Stimulation of the right dorsolateral prefrontal cortex reduces conflict-induced forgetting

Retrieval-induced forgetting is a phenomenon whereby retrieving certain memories can impair the recall of related information. We tested the hypothesis that inhibitory mechanisms play a pivotal role in retrieval-induced forgetting, applying transcranial magnetic stimulation to the dorsolateral prefrontal cortex, an area involved in inhibitory control, while participants retrieved memory associations. Participants learned a series of word pairs, then completed an interference task where they learned directly conflicting associations, or semantically related associates. A train of transcranial magnetic stimulation pulses was applied to the right dorsolateral prefrontal cortex (Experiment 1) or the left dorsolateral prefrontal cortex (Experiment 2) during retrieval of the interfering pairs, beginning 200 ms after stimulus onset. Participants showed robust retrieval-induced forgetting for the original pairs after retrieving conflicting associations, which was reduced when transcranial magnetic stimulation was applied to the right dorsolateral prefrontal cortex compared with a control brain site. This effect was specific to conflicting memories and did not extend to semantically related interference, indicating the right dorsolateral prefrontal cortex's critical role in inhibitory processes during retrieval. Transcranial magnetic stimulation administered to the homologous left dorsolateral prefrontal cortex had no effect on forgetting. These findings provide strong evidence for the involvement of the right dorsolateral prefrontal cortex in managing retrieval competition within an early time window (200 to 533 ms) and highlight its importance in memory control.