Neuropsychologically relevant mental abilities are studied in healthy men at different ages, in patients with clinically- diagnosed Alzheimer's disease, and in adults with Down syndrome at different ages. Tests are administered to evaluate intelligence, memory, language, visual attention, visuoperceptive and visuoconstructive ability, and perceptual-motor speed. Age- related differences in general intelligence, verbal memory, and visual memory in our sample of healthy men, ranging in age from 20 to 83 years, were found to be smaller than the differences reported in normative studies of non-health-screened adults. No significant age-related differences on verbal processing and memory were found. Age-related differences on visuospatial processing and memory were significant. In healthy adults, visual memory and the discrepancy between verbal and visuospatial ability were not correlated with regional cerebral metabolic rates for glucose (rCMRglc) as measured by positron emission tomography (PET) and 18-Fluorodeoxyglucose, but the discrepancy between visual and verbal memory was correlated with right-left parietal rCMRglc asymmetry. Neuropsychological patterns were correlated with neocortical rCMRglc patterns in patients with moderate Alzheimer's disease, but not in patients with mild Alzheimer's disease. Longitudinal study of mildly impaired patients, however, demonstrated that the development of neocortically-mediated neuropsychological impairments follows the appearance of significant neocortical rCMRglc abnormalities. Older Down syndrome adults perform worse on mental abilities tests than do younger subjects. Immediate verbal memory appears to be less affected by age in Down syndrome than are other abilities.
