The neural basis of naming impairments in Alzheimer's disease revealed through positron emission tomography

The naming impairments in Alzheimer's disease (AD) have been attributed to a variety of cognitive processing deficits, including impairments in semant ic memory, visual perception, and lexical access. To further understand the underlying biological basis of the naming failures in AD, the present inve stigation examined the relationship of various classes of naming errors to regional brain measures of cerebral glucose metabolism as measured with 18 F-Fluoro-2-deoxyglucose (FDG) and positron emission tomography (PET). Error s committed on a visual naming test were categorized according to a cogniti ve processing schema and then examined in relationship to metabolism within specific brain regions. The results revealed an association of semantic er rors with glucose metabolism in the frontal and temporal regions. Language access errors, such as circumlocutions, and word blocking nonresponses were associated with decreased metabolism in areas within the left hemisphere. Visuoperceptive errors were related to right inferior parietal metabolic fu nction The findings suggest that specific brain areas mediate the perceptua l semantic, and lexical processing demands of visual naming and that visual naming problems in dementia are related to dysfunction in specific neural circuits. (C) 1999 National Academy of Neuropsychology. Published by Elsevi er Science Ltd.