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OTOLITH ORGAN ACTIVITY WITHIN EARTH STANDARD, ONE-HALF STANDARD, AND ZERO GRAVITY ENVIRONMENTS.
NAVAL SCHOOL OF AVIATION MEDICINE PENSACOLA FLA
Pagination or Media Count:
Six individuals with bilateral labyrinthine defects and seven normal persons served as subjects. Transient periods of subgravity force 0.5G, zero G were produced by parabolic flight maneuvers in a specially equipped C-131B aircraft which accommodated a tilt chair and accessory apparatus for recording ocular counterrolling response to body tilt 25 degrees, 50 degrees. Testing under 1.0G conditions was accomplished during periods of straight and level flight. The labyrinthinedefective L-D group revelaed results which were qualitively similar to those from the normal group but markedly reduced in magnitude. This demonstrated that extra-labyrinthine factors were not significantly influencing extraocular muscle tonus, and therefore ocular counterrolling served as a valid and sensitive indicator of otolith activity under hypogravic conditions. In the normal subjects zero G induced a physiological deafferentation of the otolith organs as indicated by the lack of any significant counterrolling response when the subjects were tilted righward or leftward up to 50 degrees. When the gravitational force equalled approximately 0.5G, the magnitude of counterrolling fell substantially below the level midway between the zero and Earth standard gravity response curves. The nonlinear relationship between otolith activity and subgravity force that is implied in these data and confirmed in a follow-up study is discussed. Author
APPROVED FOR PUBLIC RELEASE