Combined effects of the light touch and cognitive task affect the components of postural sway.

The light touch (LT) of the fingertip on a rigid surface and the performance of a cognitive task (CT) affect the postural control. The current study examined the mechanisms involved in the control of postural sway (i.e., Rambling and Trembling components of the center of pressure) with the LT and CT performed individually or simultaneously. Thirteen adults stood on a force plate for 70 s while performed the LT, CT (visual searching of specific letters) or both tasks simultaneously. COP, Rambling, and Trembling mean amplitude and speed were computed. COP and Rambling trajectories were highly and Trembling moderately reduced with LT. The CT affected mainly the Rambling component, supporting the role of supraspinal control of postural sway. These findings suggested that while LT influences both supraspinal and peripheral control mechanisms, CT influences mostly the supraspinal mechanisms involved in postural sway. The combined effects of LT and CT improve the postural control with no negative consequences on CT performance.