Combined Gaze Stabilization Exercise and Cerebellar Transcranial Direct Current Stimulation on Vestibulospinal Tract and Posture

Cerebellar input modulates activity in the vestibular nuclei, the origin of the lateral vestibulospinal tract (LVST), which influences muscle tone and postural sway. Although cerebellar cathodal transcranial direct current stimulation (tDCS) reduces postural sway, suggesting potential for neuromodulation in balance control, its combined effect with vestibular-targeting exercise on LVST excitability and postural control remains unclear. This study aimed to clarify the neurophysiological and behavioral effects of combining gaze stabilization exercise (GSE) and cerebellar cathodal tDCS on LVST excitability and postural sway. Fourteen healthy adults participated in this randomized crossover study comparing GSE with sham stimulation and GSE with cerebellar cathodal tDCS. The center of pressure (COP) total trajectory length, rectangular area, and LVST excitability were measured before and after each intervention. LVST excitability was evaluated using the galvanic vestibular stimulation-conditioned H-reflex (GVS-H). Both stimulation conditions significantly reduced COP total trajectory length compared to baseline, suggesting that the GSE intervention effectively improved postural stability. However, no significant interaction effects were observed for either GVS-H or the COP rectangular area. Therefore, although GSE effectively reduces postural sway, combining GSE with cerebellar cathodal tDCS provides no further benefit or LVST modulation. This study underscores the established effectiveness of GSE alone.