ERPを指標とした競合と反応抑制の量的関係の検討

This study examined the hypothesis (Jones, Cho, Nystrom, Cohen, & Braver, 2002) that the amount of conflict raised by incongruent stimuli in a flanker task affects subsequent response inhibition, using eventrelated potentials. Eleven participants responded selectively with their hands to the stimuli that consisted of a target arrow neighbored by congruent or incongruent distractor arrows. The amount of conflict was manipulated by varying the number of incongruent distractors (i.e. the stimuli included two incongruent distractor arrows for small-conflict condition or four incongruent distractor arrows for large-conflict). The results showed the response times were longer for the large-conflict incongruent stimuli, followed by the small conflict, and then the congruent, suggesting more conflict in large-conflict stimuli. The response times (RTs) in congruent condition became longer when the conflict has been occurred in the preceding trial. But the RTs were almost the same regardless of whether the preceding trial was small-conflict or large-conflict trial. The latency of lateralized readiness potential which can be a measure of response preparation, for congruent condition also showed the delay by presence of conflict in preceding trial, but was not sensitive to the amount of conflict. P300 latency for congruent condition became longer after the conflict trial. These findings suggest that (1) there was no ERP evidence suggesting the quantitative relation between conflict and response inhibition, and (2) response inhibition triggered by conflict detection could contribute to the prolongation of the evaluation time for the stimuli.