[Visual-manual tracking and vestibular function during 7-day dry immersion].

The seven-day DI experiment provided an opportunity to study the effects of decreased proprioceptive, tactile and support afferentation on the vestibular function and visual-manual tracking. Before and after immersion, six subjects participated in videooculographic evaluation of the static torsion otolith-cervicoocular reflex (OCOR) in response to head inclination at 30 degrees in the frontal plane and dynamic vestibular-cervicoocular reactions to head longitudinal rotations at 0.125 Hz. In addition, the hand-eye motor coordination of tracking a jerky (sinusoidal) or smooth (linear) movement of point targets along the horizontal or the vertical was evaluated based on the data of electrooculography and records of manipulations with the joystick during immersion. The computerized test was performed in virtual spectacles dsplaying images of visual stimuli and hand motor acts. Computed parameters included latent reaction time, amplitude, speed and time of eye and hand movements, and gains of optooculomotor reactions and manual tracking as a ratio of eye/hand to visual stimulus speed. Testing was fulfilled before the experiment, in 3 hrs. of immersion, on days 3 and 6 of staying in the bath, in the initial hours after immersion, and on day 3 of recovery. It was shown that removal of support and minimization of proprioceptive afferentation had a profound effect on the ocular tracking rather than hand pursuance of visual stimulus. Accuracy of manual tracking was better comparing with the eye tracking in all the subjects. This was the first time when we observed changes in the peripheral vestibular system in two out of 6 subjects, i.e. inversion of static torsion OCOR and positional nystagmus on the background of converted reflex which did not mar the parameters of oculo-manual tracking.