Visuo-postural sensitivity to sinusoidal modulations of viewpoint in VR
Jordan J. Garner, Colleen P. Chen, Michael D’Zmura · 2020
With the increasing adoption of mixed reality technology, it is crucial to identify and avoid displays that cause noxious effects among users, such as loss of balance or motion sickness. Towards this end, we examined the effects of sinusoidal modulations of viewpoint on standing posture. These modulations varied the position of the user’s viewpoint in a virtual environment (VE) over time along either the left-right or the forwards-backwards direction; each had a chosen amplitude and temporal frequency. We measured the resulting change in posture at the frequency of visual stimulation, the socalled steady-state visually evoked posture response (SSVEPR), and used a signal-to-noise ratio (SNR) method to assess SSVEPR strength. These posture responses are described well by sigmoid functions of viewpoint modulation amplitude, allowing one to estimate the lowest amplitude of the visual stimulus that generates a just-detectable posture response. Results suggest that the visuo-postural control system’s sensitivity to viewpoint modulation increases with the frequency of the stimulus. Results also suggest that there is a speed threshold for viewpoint movement that must be met or exceeded if a posture response is to be produced. The results are similar for both left-right and forwards-backwards modulations, and for conditions in which users either moved through the VE or were stationary in the VE while viewpoint was modulated. These results shed light on which features of visual self-motion stimuli drive postural responses.