Rita Y. Emmerson

EEG and event-related potentials in normal aging

Abbreviations

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.

Electrophysiology and Aging: Slowing, Inhibition, and Aerobic Fitness

Just as gray hair and wrinkles are the physical hallmarks of aging, certain behavioral characteristics distinguish the old from the young. In general, elderly people are slower, have poorer memory, and are less able to solve complex or novel problems. These age-related changes are typically attributed to degenerative processes in the central nervous system (CNS) and are reflected in the brain’s electrical activity. The electroencephalogram (EEG) and event-related potentials (ERPs) have been used extensively to study changes in brain function throughout development and adult aging. In this chapter, literature describing age differences in EEG and ERPs are reviewed and the hypothesis that these electrophysiological measures reflect slowing and a relative inflexibility of function within the CNS are developed. It is proposed that some age differences in EEG and ERPs are the result of reduced CNS functioning and that changes in inhibitory strength may underlie age-related decline in cognitive abilities, particularly those that require “mental flexibility.” Also reviewed and discussed are recent and exciting findings indicating that variability of some behavioral and electrophysiological measures may be related to individual differences in frequency and intensity of physical activity and resulting cardiovascular fitness.