Virtual reality (VR) environments can be used to stimulate movement, motor imagery, and affect. We developed visual stimuli to generate fear under a simple VR environment using a smartphone. This study aimed to evaluate the influence of automatic nerve activity and standing postural sway within this VR environment.

Seventeen healthy adults were instructed to stand on a stabilometer with an outward-facing camera mounted to the VR headset. The subjects were evaluated with or without VR stimuli for each of the following conditions: (1) control (no VR), (2) gazing a human in front of oneself on VR, and (3) gazing a ball coming toward oneself on VR. Body sway while standing upright was recorded for 60seconds with 200Hz sampling. Heart rate variability was measured by a wearable heart rate sensor, and the low-to-high frequency (LH/HF) ratio was calculated for sympathetic nerve activity during each condition. At the end of each condition, we evaluated “surprises” and “fears” subjectively felt under each condition using a visual analog scale (VAS). We compared the results from each of these conditions with Kruskal–Wallis and Steel–Dwass test. The level of significance was set at P<0.05.

The results revealed that fear-VAS was significantly higher under condition 3 (P<0.05). Additionally, the LF/HF tended to higher, and total length of the body sway tended to smaller than other conditions.

Using a simple VR system, we observed that fear stimuli induced motor inhibition, such as “freezing” by activating the limbic system.