Effects of stimulating the supplementary motor area with a transcranial alternating current for bimanual movement performance.

•tACS was applied over the SMA during bimanual movement tasks.•tACS effects depended on the stimulus frequency and participant’s motor performance.•γ-tACS reduced improvement in motor performance in high-performing participants.•The opposite stimulus effect was observed for the β- and γ-band frequencies.•tACS over the SMA may modulate the maintenance and updating of motor plans.