Astronaut, Central Nervous System, Circadian Rhythm, Countermeasure, Gravitational Unloading, Ionizing Radiation, Microgravity, Neurocognitive, Neurosensory, Perception, Psychomotor Performance, Sleep, Stress, Spaceflight, Space Exploration, Space Motion
Several commercial enterprises and government space agencies are in the process of planning crewed long-duration, exploration-class space missions to destinations such as the Moon or Mars. Despite the essential protection afforded by spacecraft and life support systems, the space environment exposes the nervous system to significant physiological stressors, including microgravity, ionizing radiation, and prolonged isolation and confinement. While the nervous system exhibits a remarkable capacity to adapt to novel physical conditions, including the space environment, much uncertainty remains among space medical researchers regarding the limits of the nervous systems ability to endure the challenges associated with extended space missions. Perturbations to neurosensory, perceptual, and neurocognitive systems will likely remain a challenge when transitioning from the spacecraft to extraterrestrial bodies, as is the case when astronauts initially return to Earth. Thus far, the available evidence regarding the effects of long-duration spaceflight on cognitive and psychomotor performance is conflicting, and no definitive conclusion can be drawn as of yet. Small sample sizesinherent to this area of investigationhave placed constraints on research progress. Animal research simulating exposure to levels of ionizing radiation that will be encountered outside of the Earths magnetosphere suggests that in the absence of suitable countermeasures, neural function and structure will be significantly compromised. Going forward, research efforts should focus on the nervous systems capability to adapt to hypogravity conditions (resembling Mars and the Moon), and also how nervous system function will be affected by ionizing radiation. Further, engineers and scientists alike should continue to work on developing more effective countermeasures to mitigate the deleterious health effects associated with human space exploration.