Altered sensorimotor control of the body as an etiological factor in space motion sickness

Exposure to nonterrestrial force levels affects the activity of gravitoinertial force sensitive receptors of the body, both of labyrinthine and nonlabyrinthine origin. It also disrupts the normal patterning of motor control of body orientation and movement. The patterns and levels of muscle innervation necessary to achieve particular body configurations and to bring about particular body movements are greatly affected by background force level and body orientation relative to the force vector. The present studies demonstrate that such altered sensorimotor control of head and body posture along with altered vestibulomotor control are evocative of motion sickness. This observation has explanatory significance both for space motion sickness and the re-entry disturbances that occur after prolonged spaceflight.