Commentary on neurophysiology, plasticity, and morphology of aging: the search for a critical substrate

It is becoming increasingly apparent that several issues must be considered in interpreting the neural bases of behavioral differences in aged animals. Prior assumptions need to be modified to account for the potential increase in number of age-related brain changes likely to be uncovered in the coming years as investigation of the aging process proceeds. It will therefore be necessary to rule out processes irrelevant for the particular behavioral/physiological mechanisms under study. Thus, a simple correlation between any one anatomical or physiological measure will not suffice in the future to adequately explain the nature of the age-related behavioral deficits in the human brain.