Previous studies of proactive interference (PI) have revealed the involvement of the left inferior frontal gyrus (IFG) in resolution of PI during working memory/item recognition. PI resolution is thought to require: (1) inhibition of inappropriate attribution of familiarity to the probe and resultant inappropriate response tendencies; and (2) inhibition of PI per se regardless of the appropriateness of the attribution of familiarity. It is not clear, however, whether the IFG supports inhibition of inappropriate response tendencies or inhibition of PI per se. In the present functional magnetic resonance imaging study, we dissociate these possibilities using a recency judgment paradigm. Recency judgments, judgments of the relative temporal order of two studied items, provided an opportunity of examining three types of trials that differed in the way PI influenced the current trials: the trials where PI from previous trials was congruent with the current trials (C-PI trials); the trials where PI was incongruent with the current trials (I-PI trials); and the trials where no PI influenced the current trials (N-PI trials). Relative to the N-PI trials, the I-PI trials elicited the significant left IFG activation associated with PI resolution, consistent with previous studies using working memory/item recognition. We found that the IFG activation was related not to inhibition of inappropriate response tendencies (I-PI vs. C-PI), but to inhibition of PI per se (C-PI vs. N-PI). These results indicate that the left IFG plays its control role regardless of whether or not PI is congruent with correct performance of current trials.
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