Oculomotor function during space flight and susceptibility to space motion sickness

Area of Science:

• Neuroscience
• Space Physiology

Background:

• Space motion sickness (SMS) affects astronauts, impacting performance.
• Understanding the vestibulo-ocular reflex (VOR) and saccadic eye movements (SEM) is crucial for spaceflight adaptation.

Purpose of the Study:

• To investigate the effects of weightlessness on VOR and SEM.
• To correlate VOR and SEM changes with SMS susceptibility and occurrence.

Main Methods:

• Studied 18 subjects before and during Space Shuttle missions.
• Assessed horizontal VOR using active sinusoidal head oscillation (VVOR, VOR-ES, VOR-S).
• Recorded eye movements via electrooculography and head position via potentiometer.

Main Results:

• No significant in-flight changes in VOR gain, phase, or waveform.
• Increased saccadic latency and decreased saccadic velocity observed.
• Preflight VOR suppression differences noted between SMS-susceptible and non-susceptible individuals.

Conclusions:

• Weightlessness primarily affects SEM, not VOR, in most subjects.
• SMS susceptibility is linked to impaired VOR suppression and altered SEM during spaceflight.