Absolute number of neurons and thickness of the cerebral cortex during aging, senile and vascular dementia, and Pick's and Alzheimer's diseases.

Abstract

The absolute number of neurons and thickness of the cortex were studied in areas 6, 10, 18, 21, 21/38 and 40 and in the subiculum of mentally healthy persons of different ages and in patients with senile and vascular dementia or with Pick's or Alzheimer's disease. In old age the mean absolute number of neurons in mentally healthy persons is reduced by 20%, while the thickness of the cortex on the free surface of the gyri remains unchanged. In persons with senile and vascular dementia the number of nerve cells is reduced by 35–38%, but there is no decrease in the thickness of the cortex on its free surface. In Alzheimer's disease the number of nerve cells is reduced by half and the thickness of the cortex by 6%. Pick's disease is characterized by mass death of nerve cells in the affected areas, leading to a reduction of 14–30 in their number, and to a decrease in thickness of the cortex by half. The subicular cortex thickness in old age is reduced by 28% and in diseases leading to dementia by 47–71%.