Postural Time-To-Contact, Real-Time Visual Feedback Of Postural Activity, And Motion Sickness

Abstract

The postural instability theory of motion sickness predicts that the subjective symptoms of motion sickness will be preceded by unstable control of posture. In previous research, it has been confirmed with measures of the spatial magnitude and temporal dynamic of postural activity. In the first chapter, I introduced a new measure (postural time-to-contact (VTC)) which is related to the risk of falling. Standing participants were exposed to visual oscillation stimuli. I measured the kinematics of the body’s center of pressure. The results show that postural time-to-contact differed between the Well and Sick groups before and during the exposure to the visual motion stimuli. The multifractality of sway differed between the Well and Sick groups during the room exposure. In Chapter 2, I examined the real-time feedback of body’s center of pressure with the same protocol as Chapter 1. The chi-square test between the sickness and the display format (blank screen and real-time feedback) suggests that the real-time feedback increases the risk of motion sickness. Body sway also differed before any participants experienced subjective symptoms of motion sickness. In Chapter 3, I measured the correlation between postural measures and motion sickness symptoms severity (TSS). The change of TSS has a higher Pearson correlation to the VTC in the blank screen condition than the motion sickness susceptibility total score (MSSQt). Principal component analysis (PCA) and linear discriminant analysis (LDA) were implemented to construct motion sickness susceptibility score of postural activity (MSSPA). The LDA score in the blank screen condition outperformed the PCA score in both conditions, the LDA score in the feedback condition and the MSSQt regarding its relation to motion sickness symptom severity score. Since this experiment was completed in a moving room setting (open-loop), further examination of MSSPA in the tablet computer, simulator and virtual reality (closed-loop).