Gravity, which is sensed directly by the otolith organs and indirectly by proprioceptors and exteroceptors, provides the CNS a fundamental reference for estimating spatial orientation and coordinating movements in the terrestrial environment. The sustained absence of gravity during orbital space flight creates a unique environment that cannot be reproduced on Earth. Insertion into orbit removes this fundamental CNS reference and triggers neuro-adaptive processes that optimize performance for the microgravity environment. Return to Earth reintroduces this reference and triggers neuro-adaptive processes that return performance to terrestrial norms. Owing to the untoward effects of these adaptive responses on astronaut performance, their behavioral manifestations have been fairly well characterized; however, the anatomical sites involved and neurological mechanisms responsible have not. Understanding the cellular and molecular bases for these adaptive responses may be among the greatest challenges of modern neuroscience (Pompeiano, 2002), but the payoff may be improved quality of life for aging individuals, improved therapies for spinal cord injuries and vestibular disorders, improved techniques for rehabilitation from sensory-motor injuries, improved training for elite athletes, and safe extension of both time and distance for human space exploration. Recent results from investigations aboard the space shuttle have begun to identify both sites and mechanisms of vestibular system adaptation, and have demonstrated the feasibility of using orbiting laboratories to investigate the fundamental role that gravity plays in neurological processes. Future laboratory capabilities aboard the International Space Station should expand the role of space flight in exploring fundamental questions in neurophysiology, and these answers, in turn, should reduce the limitations of neurophysiology on space exploration.

View Presentation

Last updated: