Visual Processing in Monkey Extrastriate Cortex

The neuronal processes that lead to visual perception have attracted intense interest since Kuffier's studies of receptive field organization in cat retinal ganglion cells over three decades ago (Kuffier 1953). A variety of ana­ tomical and physiological approaches have been employed to analyze the organization of thc visual pathway between the retina and striate cortex (VI ) and the transformations of visual information that occur at each stage (see Hubel & Wiesel 1977, Stone 1 983, Shapley & Lennie 1985). The growth in understanding of the retinostriate pathway has been accompanied by increasing interest in visual processing in the expanse of extrastriate cortex beyond V I . Studies of extrastriate cortex in many spec­ ies showed that it comprises a mosaic of visual areas that can be dis­ tinguished by several anatomical and physiological criteria (reviewed by Kaas 1 978, Zeki 1 978, Cowey 1979, Van Essen 1 979, 1985, Wagor et al 1980, Tusa et al 1 98 1) . The literature in this field is large, and we do not attempt to review all relevant studies. Rather, we concern ourselves with three recent devel­ opments that have yielded insight into information processing and flow within extrastriate cortex. The first of these is the convergence of ana tom-