The Causal Role of Beta Band Desynchronization: Individualized High-Definition Transcranial Alternating Current Stimulation Improves Bimanual Motor Control
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Objective
To unveil if 3 mA peak-to-peak high-definition β transcranial alternating current stimulation (tACS) applied over C4 –the area overlaying the right sensorimotor cortex– enhances bimanual motor control and affects movement-related β desynchronization (MRβD), thereby providing causal evidence for the polymorphic role of MRβD in motor control.
Methods
In this sham-controlled, crossover study, 36 participants underwent 20 minutes of fixed 20 Hz tACS; tACS individualized to peak β activity during motor planning at baseline; and sham tACS randomized over three consecutive days. 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 MRβD during motor planning compared to fixed tACS. No offline effects of fixed and individualized tACS on MRβD were found compared to sham, although tACS effects did trend towards the hypothesized MRβD increase. Throughout the course of the study, MRβD and bimanual motor performance improved. Exclusively during motor planning, MRβD was positively associated to bimanual motor performance improvements, emphasizing the functionally polymorphic role of MRβD. tACS was well tolerated and no side-effects occurred.
Conclusion
Individualized β-tACS improves bimanual motor control and enhances motor planning MRβD online. These findings provide causal evidence for the importance of MRβD when planning complex motor behavior.
