Seasickness Susceptability and Vestibular Time Constant

Tc was evaluated by the rotational velocity step test using the OtoaccessTM interface (Interacoustics Nydiag 200, Middlefart, Denmark). Subjects were seated on the rotatory chair wearing videonystagmography goggles with their heads supported and tilted 30° forward, thus bringing the horizontal semicircular canals plane perpendicular to the axis of rotation. Standard videonystagmography techniques were employed to record eye-movements. Subsequent to eye movements' calibration, the chair was accelerated about the yaw axis at 30°/sec2 to a maximal velocity of 90°/sec, followed by rotation at a constant velocity. After 57 seconds of constant velocity rotation, the chair was decelerated to zero velocity at 30°/sec2. The described velocity step was conducted both clockwise and counter-clockwise, giving a total run time of 4 minutes.