Development and Plasticity of Extrastriate Visual Cortex in Monkeys

Abstract

The extrastriate visual cortex of the monkey has in recent decades come to include an ever-expanding portion of the neocortical domain as more and more traditional “association” or even motor territories are shown to have significant visual connections, visual responsiveness, or role in visual behavior (Felleman and van Essen, 1991; also see the chapter by Gross in this volume). In this chapter, discussion will be restricted (or broadened, depending upon one’s viewpoint) to consideration of cortical zones shown to have at least some visual sensory responsiveness and direct connectivity with other, unimodal visual areas. First, we will consider the normal anatomical, physiological, and metabolic development of extrastriate visual cortex, including the prenatal specification of visual areas. Next, we will discuss the plasticity of extrastriate visual cortex in adulthood by examining the ability of extrastriate areas to function in parallel with striate cortex and the consequences of damage to extrastriate cortex in adult monkeys. In addition, we will examine evidence for learning-or experience-dependent plasticity in the response properties of neurons in extrastriate cortex. In the subsequent section, we will address the special plasticity associated with damage to visual cortex in developing animals. We will then briefly compare the development and plasticity of extratriate cortex in monkeys with phenomena described for other mammalian groups. In the final section, we will summarize the data presented and comment on general principles of extrastriate and cerebral cortical development.