Background/Objective: Slow-Phase Eye Velocity Time constant (SPEV TC) and Perceived Rotational Duration (PRD) are measurable objective outcomes of rotational chair step-velocity test. These two variables are dependent on the efficacy of the central velocity storage. If sensory conflict from the step-velocity of the rotational chair elicits motion sickness, the SPEV TC and PRD in individuals with varying susceptibility to motion sickness should be affected. We determined if Central Vestibular Sensitivity (CVS) characteristics differ among individuals with a range of Motion Sickness Susceptibility (MSS). Methods: Participants were allocated to two groups based on MSS (low and high) as identified on the short version of the Motion Sick Susceptibility Questionnaire (MSSQ-S). We evaluated the specific relationship between MSS and the characteristics of CVS through the SPEV TC and PRD from the step-velocity test. Results: Results showed significant differences in the PRD between these two groups. 180°/s Per-rotatory PRD is most significantly different (p = 0.005) followed by 50°/s post-rotatory PRD (CCW, p = 0.007; CW, p = 0.021) and log of 180°/s post-rotatory PRD (p = 0.042). Multiple regression analysis indicated that CCW post-rotatory PRD at 50°/s was a strong predictor of MSS. Conclusions: High MSS individuals were observed with elevated PRD in general, indirectly suggesting greater velocity storage efficiency, hence, greater CVS; CVS is therefore positively correlated with MSS. PRD could be a reliable clinical indicator of motion sick susceptibility and may help with the selection of personnel working in motion sick environments and with the verification of motion sickness therapeutic interventions.
Keywords: motion sickness susceptibility; perceived rotational duration; slow-phase eye velocity; time constant; velocity storage mechanism; vestibular.