Visual areas in the lateral temporal cortex of the ferret (Mustela putorius).

Using systematic electrophysiological mapping, architectonics and the global pattern of interhemispheric connectivity, we have identified three visual areas in the lateral most part of the posterior suprasylvian gyrus. The most posterior and largest area we call area 20a and anterior to this we defined a smaller area, area 20b. These areas lie lateral to the visual areas 18, 19 and 21 and posterior to a third, but incompletely defined, visual area, area PS. Areas 20a and 20b, emphasize the representation of the upper hemifield. Their interhemispheric connections conform to the so called 'midline rule' in that they are abundant in regions representing central portions of the visual field, scarce or absent elsewhere. These areas are probably homologous to the homonymous areas of the cat and might be indicative of a Bauplan from which the temporal areas of primates may have evolved.