MOTOR FUNCTION IN MICROGRAVITY - MOVEMENT IN WEIGHTLESSNESS

Microgravity provides unique, though experimentally challenging, oppor tunities to study motor control. A traditional research focus has been the effects of linear acceleration on vestibular responses to angular acceleration. Evidence is accumulating that the high-frequency vestib ule-ocular reflex (VOR) is not affected by transitions from a 1 g line ar force field to microgravity (<1 g); however, it appears that the th ree-dimensional organization of the VOR is dependent on gravitoinertia l force levels. Some of the observed effects of microgravity on head a nd arm movement control appear to depend on the previously undetected inputs of cervical and brachial proprioception, which change almost im mediately in response to alterations in background force levels. Recen t studies of post-flight disturbances of posture and locomotion are re vealing sensorimotor mechanisms that adjust over periods ranging from hours to weeks.