Unmasking of visual deficits following unilateral prestriate lesions in man

The primate visual cortex is a mosaic of different areas which are roughly organized into two major pathways, a dorsal one along an occipito-parietal channel and a ventral one along an occipito-temporal channel. It is known that visual stimuli are processed differently within these two systems and one might expect therefore that behavioral deficits would differ according to the channel damaged by cerebral lesions. Two patients with left prestriate lesions presented perceptual deficits in the right visual field. These deficits involved reading, recognition of line drawings and colour perception and would be compatible with a dysfunction of the ventral system. Magnetic resonance imaging analysis confirmed that this was the case.