Abstract
BackgroundThe vestibular (otolith) function is highly suppressed during space flight (SF) and the study of these changes is very important for the safety of the space crew during SF missions. The vestibular function (particularly, otolith-ocular reflex–OOcR) in clinical and space medicine is studied using different methodologies. However, different methods and methodologies can influence the outcome results.ObjectiveThe current study addresses the question of whether the OOcR results obtained by different methods are different, and what the role is of the different afferent systems in the modulation of the OOcR.MethodsA total of 25 Russian cosmonauts voluntarily took part in our study. They are crewmembers of long duration space missions on the International Space Station (ISS). Cosmonauts were examined in pre- and post-flight “Sensory Adaptation” and “Gaze Spin” experiments, twice before (preflight) and three times after SF (post-flight). We used two different video oculography (VOG) systems for the recording of the OOcR obtained in each experiment.ResultsComparison of the two VOG systems didn’t result into significant and systematic differences in the OOcR measurements. Analysis of the static torsion otolith–ocular reflex (OOR), static torsion otolith–cervical–ocular reflex (OCOR) and static torsion otolith–ocular reflex during eccentric centrifugation (OOREC) shows that the OOREC results in a lower OOcR response compared to the OOR and OCOR (before flight and late post-flight). However, all OOcRs were significantly decreased in all cosmonauts early post-flight.ConclusionAnalysis of the results of ocular counter rolling (OCR) obtained by different methods (OOR, OCOR, and OOREC) showed that different afferent systems (tactile-proprioception, neck-cervical, visual and vestibular afferent input) have an impact on the OOcR.
Highlights
Long-term weightlessness during space flight (SF) is a unique way to modify the input signals from the otoliths, which allows the identification of the character and dynamics of vestibular function changes (VF)
A possible reason for this could be the duration of the shuttle missions,
We can conclude that measurements of the otolith reflex obtained by different video oculography (VOG)-systems are unbiased and independent from the type of used system
Summary
Long-term weightlessness during SF is a unique way to modify the input signals from the otoliths, which allows the identification of the character and dynamics of vestibular function changes (VF) These modifications are accompanied by the development of space adaptation syndrome and space motion sickness. A possible reason for this could be the duration of the shuttle missions,
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