Dendritic extent in human CA_2-3 hippocampal pyramidal neurons in normal aging and senile dementia

The extent of dendritic trees of pyramidal neurons of the CA_2-3 field of the hippocampus of 20 human brains obtained at autopsy was quantified in Golgi Cox-stained tissue. Fifteen cases were neurologically and psychiatrically normal and ranged in age from 43 to 95 years. Five cases had a progressive, dementing disease consistent with the diagnosis of senile dementia (SD) of the Alzheimer's type. Dendritic extent of both the apical and basal trees of CA_2-3 pyramidal neurons was found to be unchanged from middle age to very old age. This finding of net stability of dendritic extent is in contrast to previous quantitative reports of either continued dendritic growth in human parahippocampal gyrus or of dendritic growth followed by regression in human dentate gyrus. This finding is consistent with the suggestion that changes in dendritic extent in normal aging are a function of the balance between regressive and proliferative influences and are region specific. In cases with SD, dendritic extent of both the apical and basal trees was found to be similar to that of the normal age-matched cases. These data are consistent with those of others suggesting relative sparing of the CA_2-3 field from the degenerative changes in senile dementia.