The Role of Different Afferent Systems in the Modulation of the Otolith-Ocular Reflex After Long-Term Space Flights

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.

Sensory organization of postural control after long term space flight

“…This is not surprising given that vestibular neglect develops within the first days of SF ( Kornilova et al, 2017 ). As it was shown in studies of the vestibular-ocular reflex after SF ( Glukhikh et al, 2022 ) vestibular system recovery takes up to 9 days after landing, which can affect the recovery of the vestibular contribution in postural control.…”

“…It is known, that the perception of the horizontal and vertical distances of a visual target changes ( Clément G. et al, 2020 ). Weightlessness alters the input signals of the otoliths and their effect on the pattern and dynamics of changes in the vestibular function ( Kornilova et al, 2017 ; Glukhikh et al, 2022 ).…”

Geriatric Space Travel©

“…loss of vital nutrient uptake) Volume 7; Issue 01 Int J GeriatrGerontol, an open access journal ISSN: 2577-0748 due to the impact of a shared generic gastrointestinal microbiome, affecting eons of genetically determined and individually curated microbiomes [63][64][65][66][67]. And there is the consideration that genetic predisposition for some diseases, which might not 'activate' in 1g, may become more prevalent in altered gravity environments, There are ocular-vestibular and proprioception changes, each sense becoming more disordered the longer the journey in altered gravity [68][69][70][71][72]. Fluid dynamics in altered gravity environments create vision changes thought to be the result of a conformational change in shape of the eyeball and/all some occlusion of the optic nerve.…”