Motion sickness susceptibility correlates with otolith- and canal-ocular reflexes

Since motion sickness (MS) never occurs in individuals who lack functional vestibular apparatus, it has been suggested that MS susceptible individuals have more sensitive vestibular systems than non-susceptible people. However, previous investigations involving only stimulation of the semi-circular canals have been inconclusive. We measured gain and time constant (TC) of horizontal canal-ocular reflex (COR) and magnitude of otolith-ocular reflex (OOR). We found that MS susceptibility was not correlated to COR gain but was negatively correlated to OOR magnitude. Thus, MS susceptible individuals do not have more sensitive vestibular systems. We also found a positive correlation between MS susceptibility and TC. We hypothesize that central vestibular integration (velocity storage mechanism), by increasing low frequency vestibular inputs, would favour MS.