Support for an inhibitory model of word retrieval

Word retrieval may involve an inhibitory process in which a target word is activated and related words are suppressed. In the current functional magnetic resonance imaging (fMRI) study, we examined the inhibition of language processing cortex by the left dorsolateral prefrontal cortex (DLPFC) during word retrieval using an anagram-solving paradigm. Participants were presented with a distractor that was read aloud followed by a to-be-solved anagram. Distractor types were defined relative to orthographic overlap with the subsequent anagram solution and included related words with one letter different (e.g., "gripe" for the anagram of "price"), related pseudo-words, and unrelated words (i.e., all five letters were different). The anagram solution reaction time was slower in both the related word and related pseudo-word distractor conditions as compared to the unrelated word distractor condition, which can be attributed to greater inhibition following related distractors. The contrast of related words and unrelated words produced one activation in the left DLPFC, a region that has been associated with memory inhibition. To identify the regions that were negatively correlated with activity in the left DLPFC for related distractors, we conducted a functional connectivity analysis between this left DLPFC region and the rest of the brain. We found negatively correlated activity between the DLPFC and language processing cortex for the related word distractor condition (and the related pseudo-word distractor condition at a relaxed threshold). These findings suggest that that the left DLPFC may inhibit related word (and pseudo-word) representations in language processing cortex.