Otolith Assessment During Postflight Re-adaptation (Otolith) - 03.19.15

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Science Objectives for Everyone
Otolith Assessment During Postflight Re-adaptation (Otolith) assesses otolith (small bones of the inner ear) function in crewmembers preflight and postflight.
Science Results for Everyone
Our eyes and ears like gravity. This investigation found that the reduced sensory input of weightlessness caused changes in the function of otoliths, the small inner-ear bones, in 90 percent of astronauts. These included both typical and atypical forms of spontaneous rapid eye movements, indicating changes in functioning of the body’s vestibular or balance system. Such changes represent a typical adaptation of sensory systems to an altered sensory environment and are specific to individuals in terms of the level, time, duration, and dynamics. This seems to suggest that the pattern of changes is determined by the combined effect of various sensory inputs and their relationship.

The following content was provided by Andrew H. Clarke, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.
Experiment Details


Principal Investigator(s)

  • Andrew H. Clarke, Ph.D., Charite Medical School, Berlin, Germany

  • Co-Investigator(s)/Collaborator(s)
  • Floris L. Wuyts, Ph.D., University of Antwerp, Antwerp, Belgium
  • Scott J. Wood, Ph.D., Azusa Pacific University, Azusa, CA, United States

  • Developer(s)
    Kayser Threde, Munich, Germany

    Sponsoring Space Agency
    European Space Agency (ESA)

    Sponsoring Organization
    Information Pending

    Research Benefits
    Information Pending

    ISS Expedition Duration
    April 2008 - September 2011

    Expeditions Assigned

    Previous ISS Missions
    Otolith first began on ISS Expedition 18.

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    Experiment Description

    Research Overview

    • Otolith Assessment During Postflight Re-adaptation (Otolith) will assess otolith (small bones of the inner ear) function before and after space flight to this evaluate otolith-ocular response (OOR) and the subjective visual vertical (SVV) to assess unilateral utricle function. Vestibular evoked myogenic potentials (VEMP) will be recorded in order to assess unilateral saccule function.

    • Together this represents a comprehensive examination of all aspects of the otolith system, providing critical information on the validity of the otolith asymmetry hypothesis and on the post flight adaptation of the individual otolith functions.

    Information Pending

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    Space Applications
    Information Pending

    Earth Applications
    Information Pending

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    Operational Requirements
    Information Pending

    Operational Protocols
    Information Pending

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    Results/More Information

    The compensatory eye movements with the head/neck movements, or the otolith–cervical–ocular reflex (OCOR), was studied to determine the roll the vestibular system plays in ocular impairments in 16 ground subjects after a seven days of “dry” horizontal immersion, and 14 cosmonauts after a prolonged exposure to weightlessness (for 126–195 days). After spaceflight, the absence, inversion (feeling of hanging upside down), or a sharp decrease in eye movements evoked by head movements indicates a deep deconditioning of the otolith (inner ear) function because of reduced sensory input to the central nervous system from the vestibular organs from weightlessness. A study of spontaneous oculomotor activity (SOA) and OCOR after prolonged exposure to microgravity and in subjects who were exposed to the immersion bath demonstrated that the responses to both environments were similar. However, the patterns, duration, and depth of changes observed after spaceflight versus immersion were different. After immersion, these reactions were found only in 60% of the examined subjects and they were less pronounced and less durable, while the same impairments were observed in 90% of cosmonauts and in addition, they were more profound and long lasting. In 33% of the cosmonauts examined, the amplitude of the compensatory eye counter rolling remained still reduced at 8−9 days post-flight as compared to the pre-flight value. The increase of SOA in 55% of cosmonauts after flight and in 12% of the subjects exposed to immersion (development of gaze-evoked nystagmus; i.e., involuntary eye movement, and both typical and atypical forms of spontaneous nystagmus) indicates involvement of the vestibular system’s central mechanisms and reflects changes in functioning of the vestibular nuclei, the midbrain reticular formation (parts of the brainstem, important in regulating consciousness or wakefulness), and the cerebellum. OCOR restoration after returning to Earth requires a certain amount of time for readaptation of the otolith function to Earth’s gravity. The changes in the vestibular system represent a typical adaptation response of the sensory systems to the altered sensory environment; these changes depend on the time of rearrangement between sensory connections under the conditions of Earth’s gravity. However, these reactions have individual specific features in terms of the level of expression, time, duration, and dynamics. This seems to suggest that the pattern of changes in OCOR is determined by the combined effect of various sensory input signals and their collective relationship.

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    Results Publications

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

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    Related Websites
    The information on this page is provided courtesy of the ESA Erasmus Experiment Archive.

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