Kornilova L.N., Naumov I.A., Glukhikh D.O., Smirnov Yu.I., Khabarova E.V.
Created and approved (2010-2013) in clinic and model experiments innovative computerized method of differential diagnosis of disorders of the vestibular system, intersensory interactions and visual tracking (hardware-software complexes (HSC) «OCULOSTIM», «OCULOSTIM–CM», «VIRTUAL») was successfully implemented in the practice of pre-and post-flight assessment of cosmonauts and aboard the ISS during the ISS-37/38 expedition of Ryazansky S.N. and Kotov O.V. in 2013 (space experiment «VIRTUAL»).
Space experiment (SE) «VIRTUAL» is aimed to study spatial orientation and interaction of afferent systems in weightlessness and will provide new data on the role of gravity in functioning of the vestibular system, the nature of intersensory interaction and accuracy of visual perception.
Within the SE «VIRTUAL» specialists from the laboratory of VESTIBULAR PHYSIOLOGY at the SSC RF – IBMP RAS for the first time will be able to obtain unique data on functioning of the vestibular system and visual tracking, starting with 2-3 days of staying aboard the ISS, i.e. in the acute phase of adaptation to weightlessness and development of space motion sickness.
SPACE EXPERIMENT «VIRTUAL»
The experiment is carried out before, during and after spaceflight and consists of two stages:
STAGE 1 of the SE «VIRTUAL» – study the effects of weightlessness on the otolith function and the function of the semicircular canals using videooculography (VOG).
The objectives of Stage 1 are:
- to study the effects of weightlessness on the otolith function and the function of the semicircular canals;
- to determine the nature of the interaction of the otolith-oculomotor and cupular-oculomotor subsystems in altered gravity;
- to clarify the role of the otolith function in interaction of afferent systems;
- to study of spontaneous eye movements.
Using of the VOG-complex (Fig. 1) is particularly important because, unlike other methods of recording eye movements, VOG allows registration of torsion ocular counter-rolling – i.e. reaction of the otolith subsystem of the vestibular apparatus to spatial changes of the head or body’ position. Being a gravity-dependent, otolith function works incorrectly in weightlessness, which leads to the development of sensory conflict between the otoliths and semicircular canals, and is one of the main reasons for the development of space motion sickness.
Fig. 1. VOG-complex ETD, using for the stage 1 of the SE «VIRTUAL»
Using of the ETD allows us to receive objective and accurate data on cosmonauts eye movements (high frequency (up to 200-400 Hz) infrared cameras for recording of horizontal, vertical and torsional components, error < 0.01°) and head movements (3-d accelerometers and angular velocity sensors) both on Earth and in spaceflight (Fig. 2).
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Fig. 2. Stage 1 of the SE «VIRTUAL»: a) on Earth, b) during spaceflight aboard the ISS
Performing of the stage 1 of the SE «VIRTUAL» aboard the ISS started in 2013 since the ISS-37/38 expedition of Ryazansky S.N. and Kotov O.V. (Fig. 3).
Fig. 3. Space experiment «VIRTUAL» aboard the ISS during the ISS-37/38/39 expeditions (Ryazansky S.N., Kotov O.V., Turin M.V.)
Expected results are:
- obtaining new data on the role of the otolith function in the formation of the spatial orientation, of the nature of interaction of afferent systems and mechanisms of sensory interactions;
- determination of the nature of interaction of the otolith-oculomotor and cupular-oculomotor subsystems in altered gravity;
- monitoring of the state of vestibular function of cosmonauts, beginning with a 2-3 days of staying aboard the ISS.
STAGE 2 of the SE «VIRTUAL» – study of disorders of visual tracking, developing in weightlessness, and their relationship with impaired vestibular function.
Performing both stages of the SE «VIRTUAL» is planned in 2015. The objectives of Stage 2 are:
- to study the effects of weightlessness on accuracy and speed characteristics of all forms of visual tracking;
- to study the effects of visually-induced illusions (vections) in weightlessness on accuracy and speed characteristics of all forms of visual tracking;
- to study the dependence of performance of visual tracking in weightlessness on the state of vestibular function.
Stage 2 of the SE «VIRTUAL» is to perform a battery of computerized tests designed to study oculomotor reactions upon presentation of various visual stimuli. Visual stimulus is a small spot sized to 1° (foveal stimulus), moving along a given motion’ law both on the clear (black) field screen (virtual reality glasses) and against the background of additional retinal optokinetic stimulation (ROKS) – displayed on the screen’ background blurry spots (ellipses), different in shape and diameter, and moving in a certain law of motion at ~ 6-9 deg/sec) (Fig. 4).
Fig. 4. Visual stimuli used in the study of visual tracking
To carry out the stage 2 of the SE “VIRTUAL” we plan to use the onboard laptop RSE Med, complex «NEUROLAB-2000M» for recording of eye movements using electrooculography (Fig. 5a, 5c) and virtual reality glasses for visual and sound stimulation (Fig. 5b), specially designed in accordance with the requirements of the S.P. Korolev Rocket and Space Corporation “ENERGIA” for use aboard the ISS.
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Fig. 5. Equipment, using to carry out the stage 2 of the SE «VIRTUAL»:
a) complex «NEUROLAB-2000M», b) virtual reality glasses, c) complex «NEUROLAB-2000M» aboard the ISS (cosmonaut Volkov S.A.)
Despite the already accumulated and extensive database of visual tracking studies before, during and after spaceflight (space experiments aboard the orbital stations «Salyut» and «MIR», 1984-1999), stage 2 of the SE «VIRTUAL» for the first time will provide objective and accurate data on the effects of weightlessness on the performance and characteristics of visual tracking (fixational saccades, gaze holding, smooth pursuit with and without additional ROKS) throughout the whole spaceflight, and starting from first 2-3 days of staying aboard the ISS. Differences between early space experiments and the SE “VIRTUAL” lie in the use of modern high-precision means/equipment of registration of eye and head movements, as well as by using a battery of computerized tests allows to study and assess almost all forms of visual tracking.
Carrying out of both phases of the SE «VIRTUAL» is particularly important by the fact that the resulting in-flight data is compared with the pre- and post-flight studies of vestibular function and visual tracking (science experiments «SENSORY ADAPTATION» and «GazeSPIN»). Such comparison and comparative analysis of unique results of various scientific experiments carried out before, during and after spaceflight, will allows to develop a methodology for prognosis the state of the vestibular system, for prognosis the reliability of spatial orientation and visual tracking in complex, dynamic and visual conditions causing disorientation and illusions of spatial position.
Further evolution of space experiments aboard the ISS is the SE «PURSUIT», aimed at the study of the visual and visual-manual tracking in weightlessness.
Start of the SE «PURSUIT» is planned in 2015-2016.
For contributing in preparation of the onboard space experiments and related documentation, laboratory of VESTIBULAR PHYSIOLOGY expresses special thanks to head of the department, a neurologist from the State Organization “Yu.A. Gagarin Research & Test Cosmonaut Training Center” Vasin A.V. and a former employee of our laboratory Makarova S.M..