Abstract
<title>Abstract</title> <p>Background Transcranial pulsed current stimulation (tPCS) is an emerging non-invasive neuromodulation approach with potential applications in neurorehabilitation. However, the influence of stimulation montage polarity on motor cortical excitability and motor function remains poorly understood. This pilot study investigated the feasibility and preliminary neurophysiological and behavioural effects of two bipolar 400 Hz cortico-cerebellar tPCS montages on corticospinal excitability, cortico-cortical excitability, and hand dexterity in healthy adults. Methods Twenty-six healthy adults participated in a double-blind, randomized, sham-controlled, counterbalanced crossover pilot study. Participants completed three stimulation conditions: (1) anodal primary motor cortex with cathodal cerebellar stimulation (M1+/CB−), (2) reversed polarity stimulation (M1−/CB+), and (3) sham stimulation, with sessions separated by at least 48 hours. Corticospinal excitability was assessed using single-pulse transcranial magnetic stimulation, while cortico-cortical excitability was evaluated using paired-pulse measures of intracortical facilitation and inhibition. Hand dexterity was assessed using the Purdue Pegboard Test before and immediately after stimulation. Results The M1+/CB− montage produced preliminary evidence of enhanced corticospinal excitability, increased intracortical facilitation, and improved hand dexterity compared with sham stimulation. In contrast, the M1−/CB+ montage resulted in reduced corticospinal excitability without measurable changes in cortico-cortical excitability or hand dexterity. No significant changes were observed following sham stimulation. Conclusions This pilot study demonstrates that bipolar 400 Hz cortico-cerebellar tPCS produces polarity-dependent modulation of motor system function. Anodal motor cortex combined with cathodal cerebellar stimulation may facilitate corticospinal output and motor performance, whereas reversed polarity may exert inhibitory effects. These preliminary findings provide a foundation for future studies investigating optimized tPCS protocols and their potential application in neurorehabilitation.</p>