Differences in otolith and abdominal viscera graviceptor dynamics: implications for motion sickness and perceived body position.

Human graviceptors, located in the trunk by Mittelstaedt, probably transduce acceleration by abdominal viscera motion. As demonstrated previously in biodynamic vibration and impact tolerance research, the thoraco-abdominal viscera exhibit a resonance at 4 to 6 Hz. Behavioral observations and mechanical models of otolith graviceptor response indicate a phase shift, increasing with frequency between 0.01 and 0.5 Hz. Consequently, the potential exists for intermodality sensory conflict between vestibular and visceral graviceptor signals, at least at the mechanical receptor level. The frequency range of this potential conflict corresponds with the primary frequency range for motion sickness incidence in transportation, in subjects rotated about Earth-horizontal axes (barbecue spit stimulation), and in periodic parabolic flight microgravity research, and also for erroneous perception of vertical oscillations in helicopters. We discuss the implications of this hypothesis for previous self-motion perception research and suggestions for various future studies.