Central Vestibular Sensitivity affects Motion Sick Susceptibility through the efficacy of the Velocity Storage Mechanism.

Abstract

Background: Slow-phase eye velocity–time constant (SPEV–TC) and perceived rotational dur ation (PRD) are measurable objective outcomes of the 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. Objective: To determine if central vestibular sensitivity (CVS) characteristics differ among indi viduals with a range of motion sickness susceptibility (MSS). Methods: Participants were allocated to two groups based on MSS (low and high) as identified in 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 pre-rotatory PRD is most significantly different (p ¼ .005) followed by 50 /s post-rotatory PRD (counter clock-wise [CCW], p ¼ .007; clock-wise [CW], p ¼ .021) and log of 180 /s post-rotatory PRD (p ¼ .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 sug gesting greater velocity storage efficiency, hence, greater CVS; CVS is therefore positively corre lated 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 verifica tion of motion sickness therapeutic interventions.