On the tip of the tongue: An event-related fMRI study of semantic retrieval failure and cognitive conflict

The tip of the tongue (TOT) state refers to a temporary inaccessibility of information that one is sure exists in long-term memory and is on the verge of recovering. Using event-related fMRI, we assessed the neural correlates of this semantic retrieval failure to determine whether the anterior cingu late-lateral prefrontal neural circuit posited to mediate conflict resoluti on is engaged during metacognitive conflicts that arise during the TOT. Res ults revealed that, relative to successful retrieval or unsuccessful retrie val not accompanied by a TOT, retrieval failures accompanied by TOTs elicit ed a selective response in anterior cingulate-prefrontal cortices. During a TOT, cognitive control mechanisms may be recruited in attempts to resolve the conflict and retrieval failure that characterize this state.