title: Central adaptation to repeated galvanic vestibular stimulation: implications for pre-flight astronaut training.
abstract: Healthy subjects (N = 10) were exposed to 10-min cumulative pseudorandom bilateral bipolar Galvanic vestibular stimulation (GVS) on a weekly basis for 12 weeks (120 min total exposure). During each trial subjects performed computerized dynamic posturography and eye movements were measured using digital video-oculography. Follow up tests were conducted 6 weeks and 6 months after the 12-week adaptation period. Postural performance was significantly impaired during GVS at first exposure, but recovered to baseline over a period of 7-8 weeks (70-80 min GVS exposure). This postural recovery was maintained 6 months after adaptation. In contrast, the roll vestibulo-ocular reflex response to GVS was not attenuated by repeated exposure. This suggests that GVS adaptation did not occur at the vestibular end-organs or involve changes in low-level (brainstem-mediated) vestibulo-ocular or vestibulo-spinal reflexes. Faced with unreliable vestibular input, the cerebellum reweighted sensory input to emphasize veridical extra-vestibular information, such as somatosensation, vision and visceral stretch receptors, to regain postural function. After a period of recovery subjects exhibited dual adaption and the ability to rapidly switch between the perturbed (GVS) and natural vestibular state for up to 6 months.
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Valentina
authors.initials: V
authors.lastname: Dilda
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Tiffany R
authors.initials: TR
authors.lastname: Morris
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Don A
authors.initials: DA
authors.lastname: Yungher
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America; School of Psychology, University of Sydney, Sydney, Australia.
authors.forename: Hamish G
authors.initials: HG
authors.lastname: MacDougall
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Moore
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D018480:Astronauts; D004558:Electric Stimulation / Q000379:methods*; D053483:Eye Movement Measurements; D005133:Eye Movements; D006801:Humans; D008297:Male; D011187:Posture; D012677:Sensation; D013026:Space Flight; D014724:Vestibular Function Tests