Visual Processing in the Primate Brain

The visual system is the most widely studied and perhaps the best understood mammalian sensory system. Not only have the details of its anatomical features been well described, but the behavior of it neurons have also been characterized at many stages of the neural pathway. This chapter focuses on the visual system of nonhuman primates and deals with the way the primate visual system performs the analysis of various attributes of the visual image and then integrates these attributes into a percept of a visual scene. It shows how such fundamental dimensions of visual stimuli as spatial and temporal variations in luminance and chromaticity are first encoded at the level of the retina, and the manner in which the encoding of other more complex stimulus features, such as motion, complex form and depth, emerge at the level of visual cortex. Finally, modulation of visual cortical activity by such cognitive phenomena as memory and attention are discussed. Keywords: dorsal visual stream; lateral geniculate nucleus; neurophysiology; nonhuman primates; parietal cortex; retina; striate cortex; temporal cortex; ventral visual stream