EVENT-RELATED POTENTIALS AND AGING - IDENTIFICATION OF DEVIANT VISUAL-STIMULI

The effects of aging on event-related potentials (ERPs) were investigated in visual tasks. The stimuli (two angles within a frame) were frequent (standard) or deviant (differing from the standard either in the orientation of the two angles, in the thickness of the frame, or in both). The target stimuli were defined either by the presence of only one deviant feature, or by the conjunction of the deviant features. The deviant stimuli elicited an increased P2, a posterior N2, on N2b, and a tate positivity (Go and Nogo P3). The latencies of all but the P2 were longer in the older subjects. In the younger group, the target stimuli elicited a larger late positivity than the non-target stimuli that had deviant features, whereas in the older group the target stimuli did not elicit a larger P3 than the stimuli with two deviant features, even when this deviant was a non-target. In contrast to the younger group, in the older group we obtained no P3 over the temporal and occipital locations. We found a reduction of P3 over the posterior location even in a group of middle-aged (mean age = 39 years) subjects. In tasks with only one target feature, the false alarm rate was higher in the elderly subjects. These results suggest a gradual age-related slowing down of the attentive processing of deviant visual patterns, and a decrease of inhibitory functions in the elderly group.