Higher cortical visual deficits.

PURPOSE OF REVIEW: This article reviews the various types of visual dysfunction that can result from lesions of the cerebral regions beyond the striate cortex.

RECENT FINDINGS: Patients with dyschromatopsia can exhibit problems with color constancy. The apperceptive form of prosopagnosia is associated with damage to posterior occipital and fusiform gyri, and an associative/amnestic form is linked to damage to more anterior temporal regions. Pure alexia can be accompanied by a surface dysgraphia. New word-length effect criteria distinguish pure alexia from hemianopic dyslexia. Subtler problems with perception of numbers and faces can be seen in patients with pure alexia as well. Also, a developmental form of topographic disorientation, which is due to problems with forming cognitive maps of the environment, has been discovered. In Balint syndrome, added features of decreased flexibility of attention in simultanagnosia include local and global capture. Balint syndrome can affect not just localization in space, but also in time, as manifest in sequence agnosia.

SUMMARY: Lesions at intermediate levels of a processing hierarchy can cause difficulty with color perception or motion perception. At a higher level, ventral lesions of the occipitotemporal lobes can lead to a variety of problems with object recognition. Dorsal lesions of the occipitoparietal lobes can cause difficulty with spatial localization and guidance.