Effects of Cerebellar Transcranial Alternating Current Stimulation at Frequencies Surrounding the Gait Cycle Frequency on Spatiotemporal Gait Parameters.

The cerebellum has been implicated in generating human gait rhythms, and transcranial alternating current stimulation (tACS) at the gait cycle frequency over the cerebellum has been demonstrated to synchronize the gait rhythm. However, whether modulating the tACS frequency to be slower or faster than the normal gait cycle frequency alters the gait rhythms remains unclear. Therefore, we investigated the effects of tACS on the spatiotemporal gait parameters at slower and faster frequencies around the gait cycle frequency over the cerebellum. Eighteen healthy young adults with right-sided dominance performed treadmill walking with tACS under the following stimulation frequency conditions, each applied for 5 min in counterbalanced order: normal gait cycle frequency (100% rhythm), slower and faster gait cycle frequencies (90% and 110% rhythms, respectively), and sham stimulation. Gait cycle time, stance time, swing time, and stride length were assessed using optical sensors for each tACS condition. Changes in these spatiotemporal parameters and their coefficients of variation during tACS (subtraction of the initial 1 min from the last 1 min) were calculated. Repeated-measures one-way analysis of variance revealed a significant main effect on the change in stance time. Multiple comparisons demonstrated a significant difference in the changes in stance time between the 90% and 110% rhythm conditions, with a longer stance time observed in the 90% rhythm condition than in the 110% rhythm condition. Therefore, applying gait-combined tACS over the cerebellum at slower and faster frequencies than the normal gait cycle frequency differentially changed the stance time.