Hippocampal pyramidal cells and aging in the human: a quantitative study of neuronal loss in sectors CA1 to CA4.

A number of investigators have proposed that hippocampal pathology contributes to the memory impairment seen in normal aging. The published morphometric studies of aging-associated quantitative changes in pyramidal cells in human hippocampus have yielded somewhat inconsistent results. We measured the volume, pyramidal cell density, and neuronal and nuclear cross-sectional areas in sectors CA1 through CA4 in right and left hippocampi from the brains of 23 normal subjects (age range 4 to 98 years) in the Yakovlev Collection. All four hippocampal sectors tended to show a decline in volume and pyramidal cell density with age, but the degree of neuronal loss was statistically significant only in CA4. The aging-related cell loss did not appear to be linear, but was most obvious after age 65. Elderly subjects had 19% (CA1), 16% (CA2), 17% (CA3), and 25% (CA4) lower mean pyramidal cell density compared with subjects under age 65. The relatively greater neuronal loss in CA4 could possibly be related to its high catecholaminergic innervation.