Visuomotor Adaptation Brain Changes During a Spaceflight Analog With Elevated Carbon Dioxide (CO₂): A Pilot Study

Area of Science:

• Neuroscience
• Space Physiology
• Human Adaptation

Background:

• Astronauts face environmental challenges like microgravity, elevated CO2, and isolation on the ISS.
• Head down tilt bed rest (HDBR) simulates spaceflight factors such as body unloading and fluid shifts.
• Previous work explored HDBR with elevated CO2 (HDBR+CO2) on visuomotor adaptation; this study examines its neural effects.

Purpose of the Study:

• To investigate the effects of HDBR+CO2 on brain activity during visuomotor adaptation.
• To compare brain activity changes between HDBR+CO2 and HDBR alone to isolate CO2 effects.
• To explore potential correlations between brain activity changes and visuomotor performance.

Main Methods:

• Eleven participants underwent functional MRI (fMRI) during a visuomotor adaptation task before, during, and after 30-day HDBR+CO2.
• Brain activity was analyzed across different phases: baseline, early adaptation, late adaptation, and de-adaptation.
• A comparison was made with a separate cohort (n=8) undergoing 60-day HDBR without elevated CO2.

Main Results:

• During early adaptation under HDBR+CO2, participants showed decreased activation in temporal and subcortical regions, followed by recovery.
• Late adaptation revealed increased activation in the right fusiform gyrus and right caudate nucleus, normalizing post-bed rest.
• No significant differences in brain activity changes were found between HDBR+CO2 and HDBR-only groups, indicating bed rest as the primary driver. No correlations between brain changes and performance were observed.

Conclusions:

• Visuomotor adaptation under HDBR+CO2 involves dynamic changes in brain activity, primarily driven by the effects of unloading rather than elevated CO2.
• These findings are crucial for understanding astronaut adaptation to altered sensory inputs during long-duration space missions.
• The study provides novel insights into the neural correlates of visuomotor adaptation in simulated spaceflight conditions.