Gaze control in microgravity. 1. Saccades, pursuit, eye-head coordination

Area of Science:

• Neuroscience
• Space Physiology
• Oculomotor Systems

Background:

• Long-duration spaceflight impacts human physiology, including sensorimotor systems.
• Understanding oculomotor control adaptations is crucial for astronaut health and mission success.

Purpose of the Study:

• To investigate changes in gaze control subsystems during spaceflight.
• To analyze eye and head movement coordination during target orientation and tracking in microgravity.

Main Methods:

• Experiment conducted on two cosmonauts during the Aragatz mission on the Mir space station.
• Analysis of oculomotor subsystems: gaze orientation (head-fixed and head-free) and pursuit.
• Comparison of in-flight data with pre-flight (earth-based) measurements.

Main Results:

• Head-fixed gaze orientation showed modified saccade 'main sequence' relationships: increased peak velocity, shorter duration, decreased latency, and improved accuracy in flight.
• Head-free gaze orientation involved coordinated eye-head movements, with a greater eye contribution to stabilization observed in flight.
• Horizontal pursuit remained smooth in flight. Vertical pursuit exhibited an asymmetry, with upward tracking relying on saccades and downward tracking using smooth pursuit with catch-up saccades, an asymmetry maintained in microgravity.

Conclusions:

• Spaceflight significantly alters saccadic eye movements, enhancing performance metrics.
• Microgravity induces changes in eye-head coordination strategies for gaze stabilization.
• Vertical gaze tracking demonstrates an inherent asymmetry influenced by the oculomotor system's interaction with microgravity.