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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Neurovestibular/Ocular Physiology• Anatomy of the vestibular organs• Proprioception and Exteroception• Vestibular illusions• Space Motion Sickness• Artificial gravity issues• Eye issues in space flight
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© 2019 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Anatomy of the Ear
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From James T. Joyner, ed., NOAA Diving Manual, Best Publishing, 2001
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Vestibular System
From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Vestibular Sense Organs
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Sensing Roles of Vestibular Organs
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Semicircular Canal Responses
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Orientation of Semicircular Canals
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From Susanne E. Churchill, ed., Fundamentals of Space Life Sciences, Krieger Publishing, 1997
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Ocular Nystagmus
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Otolith Responses
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Ocular Countertorsion
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Categories of Sensing• Proprioception (internal to body)
– “Self-Sensing”– Vestibular (inertial forces)– Muscle and tendon sensors (extension)– Joint sensors (angle)
• Exteroception (external to body)– Visual– Auditory– Cutaneous
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Thresholds of Rotational Perception• Rotational accelerations
– Yaw: 0.14 deg/sec2
– Roll and Pitch: 0.5 deg/sec2
• Mulder’s Constant– Acceleration x excitation time = 2 deg/sec– 5 deg/sec2 x 0.5 sec -> sensed– 10 deg/sec2 x 0.1 sec -> not sensed
• Rotational velocities - minimum perceived rotation rates 1-2 deg/sec (all axes)
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Transfer Function of Semicircular Canals
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Thresholds of Translational Perception• ax: 0.006 g• ay: 0.006 g• az: 0.01 g• Apparent change in direction of g vector = 1.5°
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Somatogyral Illusions
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Coriolis Illusion
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Somatogravic Illusion
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Inversion Illusion
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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G-Excess Illusion
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Vestibular Adaptation to Space Flight• Otolith Tilt-Translation Reinterpretation (OTTR)
– Otolith signals are interpreted as translation rather than tilt
– Decays ~ 1 week post-flight
• Emphasis on visual and proprioceptive cues– Field dependent - orient in reference to nearby objects– Body oriented - assume world orientation is fixed by
body orientation– Inversion illusions
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Space Motion Sickness• “Space Adaptation Syndrome”• 2/3 of astronauts report some effects• Symptoms
– Primary: stomach discomfort, nausea, vomiting– Secondary: pallor, cold sweats, salivation, depressed
appetite, fatigue
• No correlation to susceptibility to motion sickness• Primary hypothesis: sensory conflict (Treisman’s
Theory)
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Progression of Space Motion Sickness
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From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
SAS Experience of First 34 Shuttle Flights
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0
24
48
72
96
120
First Flight Subsequent FlightNone Mild Moderate Severe
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
SAS Experience of First 34 Shuttle Flights
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0.00
0.25
0.50
0.75
1.00
First Flight % Subsequent Flight %
None Mild Moderate Severe
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Space Motion Sickness Countermeasures• Preflight training
– Desensitization– Autogenic feedback training (AFT)
• Pharmaceuticals– Oral - scopolamine/dex-amphetamine (Scopdex)– Transdermal - scopolamine– Intramuscular - promethazine
• Mechanical systems– Pressurized insoles– Load suits– Neck restraints
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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1
10
100
1000
10000
0 2 4 6
Rotation Rate (rpm)
Lunar gravityMars gravity0.5*Earth gravity0.75*Earth gravityEarth gravity
Artificial Gravity
€
grotation =ω 2r
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Allowable Rotation Rates• Select groups (highly trained, physically fit) can
become acclimated to 7 rpm• 95% of population can tolerate 3 rpm• Sensitive groups (elderly, young, pregnant women)
may have tolerance levels as low as 1 rpm
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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Eye Issues in Space Flight• Early (Mercury/Gemini) astronauts reported
hyperacuity on orbit (resolution of cars/trucks/boats) - not verified in controlled conditions
• Recent results indicate some astronauts have noticeable visual degradation on long-term flights - may or may not return to pre-flight conditions post-flight
• Concern for long-term human exploration - lose ability to see well prior to Mars landing?
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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VIIP Syndrome• VIIP=Visual Impairment Intracranial Pressure • Assumed to be due to fluid shift on-orbit
– Backs of eyes (w/ retina) moved forward towards lenses– Choroidal folds (“stretch marks”)– Inflamed optic nerves
• About 60% of long-duration crew notice some visual effects
• One crew went from 20/20 to 20/100 in six months - recovered to 20/50 post-flight
• Similar to idiopathic intracranial hypertension, papilledema (optic nerve swelling) on ground
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
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VIIP Diagnosis/Treatment• Need to monitor intracranial pressure
– Spinal tap – Direct measurement through skull– CT scans– Looking for flight-compatible bioinstrumentation
• Mitigation: reduce intracranial pressure/fluid shift– Lower body negative pressure– “Penguin” suits– Cerebral-spinal drainage– Pharmacological approaches?
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Neurovestibular Physiology ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
References• R. L. DeHart, ed., Fundamentals of Aerospace
Medicine, Second Edition Williams and Wilkins, 1996
• A. E. Nicogossian, C. L. Huntoon, and S. L. Pool, Space Physiology and Medicine, Third Edition Lea and Febiger, 1994
• A. E. Nicogossian, S. R. Mohler, O. G. Gazenko, and A. I. Grigoriev, eds., Space Biology and Medicine (Volume III, Book 1: Humans in Spaceflight) American Institute of Aeronautics and Astronautics, 1996
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