The Effects of Monophasic Anodal Transcranial Pulsed Current Stimulation on Corticospinal Excitability and Motor Performance in Healthy Young Adults: A Randomized Double-Blinded Sham-Controlled Study.

Introduction: Transcranial pulsed current stimulation (tPCS) could be used to deliver electrical pulses at different frequencies to entrain the cortical neurons of the brain. Frequency dependence of these pulses in the induction of changes in corticospinal excitability (CSE) has not been reported. Objective: We aimed to assess the effect of anodal tPCS (a-tPCS) at theta (4 Hz), and gamma (75 Hz) frequencies on CSE as assessed by the peak-to-peak amplitude of transcranial magnetic stimulation (TMS)-induced motor-evoked potentials (MEPs) and motor performance. Method: In a randomized, double-blinded, sham-controlled, crossover design study, 17 healthy participants attended 3 experimental sessions and received either a-tPCS at 4 and 75 Hz, or sham a-tPCS with 1.5 mA for 15 min. The amplitude of TMS-induced resting MEPs and time for completion of the grooved pegboard test were recorded at baseline, immediately after, and 30 min after a-tPCS. Results: Both a-tPCS at 75 and 4 Hz showed significantly increased CSE compared with sham. The a-tPCS at 75 Hz induced significantly higher CSE changes compared with 4 Hz. There was a significant increase in intracortical facilitation and a significant reduction in short-interval intracortical inhibition with both 4 and 75 Hz stimulations. However, the inhibition and facilitation did not correlate with CSE. Motor performance was unaffected by the interventions. Conclusion: The high CSE changes in M1 in a-tPCS at 75 Hz provide an initial understanding of the frequency-specific effect of a-tPCS. More research is needed to establish this concept and to assess its behavioral relevance. Impact statement Transcranial pulsed current stimulation (tPCS) is a novel brain stimulation technique that can modulate neural oscillation via the pulsatile current induced by the stimulation. Using anodal tPCS, we demonstrate the neuromodulatory effect induced by the stimulation at theta and gamma frequencies. Our findings recommend anodal tPCS as a potential therapeutic tool for treating many neurological conditions with altered theta and gamma neural oscillatory activity.