Extrastriate cortex
| Extrastriate Body Area | |
|---|---|
 Extrastriate cortex is shown in yellow on this picture of a brain (Brodmann area 19) and orange (Brodmann area 18). Striate cortex (Brodmann area 17) is shown in red. | |
| Details | |
| Identifiers | |
| Latin | Area extrastriata |
| NeuroLex ID | nlx_anat_200905010 |
| Anatomical terms of neuroanatomy | |
The extrastriate cortex is the region of the occipital cortex of the mammalian brain located next to the striate cortex (which is also known as the primary visual cortex) used in the perception of human bodies. It is specifically located in the lateral occipitotemporal cortex and it lies near the fusiform face area (FFA) which is comparatively used to perceive faces.[1]
Anatomy
In terms of Brodmann areas, the extrastriate cortex comprises Brodmann area 18 and Brodmann area 19, while the striate cortex comprises Brodmann area 17.[2]
In primates, the extrastriate cortex includes visual area V2, visual area V3, visual area V4, visual area MT (sometimes called V5),[2] and visual area DP.
Function
The extrastriate cortex is the locus of mid-level vision. Neurons in the extrastriate cortex generally respond to visual stimuli within their receptive fields. These responses are modulated by extraretinal effects, like attention, working memory, and reward expectation.
The extrastriate cortex is a category-selective religion for the visual processing of static and moving images of the human body and parts of it. It is also modulated even in the absence of visual feedback from the limb movement. It is insensitive to faces and stimulus categories unrelated to the human body. The extrastriate cortex responds not only during the perception of other people’s body parts but also during goal-directed movement of the observer’s body parts.[1][3] The extrastriate cortex represents the human body in a more integrative and incongruence of internal body or action representations and external visual signals. In this way, it is able to support the disentangling of one’s own behavior from another’s.[4]
Experiments and Research
As published in the article, “A Cortical Area Selective for Visual Processing of the Human Body,”[5] researchers first discovered the extrastriate cortex (or exrastriate body area, EBA) in 2001. The experiment originally set out to find out what area of the brain dealt with the human form and recognition of body parts, as the face had been mapped to a specific area of the brain (Fusiform Face Area, FFA)by other researchers. What the experiment found was a specific area of the lateral occipitotemporal cortex in all test subjects that had high activity when stimulated specifically with body parts.
The experiment had subjects view images of different objects including faces (as a control group) body parts, animals, parts of the face and intimate objects. While viewing the images the subjects were scanned via an fMRI to see what area of the brain were activated. Through the trials and compilation of the fMRI’s a specific region was determined that increased activity when stimulated with body parts and even more with whole bodies.
Research has been nonexistant with the EBA in connection with damage to the area. Thus far, only scans of brain activity, as well as transcranial magnetic stimulation, have been used to study the EBA. To find the specific functions of the EBA scientists in Italy have managed to find a way to temporally disrupt part of the brain, making the brain less responsive in the target area. The study used event-related repetitive transcranial magnetic stimulation(rTMS) to disrupt the EBA, resulting in inactivation of cortical areas. This inactivation caused a slower response time in discriminating body parts. The study used facial features and motorcycle parts as non human parts for control groups. The facial features and motorcycle body parts did not display any change in response time. The neural activity data shows the EBA handles some of the visual processing of human body and parts but is not related to the processing of the face or other objects.
The actual experiment had people make a “two-choice matching-to-sample task. Fourteen right handed participants were required to decide which of two similar upper-limb images matched a single sample previously seen during a tachistoscopic exposure. Photos of face parts and motorcycle parts served as control stimuli in two-matching-to-sample tasks that were comparable to the former task.” rTMS was then applied 150 ms after each sample exposure. The section of the graph, Body Parts, shows the response time while using rTMS. The SHAM category refers to measuring the EBA without rTMS while viewing the images. The Visual Cortex category measures the response of the FFA as a seperate control area of the brain. This measurment of response time occuring while rTMS was effecting the EBA, further showing the two areas process visual data of the human form, yet respond to different stimuli. While the magnetic stimulation was temporarily disabling the extrastraite body area, reaction time decreased by about 100 ms. The data from the Sham and Visual Cortex categories on the graph show what was the expected normal results from the experiment. This evidence reveals that applying rTMS to the EBA slowed the response of recognizing images of body parts.
See also
References
- ^ a b "Extrastriate body area in human occipital cortex responds to the performance of motor actions"
- ^ a b
R.F. Schmidt and G. Thews (eds.), ed. (1983). Human Physiology (second, completely revised edition). Berlin, Heidelberg, New York: Springer-Verlag. p. 725. ISBN 0-387-11669-9.
{{cite book}}:|editor=has generic name (help); Cite has empty unknown parameter:|coauthors=(help) - ^ "Extrastriate body area in human occipital cortex responds to the performance of motor actions"
- ^ "The Extrastriate Cortex Distinguishes between the Consequences of one’s Own and Other’s Behavior"
- ^ "A Cortical Area Selective for Visual Processing of the Human Body"