. What do you call a person who speaks one language? An American."<ref>{{cite book|last1=Gramling|first1=David|title=The Invention of Monolingualism|date= 6 October 2016|publisher=Bloomsbury Publishing|isbn=1501318055|pages=60-61}}</ref>

There is also increasing pressure on [[multilingualism|bilingual]] [[immigrants]] to renounce their [[mother tongue]] and to adopt their host country's language. As a result, even though there may be immigrants from a wide variety of nationalities and cultures, the main language spoken in the country does not reflect them.{{Citation needed|date=February 2015}}

==Costs==
Snow and Hakuta<ref name="snow" /> write that in a cost-benefit analysis, the choosing of English as the official and national language often comes with additional costs on the society, as the alternative choice of multilingualism has its own benefits.

===Education===
Some of the education budget is allocated for foreign-language training, but [[fluency]] of foreign-language students is lower than those who learned it at home.<ref name="snow" />

===Economic===
[[International business]] may be impeded by a lack of people competent in other languages.<ref name="snow" />

===National security===
Money has to be spent to train foreign-service personnel in foreign languages.<ref name="snow" />

===Time and effort===
Compared to the maintenance of a language that is learned at home, more time, effort and hard work are required to learn it in school.<ref name="snow" />

===Job opportunities===
Kirkpatrick asserts that monolinguals are at a disadvantage to bilinguals in the international job market.<ref>{{cite journal |last=Kirkpatrick |first=Andy |year=2000 |title=The disadvantaged monolingual: Why English alone is not enough. |journal=Australian Language Matters |volume=8 |issue=3 |pages=5–7 }}</ref>

==In the media==
[[Lawrence Summers]], in an article published in the ''[[New York Times]]'',<ref>{{cite news |url=https://www.nytimes.com/2012/01/22/education/edlife/the-21st-century-education.html?pagewanted=all |last=Summers |first=Lawrence H. |title=What You (Really) Need to Know |work=New York Times |date=20 January 2012}}</ref> discusses how to prepare for the future advancement of America. He also questioned the importance and necessity of learning foreign languages by remarking that "English's emergence as the [[global language]], along with the rapid progress in [[machine translation]] and the fragmentation of languages spoken around the world, makes it less clear that the substantial investment necessary to speak a foreign tongue is universally worthwhile."

Others have disagreed with Summers' view. A week later, the ''New York Times'' hosted a discussion among six panelists,<ref>{{cite news |url=https://www.nytimes.com/roomfordebate/2012/01/29/is-learning-a-language-other-than-english-worthwhile |date=29 January 2012 |title=English Is Global, So Why Learn Arabic? |work=New York Times |last1=Berdan |first1=Stacie Nevadomski |last2=Jackson |first2=Anthony |last3=Erard |first3=Michael |last4=Ho |first4=Melanie |last5=Suarez-Orozco |first5=Marcelo M. |last6=Lewis |first6=Clayton}}</ref> all of whom were for learning foreign languages and cited the benefits and advantages and the changing global landscape.

==See also==
*[[Multilingualism]]
*[[Languages of the United Kingdom]]
*[[Languages of the United States]]
*[[Linguistic imperialism]]
*[[List of multilingual countries and regions]]

==References==
{{Reflist}}

* Bialystok, E., Craik, F. & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Neuropsychology & Neurology, Linguistics & Language & Speech, 16(4), 240-250.
* Core, C., Hoff, E., Rumiche, R., & Senor, M. (2011). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637-1649.
* Kapa, L., & Colombo, J. (2013). Attentional control in early and later bilingual children.Cognitive Development, 28(3), 233-246.

==External links==
{{Wiktionary|monoglottism|monolingualism|unilingualism}}
*[https://litigation-essentials.lexisnexis.com/webcd/app?action=DocumentDisplay&crawlid=1&crawlid=1&doctype=cite&docid=14+Cardozo+L.+Rev.+1713&srctype=smi&srcid=3B15&key=30ce6efd643c7fdf6f394561a88d0a65 Monolingualism and Judaism] by Jose Faur, contrasting the Greek monolingualism with the polyglot culture of the Hebrews

[[Category:Monolingualism]]

Monolingualismus

2018-04-28T03:51:57Z

176.228.51.29: /* Predominance of English */

'''Monoglottism''' ([[Greek language|Greek]] μόνοσ ''monos'', "alone, solitary", + γλώττα ''glotta'', "tongue, language") or, more commonly, '''monolingualism''' or '''unilingualism''', is the condition of being able to speak only a single language, as opposed to [[multilingualism]]. In a different context, "unilingualism" may refer to a [[language policy]] which [[forced language|enforces]] an official or [[national language]] over others.

Being '''monolingual''' or '''unilingual''' is also said of a text, [[dictionary]], or conversation written or conducted in only one language, and of an [[entity]] in which a single language is either used or officially recognized (in particular when being compared with bilingual or multilingual entities or in the presence of individuals speaking different languages). Note that mono''glottism'' can only refer to lacking the ''ability'' to speak several languages. Multilingual speakers outnumber monolingual speakers in the world's population.<ref>G. Richard Tucker (1999)[http://www.cal.org/resources/Digest/digestglobal.html A Global Perspective on Bilingualism and Bilingual Education] {{webarchive|url=https://web.archive.org/web/20120822104004/http://www.cal.org/resources/Digest/digestglobal.html |date=2012-08-22 }} Carnegie Mellon University CALL Digest EDO-FL-99-04</ref>

Suzzane Romaine pointed out, in her 1995 book ''Bilingualism'', that it would be weird to find a book titled ''Monolingualism''.<ref>{{cite book |last=Romaine |first=Suzzane |year=1995 |publisher=Wiley-Blackwell |title=Bilingualism |pages=1 |isbn=978-0-631-19539-9}}</ref> This statement reflects the traditional assumption that linguistic theories often take on: that monolingualism is the norm.<ref>{{cite journal |last=Pavlenko |first=Aneta |title=L2 influence on L1 in late bilingualism. |journal=Issues in Applied Linguistics. |year=2000 |volume=11 |issue=2 |pages=175–206 }}</ref> Monolingualism is thus rarely the subject of scholarly publications, as it is viewed to be an unmarked or prototypical concept where it has the sense of being normal and [[multilingualism]] is the exception.<ref name="ellis">{{cite journal |last=Ellis |first=Elizabeth |title=Monolingualism: The unmarked case |journal=Estudios de Sociolingüística. |year=2006 |volume=7 |issue=2 |pages=173–196}}</ref>

The assumption of normative monolingualism is also often the view of monolinguals who speak a [[world language|global language]], like the [[English language]]. Crystal (1987) said that this assumption is adopted by many in Western society.<ref>{{cite book |last=Crystal |first=David |year=1987 |publisher=Cambridge University Press |title=The Cambridge Encyclopaedia of Language |isbn=978-0-521-55967-6}}</ref> One explanation is provided by Edwards, who in 2004 claimed that evidence of the "monolingual mindset" can be traced back to 19th century [[Europe]], when the nation was rising and a dominant group had control{{what|date=December 2013}}, and European mindsets on language were carried forth to its [[colonies]], further perpetuating the monolingual mindset.<ref>{{cite book |last1=Edwards |first1=Viv |title=Multilingualism in the English-speaking world. |publisher=Wiley-Blackwell |year=2004 |isbn=978-0-631-23613-9 |pages=3–5}}</ref>

Another explanation is that the nations who speak the [[English language]] are both “the producers and beneficiaries of English as a [[world language|global language]]” and the populations within these countries tend to be monolingual.<ref name="ellis"/>

==Comparison with multilingualism==
===Vocabulary size and verbal fluency===
According to a study on lexical access,<ref>{{cite journal |last1=Bialystok |first1=Ellen |last2=Craik |first2=Fergus I.M |last3=Luk |first3=Gigi. |title=Lexical access in bilinguals: Effects of vocabulary size and executive control |journal=Journal of Neurolinguistics |volume=21 |issue=6 |pages=522–538 |year=2008 |doi=10.1016/j.jneuroling.2007.07.001}}</ref> monolinguals often maintain a wider [[vocabulary]] in a target language relative to a comparable [[bilingual]], and that increases the efficiency of word retrieval in monolinguals. Monolinguals also access words more often than bilinguals in a target language.

In letter fluency tasks, monolinguals in the study were also able to respond with more words to the letter cue than bilinguals, but such an effect was not seen in bilinguals with a high [[vocabulary]] score.

Also, monolinguals performed better than bilinguals on verbal fluency in the study. If the [[vocabulary abilities]] were made to be more comparable, however, many of the differences would disappear, indicating that [[vocabulary]] size may be a factor that moderated a person's performance in verbal fluency and naming tasks. The same study also found that bilinguals, in a version of the letter fluency task that placed more demand on executive control, performed better than monolinguals. Thus, once [[vocabulary]] abilities were controlled, bilinguals performed better on letter fluency possibilities by the enhanced frontal executive processes in the [[brain]].

It is important to note here that bilinguals' overall vocabulary size in both languages combined was equivalent to monolinguals' in one language. While monolinguals may excel in vocabulary size for the one language they speak, their vocabulary content is not greater. Bilinguals may have smaller vocabularies in each individual language, but when their vocabularies were combined, the content size was approximately similar to that of the monolingual. Monolingual children demonstrated larger vocabulary scored than their bilingual peers, but bilingual children's vocabulary scores still increased with age, just like the monolingual children's vocabulary scores (Core et al., 2011). Despite a variation in vocabulary scores, there was absolutely no difference between monolingual and bilingual children in terms of total vocabulary size and total vocabulary gains (Core et al., 2011). Bilingual children and monolingual children have the same vocabulary size and gain the same vocabulary knowledge.

===Creative functioning===
In a study testing for creative functioning that involved monolingual and bilingual children in [[Singapore]],<ref>{{cite journal |last1=Torrance |first1=E. Paul |last2=Gowan |first2=John.C. |last3=Wu |first3=Jing-Jyi |last4=Aliotti |first4=Nicholas C. |title=Creative functioning of monolingual and bilingual children in Singapore |journal=Journal of Educational Psychology |volume=61 |issue=1 |pages=72–75 |year=1970 |doi=10.1037/h0028767}}</ref> researchers found that monolinguals performed better on fluency and flexibility than bilinguals. The trend was reversed, however, on tests for originality and elaboration.

===Mental well-being===
In another recent study in [[Canada]], it has been shown that monolinguals were worse at the onset of [[senility]] than bilinguals.<ref>{{cite news|url=http://www.biologynews.net/archives/2007/01/11/canadian_study_shows_bilingualism_has_protective_effect_in_delaying_onset_of_dementia_by_four_years.html|title=Canadian study shows bilingualism has protective effect in delaying onset of dementia by 4 years|work= Biology News Net|date=January 11, 2007}}</ref> In the study, it seems that being [[bilingual]] is associated with a delay of [[dementia]] by four years as compared to monolinguals. Bialystok's most recent work also shows that lifelong bilingualism can delay symptoms of [[dementia]].<ref name="university affairs">{{cite web|url=http://www.universityaffairs.ca/the-rise-of-the-monoglots.aspx |title=The rise of the monoglots |publisher=University Affairs.ca |date=August 5, 2008 |accessdate=11 March 2012}}</ref>

It is believed that bilingualism contributes to cognitive reserve by preventing effects of cognitive delay and prolonging the onset of sicknesses such as dementia. Cognitive reserve refers to the idea that engaging in stimulating physical or mental activity maintains cognitive functioning (Bialystok et al., 2012). In that case, knowing more than one language is similar to stimulating mental activity. To test whether or not bilingualism contributes to cognitive reserve, Bialystok et al. (2012) looked at hospital records among monolingual and bilingual adults who have dementia. The researchers found that elderly bilingual adults were diagnosed with dementia about three to four years later than elderly monolingual adults. The results have been replicated and validated, with outside factors being controlled. In fact, outside factors such as socioeconomic status and cultural differences always helped monolinguals, making the argument the bilingualism contributes to cognitive reserve even stronger (Bialystok et al., 2012). That finding enhances the fact that bilinguals are at an advantage because of their ability to speak two languages, not because of outside factors. A probable explanation for this phenomenon is that knowledge of multiple languages keeps the brain alert and therefore more mentally aware for a longer period of time.

===Emotion and behaviour===
A study conducted with children in their early school years suggested that there are emotional and behavioural benefits to being bilingual.<ref>{{cite journal |last1=Han |first1=Wen-Jui |last2=Huang |first2=Chien-Chung |title=The forgotten treasure: Bilingualism and Asian children's emotional and behavioural health |journal=American Journal of Public Health |year=2010 |volume=100 |issue=5 |pages=831–838 |doi=10.2105/ajph.2009.174219}}</ref> In the same study, the findings show that monolingual children, in particular non-English monolingual children, display more poor behavioural and emotional outcomes in their school years. The non-English monolingual children had the highest level of externalizing and internalizing behaviourial problems by fifth grade(around 10–11 years of age), even though the children were all measured to have similar levels of internalizing and externalizing behaviourial problems at the start{{what|date=December 2013}}. In contrast, the fluent [[bilingual]] and non-English dominant bilingual children were found to have the lowest level of these behaviourial problems. The authors suggest that monolingualism seems to be a risk factor. However, if there is a supportive school environment with teachers who are experienced in [[ESL]] (English as a Second Language), children seem to have better emotional constitution.

===Memory performance===
In a study conducted at the [[University of Florida]], which compared Native-English [[bilingual]]s to English monolinguals, although there was no difference in accuracy between the two groups, there was an evident slower response rate from bilinguals on tasks that involve latency of recognition of a list of abstract words and [[lexical decision task]]s.<ref>{{cite journal |last1=Ransdell |first1=Sarah Ellen |last2=Fischler |first2=Ira |title=Memory in a monolingual mode:When are bilinguals at a disadvantage? |journal=Journal of Memory and Language |year=1987 |volume=26 |pages=392–405 |doi=10.1016/0749-596x(87)90098-2}}</ref> For these two tasks, language-specific and data driven processes were more prevalent, that is, the tasks were driven by the dominant language and the data (the words used in the task). The study differed from prior research that there is more balance in familiarity of the [[dominant language]]. Magiste's (1980) hypothesis that it could have been due to differential familiarity with the [[dominant language]] is suggested to be a possible reason for the bilingual disadvantage.<ref>{{cite journal |last=Magiste |first=Edith |year=1980 |title=Memory for numbers in monolinguals and bilinguals |journal=Acta Psychologica |volume=46 |pages=63–68 |doi=10.1016/0001-6918(80)90059-1}}</ref> They explained that for bilinguals, it could be because the acquiring and using of the [[second language]] meant that there was less time to process English, as compared to the monolingual participants in the study.

However, evidence from a research study shows that bilinguals have a faster reaction time in most working memory tasks. While a lot of research asserts that monolingual children outperform bilingual children, other research asserts the opposite. Research by Bialystok et al., as reported by Kapa and Colombo (2013, p. 233) shows that bilingual individuals perform better than monolingual individuals on a wide variety of cognitive tests, thus demonstrating cognitive control advantages. Two different concepts, attentional inhibition and attentional monitoring, are used to measure attentional control. In terms of attentional control, early bilingual learners showed the greatest advantage, compared to monolingual speakers and late bilingual speakers. In terms of overall performance on ATN, the three groups performed equally, but when age and verbal ability variables were controlled, there was a difference in reaction time. The early bilingual children's reaction time was tremendously faster than the monolingual children, and only slightly faster than the late bilingual children (Kapa & Colombo, 2013). Early bilingual learners showed that they simply responded most efficiently to the task at hand. The results from this study demonstrate the advantages bilingual children have with attentional control. This is likely because bilingual children are used to balancing more than one language at time, and are therefore used to focusing on which language is necessary at a certain time. By constantly being aware of what language to use and being able to successfully switch between languages, it makes sense that bilingual children would be better at directing and focusing their attention.

===Verbal and non-verbal cognitive development===
A 2012 study by the [[University of York]] published in ''Child Development'' journal<ref>{{cite web |url=http://www.dushi.ca/tor/education/bencandy.php/fid18/aid1819 |title=最新研究：双语儿童比单语小孩更聪慧 |publisher=加拿大都市网 |date=10 February 2012 |accessdate=23 March 2013}}</ref> reviewed the effects of the development of a child's verbal and non-verbal language, matched between monolinguals and bilinguals in a particular language. Researchers compared about 100 6-year-old monolingual and [[bilingual]] children (monolingual in English; bilingual in English and Mandarin, bilingual in French and English, bilingual in Spanish and English), to test their verbal and [[non-verbal communication]] [[cognitive development]]. The research takes into consideration factors like the similarity of the language, the cultural background and education experience. These students mostly come from public schools from various areas, having similar social and economic background.

Results show that in the child's early stage, multilingual kids are very different from one another in their language and [[cognitive]] skills development, and also when compared to monolingual children. When compared to monolinguals, multilingual children are slower in building up their [[vocabulary]] in every language. However, their metalinguistic development allowed them to understand better the structure of the language. They also performed better in non-verbal control tests. A non-verbal control test refers to the ability to focus and then able to divert their attention when being instructed to.

==Reasons for persistence==
===Convergence principle===
According to the convergence principle,<ref name="snow">{{cite book|title=Language Loyalties: A Source Book on the Official English Controversy. |chapter=The Costs of Monolingualism |last1=Snow |first1=Catherine E.|last2=Hakuta |first2=Kenji |editor=Crawford, J.|publisher=The University of Chicago |year=1992 |pages=384–394 |url=http://www.stanford.edu/~hakuta/Publications/(1992)%20-%20THE%20COST%20OF%20MONOLINGUALISM.pdf |accessdate=9 March 2012}}</ref> language style tends to change to that of people who are liked and admired. Conversations in which one party speaks a language different from the other persons both are hard to maintain and have reduced intimacy. Thus, speech is usually adapted and accommodated for convenience, lack of misunderstanding and conflict and the maintenance of intimacy. In intermarriages, one partner tends to become monolingual, which also usually applies to the children.

===Predominance of English===
{{see also|English-only movement}}
The predominance of [[English language|English]] in many sectors, such as world trade, [[technology]] and [[science]], has contributed to English-speaking societies being persistently monolingual, as there is no relevant need to learn a [[second language]] if all dealings can be done in their [[native language]]<ref>{{cite journal |last=Peel |first=Quentin |title=The monotony of monoglots |journal=Language Learning Journal |volume=23 |issue=1 |pages=13–14 |year=2001 |doi=10.1080/09571730185200041}}</ref>; that is especially the case for English-speakers in the [[United States]], particularly the [[Northeastern United States|Northeastern]], [[Midwestern United States|Midwestern]], and most of the [[Southern United States]], where everyday contact with other languages, such as [[Spanish language|Spanish]] and [[French language|French]] is usually limited. The country's large area and the most populous regions' distance from large non-English-speaking areas, such as [[Mexico]] and [[Quebec]], increase the geographic and economic barriers to foreign travel.<ref>{{cite news|url=http://news.gallup.com/poll/1825/about-one-four-americans-can-hold-conversation-second-language.aspx|title=About One in Four Americans Can Hold a Conversation in a Second Language}}</ref> Although the country is economically interdependent with trade partners such as [[China]], American corporations and heavily-Americanized subsidiaries of foreign corporations both mediate and control most citizens' contact with most other nations' products. There is a popular joke: "What do you call a person who speaks three languages? A trilingual. What do you call a person who speaks two languages? A bilingual. What do you call a person who speaks one language? An American."<ref>{{cite book|last1=Gramling|first1=David|title=The Invention of Monolingualism|date= 6 October 2016|publisher=Bloomsbury Publishing|isbn=1501318055|pages=60-61}}</ref>

There is also increasing pressure on [[multilingualism|bilingual]] [[immigrants]] to renounce their [[mother tongue]] and to adopt their host country's language. As a result, even though there may be immigrants from a wide variety of nationalities and cultures, the main language spoken in the country does not reflect them.{{Citation needed|date=February 2015}}

==Costs==
Snow and Hakuta<ref name="snow" /> write that in a cost-benefit analysis, the choosing of English as the official and national language often comes with additional costs on the society, as the alternative choice of multilingualism has its own benefits.

===Education===
Some of the education budget is allocated for foreign-language training, but [[fluency]] of foreign-language students is lower than those who learned it at home.<ref name="snow" />

===Economic===
[[International business]] may be impeded by a lack of people competent in other languages.<ref name="snow" />

===National security===
Money has to be spent to train foreign-service personnel in foreign languages.<ref name="snow" />

===Time and effort===
Compared to the maintenance of a language that is learned at home, more time, effort and hard work are required to learn it in school.<ref name="snow" />

===Job opportunities===
Kirkpatrick asserts that monolinguals are at a disadvantage to bilinguals in the international job market.<ref>{{cite journal |last=Kirkpatrick |first=Andy |year=2000 |title=The disadvantaged monolingual: Why English alone is not enough. |journal=Australian Language Matters |volume=8 |issue=3 |pages=5–7 }}</ref>

==In the media==
[[Lawrence Summers]], in an article published in the ''[[New York Times]]'',<ref>{{cite news |url=https://www.nytimes.com/2012/01/22/education/edlife/the-21st-century-education.html?pagewanted=all |last=Summers |first=Lawrence H. |title=What You (Really) Need to Know |work=New York Times |date=20 January 2012}}</ref> discusses how to prepare for the future advancement of America. He also questioned the importance and necessity of learning foreign languages by remarking that "English's emergence as the [[global language]], along with the rapid progress in [[machine translation]] and the fragmentation of languages spoken around the world, makes it less clear that the substantial investment necessary to speak a foreign tongue is universally worthwhile."

Others have disagreed with Summers' view. A week later, the ''New York Times'' hosted a discussion among six panelists,<ref>{{cite news |url=https://www.nytimes.com/roomfordebate/2012/01/29/is-learning-a-language-other-than-english-worthwhile |date=29 January 2012 |title=English Is Global, So Why Learn Arabic? |work=New York Times |last1=Berdan |first1=Stacie Nevadomski |last2=Jackson |first2=Anthony |last3=Erard |first3=Michael |last4=Ho |first4=Melanie |last5=Suarez-Orozco |first5=Marcelo M. |last6=Lewis |first6=Clayton}}</ref> all of whom were for learning foreign languages and cited the benefits and advantages and the changing global landscape.

==See also==
*[[Multilingualism]]
*[[Languages of the United Kingdom]]
*[[Languages of the United States]]
*[[Linguistic imperialism]]
*[[List of multilingual countries and regions]]

==References==
{{Reflist}}

* Bialystok, E., Craik, F. & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Neuropsychology & Neurology, Linguistics & Language & Speech, 16(4), 240-250.
* Core, C., Hoff, E., Rumiche, R., & Senor, M. (2011). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637-1649.
* Kapa, L., & Colombo, J. (2013). Attentional control in early and later bilingual children.Cognitive Development, 28(3), 233-246.

==External links==
{{Wiktionary|monoglottism|monolingualism|unilingualism}}
*[https://litigation-essentials.lexisnexis.com/webcd/app?action=DocumentDisplay&crawlid=1&crawlid=1&doctype=cite&docid=14+Cardozo+L.+Rev.+1713&srctype=smi&srcid=3B15&key=30ce6efd643c7fdf6f394561a88d0a65 Monolingualism and Judaism] by Jose Faur, contrasting the Greek monolingualism with the polyglot culture of the Hebrews

[[Category:Monolingualism]]

Monolingualismus

2018-04-28T03:50:51Z

176.228.51.29: /* Predominance of English */

'''Monoglottism''' ([[Greek language|Greek]] μόνοσ ''monos'', "alone, solitary", + γλώττα ''glotta'', "tongue, language") or, more commonly, '''monolingualism''' or '''unilingualism''', is the condition of being able to speak only a single language, as opposed to [[multilingualism]]. In a different context, "unilingualism" may refer to a [[language policy]] which [[forced language|enforces]] an official or [[national language]] over others.

Being '''monolingual''' or '''unilingual''' is also said of a text, [[dictionary]], or conversation written or conducted in only one language, and of an [[entity]] in which a single language is either used or officially recognized (in particular when being compared with bilingual or multilingual entities or in the presence of individuals speaking different languages). Note that mono''glottism'' can only refer to lacking the ''ability'' to speak several languages. Multilingual speakers outnumber monolingual speakers in the world's population.<ref>G. Richard Tucker (1999)[http://www.cal.org/resources/Digest/digestglobal.html A Global Perspective on Bilingualism and Bilingual Education] {{webarchive|url=https://web.archive.org/web/20120822104004/http://www.cal.org/resources/Digest/digestglobal.html |date=2012-08-22 }} Carnegie Mellon University CALL Digest EDO-FL-99-04</ref>

Suzzane Romaine pointed out, in her 1995 book ''Bilingualism'', that it would be weird to find a book titled ''Monolingualism''.<ref>{{cite book |last=Romaine |first=Suzzane |year=1995 |publisher=Wiley-Blackwell |title=Bilingualism |pages=1 |isbn=978-0-631-19539-9}}</ref> This statement reflects the traditional assumption that linguistic theories often take on: that monolingualism is the norm.<ref>{{cite journal |last=Pavlenko |first=Aneta |title=L2 influence on L1 in late bilingualism. |journal=Issues in Applied Linguistics. |year=2000 |volume=11 |issue=2 |pages=175–206 }}</ref> Monolingualism is thus rarely the subject of scholarly publications, as it is viewed to be an unmarked or prototypical concept where it has the sense of being normal and [[multilingualism]] is the exception.<ref name="ellis">{{cite journal |last=Ellis |first=Elizabeth |title=Monolingualism: The unmarked case |journal=Estudios de Sociolingüística. |year=2006 |volume=7 |issue=2 |pages=173–196}}</ref>

The assumption of normative monolingualism is also often the view of monolinguals who speak a [[world language|global language]], like the [[English language]]. Crystal (1987) said that this assumption is adopted by many in Western society.<ref>{{cite book |last=Crystal |first=David |year=1987 |publisher=Cambridge University Press |title=The Cambridge Encyclopaedia of Language |isbn=978-0-521-55967-6}}</ref> One explanation is provided by Edwards, who in 2004 claimed that evidence of the "monolingual mindset" can be traced back to 19th century [[Europe]], when the nation was rising and a dominant group had control{{what|date=December 2013}}, and European mindsets on language were carried forth to its [[colonies]], further perpetuating the monolingual mindset.<ref>{{cite book |last1=Edwards |first1=Viv |title=Multilingualism in the English-speaking world. |publisher=Wiley-Blackwell |year=2004 |isbn=978-0-631-23613-9 |pages=3–5}}</ref>

Another explanation is that the nations who speak the [[English language]] are both “the producers and beneficiaries of English as a [[world language|global language]]” and the populations within these countries tend to be monolingual.<ref name="ellis"/>

==Comparison with multilingualism==
===Vocabulary size and verbal fluency===
According to a study on lexical access,<ref>{{cite journal |last1=Bialystok |first1=Ellen |last2=Craik |first2=Fergus I.M |last3=Luk |first3=Gigi. |title=Lexical access in bilinguals: Effects of vocabulary size and executive control |journal=Journal of Neurolinguistics |volume=21 |issue=6 |pages=522–538 |year=2008 |doi=10.1016/j.jneuroling.2007.07.001}}</ref> monolinguals often maintain a wider [[vocabulary]] in a target language relative to a comparable [[bilingual]], and that increases the efficiency of word retrieval in monolinguals. Monolinguals also access words more often than bilinguals in a target language.

In letter fluency tasks, monolinguals in the study were also able to respond with more words to the letter cue than bilinguals, but such an effect was not seen in bilinguals with a high [[vocabulary]] score.

Also, monolinguals performed better than bilinguals on verbal fluency in the study. If the [[vocabulary abilities]] were made to be more comparable, however, many of the differences would disappear, indicating that [[vocabulary]] size may be a factor that moderated a person's performance in verbal fluency and naming tasks. The same study also found that bilinguals, in a version of the letter fluency task that placed more demand on executive control, performed better than monolinguals. Thus, once [[vocabulary]] abilities were controlled, bilinguals performed better on letter fluency possibilities by the enhanced frontal executive processes in the [[brain]].

It is important to note here that bilinguals' overall vocabulary size in both languages combined was equivalent to monolinguals' in one language. While monolinguals may excel in vocabulary size for the one language they speak, their vocabulary content is not greater. Bilinguals may have smaller vocabularies in each individual language, but when their vocabularies were combined, the content size was approximately similar to that of the monolingual. Monolingual children demonstrated larger vocabulary scored than their bilingual peers, but bilingual children's vocabulary scores still increased with age, just like the monolingual children's vocabulary scores (Core et al., 2011). Despite a variation in vocabulary scores, there was absolutely no difference between monolingual and bilingual children in terms of total vocabulary size and total vocabulary gains (Core et al., 2011). Bilingual children and monolingual children have the same vocabulary size and gain the same vocabulary knowledge.

===Creative functioning===
In a study testing for creative functioning that involved monolingual and bilingual children in [[Singapore]],<ref>{{cite journal |last1=Torrance |first1=E. Paul |last2=Gowan |first2=John.C. |last3=Wu |first3=Jing-Jyi |last4=Aliotti |first4=Nicholas C. |title=Creative functioning of monolingual and bilingual children in Singapore |journal=Journal of Educational Psychology |volume=61 |issue=1 |pages=72–75 |year=1970 |doi=10.1037/h0028767}}</ref> researchers found that monolinguals performed better on fluency and flexibility than bilinguals. The trend was reversed, however, on tests for originality and elaboration.

===Mental well-being===
In another recent study in [[Canada]], it has been shown that monolinguals were worse at the onset of [[senility]] than bilinguals.<ref>{{cite news|url=http://www.biologynews.net/archives/2007/01/11/canadian_study_shows_bilingualism_has_protective_effect_in_delaying_onset_of_dementia_by_four_years.html|title=Canadian study shows bilingualism has protective effect in delaying onset of dementia by 4 years|work= Biology News Net|date=January 11, 2007}}</ref> In the study, it seems that being [[bilingual]] is associated with a delay of [[dementia]] by four years as compared to monolinguals. Bialystok's most recent work also shows that lifelong bilingualism can delay symptoms of [[dementia]].<ref name="university affairs">{{cite web|url=http://www.universityaffairs.ca/the-rise-of-the-monoglots.aspx |title=The rise of the monoglots |publisher=University Affairs.ca |date=August 5, 2008 |accessdate=11 March 2012}}</ref>

It is believed that bilingualism contributes to cognitive reserve by preventing effects of cognitive delay and prolonging the onset of sicknesses such as dementia. Cognitive reserve refers to the idea that engaging in stimulating physical or mental activity maintains cognitive functioning (Bialystok et al., 2012). In that case, knowing more than one language is similar to stimulating mental activity. To test whether or not bilingualism contributes to cognitive reserve, Bialystok et al. (2012) looked at hospital records among monolingual and bilingual adults who have dementia. The researchers found that elderly bilingual adults were diagnosed with dementia about three to four years later than elderly monolingual adults. The results have been replicated and validated, with outside factors being controlled. In fact, outside factors such as socioeconomic status and cultural differences always helped monolinguals, making the argument the bilingualism contributes to cognitive reserve even stronger (Bialystok et al., 2012). That finding enhances the fact that bilinguals are at an advantage because of their ability to speak two languages, not because of outside factors. A probable explanation for this phenomenon is that knowledge of multiple languages keeps the brain alert and therefore more mentally aware for a longer period of time.

===Emotion and behaviour===
A study conducted with children in their early school years suggested that there are emotional and behavioural benefits to being bilingual.<ref>{{cite journal |last1=Han |first1=Wen-Jui |last2=Huang |first2=Chien-Chung |title=The forgotten treasure: Bilingualism and Asian children's emotional and behavioural health |journal=American Journal of Public Health |year=2010 |volume=100 |issue=5 |pages=831–838 |doi=10.2105/ajph.2009.174219}}</ref> In the same study, the findings show that monolingual children, in particular non-English monolingual children, display more poor behavioural and emotional outcomes in their school years. The non-English monolingual children had the highest level of externalizing and internalizing behaviourial problems by fifth grade(around 10–11 years of age), even though the children were all measured to have similar levels of internalizing and externalizing behaviourial problems at the start{{what|date=December 2013}}. In contrast, the fluent [[bilingual]] and non-English dominant bilingual children were found to have the lowest level of these behaviourial problems. The authors suggest that monolingualism seems to be a risk factor. However, if there is a supportive school environment with teachers who are experienced in [[ESL]] (English as a Second Language), children seem to have better emotional constitution.

===Memory performance===
In a study conducted at the [[University of Florida]], which compared Native-English [[bilingual]]s to English monolinguals, although there was no difference in accuracy between the two groups, there was an evident slower response rate from bilinguals on tasks that involve latency of recognition of a list of abstract words and [[lexical decision task]]s.<ref>{{cite journal |last1=Ransdell |first1=Sarah Ellen |last2=Fischler |first2=Ira |title=Memory in a monolingual mode:When are bilinguals at a disadvantage? |journal=Journal of Memory and Language |year=1987 |volume=26 |pages=392–405 |doi=10.1016/0749-596x(87)90098-2}}</ref> For these two tasks, language-specific and data driven processes were more prevalent, that is, the tasks were driven by the dominant language and the data (the words used in the task). The study differed from prior research that there is more balance in familiarity of the [[dominant language]]. Magiste's (1980) hypothesis that it could have been due to differential familiarity with the [[dominant language]] is suggested to be a possible reason for the bilingual disadvantage.<ref>{{cite journal |last=Magiste |first=Edith |year=1980 |title=Memory for numbers in monolinguals and bilinguals |journal=Acta Psychologica |volume=46 |pages=63–68 |doi=10.1016/0001-6918(80)90059-1}}</ref> They explained that for bilinguals, it could be because the acquiring and using of the [[second language]] meant that there was less time to process English, as compared to the monolingual participants in the study.

However, evidence from a research study shows that bilinguals have a faster reaction time in most working memory tasks. While a lot of research asserts that monolingual children outperform bilingual children, other research asserts the opposite. Research by Bialystok et al., as reported by Kapa and Colombo (2013, p. 233) shows that bilingual individuals perform better than monolingual individuals on a wide variety of cognitive tests, thus demonstrating cognitive control advantages. Two different concepts, attentional inhibition and attentional monitoring, are used to measure attentional control. In terms of attentional control, early bilingual learners showed the greatest advantage, compared to monolingual speakers and late bilingual speakers. In terms of overall performance on ATN, the three groups performed equally, but when age and verbal ability variables were controlled, there was a difference in reaction time. The early bilingual children's reaction time was tremendously faster than the monolingual children, and only slightly faster than the late bilingual children (Kapa & Colombo, 2013). Early bilingual learners showed that they simply responded most efficiently to the task at hand. The results from this study demonstrate the advantages bilingual children have with attentional control. This is likely because bilingual children are used to balancing more than one language at time, and are therefore used to focusing on which language is necessary at a certain time. By constantly being aware of what language to use and being able to successfully switch between languages, it makes sense that bilingual children would be better at directing and focusing their attention.

===Verbal and non-verbal cognitive development===
A 2012 study by the [[University of York]] published in ''Child Development'' journal<ref>{{cite web |url=http://www.dushi.ca/tor/education/bencandy.php/fid18/aid1819 |title=最新研究：双语儿童比单语小孩更聪慧 |publisher=加拿大都市网 |date=10 February 2012 |accessdate=23 March 2013}}</ref> reviewed the effects of the development of a child's verbal and non-verbal language, matched between monolinguals and bilinguals in a particular language. Researchers compared about 100 6-year-old monolingual and [[bilingual]] children (monolingual in English; bilingual in English and Mandarin, bilingual in French and English, bilingual in Spanish and English), to test their verbal and [[non-verbal communication]] [[cognitive development]]. The research takes into consideration factors like the similarity of the language, the cultural background and education experience. These students mostly come from public schools from various areas, having similar social and economic background.

Results show that in the child's early stage, multilingual kids are very different from one another in their language and [[cognitive]] skills development, and also when compared to monolingual children. When compared to monolinguals, multilingual children are slower in building up their [[vocabulary]] in every language. However, their metalinguistic development allowed them to understand better the structure of the language. They also performed better in non-verbal control tests. A non-verbal control test refers to the ability to focus and then able to divert their attention when being instructed to.

==Reasons for persistence==
===Convergence principle===
According to the convergence principle,<ref name="snow">{{cite book|title=Language Loyalties: A Source Book on the Official English Controversy. |chapter=The Costs of Monolingualism |last1=Snow |first1=Catherine E.|last2=Hakuta |first2=Kenji |editor=Crawford, J.|publisher=The University of Chicago |year=1992 |pages=384–394 |url=http://www.stanford.edu/~hakuta/Publications/(1992)%20-%20THE%20COST%20OF%20MONOLINGUALISM.pdf |accessdate=9 March 2012}}</ref> language style tends to change to that of people who are liked and admired. Conversations in which one party speaks a language different from the other persons both are hard to maintain and have reduced intimacy. Thus, speech is usually adapted and accommodated for convenience, lack of misunderstanding and conflict and the maintenance of intimacy. In intermarriages, one partner tends to become monolingual, which also usually applies to the children.

===Predominance of English===
{{see also|English-only movement}}
The predominance of [[English language|English]] in many sectors, such as world trade, [[technology]] and [[science]], has contributed to English-speaking societies being persistently monolingual, as there is no relevant need to learn a [[second language]] if all dealings can be done in their [[native language]];<ref>{{cite journal |last=Peel |first=Quentin |title=The monotony of monoglots |journal=Language Learning Journal |volume=23 |issue=1 |pages=13–14 |year=2001 |doi=10.1080/09571730185200041}}</ref> that is especially the case for English-speakers in the [[United States]], particularly the [[Northeastern United States|Northeastern]], [[Midwestern United States|Midwestern]], and most of the [[Southern United States]], where everyday contact with other languages, such as [[Spanish language|Spanish]] and [[French language|French]] is usually limited. The country's large area and the most populous regions' distance from large non-English-speaking areas, such as [[Mexico]] and [[Quebec]], increase the geographic and economic barriers to foreign travel.<ref>{{cite news|url=http://news.gallup.com/poll/1825/about-one-four-americans-can-hold-conversation-second-language.aspx|title=About One in Four Americans Can Hold a Conversation in a Second Language}}</ref> Although the country is economically interdependent with trade partners such as [[China]], American corporations and heavily-Americanized subsidiaries of foreign corporations both mediate and control most citizens' contact with most other nations' products. There is a popular joke: "What do you call a person who speaks three languages? A trilingual. What do you call a person who speaks two languages? A bilingual. What do you call a person who speaks one language? An American."<ref>{{cite book|last1=Gramling|first1=David|title=The Invention of Monolingualism|date= 6 October 2016|publisher=Bloomsbury Publishing|isbn=1501318055|pages=60-61}}</ref>

There is also increasing pressure on [[multilingualism|bilingual]] [[immigrants]] to renounce their [[mother tongue]] and to adopt their host country's language. As a result, even though there may be immigrants from a wide variety of nationalities and cultures, the main language spoken in the country does not reflect them.{{Citation needed|date=February 2015}}

==Costs==
Snow and Hakuta<ref name="snow" /> write that in a cost-benefit analysis, the choosing of English as the official and national language often comes with additional costs on the society, as the alternative choice of multilingualism has its own benefits.

===Education===
Some of the education budget is allocated for foreign-language training, but [[fluency]] of foreign-language students is lower than those who learned it at home.<ref name="snow" />

===Economic===
[[International business]] may be impeded by a lack of people competent in other languages.<ref name="snow" />

===National security===
Money has to be spent to train foreign-service personnel in foreign languages.<ref name="snow" />

===Time and effort===
Compared to the maintenance of a language that is learned at home, more time, effort and hard work are required to learn it in school.<ref name="snow" />

===Job opportunities===
Kirkpatrick asserts that monolinguals are at a disadvantage to bilinguals in the international job market.<ref>{{cite journal |last=Kirkpatrick |first=Andy |year=2000 |title=The disadvantaged monolingual: Why English alone is not enough. |journal=Australian Language Matters |volume=8 |issue=3 |pages=5–7 }}</ref>

==In the media==
[[Lawrence Summers]], in an article published in the ''[[New York Times]]'',<ref>{{cite news |url=https://www.nytimes.com/2012/01/22/education/edlife/the-21st-century-education.html?pagewanted=all |last=Summers |first=Lawrence H. |title=What You (Really) Need to Know |work=New York Times |date=20 January 2012}}</ref> discusses how to prepare for the future advancement of America. He also questioned the importance and necessity of learning foreign languages by remarking that "English's emergence as the [[global language]], along with the rapid progress in [[machine translation]] and the fragmentation of languages spoken around the world, makes it less clear that the substantial investment necessary to speak a foreign tongue is universally worthwhile."

Others have disagreed with Summers' view. A week later, the ''New York Times'' hosted a discussion among six panelists,<ref>{{cite news |url=https://www.nytimes.com/roomfordebate/2012/01/29/is-learning-a-language-other-than-english-worthwhile |date=29 January 2012 |title=English Is Global, So Why Learn Arabic? |work=New York Times |last1=Berdan |first1=Stacie Nevadomski |last2=Jackson |first2=Anthony |last3=Erard |first3=Michael |last4=Ho |first4=Melanie |last5=Suarez-Orozco |first5=Marcelo M. |last6=Lewis |first6=Clayton}}</ref> all of whom were for learning foreign languages and cited the benefits and advantages and the changing global landscape.

==See also==
*[[Multilingualism]]
*[[Languages of the United Kingdom]]
*[[Languages of the United States]]
*[[Linguistic imperialism]]
*[[List of multilingual countries and regions]]

==References==
{{Reflist}}

* Bialystok, E., Craik, F. & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Neuropsychology & Neurology, Linguistics & Language & Speech, 16(4), 240-250.
* Core, C., Hoff, E., Rumiche, R., & Senor, M. (2011). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637-1649.
* Kapa, L., & Colombo, J. (2013). Attentional control in early and later bilingual children.Cognitive Development, 28(3), 233-246.

==External links==
{{Wiktionary|monoglottism|monolingualism|unilingualism}}
*[https://litigation-essentials.lexisnexis.com/webcd/app?action=DocumentDisplay&crawlid=1&crawlid=1&doctype=cite&docid=14+Cardozo+L.+Rev.+1713&srctype=smi&srcid=3B15&key=30ce6efd643c7fdf6f394561a88d0a65 Monolingualism and Judaism] by Jose Faur, contrasting the Greek monolingualism with the polyglot culture of the Hebrews

[[Category:Monolingualism]]