UNUSUAL VESTIBULAR AND VISUAL INPUT IN HUMAN DYNAMIC BALANCE AS A MOTION SICKNESS SUSCEPTIBILITY TEST

Background: Motion sickness (MS)is commonly thought to arise from a se nsory conflict. However, few quantitative methods based on this theory are available to detect MS susceptibility. Hypothesis: It was asked w hether the standardized unusual stimulation of a single sensory channe l under quantified dynamic balance conditions in man could elicit a se nsory conflict and therefore trigger motion sickness (MS). Methods: Ve stibular and visual channels were stimulated by galvanic current and r otating prismatic glasses, respectively. The moving platform used to c reate the requirements for dynamic balance conditions was chosen not o nly to worsen the malaise but also to obtain an objective measurement of the balance consequences of the stimulations. Results: Both vestibu lar and visual stimulation, applied separately, elicited MS-like sympt oms (in 56% and 73% of subjects, respectively) and stereotyped balance reactions. A relationship was found between subjective MS-like sympto ms and objective measurements of dynamic balance performance. Subjects sensitive to unusual vestibular messages differed from the others by a greater increase in the parameters indicating a difficulty of balanc e whereas subjects sensitive to unusual visual messages were recognize d by the strategy they used to balance themselves. Conclusions: These results demonstrated that a sensory conflict can trigger MS-like sympt oms. We conclude that the measured parameters of a global somatomotor activity, such as the dynamic balance task proposed here, could be use ful for objectively detecting subjects predisposed to MS, for training them and testing the efficiency of anti-MS drugs.