Cerebellar Transcranial Alternating Current Stimulation Accelerates Motor Adaptation via the Modulation of Cortical Synchrony

Motor adaptation is a form of motor learning that enables the updating of motor commands in response to sensory inputs, requiring computations at the cerebellar level that must be integrated into cerebral cortical networks for their implementation. We proposed that cerebellar-cortical integration, which underlies motor adaptation, is related to the modulation of frequency-specific oscillatory activity. We examined motor error and electrophysiological correlates (power spectrum and phase locking value analysis) measured during different sessions of transcranial alternating stimulation (tACS) delivered to the cerebellum at relevant frequencies (50 Hz, 20 Hz, or sham). We found that 50 Hz tACS, but not 20 Hz or sham stimulation, reduced movement error, especially in initial practice trials. Electroencephalography (EEG) analysis revealed modulation of spectral power and phase synchrony (wPLI) in frontal, parietal, and occipital regions, with specific patterns for both the frequency range and the task stage. Power and wPLI modulation under fifty Hz stimulation were associated with the magnitude of motor adaptation. Our findings suggest that frequency-specific neural oscillations play a crucial role in the effective integration between the cerebellum and cortical regions of the brain. Significance: Our data indicate that cerebellar tACS at approximately 50 Hz may serve as an effective neuromodulation strategy to enhance motor adaptation in humans, with specific neural correlates.