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Gait-combined transcranial alternating current stimulation around gait cycle frequency over cerebral motor areas
Ryosuke Kitatani1, Runa Sorimachi2, Akane Amano3
1Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan; Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan; Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Abstract:
Cerebral motor areas, such as the primary motor cortex (M1), premotor cortex (PM), and supplementary motor area, are rhythmically activated within the gait cycle, and transcranial alternating current stimulation (tACS) at the gait cycle frequency over the M1 entrains gait rhythm and improves gait variability. However, whether altering the tACS frequencies to be slower or faster than the normal gait cycle frequency changes and improves gait rhythms remains unclear. Therefore, we investigated the effects of different tACS frequencies around the gait cycle frequency over the C1 and C2 targeting the M1 (Experiment 1) and over the FC3 and FC4 targeting the PM (Experiment 2) on spatiotemporal gait parameters in 30 healthy young adults. Each experiment involved treadmill gait measurements with 5-min tACS at the following four conditions: normal gait cycle frequency (100% rhythm), slower and faster gait cycle frequencies (90% and 110% rhythms, respectively), and sham stimulation. Spatiotemporal gait parameters (gait cycle time, stance time, swing time, and stride length) were measured using optical sensors for each tACS condition. Gait-combined tACS over the M1 in the 110% rhythm frequency significantly decreased the change in coefficient of variation (CV) of swing time compared with the 90% rhythm frequency and sham stimulation. Furthermore, gait-combined tACS over the PM in the 100% rhythm frequency significantly decreased the change in CV of stride length compared with the sham stimulation. Therefore, gait-combined tACS at natural or faster frequencies than the normal gait cycle frequency over the cerebral motor areas decreased the spatiotemporal gait variabilities.