Prefrontal oscillatory stimulation modulates access to cognitive control references in retrospective metacognitive commentary

• Efficient metacognitive commentary was observed following bilateral theta-rhythm stimulation.
• Increased bilateral prefrontal cortex theta-band connectivity is associated with enhanced working memory and confident metacognitive evaluations.
• Prefrontal cognitive control function may serve as a reliable predictor of retrospective metacognitive awareness.

ObjectiveWe intended to examine how theta-rhythm transcranial alternating current stimulation (tACS) (versus sham non-active stimulation) modulated associations between working memory accuracy and later retrospective self-evaluation scores.MethodsHealthy participants were required to complete a verbal working memory task while receiving tACS bilaterally over the dorsolateral prefrontal cortex (DLPFC) versus sham DLPFC stimulation. After completion of the online and post-stimulation working memory tasks, participants were asked to rate the level of success-confidence on the two preceding working memory tasks.ResultsAs expected, online working memory accuracy was improved in the active bilateral DLPFC condition versus sham stimulation. Importantly, this working memory enhancement was related to post-stimulation self-evaluation scores.ConclusionsTheoretically, our findings indicated that cognitive-control representations (e.g., working memory accuracy) could serve as the optimal frame of reference for later retrospective metacognitive judgments.SignificanceNoninvasive application of bi-frontal oscillatory currents might enhance functional connectivity between prefrontal regulatory components of working memory and retrospective monitoring in humans. Importantly, along with recent electrophysiological finding indicating interaction of tACS with ongoing oscillatory activity, our preliminary findings support the feasibility of utilizing tACS to treat theta-rhythm functional disconnectivity and related cognitive impairments in schizophrenia.