Consecutive repetition effects for affective-distractor pictures in a visual oddball task: electrophysiological evidence from an ERP study.

Although repeated affective stimuli can promote habituation, most studies of event-related potentials (ERPs) have focused on habituation to targets that are repeated non-consecutively. However, the neural mechanisms underlying the consecutive repetition effects of affective-distractor stimuli are unclear. Using a three-stimulus oddball task (standard vs. target vs. distractor ratio: 60%:20%:20%) and measures of ERPs, we assessed the repetition effects of affective-distractor pictures that were repeated consecutively. Participants (N=16) were asked to distinguish the size of a geometric surface; they were asked to selectively respond to the target stimuli (larger geometric surfaces) and to ignore the standard stimuli (smaller geometric surfaces) and affective-distractor pictures. Forty pictures portraying a neutral affect and 40 pictures portraying a negative affect were taken from the Chinese Affective Picture System. Each picture was pseudo-randomly selected and consecutively repeated three times, and ERPs were recorded for the repeated affective-distractor pictures. Stimulus repetition was associated with amplitude increases for P3 and amplitude decreases for N1 and N2 as the presentations proceeded. Peak latency remained stable. The P2, N2, and P3 amplitudes were greater during negative vs. neutral pictures. The affective effects did not interact with stimulus repetition at any latency range. The results suggest that consecutive repetition and affective stimuli modulate ERP outcomes independently.