The causal role of beta band desynchronization: Individualized high-definition transcranial alternating current stimulation improves bimanual motor control

Abstract

Objective: To unveil if 3 mA peak-to-peak high-definition (3 transcranial alternating current stimulation (tACS) applied over C4 -the area overlaying the right sensorimotor cortex-enhances bimanual motor control and affects movement-related (3 desynchronization (MR(3D), thereby providing causal evidence for the polymorphic role of MR(3D in motor control. Methods: In this sham-controlled, crossover study, 36 participants underwent 20 min of fixed 20 Hz tACS; tACS individualized to peak (3 activity during motor planning at baseline; and sham tACS randomized over three consecutive days. Each participant underwent all three conditions for a total of 108 sessions, ensuring withinsubject comparisons. Before, during, and after tACS, participants performed a bimanual tracking task (BTT) and 64-channel electroencephalography (EEG) data was measured. Spatiotemporal and temporal clustering statistics with underlying linear mixed effect models were used to test our hypotheses. Results: Individualized tACS significantly improved bimanual motor control, both online and offline, and increased online MR(3D during motor planning compared to fixed tACS. No offline effects of fixed and individualized tACS on MR(3D were found compared to sham, although tACS effects did trend towards the hypothesized MR(3D increase. Throughout the course of the study, MR(3D and bimanual motor performance increased. Exclusively during motor planning, MR(3D was positively associated to bimanual motor performance improvements, emphasizing the functionally polymorphic role of MR(3D. tACS was well tolerated and no side-effects occurred. Conclusion: Individualized (3-tACS improves bimanual motor control and enhances motor planning MR(3D online. These findings provide causal evidence for the importance of MR(3D when planning complex motor behavior.