Comparative studies of neuronal perikaryon size and shape in the aging cerebral cortex.

The stereological investigation comprised three groups of people aged 19 to 44, 65 to 74 and 85 to 94. Perikaryal area and circumference of cortical neurons in the superior part of the cerebral precentral gyrus were determined. Opening classes of single neurons were measured with the Leitz texture analyzer to calculate size and shape. A multivariate statistical procedure allowed comparison of the neuronal parameters between all groups. The measurements yielded smaller perikarya in the oldest group as opposed to larger ones in the young subjects. No differences were seen between young subjects and the 65 to 74-year-old group, which, in contrast, revealed as only group age-dependent changes in cerebral capillaries and small blood vessels. The differences in perikaryal size indicated that senile atrophy of neurons was most apparent in the external pyramidal layer. An influence of decreased motor impulses from the periphery on the atrophic process of neurons with predominant receptor function cannot be excluded.