Abstract
Astronauts returning from spaceflight typically show transient declines in mobility and balance. Other sensorimotor behaviors and cognitive function have not been investigated as much. Here, we tested whether spaceflight affects performance on various sensorimotor and cognitive tasks during and after missions to the International Space Station (ISS). We obtained mobility (Functional Mobility Test), balance (Sensory Organization Test-5), bimanual coordination (bimanual Purdue Pegboard), cognitive-motor dual-tasking and various other cognitive measures (Digit Symbol Substitution Test, Cube Rotation, Card Rotation, Rod and Frame Test) before, during and after 15 astronauts completed 6 month missions aboard the ISS. We used linear mixed effect models to analyze performance changes due to entering the microgravity environment, behavioral adaptations aboard the ISS and subsequent recovery from microgravity. We observed declines in mobility and balance from pre- to post-flight, suggesting disruption and/or down weighting of vestibular inputs; these behaviors recovered to baseline levels within 30 days post-flight. We also identified bimanual coordination declines from pre- to post-flight and recovery to baseline levels within 30 days post-flight. There were no changes in dual-task performance during or following spaceflight. Cube rotation response time significantly improved from pre- to post-flight, suggestive of practice effects. There was also a trend for better in-flight cube rotation performance on the ISS when crewmembers had their feet in foot loops on the “floor” throughout the task. This suggests that tactile inputs to the foot sole aided orientation. Overall, these results suggest that sensory reweighting due to the microgravity environment of spaceflight affected sensorimotor performance, while cognitive performance was maintained. A shift from exocentric (gravity) spatial references on Earth toward an egocentric spatial reference may also occur aboard the ISS. Upon return to Earth, microgravity adaptions become maladaptive for certain postural tasks, resulting in transient sensorimotor performance declines that recover within 30 days.
Highlights
We identified significant pre-flight to post-flight balance declines, reflected as decreases in Equilibrium Quotient scores on both the SOT-5 (p = 0.010, Figure 3), and SOT-5M (p = 0.001, Figure 4)
We evaluated the effects of the microgravity environment on astronauts’ sensorimotor and cognitive performance with a range of behavioral measures collected before, during, and following missions to the ISS
We found marked decreases in balance, mobility and bimanual coordination following exposure to the microgravity environment
Summary
There are well-documented changes in human sensorimotor performance following spaceflight, including post-flight declines in locomotion, balance, and fine motor control (Thornton and Rummel, 1977; Paloski et al, 1992, 1994; Reschke et al, 1994a,b, 1998; Black et al, 1995; McDonald et al, 1996; Bloomberg et al, 1997; Layne et al, 1997, 1998; Newman et al, 1997; Bock et al, 2003; Campbell et al, 2005; Rafiq et al, 2006). Sensorimotor re-adaptation to the Earth’s gravity occurs in the weeks following return, with performance returning to pre-flight levels with about 6 days on a variety of functional tasks (Miller et al, 2018) to 15 days for the functional mobility test (FMT; Mulavara et al, 2010)
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