Semantic memory is impaired in both dementia with Lewy bodies and dementiaof Alzheimer's type: a comparative neuropsychological study and literaturereview

Objective-To test the hypothesis that semantic impairment is present in bot h patients with dementia with Lewy bodies (DLB) and those with dementia of Alzheimer's type (DAT). Methods-A comprehensive battery of neuropsychological tasks designed to ass ess semantic memory, visuoperceptual function, verbal fluency, and recognit ion memory was given to groups of patients with DLB (n=10), DAT (n=10) matc hed pairwise for age and mini mental state examination (MMSE), and age matc hed normal controls (n=15). Results-Both DLB and DAT groups exhibited impaired performance across the r ange of tasks designed to assess semantic memory. Whereas patients with DAT showed equivalent comprehension of written words and picture stimuli, pati ents with DLB demonstrated more severe semantic deficits for pictures than words. As in previous studies, patients with DLB but not those with DAT wer e found to have impaired visuoperceptual functioning. Letter and category f luency were equally reduced for the patients with DLB whereas performance o n fetter fluency was significantly better in the DAT group. Recognition mem ory for faces and words was impaired in both groups. Conclusions-Semantic impairment is not limited to patients with DAT. Patien ts with DLB exhibit particular problems when required to access meaning fro m pictures that is most likely to arise from a combination of semantic and visuoperceptual impairments.