Laminar distribution of neuritic plaques in normal aging, Alzheimer's disease and Down's syndrome.

Quantitative studies of neuritic (senile) plaques in six cortical layers were carried out in brains from people with confirmed clinical and neuropathological diagnosis of senile dementia of the Alzheimer type (SDAT) and Down's syndrome (DS). The same studies were performed on brains of normal old-aged people. In Alzheimer disease (AD) and DS cases the highest numbers of neuritic plaques (NP) were observed in temporal lobe layers III and II and occipital lobe layers III, IV and II. In normal old-aged people the highest numbers of NP were found in temporal lobe III and V and in occipital lobe IV, III, and V layer. The plaque numbers in both temporal and occipital cortices of AD and DS were significantly higher than that of normal old-aged people but there was no difference between AD and DS.