Illusory self-motion (Vection) may be inhibited by hypobaric hypoxia

Introduction: Previous reports have shown that higher altitudes can alter human perception. We add further evidence to this claim, describing a new finding in which higher altitudes inhibit the perception of illusory self-motion, i.e., vection. Method: We compared vection strength under both normal and high altitude (hypobaric hypoxia) conditions. In the high altitude condition, atmospheric pressure in the climatic chamber was decreased to 13,123 ft (4000 m; 492 ft/150 m · min ^-1) for 28 min and then maintained at the 13,123-ft (4000-m) level for 30 min by a preprogrammed operation. Vection was induced by an optic flow stimulus. Results: Significant differences were observed between the normal and high altitude conditions for all three of the vection strength measurements (latency, duration, and magnitude). Vection was decreased by 14.6%, and S_PO₂ was decreased by 16.7% in the hypoxia condition. Conclusion: Vection was inhibited in the high altitude condition. Applications of this finding include informing aircraft pilots of this effect of self-motion perception inhibition at higher altitudes to promote safer flying.