Constructional Apraxia in Alzheimer's Disease Correlates with Neuritic Neuropathology in Occipital Cortex
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doi: 10.1016/S0006-8993(96)00983-3; Shelves: QP376 .B72 Memorial Periodicals
A variety of measures of neuropathology in Alzheimer's disease (AD) correlate with dementia severity. However, the role of β-amyloid protein and abnormally phosphorylated tau protein in the decline of specific cognitive abilities is unknown. ‘Constructional praxis’ (e.g. copying, constructing) is believed to require integrity of the parietal-occipital lobes. Unlike most other cognitive tasks, some AD patients are able to perform some constructional tasks even late in the disease course. Thus, it may be an ideal task to evaluate the relationship between various measures of AD neuropathology and cognitive performance. Fixed brain tissue was obtained from 16 AD patients who were cognitively assessed shortly before death. Parietal, frontal, entorhinal, and occipital cortices were examined by immunocytochemistry for β-amyloid protein and abnormally phosphorylated tau protein at both early and later stages of neuropil thread and tangle formation. Constructional praxis in AD was strongly related to early-stage tau hyperphosphorylation in occipital cortex. Praxis ability was specific in that it was not significantly related to pathology in other areas and non-constructive tasks were not associated with occipital cortex pathology. In contrast, global dementia severity was related to β-amyloid deposition in entorhinal, parietal, and frontal regions. These findings suggest that occipital cortex is critical for some constructional praxis tasks and that some regionally localizable tasks may be good indices of underlying pathology in corresponding brain regions.