Abstract
Background: Spaceflight has been associated with changes in gait and balance; it is unclear whether it affects cognition. Head down tilt bed rest (HDBR) is a microgravity analog that mimics cephalad fluid shifts and body unloading. In consideration of astronaut’s health and mission success, we investigated the effects of HDBR on cognition and sensorimotor function. Furthermore, we investigated if exercise mitigates any cognitive and sensorimotor sequelae of spaceflight.Method: We conducted a 70-day six-degree HDBR study in 10 male subjects who were randomly assigned to a HDBR supine exercise or a HDBR control group. Cognitive measures (i.e., processing speed, manual dexterity, psychomotor speed, visual dependency, and 2D and 3D mental rotation) and sensorimotor performance (functional mobility (FMT) and balance performance) were collected at 12 and 8 days pre-HDBR, at 7, 50, and 70 days in HDBR, and at 8 and 12 days post-HDBR. Exercise comprised resistance training, and continuous and high-intensity interval aerobic exercise. We also repeatedly assessed an outside-of-bed rest control group to examine metric stability.Results: Small practice effects were observed in the control group for some tasks; these were taken into account when analyzing effects of HDBR. No significant effects of HDBR on cognition were observed, although visual dependency during HDBR remained stable in HDBR controls whereas it decreased in HDBR exercise subjects. Furthermore, HDBR was associated with loss of FMT and standing balance performance, which were almost fully recovered 12 days post-HDBR. Aerobic and resistance exercise partially mitigated the effects of HDBR on FMT and accelerated the recovery time course post-HDBR.Discussion: HDBR did not significantly affect cognitive performance but did adversely affect FMT and standing balance performance. Exercise had some protective effects on the deterioration and recovery of FMT.
Highlights
Spaceflight Effects on Sensorimotor Performance and Cognitive Function Spaceflight has been associated with deterioration of locomotor function (Mulavara et al, 2010) and postural stability (Cohen et al, 2012) in astronauts after their return to Earth
Significant interaction effects were observed for the accuracy measure of the rod and frame test, and all FMT outcome measures except for time needed to complete the second half of the FMT
Main effects of time were observed for all cognitive measures except for the rod and frame test, time needed to complete the second half of the FMT, and Sensory Organization Tests (SOTs)-5
Summary
Spaceflight Effects on Sensorimotor Performance and Cognitive Function Spaceflight has been associated with deterioration of locomotor function (Mulavara et al, 2010) and postural stability (Cohen et al, 2012) in astronauts after their return to Earth. These adverse effects of spaceflight have been ascribed to several factors including muscle unloading and reinterpretation of vestibular inputs (Young et al, 1984). We are currently conducting a study investigating the extent, longevity, and neural bases of spaceflight effects on neurocognitive and sensorimotor performance in a group of astronauts and in a terrestrial study using head downtilt bed rest (HDBR) as a microgravity analog. We investigated if exercise mitigates any cognitive and sensorimotor sequelae of spaceflight
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