Rocking or rolling--perception of ambiguous motion after returning from space

Area of Science:

• Neuroscience
• Space Physiology
• Human Factors

Background:

• Spaceflight alters the central nervous system's integration of vestibular and other sensory information.
• These adaptive changes can cause disorientation and coordination issues upon return to Earth.
• Understanding motion perception shifts is crucial for astronaut safety and mission success.

Purpose of the Study:

• To compare astronaut perception of tilt and translation motion before and after spaceflight.
• To investigate the frequency dynamics of motion perception, particularly at low frequencies (around 0.3 Hz).
• To assess the impact of microgravity adaptation on spatial orientation.

Main Methods:

• Eleven astronauts were tested using a motion-based tilt-translation device and a variable radius centrifuge.
• Testing occurred before and immediately after a two-week Space Shuttle mission.
• Verbal reports of perceived motion were collected and analyzed.

Main Results:

• Roll tilt perception was overestimated post-flight, recovering within 1-2 days.
• Perception of linear translation was also overestimated immediately after flight.
• Recovery times varied: 2 days for lateral translation and 8 days for fore-aft translation.

Conclusions:

• Spaceflight induces a significant shift in the frequency dynamics of tilt-translation motion perception.
• These perceptual changes highlight the brain's adaptation to weightlessness.
• Findings have implications for manual control tasks, such as spacecraft landing, in future long-duration missions.