POSTURE, LOCOMOTION, SPATIAL ORIENTATION, AND MOTION SICKNESS AS A FUNCTION OF SPACE-FLIGHT

This article summarizes a variety of newly published findings obtained by the Neuroscience Laboratory, Johnson Space Center, and attempts to place this work within a historical framework of previous results on posture, locomotion, motion sickness, and perceptual responses that ha ve been observed in conjunction with space flight. In this context we have taken the view that correct transduction and integration of signa ls from all sensory systems is essential to maintaining stable vision, postural and locomotor control, and eye-hand coordination as componen ts of spatial orientation. The plasticity of the human central nervous system allows individuals to adapt to altered stimulus conditions enc ountered in a microgravity environment. However, until some level of a daptation is achieved, astronauts and cosmonauts often experience spac e motion sickness, disturbances in motion control and eye-hand coordin ation, unstable vision, and illusory motion of the self, the visual sc ene, or both. Many of the same types of disturbances encountered in sp ace flight reappear immediately after crew members return to earth. Th e magnitude of these neurosensory, sensory-motor and perceptual distur bances, and the time needed to recover from them, tend to vary as a fu nction of mission duration and the space travelers prior experience wi th the stimulus rearrangement of space flight. To adequately chart the development of neurosensory changes associated with space flight, we recommend development of enhanced eye movement systems and body positi on measurement. We also advocate the use of a human small radius centr ifuge as both a research tool and as a means of providing on-orbit cou ntermeasures that will lessen the impact of living for long periods of time with out exposure to altering gravito-inertial forces. (C) 1998 Elsevier Science B.V. All rights reserved.