From Pigments to Perception

Abstract

Most primates are highly visual creatures, capable of a wide variety of difficult tasks that must be carried out in a complex visual environment. It is therefore hardly surprising that a very large expanse of cerebral cortex is devoted to analyzing and interpreting the relatively raw messages transmitted from the retina. Over the past three decades, much progress has been made in elucidating the organization and function of visual cortex. In this chapter we briefly review recent progress in understanding several aspects of visual processing in the macaque monkey, as revealed by both anatomical and physiological studies. The first topic concerns the nature of information flow through the visual cortex as revealed by analysis of the numerous pathways that interconnect different visual areas. The guiding hypothesis is that the cortex is arranged as a distributed hierarchical system, in which there are many distinct levels of analysis. The second topic concerns parallel processing streams and their relationship to the M and P pathways established within the retina. The third topic deals with the functional significance of the feedback pathways that form a prominent characteristic of the cortical hierarchy. The function of feedback pathways in sensory processing has been an intriguing but elusive issue. There are probably many such functions, and here we emphasize their possible role in modulating neural responses according to the broader context of the visual environment.