Objective: To elucidate cortical involvement in postural control during unipedal stance by observing corticomuscular coherence (CMC) between the sensorimotor cortex and ankle joint muscles. Methods: Twenty-one participants performed three tasks: bipedal stance, unipedal stance, and isometric contraction. We measured the maximal peak of CMC (CMCmax) between electroencephalograms overlying the foot representation area and surface electromyograms from the tibialis anterior (TA), medial

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... s (MG), lateral gastrocnemius (LG), and soleus (SOL), respectively, for each task. We measured the center of pressure (COP) during both stance tasks. Results: Although there was no significant CMC during bipedal stance, significant CMC was observed for all muscles during unipedal stance, with larger COP fluctuation. The results revealed significant differences in CMCmax between unipedal and bipedal stance tasks (TA, p = 0.002; MG, p = 0.016; LG, p = 0.003; SOL, p = 0.009). Additionally, CMCmax was obtained in higher frequency bands during the unipedal stance task than during the isometric contraction task. Conclusions: Significant CMC indicates direct involvement of the sensorimotor cortex in postural control during unipedal stance. Significance: Greater postural demands due to narrow base-of-support during unipedal stance requires voluntary control of muscle activity by the sensorimotor cortex.