Dendritic extent in human dentate gyrus granule cells in normal aging and senile dementia.

Granule cells of the hippocampal dentate gyrus of 22 human brains obtained at autopsy were studied in Golgi-Cox stained tissue. Seventeen cases were cognitively normal and ranged from 43 to 95 years of age. Five cases had a progressive, dementing disease consistent with the diagnosis of senile dementia (SD) of the Alzheimer's type. Dendritic extent of granule cells was found to increase in normal aging between middle age (fifties) and early old age (seventies). However, dendritic regression was found in the oldest old (nineties). This finding of dendritic regression following growth is in contrast to previous quantitative reports of continued dendritic growth in parahippocampal gyrus of normal aging human brain and suggests that changes in dendritic extent in normal aging are region and age specific. In cases with SD, dendritic extent was greatly reduced when compared with the normal cases of the same age (seventies) and slightly reduced when compared with middle-aged cases. The very old normal and SD cases were similar in dendritic extent, suggesting that the functional and memory deficits characteristic of SD cannot be explained solely on the basis of the static status of dendritic extent of single neurons.