Pyramidal neurons in two subdivisions of CA1 (CA1 and CA1a+b) of hippocampus from human brains obtained at autopsy were studied in Golgi Cox-stained tissue. Seventeen cases were a part of a normal aging series, ranging in age from 43 to 95 years; and 5 cases had Alzeiheimer'z disease (AD). Dendritic extent of apical and basal trees was found to be stable in normal aging. In AD there was a significant loss of total dendritic length and/or average segment length for the apical and basal trees of both subdivisions of CA1. This finding is consistent with the findings of severe pathology in CA1 reported by others. The reductions in overall dendritic extent in CA1a+b in AD could be attributed largely to alterations in the lenghts of the terminal segments. Apical and basal trees of CA1c were more severely affected by AD than those of CA1a+b and showed more widespread reductions in numbers of segments as well as lengths of segments.
