The human dorsal and ventral visual streams: Behavioural and fMRI studies of the consequences of selective brain lesions

There has been an explosion of knowledge over the past 15 years about how different areas of the human brain contribute to our visual experience of the world. These advances have come from a convergence of several different methodologies: brain imaging, studies of patients with specific kinds of brain damage, and physiological studies of animals. A.D. Milner and M.A. Goodale have summarized these developments in a recent book (Sight Unseen , Oxford University Press, 2003). The present application is directed at combining two of these investigative methods, by not only studying the behaviour and perceptual abilities of certain patients with specific brain damage, but also studying which parts of their brains are active during such tests by means of functional neuroimaging (fMRI). This should help us understand better the functions of the two visual streams, as well as how the brain can adjust to severe damage to one of the two streams.

Recent structural and functional MRI studies have shown that the visual form agnosic patient D.F. has sustained bilateral brain damage that corresponds closely to the location of the shape processing area LO. The proposed programme of investigation will be based partly on a series of further behavioural and fMRI studies on D.F. and a second patient with visual form agnosia (S.B.) who (from structural MRI) also appears to have bilateral damage to area LO. These studies will be complemented by a series of parallel studies of patients with optic ataxia (I.G. and A.T.), who have area LO intact, but instead have bilateral damage to the dorsal visual stream, in and around the intraparietal sulcus.