Previous studies showed that natural walking reduces the susceptibility to VR sickness. However, many users still experience VR sickness when wearing VR headsets that allow free walking in room-scale spaces. This paper studies VR sickness and postural instability while the user walks in an immersive virtual environment using an electroencephalogram (EEG) headset and a full-body motion capture system. The experiment induced VR sickness by gradually increasing the translation gain beyond the user's detection threshold. A between-group comparison between participants with and without VR sickness symptoms found some significant differences in postural stability but found none on gait patterns during the walking. In the EEG analysis, the group with VR sickness showed a reduction of alpha power, a phenomenon previously linked to a higher workload and efforts to maintain postural control. In contrast, the group without VR sickness exhibited brain activities linked to fine cognitive-motor control. The EEG result provides new insights into the postural instability theory: participants with VR sickness could maintain their postural stability at the cost of a higher cognitive workload. Our result also indicates that the analysis of lower-frequency power could complement behavioural data for continuous VR sickness detection in both stationary and mobile VR setups.

翻译：既往研究表明，自然行走可降低对VR晕动症的易感性。然而，许多用户在佩戴支持自由行走的VR头显时仍会感到不适。本文通过脑电图设备与全身运动捕捉系统，研究用户在沉浸式虚拟环境中行走时的VR晕动症与姿势不稳定性。实验通过逐步提高超出用户感知阈值的平移增益来诱发VR晕动症。对有/无VR晕动症状的两组被试进行组间比较发现，虽然步态模式无显著差异，但姿势稳定性存在显著差异。脑电图分析显示，有晕动症组呈现出α波功率下降现象——这与先前研究发现的较高认知负荷及维持姿势控制的努力相关；而无晕动症组则表现出与精细认知-运动控制相关的脑活动。该脑电图结果为姿势不稳定性理论提供了新视角：有VR晕动症者虽能维持姿势稳定性，但需付出更高的认知负荷代价。研究结果还表明，低频功率分析可作为行为数据的补充，用于静态与移动VR场景中持续性VR晕动症的检测。