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
ISU Alumni Conference 2007 – Beijing, China – August 2007
Steve Ulrichand
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
ISU SSP 2007 Call for Bungee-o-nauts• Overwhelming response of 12 applicants
• Selection based on crew composition and compatibility
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)
Presentation Outline
1. Motivation
2. Vestibulo-Ocular Reflex
3. Experimental Setup
4. Instrumentation
5. Results
6. Summary
0
20
40
60
80
100
120
140
Hea
rt R
ate
(bpm
)
Pre-Launch Peak Post-Launch
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.