Figure 4.

Standing balance using only visual cues. (A) Subjects stood in a robotic balance simulator while either all sensory cues (see Figure 3A) or only visual cues of balance were provided (see Figure 3C). Angular oscillations of a representative subject (left) when balancing with all cues or only vision show an increase in angular sway when balancing with only vision. Mean removed root-mean-square (RMS) of angular oscillations of all subjects tested (n = 10, right) exhibited the same increase when using visual cues to balance (paired t-test; t₉ = −13.2, P < 0.001). Squares represent the “all cues” condition and circles represent the “vision only” condition. (B) Four of the original 10 subjects subsequently went through 5 days of training (~20 min per day) under the vision only condition. Angular oscillations of a representative subject (left) show a decrease after 100 min (5 days) of training compared to the pre-training vision only condition. Mean-removed RMS of angular oscillations progressively decreased with each session of training (circles), but always remained above the all cues conditions (squares). For illustrative purposes, the blue line shows the fitting of mean angle RMS to an exponential function (y = 4.4893 e^{−0.1829 x}) using a least-square method. In both graphs, horizontal lines represent the mean of standard oscillation across all subjects and *P < 0.001.