Effects of repetition and competition on activity in left prefrontal cortex during word generation

Neuroimaging studies have revealed an association between word generation a nd activity in the left inferior frontal gyrus (IFG) that is attentuated wi th item repetition. The experiment reported here examined the effects of re peated word generation, under conditions in which completion was either dec reased or increased, on activity measured during whole-brain echoplanar fun ctional magnetic resonance imaging. Activity in left IFG decreased during r epetition conditions that reduced competition but increased during repetiti on conditions that increased competition; this pattern was contrasted to re petition effects observed in other cortical areas, specifically regions of left temporal cortex. The increase in left IFG activity, which is not predi cted by a simple semantic retrieval account of prefrontal function, is cons istent with the hypothesis that left IFG subserves the selection of semanti c knowledge among competing alternatives.