The Effects Of Frequency-changed Temporal Interference Stimulation On The Excitability Of The Primary Motor Cortex

Temporal interference stimulation (TI) is a new non-invasive brain stimulation technique, which can generate amplitude-modulated waveform in target brain region via two high frequency alternating currents and the target region can be superficial or deep by tuning the parameters of the two currents. Transcranial magnetic stimulation (TMS) can be used to detect excitability of target brain region and the indicators include motor-evoked potential (MEP) and rest motor threshold (RMT). PURPOSE: To investigate the effects of frequency-changed temporal interference stimulation on the excitability of primary motor cortex. METHODS: In this cross-over double-blind study, 20 healthy adults were recruited and were randomized to receive frequency-changed TI stimulation or sham stimulation with an interval of more than 48 hours. Before and after the stimulation, participants were completed TMS test. Frequency-changed TI stimulation was based on two alternating currents, and in this study the peak to peak value of each alternating current was set to 4 mA. The frequency of one current was set to 2000 Hz, and the frequency difference between these two alternating currents were time-varying (i.e., 5, 10, 20, 40 Hz), so the frequency of the other current also changed with time (i.e., 2005, 2010, 2020, 2040 Hz). The TI stimulation lasted for 20 min, and the sham condition only contained 30s ramp-up phase and 30s ramp-down phase. RESULTS: All participant completed the experiment and only mild side effect were reported. There were significant interaction effects for the MEP and RMT. The post hoc analysis showed that compared to sham condition, MEP in TI condition was significantly increased after stimulation (F = 6.106, P < 0.01) and RMT was significantly decreased after stimulation (F = 7.505, P < 0.01). No significant differences were observed in other indexes. CONCLUSION: These findings indicated that frequency-changed temporal interference stimulation can effectively affect the excitability of primary motor cortex. This study was supported by the National Natural Science Foundation of China (11932013)