AGING, STIMULUS IDENTIFICATION AND THE EFFECT OF PROBABILITY - AN EVENT-RELATED POTENTIAL STUDY

Event-related potentials (ERPs) of younger and older subjects were com pared in a simple reaction time (SRT) and in two GoNogo (20% and 80% t arget probability) tasks. At the T5 location, the NA component (the di fference between the ERPs elicited by the frequent stimuli in the GoNo go tasks on the one hand, and the ERPs in the SRT task on the other ha nd) emerged earlier in the younger group. The N2b was larger in the yo unger group, and in this group the rare stimuli of the 80% GoNogo task elicited an enlarged N2. When compared to the older group, the stimul us probability in the younger group had a larger effect on the amplitu de of the late positivity. The results show age-related changes at an early stage of the information processing activity, and larger sensiti vity of the orienting system in the younger subjects.