Life span changes in electrophysiological measures of inhibition.

Three electrophysiological findings which provide suggestive evidence of weakened inhibition in children and the elderly are reviewed. First, compared to young adults, electrophysiological recordings from old adults show a greater incidence of EEG alpha in anterior cortical areas and of somatosensory evoked potentials in occipital areas, and a reduction in heterogeneity of EEG and ERP activity across recording sites. These findings suggest a relative weakening of central inhibition in old age and a loss of functional independence of cortical centers. Second, visually evoked potentials from children and the elderly demonstrate a relative lack of differentiation between patterned and unpatterned stimuli. Inhibition is known to be important within the visual system for the detection of lines and contours. Finally, children and the elderly do not dampen (inhibit) their electrophysiological responses to sensory stimuli as effectively as subjects of an intermediate age. These age-related differences in electrophysiological responsivity appear to parallel age changes in behavioral measures which are also believed to reflect weakened inhibition. The electrophysiological measures, which reflect maturity and health of CNS structural and chemical systems, indicate that inhibition plays an increasing role in the shaping of behavior as children approach late adolescence but a diminishing role as adults live beyond the fifth decade. Recent research, however, suggests that the magnitude of inhibitory loss in old age may be related to cardiovascular health. Older men who frequently participated in vigorous physical activity showed significantly less inhibitory loss than age-matched peers who seldom exercised.