SENSITIVITY OF MEDIAL/LATERAL BALANCE CONTROL TO VISUAL DISTURBANCES WHILE WALKING IN YOUNG AND OLDER ADULTS

Abstract

Humans integrate multiple sources of sensory information to estimate body orientation in space. Balance control experiments while standing provide evidence that the contributions of these sensory channels change under different conditions in a process called sensory reweighting. This study aims to address whether there is evidence for sensory reweighting while walking and explores age-related differences in medial/lateral balance control under visually perturbing walking conditions. Thirty young adults (18-35 years) and thirty older adults (55-79 years) walked on a self-paced treadmill within a virtual environment that delivered frontal plane multi-sine visual disturbances at three amplitudes (6{degrees}, 10{degrees}, and 15{degrees}). Frequency response functions were used to quantify visual sensitivity to balance disturbances, while spatiotemporal gait parameters (e.g., step width, step-width variability) were measured to assess balance control. Visual sensitivity decreased in both populations with increasing stimulus amplitude, analogous to the sensory reweighting hypothesis in balance control while standing. Despite the decrease in visual sensitivity, the compensatory upweighting of other sensory systems was not observed through measurements of remnant sway. Older adults exhibited higher visual sensitivity at all amplitudes compared to young adults, indicating a more sensitive response to visual disturbances to balance control. Both groups showed increases in step width and step width variability with higher visual amplitudes, with older adults demonstrating more pronounced effects. Weak correlations existed between changes in visual sensitivity and changes in step width and step width variability suggesting a limited interaction between sensory reweighting and gait stability.