ISU Alumni Conference 2007 – Beijing, China – August 2007 Steve Ulrich and Adam Rasheed Space Life Sciences Department International Space University Adaptivity of the Vestibulo-Ocular Reflex to High Accelerations and Tumbling Motions

Motivation  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

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

Vestibulo-Ocular Reflex  The Vestibular System  Vestibulo-Ocular Reflex (VOR) Connects the labyrinth to the muscles which rotate the eyes Automatic control system that stabilizes the eyes Otolith organs

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  VOR Gain Measurement Techniques Classical Technique  Drawback: Qualitative (not accurate) Video-Based Techniques  Drawback: Specialized equipment is required (heavy and expensive) Gaze Deviation Technique (Watt et al., 1985)  Advantage: Simple and relatively accurate Source: Canada in Space, 1987

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

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

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

Experimental Setup  Video

Experimental Setup  ISU SSP 2007 Call for Bungee-o-nauts Overwhelming response of 12 applicants Selection based on crew composition and compatibility

Experimental Setup  Crew Members International, intercultural and interdisplinary crew

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

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)

Instrumentation  Questionnaire

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

Results  Acceleration determined using frame-by-frame analysis

Results  Accelerometer Data saturated at 2g

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

Results  Heart-rate monitor Average heart rates during different phases of the test

Results  Questionnaire Major Symptoms Experienced  Headache  Diziness  Sweating  Stomach Awareness  Shaking Other Symptoms Experienced  Nausea when leaning forward  Floating head  High level of stress after the first ride  Increase in heart rhythm

Results  Questionnaire Time Recovery and Training Effect  Sweating and shaking decreased after each ride  No effect on other symptoms Sweating Shaking

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

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

Summary  VOR Gain  Symptoms Time recovery No clear adaptation (training effect) Major symptoms = sweating and shaking Time recovery Adaptation (training effect)

Acknowledgements  Thanks to Gilles Clément, Jeff Jones, Doug Hamilton, and Erin Tranfield for their valuable mentorship and support.  The authors also wish to gratefully acknowledge our Bungee-o-nauts: Bai Ding, Erin Tegnerud, Meritxell Vinas Tio, Ayako Ono for serving as test subjects for this experiment.  This work was supported by the Space Life Science Department of the International Space University is much appreciated.

Summary