Effect of Moving Tactile Stimuli to Sole on Body Sway During Quiet Stance

Objectives: This study examined whether moving tactile stimuli applied to the soles along the anterior–posterior (AP) and medial–lateral (ML) axes induce body sway during quiet stance. Methods: Fifteen healthy participants in quiet stance received plantar moving tactile stimuli along the AP or ML axis under occluded and unoccluded vision conditions. Results: The center of pressure (COP) along the ML axis was dependent on the phase of moving tactile stimuli along the ML axis under occluded vision condition. The direction of body sway was opposite to the stimulus loci. The total COP displacement during moving tactile stimuli along the AP axis was larger than that without stimuli, particularly under occluded vision conditions. Discussion: Humans likely perceive body sway towards the stimulated side. Based on this, when humans perceive body sway along the ML axis, they compensate for it by swaying the body in the direction contralateral to the stimulated side. Body sway along the ML axis, in accordance with the plantar loci receiving input of moving tactile sensation along the same axis, becomes apparent under occluded vision condition. Through intermodal reweighting, the contribution of tactile sensation to the control of body sway along the AP axis increases to compensate for the lack of visual input regulating body sway along this axis.