The Effects of 30 Minutes of Artificial Gravity on Cognitive and Sensorimotor Performance in a Spaceflight Analog Environment

Abstract

The altered vestibular signaling and somatosensory unloading of microgravity result in sensory reweighting and adaptation to conflicting sensory inputs. Aftereffects of these adaptive changes are evident postflight as impairments in behaviors such as balance and gait. Microgravity also induces fluid shifts toward the head and an upward shift of the brain within the skull; these changes are well-replicated in strict head-down tilt bed rest (HDBR), a spaceflight analog environment. Artificial gravity (AG) is a potential countermeasure to mitigate these effects of microgravity. A previous study demonstrated that intermittent (six, 5-mins bouts per day) daily AG sessions were more efficacious at counteracting orthostatic intolerance in a 5 day HDBR study than continuous daily AG. Here we examined whether intermittent daily AG was also more effective than continuous dosing for mitigating brain and behavioral changes in response to 60 days of HDBR. Participants (n = 24) were split evenly between three groups. The first received 30 mins of continuous AG daily (cAG). The second received 30 mins of intermittent AG daily (6 bouts of 5 mins; iAG). The third received no AG (Ctrl). We collected a broad range of sensorimotor, cognitive, and brain structural and functional assessments before, during, and after the 60 days of HDBR. We observed no significant differences between the three groups in terms of HDBR-associated changes in cognition, balance, and functional mobility. Interestingly, the intermittent AG group reported less severe motion sickness symptoms than the continuous group during centrifugation; iAG motion sickness levels were not elevated above those of controls who did not undergo AG. They also had a shorter duration of post-AG illusory motion than cAG. Moreover, the two AG groups performed the paced auditory serial addition test weekly while undergoing AG; their performance was more accurate than that of controls, who performed the test while in HDBR. Although AG did not counteract HDBR-induced gait and balance declines, iAG did not cause motion sickness and was associated with better self-motion perception during AG ramp-down. Additionally, both AG groups had superior cognitive performance while undergoing AG relative to controls; this may reflect attention or motivation differences between the groups.

Daily Artificial Gravity is Associated with Greater Neural Efficiency during Sensorimotor Adaptation

“…De Martino et al (2021) analyzed the effects of AG on upright balance, finding that intermittent AG partially mitigated balance impairment from pre to post-HDBR compared to CTRLs, but continuous AG did not differ from CTRLs. This finding is somewhat in line with our own previous findings that AG may be beneficial for balance (Tays et al, 2022). We have also recently reported effects of AG on cognitive function, showing that during centrifugation there was an increased level of cognitive ability compared to controls, as measured by the Paced Auditory Serial Addition Task (PASAT; Tays et al, 2022).…”

“…This finding is somewhat in line with our own previous findings that AG may be beneficial for balance (Tays et al, 2022). We have also recently reported effects of AG on cognitive function, showing that during centrifugation there was an increased level of cognitive ability compared to controls, as measured by the Paced Auditory Serial Addition Task (PASAT; Tays et al, 2022). Basner et al, (2022) found that HDBR overall had a negative effect on cognitive performance, and that receiving AG did not mitigate these declines.…”

“…Participants lay with their head at 6° below their feet for up to several months at a time to simulate the headward fluid shifts and axial unloading of microgravity. HDBR has been shown to model some of the physiological and functional effects of spaceflight (Hargens and Vico, 2016; Reschke et al, 2009; Mulder et al, 2014; Koppelmans et al, 2015, 2017; Miller et al, 2018; Mulavara et al, 2018; Tays et al, 2022). Sensorimotor adaptation occurs in response to sensory prediction errors, i.e.…”

“…Delivering AG intermittently (6 bouts of 5 minutes) instead of continuously (1 bout of 30 minutes) reduces orthostatic intolerance more following 5 days of HDBR (Linnarsson et al, 2015). The present investigation is part of the larger Artificial Gravity Bed Rest – European Space Agency (“AGBRESA”) study; where we had previously found that those individuals who received AG had marginally better balance and mobility performance than controls who received no AG, suggesting that AG could be an effective sensorimotor countermeasure, but more than 30 minutes per day may be necessary (Tays et al, 2022).…”

“…HDBR has been shown to model some of the physiological and functional effects of spaceflight (Hargens and Vico, 2016;Reschke et al, 2009;Mulder et al, 2014;Koppelmans et al, 2015Koppelmans et al, , 2017Miller et al, 2018;Mulavara et al, 2018;Tays et al, 2022). Sensorimotor adaptation occurs in response to sensory prediction errors, i.e.…”