Effects of head-down tilt bed rest plus elevated CO₂ on cognitive performance.

Area of Science:

• Spaceflight physiology
• Cognitive neuroscience
• Environmental stressors in space

Background:

• Microgravity and elevated carbon dioxide (CO2) are key spaceflight stressors impacting astronaut cognition.
• Understanding these environmental effects is crucial for mission success and crew well-being.

Purpose of the Study:

• To investigate the impact of head-down tilt bed rest (HDBR) with and without elevated CO2 on cognitive performance.
• To determine if elevated CO2 modifies the cognitive effects of HDBR.

Main Methods:

• 19 participants underwent 30 or 60 days of 6° HDBR, with one group exposed to elevated ambient CO2 (3.73 mmHg).
• Cognitive performance was assessed using NASA's Cognition battery and alertness/mood surveys before, during, and after HDBR.
• Data were analyzed adjusting for practice and stimulus set effects.

Main Results:

• Both HDBR groups showed statistically significant, modest slowing in cognitive performance, particularly sensorimotor speed, within the first 30 days.
• Cognitive changes were consistent across groups, indicating elevated CO2 did not alter HDBR effects.
• Cognitive performance returned to pre-HDBR levels after 15 days of recovery, but 60-day HDBR participants reported increased fatigue and stress.

Conclusions:

• Prolonged HDBR induces moderate cognitive decrements, primarily affecting speed.
• Elevated ambient CO2 does not appear to exacerbate or mitigate the cognitive effects of HDBR.
• While cognitive function recovers, longer durations of HDBR may lead to subjective increases in fatigue and stress.