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Stochastic resonance (SR) is a phenomenon whereby the response of a non-linear system to a weak periodic input signal is optimized by the presence of a particular non-zero level of noise. Stochastic resonance using imperceptible stochastic vestibular electrical stimulation, when applied to normal young and elderly subjects, has been shown to significantly(More)
Postural equilibrium performance by the Skylab 1/2, 3, and 4 crewmen following exposure to weightlessness of 28, 59, and 84 days respectively was evaluated using a modified version of a quantitative ataxia test developed by Graybiel and Fregly. Performance for this test was measured under two sets of conditions. In the first, the crewman was required to(More)
Orbital spaceflight exposes astronauts to an environment in which gravity is reduced to negligible magnitudes of 10(-3) to 10(-6) G. Upon insertion into earth orbit, the abrupt loss of the constant linear acceleration provided by gravity removes the otolith stimulus for vestibular sensation of vertical orientation constantly present on Earth. Since the(More)
Decreased postural stability is observed in most astronauts immediately following spaceflight. Because ataxia may present postflight operational hazards, it is important to determine the incidence of postural instability immediately following landing and the dynamics of recovery of normal postural equilibrium control. It is postulated that postflight(More)
To better understand the effects of varying head movement frequencies on human balance control, 12 healthy adult humans were studied during static and dynamic (0.14, 0.33, 0.6 Hz) head tilts of +/- 30 degrees in the pitch and roll planes. Postural sway was measured during upright stance with eyes closed and altered somatosensory inputs provided by a(More)
Dynamic posture testing was conducted on the science crew of the Spacelab-1 mission on a single axis linear motion platform. Tests took place in pre- and post-flight sessions lasting approximately 20 min each. The pre-flight tests were widely spaced over the several months prior to the mission while the post-flight tests were conducted over the first,(More)
The effect of stimulus frequency on tilt and translation motion perception was studied during constant velocity off-vertical axis rotation (OVAR), and compared to the effect of stimulus frequency on eye movements. Fourteen healthy subjects were rotated in darkness about their longitudinal axis 10 degrees and 20 degrees off-vertical at 45 degrees /s (0.125(More)
Geometry dictates that when subjects view a near target during head rotation the eyes must rotate more than the head. The relative contribution to this compensatory response by adjustment of the vestibulo-ocular reflex gain (Gvor), visual tracking mechanisms including prediction, and convergence is debated. We studied horizontal eye movements induced by(More)
Risk of sensory-motor performance failures affecting vehicle control during space missions: a review of the evidence. a number of potentially significant biomedical risks that might limit the agency's plans for future space exploration, including missions back to the Moon and on to Mars. Among these risks is the: " Risk of Impaired Ability to Maintain(More)