Visual-manual tracking during a five-day dry immersion

The effect of low proprioceptive, tactile, and support afferentation on visual-manual tracking was determined using a five-day horizontal dry immersion, which provided support deprivation, as well as minimization of muscle activity and proprioceptive afferentation, simulating the physiological effects of microgravity. Hand-eye motor coordination was studied in the 13 subjects participating in the experiment with five-day dry immersion who tracked the jumpy and smooth movements of a point visual stimulus (linear and pendulum-like; horizontal and vertical; circular, clockwise and counterclockwise). Ocular movements were recorded using binocular electrooculography; and manual motions were recorded using a joystick with a biological visual feedback, when one of the two stimuli on the screen showed the current joystick tilt. Computerized stimulation was provided using virtual reality goggles. The following parameters were evaluated: the latent and total reaction time; the amplitudes and velocities of the eye and hand movements; and the coefficients of effectiveness (amplitude ratio) and the gain (velocity ratio). The examinations were performed before immersion, after 3 h of immersion, on days 3 and 5 of immersion, during the first hours after the termination of immersion, and three days after the immersion (in all subjects); and on days 5–7 after the immersion (in four subjects). It was shown that support deprivation and minimization of proprioceptive afferentation affected ocular tracking to a larger extent than the accuracy of manual movements following the visual stimulus. It was found that, in all subjects, manual tracking, which did not significantly change during the test sessions, was more accurate than visual tracking; in contrast, the accuracy of visual tracking changed noticeably both in the course of dry immersion and after its termination.