Associative visual agnosia without alexia.

A brain-damaged man was unable to appreciate the nature of objects and meaningful nonverbal symbols presented visually, although he could see, draw, describe, and match these stimuli. He had no difficulty understanding visually presented words. Auditory and tactile recognition of both verbal and nonverbal stimuli were normal. Our findings provide evidence that two neuropsychologic mechanisms were responsible for this disorder. One was an interhemispheric visual-verbal disconnection; the other was a specific categorization defect for visual, nonverba, meaningful stimuli. Neither mechanism alone was sufficient; both were necessary.