Aerospace Medical Association – Boston, MA 2008 Steve Ulrich Adam Rasheed International Space University Summer Session Program 2007 Jeff Jones NASA, Johnson Space Center Gilles Clement Centre National de la Recherche Scientifique Adaptivity of the Vestibulo-Ocular Reflex to High Accelerations and Tumbling Motions

Presentation Outline 1.Rationale 2. Vestibulo-Ocular Reflex 3. Experimental Setup 4. Instrumentation 5. Results 6. Summary

Rationale  Effects of micro and hyper g on vestibular system Balance problems Disorientation, visual illusions  Adaptation of vestibular system after multiple exposures?  Experiment Objective Characterize the adaptation of the vestibular system to high accelerations and tumbling motions

Vestibulo-Ocular Reflex  VOR Gain  VOR Adaptation Measure of ability to track an object while your head is moving Evaluation of the VOR performance implies measurement of the VOR gain before and after exposure to the stimulus  Hypothesis After exposure, VOR gain will first decrease and then get better [Recovery] Repeated exposures over time will result in less degradation in VOR gain [Adaptation]

Vestibulo-Ocular Reflex  Gaze Deviation Technique VOR GAIN = HEAD DEVIATION – GAZE DEVIATION HEAD DEVIATION

Experimental Setup  The Beijing High g and Tumbling Research Facility Description vertical launch followed by tumbling motions Configuration 2 person spherical cockpit Height 120 feet Maximum Acceleration 5-6 g Duration 2 minutes

Instrumentation  Acceleration Measurement 3-axis accelerometer video frame-by-frame analysis  Physiological Measurements heart-rate monitor VOR-gain measurement Questionnaire  Video monitoring on-board (crew response) vehicle tracking (handheld camera) launch camera (tripod 10 m away)

Results  Acceleration determined using frame-by-frame analysis

Results  Heart-rate monitor Typical heart rate trace during one ride

Results  VOR Gain Average of all subjects’ response Each point = average of 36 points Time recovery but no training adaptation

Results  VOR Gain Individual responses Time recovery but no training adaptation Time Recovery Training Effect

Summary  VOR Gain  Symptoms  Application to space flight Time recovery No clear adaptation (training effect) Major symptoms = sweating and shaking Time recovery Adaptation (training effect) Vestibular training to this type of stimulus is ineffective

Acknowledgements  Thanks to Gilles Clément, Jeff Jones, Doug Hamilton, and Erin Tranfield for their valuable mentorship and support.  This work was supported by the Space Life Science Department of the International Space University.

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