Decreased otolith-mediated vestibular response in 25 astronauts induced by long duration spaceflight
Faculty of Sciences. Physics
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences . Biomedical Sciences
Journal of neurophysiology. - Bethesda, Md
, p. 1-19
University of Antwerp
The information coming from the vestibular otolith organs is important for the brain when reflexively making appropriate visual and spinal corrections to maintain balance. Symptoms related to failed balance control and navigation are commonly observed in astronauts returning from space. To investigate the effect of microgravity exposure on the otoliths, we studied the otolith-mediated responses elicited by centrifugation in a group of 25 astronauts before and after 6 months of spaceflight. Ocular Counter-Rolling (OCR) is an otolith-driven reflex which is sensitive to head tilt with regard to gravity and tilts of the gravito-inertial acceleration vector during centrifugation. When comparing pre- and postflight OCR, we found a statistically significant decrease of the OCR response upon return. Nine days after return, the OCR was back at preflight level, indicating a full recovery. Our large study sample allows for more general physiological conclusions about the effect of prolonged microgravity on the otolith system. A deconditioned otolith system is thought to be the cause of several of the drawbacks seen in returning astronauts, such as spatial disorientation and orthostatic intolerance. This knowledge should be taken into for future long-term space missions.