Aging and respond-withhold tasks: effects on sustained potentials, P3 responses and late activity.

Differences in late event-related potentials (ERPs) during active respond-withhold tasks were tested with 16 young, 16 middle-aged, and 16 elderly subjects (mean ages were 30, 50 and 69 years, respectively). All subjects were selected for good health. While monopolar electroencephalograms were recorded from FZ, CZ, and PZ, subjects performed a signaled respond-withhold task to allow measurement of sustained potentials (SPs) and a non-signaled respond-withhold task for measurement of P3 responses and late activity (LA) which follows the P3. Respond and withhold trials were presented randomly with a probability of 0.5 in both tasks. Compared with younger subjects, the elderly group produced significantly larger negative mean SP amplitude during respond trials at CZ, significantly larger negative mean LA during respond trials at CZ, and significantly larger positive LA during withhold trials at all electrode locations. The elderly group also produced significantly larger P3 amplitude at FZ. The results are discussed in relation to the hypothesis that inhibition may be weaker in elderly subjects. Two further possible interpretations of the larger ERPs in elderly subjects are suggested: (1) the elderly group may have been more challenged by the tasks and their larger ERPs may reflect greater neural effort; and/or (2) the health selection procedures may have produced a group of elderly 'survivors' whose large ERPs may be characteristic of robust individuals or may reflect adaptations to aging-related changes in neural function.

Age effects on heart rate, sustained potential, and P3 responses during reaction-time tasks.

Relationships between physiological responses and slowed reaction time (RT) among elderly subjects were tested in 48 healthy young, middle-aged, and elderly men (mean ages 24, 45, and 71 years) using simple and choice RT tasks. There were age reductions in P3 amplitude and heart rate (HR) deceleration, but no effects of age on P3 latency. Sustained potential (SP or CNV) amplitude paradoxically increased with age, possibly indicating weaker inhibitory function. P3 amplitude, SP amplitude, and HR deceleration were most strongly correlated with RT among younger subjects, but SP amplitude was correlated with RT in the elderly group during the choice task. HR deceleration shared a small amount of variance with SP amplitude and RT in the young group. There was no HR-SP-RT relationship in the older groups. Choice-simple task differences in P3 amplitude and RT were correlated in the young and elderly groups. The results suggest that HR, SP, and P3 responses may reflect physiological processes related to the slower RTs of healthy elderly subjects.