Evaluating visual-vestibular interactions in motion sickness susceptibility with static subjective visual vertical, dynamic subjective visual vertical, and rod-and-frame test.

BackgroundMotion sickness (MS) occurs when the brain receives conflicting signals about body movement from the visual, vestibular, and proprioceptive systems. The otolith organs play a key role in perceiving verticality, and their function may be influenced by MS susceptibility.ObjectiveThis study aimed to investigate the effect of MS susceptibility on otolith-mediated verticality perception across different head positions.MethodsForty-seven participants were classified into two groups based on the Motion Sickness Susceptibility Questionnaire-Short Form (MSSQ-SF): an MS group (n = 24) and a control group (n = 23). All participants completed static Subjective Visual Vertical (SVV), dynamic Subjective Visual Vertical (DVV), and Rod-and-Frame Test (RFT) using a virtual reality system. Measurements were conducted in three head tilt (upright, 30° left, 30° right). The absolute deviation from true vertical was calculated for each test.ResultsWhile no significant differences were found in SVV performance between groups across head-tilt angles, the MS group exhibited significantly greater deviations in DVV at all positions and in RFT during 30° head tilts. Higher MSSQ scores correlated with greater deviations in DVV and RFT under tilt conditions.ConclusionsAlthough static verticality perception remains intact, individuals with MS exhibit greater deviations under dynamic and visually misleading conditions, suggesting subtle vestibular-perceptual deficits.