Clinical and positron emission tomography studies of visual apperceptive agnosia

Assessments of higher visual functioning and regional cerebral blood flow (rCBF) using positron emission tomography were obtained in three visual apperceptive agnosics. Their clinical impairment included difficulty appreciating the perceptual features of line drawings, letters, and other visual material, despite relatively intact elementary visual functioning and access to visual information in semantic memory. rCBF was significantly reduced in temporooccipital cortices. Our findings suggest that apperceptive agnosia is associated with massive ventral visual system dysfunction that interferes with visual perceptual processing needed for object recognition.