Evidence from two genetic syndromes for a dissociation between verbal and visual-spatial short-term memory.

Williams and Down syndromes, two genetic syndromes of abnormal neurodevelopment, are characterized by specific neuropsychological profiles and unique patterns of brain morphology. We find that the superior language ability of subjects with Williams syndrome is accompanied by significantly better performance on a verbal short-term memory task. Conversely, subjects with Down syndrome perform significantly better on a visual-spatial short-term memory task. This double dissociation provides neurogenetic evidence for the distinction between short-term storage for verbal and for visual-spatial stimuli.