The Role of Striate Cortex

Abstract

Much of what is known about the role of human striate cortex in vision comes from the study of dysfunction in patients with specific lesions of visual pathways, from the retina to the occipital lobe and the adjoining temporal and parietal regions. That evidence depends on neuro-ophthalmological, neuropsychological, and psychophysical techniques. The neuroanatomy is provided, in vivo, by modern neuroimaging techniques such as magnetic resonance imaging (MRI) (Damasio and Damasio, 1989; Damasio and Frank, 1992), and (less often) at autopsy. Positron emission tomography (PET) studies offer another window on regional localization and visual function. Comparative anatomical studies on the functional organization of the visual system, particularly in the monkey, also provide insights into the corresponding organization in the human. This chapter examines these converging lines of evidence in the context of what they tell us about the role of human striate cortex [which is also referred to as the primary visual cortex, the calcarine cortex, area 17 of Brodmann (1909), and more recently as area V1] (see Fig. 1). The emphasis in this chapter is on human brain lesion studies. In the introductory section, we start with a definition of human visual areas and deficits, and follow with comments on the human brain lesion method applied to vision, on human—monkey homologies, and on subcortical inputs to V1.