J Neurophysiol. 2020 Jan 08.
Our research described here was motivated by the puzzling finding of the Skylab M-131 experiments: head movements made while rotating that are nauseogenic and disorienting on Earth are innocuous in a weightless, 0g, environment. We describe a series of parabolic flight experiments that directly addressed this puzzle and discovered the gravity-dependent responses to semicircular canal stimulation, consistent with the principles of velocity storage. We describe a line of research that started in a different direction, investigating dynamic balancing, but ended up pointing to the gravity dependence of angular velocity-to-position integration of semicircular canal signals. Together these lines of research and the theoretical framework of velocity storage provide an answer to at least part of the M-131 puzzle. We also describe recently discovered neural circuits by which active, dynamic vestibular, multi-sensory, and motor signals are interpreted as either appropriate for action and orientation or as conflicts evoking motion sickness and disorientation.
Keywords: motion sickness; space flight; velocity storage; vestibular