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Eye Movements and Motion Perception Induced by Off-Vertical Axis Rotation (OVAR) at Small Angles of Tilt after Spaceflight (96-E007)
Principal Investigator
Research Area:
Species Studied
Scientific Name: Homo sapiens Species: Human

The vestibular system, or the balance system, is the sensory system that provides input about one's movement and orientation in space. This system is located in the inner ear where two balance-sensing organs reside, the semicircular canals and the otoliths. Each organ senses a different awareness relative to gravity. The semicircular canals sense head angular acceleration, such as when an individual is rotating; whereas, the otoliths sense both head linear acceleration and head tilt relative to gravity. As a result, during rotation at a constant velocity about an axis tilted at various degrees relative to being upright, only the otolith organs are stimulated by the change in head orientation relative to gravity. When the otoliths sense motion, they send neurosensory signals that control eye movement and to the muscles that control posture. Since gravity is equivalent to a constant linear acceleration, the absence of gravity in space can greatly affect this vestibular system, especially the role played by the otolith organs.

The objective of this experiment was to assess the changes in otolith information processing following adaptation to microgravity by comparing otolith-induced eye movements and self-motion perception before and early postflight. This objective was met by recording eye movement and self-motion perception during Off-Vertical Axis Rotation (OVAR) to accurately reflect the neural processing of otolith signals by the brain. This experiment also determined the time course of recovery of otolith-tilt responses back to baseline levels by repeating postflight data collection at regular intervals.

This experiment was designed not only to understand the fundamental mechanisms by which the central nervous system processes otolith information to derive compensatory eye movements and motion perception, but also to understand the functional organization and plasticity of the central nervous system when exposed to a novel environmental situation, such as microgravity. This experiment helped provide information for postural instability in astronauts after flight and in patients suffering from similar symptoms on Earth.

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Clement G, Pierre D., Reschke MF, Wood SJ, Clement G. Human ocular counter-rolling and roll tilt perception during off-vertical axis rotation after spaceflight. J Vestib Res. 2007; 17(5-6):209-15.[]

Clement G, Reschke M, Wood S. Neurovestibular and sensorimotor studies in space and earth benefits. Curr Pharm Biotechnol. August 2005; 6(4):267-283.[]

Wood SJ, Reschke MF, Sarmiento LA, Clement G. Tilt and translation motion perception during off-vertical axis rotation. Exp Brain Res. September 2007; 182(3):365-377.[]

Adaptation, physiological
Neural pathways
Otolithic membrane
Semicircular canals
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Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

3-D displacement (horizontal, vertical, torsion) of both right and left eyes
Joystick position
Stimuli (chair velocity, tilt angle and position)
Verbal description of subjective motion perception

Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
STS-106 09/08/2000 09/20/2000 12 days
STS-111 06/05/2002 06/19/2002 14 days
STS-112 10/07/2002 10/18/2002 11 days
STS-113 11/23/2002 12/07/2002 14 days
STS-114 07/26/2005 08/09/2005 14 days
STS-121 07/04/2006 07/17/2006 13 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
Centre National d'Etudes Spatiales (CNES)
Alternate Experiment Name
DSO 499
Proposal Date
Proposal Source