ABSTRACT
The ease with which we recognize objects in everyday life belies the underlying complexity of visual processing in the brain. However, insights into the intricacies of these processes can be drawn from the study of brain damaged subjects who have lost some of the abilities we take so much for granted. For instance, damage can result in selective impairments in the visual perception of form (Goodale, Milner, Jakobson, & Carey, 1991), color (Heywood, Cowey, & Newcombe, 1991), and motion (Zihl, Von Cramon, & Mai, 1983), suggesting that these properties are processed in separable neural pathways. We focus on selective impairments of visual form perception (or visual agnosia) in this chapter, though the other disorders are discussed. Since we have already published a number of reviews on agnosia (Humphreys & Riddoch, 1987a, 1993; Riddoch & Humphreys, 1988) we will not place so much emphasis on the different types of visual agnosia, but instead will focus our discussion on some of the current issues and controversies.
