Continuous and intermittent artificial gravity as a countermeasure to the cognitive effects of 60 days of head-down tilt bed rest

Environmental and psychological stressors can adversely affect astronaut cognitive performance in space. This study used a 6 head-down tilt bed rest (HDBR) paradigm to simulate some of the physiologic changes induced by microgravity. Twenty four participants (mean ± SD age 33.3 ± 9.2 years, N = 16 men) spent 60 consecutive days in strict HDBR. They were studied in three groups of eight subjects each. One group served as Control whereas the other two groups received either a continuous (cAG) or intermittent (iAG) artificial gravity (AG) countermeasure of 30 minute centrifugation daily (1 g acceleration at the center of mass and 2 g at the feet). The centrifugation protocol included: acceleration at 5°/s2 for 32–33 seconds until target rotation speed was achieved followed by rotation at constant velocity for either 30 minutes (cAG) or 5 minutes, with a 3minute rest, repeated six times (iAG). Deceleration was at 5°/s2 . Participants performed all 10 tests of NASA’s Cognition battery and a brief alertness and mood survey repeatedly before, during, and after the bed rest period. A modest but statistically significant slowing across a range of cognitive domains was found in all three groups during HDBR compared to baseline, most consistently for sensorimotor speed, whereas accuracy was unaffected. These changes were observed early during HDBR and did not further deteriorate or improve with increasing time in HDBR, except for emotion recognition performance. With increasing time spent in HDBR, participants required longer time to decide which facial emotion was expressed. They were also more likely to select categories with negative valence over categories with neutral or positive valence. Except for workload ratings, which were assessed lower in the Control group, continuous or intermittent AG did not modify the effect of HDBR on cognitive performance or subjective responses. Participants expressed several negative survey responses during HDBR relative to baseline, and some of the responses further deteriorated during recovery, stressing the importance of adequate medical and psychological support during extended duration HDBR studies. In conclusion, 60 days of HDBR were associated with moderate cognitive slowing and changes in emotion recognition performance, but these effects were not mitigated by either continuous or intermittent exposure to AG for 30 minutes daily. Support: NASA through 80NSSC18K0765, German Aerospace Center (DLR