\u3ci\u3eMedicine Meets Virtual Reality 21\u3c/i\u3e

Editors: James D. Westwood, Susan W. Westwood, Li Felländer-Tsai, Cali M. Fidopiastis, Randy S. Haluck, Richard A. Robb, Steven Senger, Kirby G. Vosburgh. Chapter, Varying the Speed of Perceived Self-Motion Affects Postural Control During Locomotion, co-authored by Joshua Pickhinke, Jung Hung Chien, Mukul Mukherjee, UNO faculty and staff members. Virtual reality environments have been used to show the importance of perception of self-motion in controlling posture and gait. In this study, the authors used a virtual reality environment to investigate whether varying optical flow speed had any effect on postural control during locomotion. Healthy young adult participants walked under two conditions, with optical flow matching their preferred walking speed, and with a randomly varying optic flow speed compared to their preferred walking speed. Exposure to the varying optic flow increased the variability in their postural control as measured by area of COP when compared with the matched speed condition. If perception of self-motion becomes less predictable, postural control during locomotion becomes more variable and possibly riskier.https://digitalcommons.unomaha.edu/facultybooks/1261/thumbnail.jp

The complexity of postural control variability while walking on an unstable support surface

The maintenance of balance during locomotion requires control of anteroposterior and mediolateral postural sway. Walking on the unstable support surface requires learning the dynamics of the support surface and counteracting this to maintain stability. The complexity of displacement along each axis can provide information on control processes involved in this type of behavior. In this study, 8 healthy individuals performed a locomotor task while exposed to different types of mediolateral support surface perturbations. The perturbation conditions were presented in order: stable 1, adaptation 1 (surface roll: ± 5°), stable 2, adaptation 2. All participants were exposed to the conditions in this order. Postural sway was quantified as the anteroposterior and mediolateral displacement of the pelvis. The complexity of displacement along the two movement axes was analyzed using sample entropy; a measure of variability. Statistical analyses consisted of a one-way RM ANOVA per movement axis. The analyses revealed overall higher complexity along the anteroposterior axis, indicated by larger sample entropy values. In response to the random and sinusoidal platform motion conditions, control of the pelvis became more complex. This is significantly different from locomotion on the stable support surface in the baseline and catch trials. Along the anteroposterior axis on the other hand, no significant effect of condition was observed. The results indicate learning to maintain balance while walking on an unstable support surface requires a change in complexity. Complexity of postural control increases only along the perturbation axis, suggesting the system can learn to control for perturbations along selected axes