Population coding

Population encoding is a means by which information about something is encoded in the brain. We might naively suppose that a value is represented by the activity of a set of neurons, and each value is represented by the activity of one neuron. But in practice the representation is generally that the activity of each neuron in the set is a function of the perceptual value. Each neuron has its own encoding function, so that different neurons respond differently to the same value, and the set of responses of all the neurons in the set is different for different values.

Typically an encoding function has a peak value such that activity of the neuron is greatest if the perceptual value is close to the peak value, and becomes reduced accordingly for values less close to the peak value.

If follows that the actual perceived value can be reconstructed from the overall pattern of activity in the set of neurons. A specific mathematical technique for performing such a reconstruction is the method of maximum likelihood.