AN OVER-VIEW OF AGE-RELATED-CHANGES IN THE SCALP DISTRIBUTION OF P3B

In this overview of 3 studies, the scalp distribution of the P3b compo nent (i.e. the P3 or P300) of the event-related potential elicited by target events in young and older adults was assessed, The target P3b d ata were recorded in either auditory oddball paradigms or in visual st udy tasks in which orienting activity was manipulated (as a within-sub jects variable) in investigations of indirect memory. Some of the stud ies required choice reaction time responses, whereas others required r esponses only to the target stimuli. Motor response requirements had a profound effect on the P3b scalp distribution of older but not of you nger subjects. The presence of a frontally oriented scalp focus in the topographies of the older adults in most of the tasks described here is consistent with older adults continuing to use prefrontal processes for stimuli that should have already been well encoded and/or categor ized. However, although older subjects generally had different P3b sca lp distributions than younger subjects, their scalp distributions were modulated similarly by task requirements. These data suggest that sim ilar mechanisms modulate the scalp distribution of P3b in older compar ed to younger adults. However, in the older adult,these scalp distribu tion changes in response to task demands are superimposed an a frontal ly oriented scalp focus due to a putative frontal lobe contribution to target P3b topography. (C) 1997 Elsevier Science Ireland Ltd.