Spine distribution along the apical dendrites of the pyramidal neurons in Down's syndrome. A quantitative Golgi study.

The number of spines along the apical dendrites of the pyramidal neurons in the hippocampal and cingulate gyri were counted on Golgi preparations of the brains of seven cases of Down's syndrome; they did not show neuropathological senile changes. The number of spines in the middle and distal segments of the apical dendrites of Down's syndrome group were significantly fewer than in those of the control group. The number of spines in aged noncharacteristic mentally retarded cases were not decreaed compared with the controls. The diminution of spines in Down's syndrome is considered to be rather specific in this condition and is not a common finding in other types of mental retardation. It might also be one of the early changes of dendritic degeneration related to senile plaque formation.