The Effects of Visual Backgrounds in the Virtual Environments on the Postural Stability of Standing.

A photorealistic scene in a head mount display (HMD) is considered high fidelity and associated with postural stability similar to that in the real world, but the effects of visual background under different standing conditions have not been examined. Thirty-four healthy adults performed four standing (standardized, narrow, tandem and one-leg) tasks in three scenes with an HMD, while viewing one of three scenes: a real room (real scene, RS), a photorealistic scene (VrS) and a blank scene (BS). The effects of the visual scenes and standing tasks on sway parameters were analyzed. Romberg quotients (RQs) of the sway parameters were compared between RS and VrS with reference to BS to compare visual contribution to posture stability. Sway parameters were similar during all three scenes during the standardized and narrow standing tasks, but higher in VrS and BS conditions than in the RS condition during the tandem and one-leg standing tasks. The effects of visual scenes on postural stability showed a significant interaction with the standing tasks. The BS/VsR and BS/RS ratios were close to 1.0 for the standardized and narrow standing tasks, and the magnitude of increase was lower for BS/VsR than BS/RS during the tandem and one-leg standing tasks, indicating different levels of visual dependence. The effects of virtual scenes on postural stability were task-dependent. Adjusting the amount of visual stimuli and choosing tasks with higher postural demands may result in synergic effects, but the influence of visual environments should be examined with consideration of visual targeting.