Effects of virtual reality high heights exposure during beam-walking on physiological stress and cognitive loading.

Virtual reality has been increasingly used in research on balance rehabilitation because it provides robust and novel sensory experiences in controlled environments. We studied 19 healthy young subjects performing a balance beam walking task in two virtual reality conditions and with unaltered view (15 minutes each) to determine if virtual reality high heights exposure induced stress. We recorded number of steps off the beam, heart rate, electrodermal activity, response time to an auditory cue, and high-density electroencephalography (EEG). We hypothesized that virtual high heights exposure would increase measures of physiological stress compared to unaltered viewing at low heights. We found that the virtual high height condition increased heart rate variability and heart rate frequency power relative to virtual low heights. Virtual reality use resulted in increased number of step-offs, heart rate, electrodermal activity, and response time compared to the unaltered viewing at low heights condition. Our results indicated that virtual reality decreased dynamic balance performance and increased physical and cognitive loading compared to unaltered viewing at low heights. In virtual reality, we found significant decreases in source-localized EEG peak amplitude relative to unaltered viewing in the anterior cingulate, which is considered important in sensing loss of balance. Our findings indicate that virtual reality provides realistic experiences that can induce physiological stress in humans during dynamic balance tasks, but virtual reality use impairs physical and cognitive performance during balance

Sitting/standing experiment results.

<p>Sitting/standing experiment results.</p

EEG event-related activity for cortical clusters.

<p>EEG event-related activity is shown for each cortical cluster (n = 19), with unaltered view low in red and virtual reality low in blue. Tone presentation occurred at 0 ms, preceded by 300 ms of baseline activity. We analyzed 800 ms following the tone presentation. Shading reflects the condition with significantly higher amplitude (red for unaltered view low, blue for virtual reality low). We found significant differences in the anterior cingulate cluster only.</p

Behavioral and physiological measures.

<p>Behavioral and physiological measures.</p

Percent change in failures per minute, heart rate, and response time.

<p>To assess fatigue effects, we calculated the percent change (mean±SE) between the first and last 3 minutes of each condition (n = 19). Failures per minute, heart rate, and response time are shown for unaltered view low (red), virtual reality low (dark blue), and virtual reality high (light blue). Negative percent change indicates that the value in the final 3 minutes decreased compared to the first 3 minutes. Failures per minute percent change significantly decreased in unaltered view low compared to virtual reality low. Heart rate percent change significantly increased in virtual reality high compared to virtual reality low. No other comparisons were significant between 1) unaltered view low vs. virtual reality low and 2) virtual reality low vs. virtual reality high.</p

Subject setup and virtual reality views.

<p>Typical subject setup is shown (left). All subjects walked on the same physical beam for all three conditions. In both virtual reality conditions, subjects saw a virtual beam that aligned with the physical beam. In virtual reality low, the virtual beam was the same height off the ground as in unaltered view low (top right), while the virtual beam was 15 meters off the ground in virtual reality high (bottom right).</p

EEG source localization results.

<p>EEG source localization results are shown for the 8 cortical clusters found across all subjects (n = 19). Dipole locations (top) and cluster centroids (bottom) are shown in transverse, sagittal, and coronal views (left to right). We found clusters in anterior parietal (purple), left sensorimotor (blue), right frontal (maroon), anterior cingulate (green), medial occipital (yellow), supplementary motor area (orange), left posterior parietal (red), and right sensorimotor (cyan).</p