Apperceptive visual agnosia: a case study.

A man with an infarction of his inferior temporal and occipital association cortex bilaterally, which spared primary visual cortex, had impaired visual recognition of objects, faces, colors, words, and gestures. Analysis of visual function indicated that the recognition failures resulted from an agnosia, rather than elemental visual impairment. Whereas his impairment of gesture recognition appeared to be related to an associative agnosia, his inability to recognize objects was related to an apperceptive agnosia. There may be four subtypes of apperceptive agnosia: one where the internal object representations or structural descriptions are impaired, another where an adequate percept cannot be derived, a third where the internal referent and percept are dissociated, and a fourth where both levels are impaired. Our patient demonstrated a failure to relate individual elements to the whole, a failure to integrate multiple elements, and a reliance on global perception. He had normal object imagery. These results suggest that, whereas internal representations were intact, he was unable to form adequate perceptual representations.