Yaw and pitch visual-vestibular interaction in weightlessness

Area of Science:

• Neuroscience
• Space Physiology
• Human Factors Engineering

Background:

• Spaceflight alters sensory input, challenging the human vestibular system.
• Understanding neural adaptations to weightlessness is crucial for astronaut health and performance.

Purpose of the Study:

• To investigate how sustained weightlessness affects visual-vestibular interactions in astronauts.
• To determine the neural strategies employed to cope with altered sensory information during spaceflight.

Main Methods:

• Astronauts underwent yaw and pitch visual-vestibular testing at different frequencies (0.2 and 0.8 Hz) with optokinetic stimulation (36 degrees/s).
• Control tests included oscillations in darkness and stationary optokinetic stimulation at various velocities.
• Measurements focused on vestibulo-ocular reflex (VOR) and visual-vestibular response (VVR).

Main Results:

• No significant changes were found in VOR gain, phase, bias, yaw VVR, or optokinetic (OKN) slow phase velocity (SPV).
• Significant changes occurred in pitch VVR: optokinetic contribution decreased inflight and increased postflight at 0.2 Hz.
• Vertical VOR suppression varied, being more efficient inflight and less efficient postflight at 0.8 Hz.

Conclusions:

• Astronauts reweight sensory inputs, prioritizing vision more during certain phases of spaceflight and immediately after.
• This suggests a flexible neural strategy for spatial orientation in the unique environment of weightlessness.
• Findings contribute to understanding human adaptation to microgravity and informing future space missions.