title: Modeling locomotor dysfunction following spaceflight with Galvanic vestibular stimulation.
abstract: In this study locomotor and gaze dysfunction commonly observed in astronauts following spaceflight were modeled using two Galvanic vestibular stimulation (GVS) paradigms: (1) pseudorandom, and (2) head-coupled (proportional to the summed vertical linear acceleration and yaw angular velocity obtained from a head-mounted Inertial Measurement Unit). Locomotor and gaze function during GVS were assessed by tests previously used to evaluate post-flight astronaut performance; dynamic visual acuity (DVA) during treadmill locomotion at 80 m/min, and navigation of an obstacle course. During treadmill locomotion with pseudorandom GVS there was a 12% decrease in coherence between head pitch and vertical translation at the step frequency relative to the no GVS condition, which was not significantly different to the 15% decrease in coherence observed in astronauts following shuttle missions. This disruption in head stabilization likely resulted in a decrease in DVA equivalent to the reduction in acuity observed in astronauts 6 days after return from extended missions aboard the International Space Station (ISS). There were significant increases in time-to-completion of the obstacle course during both pseudorandom (21%) and head-coupled (14%) GVS, equivalent to an ISS astronaut 5 days post-landing. An attempt to suppress head movement was evident during both pseudorandom and head-coupled GVS while negotiating the obstacle course, with a 20 and 16%, decrease in head pitch and yaw velocity, respectively. The results of this study demonstrate that pseudorandom GVS generates many of the salient features of post-flight locomotor dysfunction observed in astronauts following short and long duration missions. An ambulatory GVS system may prove a useful adjunct to the current pre-flight astronaut training regimen.
authors.affiliation: Human Aerospace Laboratory, Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA. steven.moore@mssm.edu
authors.forename: Steven T
authors.initials: ST
authors.lastname: Moore
authors.forename: Hamish G
authors.initials: HG
authors.lastname: MacDougall
authors.forename: Brian T
authors.initials: BT
authors.lastname: Peters
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Bloomberg
authors.forename: Ian S
authors.initials: IS
authors.lastname: Curthoys
authors.forename: Helen S
authors.initials: HS
authors.lastname: Cohen
mesh_terms: D000328:Adult; D018480:Astronauts; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology*; D005712:Galvanic Skin Response / Q000502:physiology*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008297:Male; D013026:Space Flight; D018561:Space Simulation; D014722:Vestibule, Labyrinth / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology; D014893:Weightlessness / Q000009:adverse effects*