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Human Ocular Counter-Rolling and Roll Tilt Perception during Off-Vertical Axis Rotation after SpaceflightOcular counter-rolling (OCR) induced by whole body tilt in roll has been explored after spaceflight as an indicator of the adaptation of the otolith function to microgravity. It has been claimed that the overall pattern of OCR responses during static body tilt after spaceflight is indicative of a decreased role of the otolith function, but the results of these studies have not been consistent, mostly due to large variations in the OCR within and across individuals. By contrast with static head tilt, off-vertical axis rotation (OVAR) presents the advantage of generating a sinusoidal modulation of OCR, allowing averaged measurements over several cycles, thus improving measurement accuracy. Accordingly, OCR and the sense of roll tilt were evaluated in seven astronauts before and after spaceflight during OVAR at 45 /s in darkness at two angles of tilt (10 and 20 ). There was no significant difference in OCR during OVAR immediately after landing compared to preflight. However, the amplitude of the perceived roll tilt during OVAR was significantly larger immediately postflight, and then returned to control values in the following days. Since the OCR response is predominantly attributed to the shearing force exerted on the utricular macula, the absence of change in OCR postflight suggests that the peripheral otolith organs function normally after short-term spaceflight. However, the increased sense of roll tilt indicates an adaptation in the central processing of gravitational input, presumably related to a re-weigthing of the internal representation of gravitational vertical as a result of adaptation to microgravity.
Document ID
20080010140
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Clement, Gilles
(Centre National de la Recherche Scientifique Toulouse, France)
Denise, Pierre
(Caen Univ. France)
Reschke, Millard
(NASA Johnson Space Center Houston, TX, United States)
Wood, Scott J.
(Universities Space Research Association Houston, TX, United States)
Date Acquired
August 24, 2013
Publication Date
January 28, 2007
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other

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