Dual-site high-density 4Hz transcranial alternating current stimulation applied over auditory and motor cortical speech areas does not influence auditory-motor mapping

BackgroundVerbal repetition of auditory speech requires the mapping of a sensory acoustic input onto articulatory motor plans (auditory-motor mapping). Recent evidence indicates that auditory-motor mapping could rely on low frequency neural synchronization (i.e., theta oscillatory phase coupling) between sensory and motor speech areas.\n\nObjectiveIn the present study, we apply dual-site high-density (HD) Transcranial Alternating Current Stimulation (TACS) above the auditory and motor cortex to induce, or disrupt, theta phase coupling between the two areas. We predicted that functionally coupling the two areas would strengthen auditory-motor mapping, compared with functionally decoupling them. We assessed the strength of auditory-motor mapping using a verbal repetition task.\n\nResultsWe found no significant effect of TACS-induced theta phase coupling on auditory-motor mapping as indexed by verbal repetition performance.\n\nConclusionAuditory-motor mapping may rely on a different mechanism than we hypothesized, for example, oscillatory phase-coupling outside the theta range. Alternatively, modulation of interregional theta-phase coupling may require more effective stimulation protocols, for example, TACS at higher intensities.