Chapter 27: Two cortical visual systems in Old World and New World primates

Abstract

This chapter focuses on two cortical visual systems in Old World and New World primates. Visual cortex is divided into multiple subdivisions, or areas, in the brains of advanced mammals such as primates. Each visual area has a distinctive and complex pattern of cortical connections. A valuable insight was made by Ungerleider and Mishkin that connection between areas of visual cortex in macaque monkeys form two major diverging pathways. Both pathways originate at the level of cortex from striate cortex. One pathway relays through a number of areas rostra1 to striate cortex and terminates in cortex of the posterior parietal lobe. The other pathway relays through a number of different areas and terminates in inferior temporal cortex. The results of more recent studies of cortical connections in macaque monkeys, when compared with those from three different species of New World monkeys and one Old World prosimian primate, suggest the hypothesis that processing streams directed toward posterior parietal and inferior temporal cortex exist in all primates.