Gestural communication in Alzheimer's disease.

Spontaneous communicative hand-arm gestures were evaluated in elderly patients with probable Alzheimer's disease (AD) and healthy controls (NC). Based on the notion that speech and gestures arise from common semantic-conceptual representations, qualitatively similar linguistic and gestural communicative impairments were expected in association with semantic memory impairment in AD. Despite equal quantity and rate of gesturing, AD and NC groups produced qualitatively different types of gestures. Patients with AD produced proportionately more referentially ambiguous gestures, fewer gestures referring to metaphoric as opposed to concrete contents, and fewer conceptually complex bimanual gestures. Impaired gestural clarity correlated with severity of linguistic/conceptual impairments and disturbed production of pantomimic movements on a test of ideomotor limb apraxia. Results are consistent with the hypothesis that a central semantic-conceptual disorder underlies the similar linguistic and gestural communication impairments in AD.