Neurochemistry of Aging

Abstract

As the period of senescence is reached (beginning at age 70), the human brain is smaller due to actual loss of cells. This decrease in size is accompanied by a relative increase in moisture content due in part to an increase in ventricular size and a relative decrease in total solids. Specifically these changes reflect a loss of nitrogen, phosphorus and lipid but an increase in sulfur and DNA. The change in the latter two substances, due to formation of “clinker substances” and pyknotic cells, suggests a decrease of functional brain tissue. The depression, if any, of oxygen uptake by brain tissue in older persons enjoying good health and mental acuity is surprisingly small, but definite changes occur in senile psychosis and organic dementia.