Difference between visual feedback and visual suppression upon the stabilization of body sway in normal subjects.

We developed a system to feedback the center of foot pressure by vision using a microcomputer. The subjects were instructed to adjust the center of foot pressure (displayed on the computer display at real time) to the point of intersection of the two stable (horizontal and vertical) lines on the computer display. The peak of the power spectra of body sway shifted significantly to the higher frequency range in the Y component (the lateral direction) in the visual feedback condition. Thus, we conclude that the visual feedback of body sway depends mainly on the error signals between the fovea and the image in the lateral direction to stabilize body sway.