About this Research Topic
Human adaptation to microgravity has been studied over the past 50 years, since the advent of manned spaceflight, across multiple physiological systems. In particular, exposure to microgravity induces adaptive central reinterpretation of visual, vestibular and proprioceptive information. This microgravity adaptive state, however, is inappropriate for a gravitational environment so that astronauts must spend time readapting to gravitational transitions e.g. Earth’s gravity following their return. During this readaptation period to gravitational transitions they experience space motion sickness, disturbances in perception, spatial orientation, posture, gait, and eye-head coordination. Following space flight crewmembers also experience loss in muscle strength and tone, changes in spinal circuitry function including altered Hoffmann reflex (H-reflex), otolithspinal reflex and stretch reflex characteristics along with modifications in proprioceptive functioning. These post-flight changes contribute to impaired mobility and decreased ability to coordinate effective landing motor strategies used for impact absorption after a jump. In addition to affected gross motor tasks, decrements in manual dexterous tasks such as tracking, pointing and grasping reveal a significant increase in reaction time to achieve the same level of accuracy, precision control of muscle contraction, as well as changes in the amplitude and velocity of eye, head, and arm movements have been documented. Postflight crewmembers often rely more on vision for postural and gait stability and many report the need for greater cognitive supervision of motor actions that previous to space flight were fully automated. Most importantly, adaptations to microgravity induce considerable variability in responses across subjects. Hence, these sensorimotor disturbances may lead to disruption in the ability to ambulate and perform functional tasks during initial reintroduction to a gravitational environment following a prolonged transit in the microgravity environment that have significant implications for performance of operational tasks immediately following landing on a planetary surface.
Advances in neuroimaging, genetics, robotics, motor learning, and nutritional sciences over the past 20 years have provided a confluence of advances providing an opportunity to mitigate these maladaptations to the microgravity environment allowing humans to adapt to gravitational transitions more successfully. What has been challenging for the field is to tightly link underlying neural processes with what is known about different approaches to mitigate the measureable behavioral changes and strategic processes that occur during adaptations after gravitational transitions.
Researchers in different disciplines have employed varying approaches to mitigate maladaptations to microgravity but with relatively little crosstalk. The purpose of this Research Topic is to publish papers across different scientific domains, in an effort to facilitate an integrative view of countermeasure approaches to overcome sensorimotor maladaptations after space flight, to foster discussion across disciplines, and to stimulate collaboration. These different approaches to mitigate maladaptations to a change in environmental conditions is parallel to the rehabilitation strategies employed to treat older adults, or in a variety of patient populations such as those suffering from Parkinson’s disease or stroke. A cross disciplinary focus will help to elucidate the neural and cognitive processes underlying adaptations, and may serve to further accelerate translational paradigms that will yield successful countermeasure or rehabilitation strategies. We welcome scientists from a variety of disciplines to submit their work. The papers responding to this call should emphasize brain function and its responsiveness to the countermeasure approaches from a system neuroscience
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