The impact of cerebellar transcranial alternating current stimulation (tACS) and simultaneous motor network activation via motor sequence learning (MSL) on movements and muscle strength

The cerebellum and its connections to the cerebrum can be modulated by noninvasive brain stimulation (NIBS) techniques, especially transcranial alternating current stimulation (tACS). This modulation may affect movements and muscle strength by increasing the cortical excitability. Moreover, the effect depends on the state of the neurons involved in these executions. Therefore, it is important to gain further insight into how cerebellar tACS with and without simultaneously activation of the motor network via motor sequence learning (MSL) affects movements and muscle strength. Using inertial measurement units (IMU) and electromyography (EMG), we were able to record and evaluate movements of 20 participants regarding this issue. We were able to demonstrate that simultaneous activation of the motor network partly led to longer task durations because it is suspected to interfere with the tACS effect. Concerning the muscle strength, a strength enhancing effect occurred, due to the irritation of the motor system by tACS and particularly the simultaneous MSL. These findings are of importance for future therapeutic approaches using tACS.