Repetition of novel stimuli in an ERP oddball paradigm: Aging effects

Unexpected task-irrelevant novel stimuli typically elicit a more frontally-focused P3 scalp topography than expected target stimuli, which elicit a parietally-maximum P3 scalp distribution. In previous studies, older adults have shown more frontally-oriented P3 activity than young adults whether elicited by target or novel stimuli. Moreover, in young adults, familiarity with the occurrence of novel stimuli led to a reduction in frontally-oriented P3 activity and a P3 scalp distribution with a more posterior orientation. For older adults, no such shift was shown. To further explore these phenomena, the effects of repeating the identical novel stimuli were assessed within the context of an auditory novelty oddball paradigm. Age-related differences were found for target P3 amplitude, latency, and scalp distribution, replicating previous findings. In addition, for the young adults, the repeated novel event, relative to the first presentation, produced a clear shift in scalp topography to a more parietal distribution for both the novelty P3 (322 ms) and a second, longer-latency P3 (564 ms), the P3₂. By contrast, the elderly showed no change in novelty P3 scalp topography with repetition, and showed an increase in frontally-oriented activity to the repeated novel events for P3₂. These data were interpreted as suggesting age-related changes in frontal-robe functioning, consistent with studies of cognitive aging and previous ERP findings in this series of studies.