Summary:It has been asserted that the neuropsychological changes associated with normal aging reflect alterations in frontal/subcortical structures. To investigate this hypothesis, the present study compared the neuropsychological performance of three groups: (a) 14 normal elderly males with no history of neurologic, psychiatric, or substance abuse history (mean age, 70 years); (b) 14 males diagnosed with AIDS dementia complex (mean age, 37.5 years); and (c) 13 male patients with AD (mean age, 71.5 years). The results indicate that, despite dramatic age differences between the normal elderly and AIDS dementia patients, there was a remarkable similarity in the neuropsychological test performance of these two groups. In contrast, patients with AD were notably worse on nearly all neuropsychological measures. The AIDS dementia complex affects primarily subcortical structures whereas AD produces cortical dysfunction. These data are consistent with prior speculations that alterations in frontal–subcortical systems contribute significantly to changes in cognitive processes most affected by aging.