Densitometric analysis of the nerve cell population of the inferior olive in aging.

Possible age-related changes in the nerve cell population of the inferior olive were studied through densitometric analysis. The mean area per nerve cell, the reciprocal of the number of cells per unit area, was derived from the distance to closest neighbor in an unselected autopsy series of specimens from 26 subjects without signs of neurological damage, aged 24 to 83 years. Kendall's rank method showed correlation between the mean area per nerve cell and the subjects' ages, with mean areal values decreasing with age. The increase in neuronal density with age was related to changes occurring in the neuropil of the adult. These changes consist of regression of olivocerebellar contacts and loss of supernumerary axonal collaterals, with a resulting decrease in the volume of the whole formation. In addition, the data supported the hypothesis that the nerve cell population of the inferior olive should not decrease with aging.