RESUMEN
In weightlessness spatial orientation largely depends on coordinated interaction of sensory systems involved in static orientation. The purpose of the present study was to quantify perception of spatial coordinates in response to optokinetic stimulation. Effects of weightlessness were simulated by dry water immersion hypokinesia. A custom-made optokinetic stimulator equipped with a device to measure perception of the gravitational vertical in response to optokinetic stimulation was used. A special platform with rubber bungee cords was employed to determine the role of the proprioceptive afferent input. It was demonstrated that during immersion day 1 the angle of erroneous perception of the vertical line consistently increased. By immersion day 3 the angle diminished suggesting adaptive developments. Additional proprioceptive inflow during immersion reduced significantly the error of perception. These findings indicate that the proprioceptive afferent input plays an important role in the mechanisms of spatial orientation at an early stage of exposure to weightlessness.
Asunto(s)
Medicina Aeroespacial , Gravitación , Modelos Biológicos , Desempeño Psicomotor/fisiología , Percepción Espacial/fisiología , Ingravidez , Adulto , Movimientos Oculares , Humanos , Masculino , Campos VisualesAsunto(s)
Movimientos Oculares , Gravitación , Núcleos Vestibulares/fisiología , Animales , Haplorrinos , Humanos , Reflejo , Vuelo EspacialRESUMEN
The effect of 7-day immersion hypokinesia on the coordination of eye and head movements during the gaze fixation reaction was investigated. The most distinct and persistent effect was an inadequate increase in the rate of eye counter-rolling that mismatched head movements. This reduced significantly the response time and accuracy: the time of gaze fixation lengthened appreciably and the number of positional errors grew considerably. These data suggest that in the oculomotor control system proprioceptive signals produce an inhibitory effect on the vestibular input.