LANGUAGE COMPREHENSION AND REGIONAL CEREBRAL DEFECTS IN FRONTOTEMPORAL DEGENERATION AND ALZHEIMERS-DISEASE

We related profiles of language comprehension difficulty to patterns o f reduced cerebral functioning obtained with high-resolution single ph oton emission computed tomography (SPECT) in patients with neurodegene rative conditions. We found different patterns of reduced relative cer ebral perfusion in patients with frontotemporal degeneration (FD) and patients with Alzheimer's disease (AD). Cognitive assessments also sho wed different patterns of impaired comprehension in patients with FD a nd patients with AD. Grammatical comprehension difficulty in FD correl ated with relative cerebral perfusion in left frontal and anterior tem poral brain regions; impaired semantic processing in AD correlated wit h relative cerebral perfusion in inferior parietal and superior tempor al regions of the left hemisphere. These findings are consistent with the hypothesis that a neural network distributed throughout the left h emisphere subserving different aspects of language comprehension, rath er than a single brain region, is responsible for understanding langua ge.