CONSTRUCTIONAL APRAXIA IN ALZHEIMERS-DISEASE CORRELATES WITH NEURITICNEUROPATHOLOGY IN OCCIPITAL CORTEX

A variety of measures of neuropathology in Alzheimer's disease (AD) co rrelate with dementia severity. However, the role of beta-amyloid prot ein and abnormally phosphorylated tan protein in the decline of specif ic cognitive abilities is unknown. 'Constructional praxis' (e.g., copy ing, constructing) is believed to require integrity of the parietal-oc cipital lobes. Unlike most other cognitive tasks, some AD patients are able to perform some constructional tasks even late in the disease co urse. Thus,it may be an ideal task to evaluate the relationship betwee n various measures of AD neuropathology and cognitive performance. Fix ed brain tissue was obtained from 16 AD patients who were cognitively assessed shortly before death. Parietal, frontal, entorhinal, and occi pital cortices were examined by immunocytochemistry for beta-amyloid p rotein and abnormally phosphorylated tau protein at both early and lat er stages of neuropil thread and tangle formation. Constructional prax is in AD was strongly related to early-stage tau hyperphosphorylation in occipital cortex. Praxis ability was specific in that it was not si gnificantly related to pathology in other areas and non-constructive t asks were not associated with occipital cortex pathology. In contrast, global dementia severity was related to beta-amyloid deposition in en torhinal, parietal, and frontal regions. These findings suggest that o ccipital cortex is critical for some constructional praxis tasks and t hat some regionally localizable tasks may be good indices of underlyin g pathology in corresponding brain regions.