[The Effects of Optokinetic Stimulation on Visual-Manual Tracking under Support-Proprioceptive Deprivation.]

: To determine the effects of additional visual stimuli (retinal optokinetic stimulation - ROKS) on characteristics of the visual-manual tracking (VMT) without support and with decreased proprioceptive afferentation there was used a horizontal "dry" immersion. Altogether 18 subjects aged from 19 to 31 years participated in the study and they were submerged into the immersion bath from 5 to 7 days. There was evaluated performance of the VMT in tasks to pursue the jerky (saccadically) and smooth (linear, pendular and circular) movement of a point visual stimulus before, during and after immersion. Eye movements were recorded using electrooculography, hand movements - by ajoystick with a biological visual feedback (one of the two visible stimuli on the screen matched the current angle of thejoystick handle). Computerized visual stimulation programs were presented to subject using a virtual reality glasses with and without additional ROKS. We analyzed time, amplitude and velocity characteristics of the visual and manual tracking (VT and MT), including efficiency ratio (e) and gain (g) as ratios of respectively amplitudes and velocities of eyes/hand movements to the stimulus movement. Without ROKS efficiency ratio and gain of both VT and MT were significantly decreased in comparison with baseline during the whole immersion and up to the R + 3 day after. The most pronounced deterioration was observed in parameters of the VT. When using a "threshold" ROKS parameters of the VT and MT weren't changed before immersion, during and after immersion - they improved (on 1-5-7 days during immersion and on R + 3 day after there was a significant improvement of the VT and MT in comparison to same tests without ROKS). The greatest impact of the ROKS was observed in parameters of the VT. Evaluations of the vestibular function (VF) were performed before and after immersion using videooculography approach. We analyzed statical torsional otolith-cervical-ocular reflex (OCOR), dynamical vestibular-cervical-ocular reactions (VCOR) and vestibular reactivity (VR), spontaneous eye movements (SpEM). On R + 1 day after immersion in 28% of subjects there was found a significant decrease of the gain of OCOR (0.12 value in comparison to 0.25 baseline) with simultaneous significant increase of parameters of VCOR/VR. There was found a correlation between parameters of VT and MT, between VF and VT and no correlation between VF and MT. It was found that removal of the support and minimization of the proprioceptive afferentation has a greater impact-upon accuracy of the VT then accuracy of the MT. When using ROKS correlations between the studied parameters were not only preserved, but also intensified. The results obtained indicate the development of sensory deprivation (and afferent deficit) under the immersion exposure and the possibility of its correction with additional ROCKS.