SEASICKNESS - CURRENT STATE OF PREVENTION AND TREATMENT ISSUE

The paper describes the current state of development of seasickness as one of movement disease variants. The given type of pathology occurs when combining different types of ship’s motion (rolling and pitching). Circular, vertical and slow movements induce more pronounced and frequent signs of seasickness than linear, horizontal and quick ones. In the view of majority of researchers, the most likely is an intersensory conflict theory i.e. violation of coherent functioning of afferent body systems performing spatial orientation, statokinetic equilibrium and keeping balance. The leading role is played by the functional dysfunction of the vestibular analyzer. The classification of means of preventing and stopping of motion sickness is given, the mechanisms of their action, specific activity and side effects are described. It has been shown that currently the most effective drugs are M-cholinergic antagonists (scopolamine hydrobromide) and H1-histamine antagonists of the 1st generation (dimenhydrinate, diphenhydramine, cyclizine, meclizine, promethazine, etc.). Of the antipsychotics and blockers of D2 receptors, prochlorperazine and metoclopramide are recommended. It is also worth to use prokinetics (domperidone, cisapride, renzapride, etc.), tranquilizers (barbiturates, benzodiazepines), sleeping pills and local anesthetics. Particular attention is paid to combination drugs, consisting of antiemetic and psychostimulating drugs, designed to maintain working capacity under the influence of seasickness factors on the body. Non-pharmacological means of preventing seasickness and alleviating its symptoms are described. The main directions of improving the system of measures aimed at maintaining efficiency in the presence of symptoms of seasickness are determined.

Sensorimotor aspects of high-speed artificial gravity: I. Sensory conflict in vestibular adaptation

Short-radius centrifugation offers a promising and affordable countermeasure to the adverse effects of prolonged weightlessness. However, head movements made in a fast rotating environment elicit Coriolis effects, which seriously compromise sensory and motor processes. We found that participants can adapt to these Coriolis effects when exposed intermittently to high rotation rates and, at the same time, can maintain their perceptual-motor coordination in stationary environments. In this paper, we explore the role of inter-sensory conflict in this adaptation process. Different measures (vertical nystagmus, illusory body tilt, motion sickness) react differently to visual-vestibular conflict and adapt differently. In particular, proprioceptive-vestibular conflict sufficed to adapt subjective parameters and the time constant of nystagmus decay, while retinal slip was required for VOR gain adaptation. A simple correlation between the strength of intersensory conflict and the efficacy of adaptation fails to explain the data. Implications of these findings, which differ from existing data for low rotation rates, are discussed.

Virtual Eyes Can Rearrange Your Body: Adaptation to Visual Displacement in See-Through, Head-Mounted Displays

Among the most critical issues in the design of immersive virtual environments are those that deal with the problem of technologically induced intersensory conflict and one of the results, sensorimotor adaptation. An experiment was conducted to support the design of a prototype see-through, head-mounted display (HMD). When wearing video see-through HMDs in augmented reality systems, subjects see the world around them through a pair of head-mounted video cameras. The study looked at the effects of sensory rearrangement caused by a HMD design that displaced the user's “virtual” eye position forward (165 mm) and above (62 mm) toward the spatial position of the cameras. The position of the cameras creates images of the world that are slightly downward and inward from normal. Measures of hand-eye coordination and speed on a manual pegboard task revealed substantial perceptual costs of the eye displacement initially, but also evidence of adaptation. Upon first wearing the video see-through HMD, subjects' pointing errors increased significantly along the spatial dimensions displaced (the y dimension, above-below the target, and z dimension, in front-behind the target). Speed of performance on the pegboard task decreased by 43% compared to baseline performance. Pointing accuracy improved by approximately 33% as subjects adapted to the sensory rearrangement, but it did not reach baseline performance. When subjects removed the see-through HMD, there was evidence that their hand-eye coordination had been altered. Negative aftereffects were observed in the form of greater errors in pointing accuracy compared to baseline. Although these aftereffects are temporary, the results may have serious practical implications for the use of video see-through HMDs by users (e.g., surgeons) who depend on very accurate hand-eye coordination.