Impact of a Model Used to Simulate Chronic Socio-Environmental Stressors Encountered during Spaceflight on Murine Intestinal Microbiota.

During deep-space travels, crewmembers face various physical and psychosocial stressors that could alter gut microbiota composition. Since it is well known that intestinal dysbiosis is involved in the onset or exacerbation of several disorders, the aim of this study was to evaluate changes in intestinal microbiota in a murine model used to mimic chronic psychosocial stressors encountered during a long-term space mission. We demonstrate that 3 weeks of exposure to this model (called CUMS for Chronic Unpredictable Mild Stress) induce significant change in intracaecal ß-diversity characterized by an important increase of the Firmicutes/Bacteroidetes ratio. These alterations are associated with a decrease of Porphyromonadaceae, particularly of the genus Barnesiella, a major member of gut microbiota in mice and humans where it is described as having protective properties. These results raise the question of the impact of stress-induced decrease of beneficial taxa, support recent data deduced from in-flight experimentations and other ground-based models, and emphasize the critical need for further studies exploring the impact of spaceflight on intestinal microbiota in order to propose strategies to countermeasure spaceflight-associated dysbiosis and its consequences on health.

A review of astronaut mental health in manned missions: Potential interventions for cognitive and mental health challenges.

Space is an isolated, confined environment for humans. These conditions can have numerous effects on astronaut mental health and safety. Psychological and social issues affect space crew due to the isolation, confinement, and prolonged separation from family and friends. This area of research is particularly crucial given the space sector's plans for Martian colonies and space tourism, as well as to aid astronauts when under high stress. Therefore, this paper reviews the effects of isolation/confinement on psychological and cognitive health; impact of radiation and microgravity on cognitive health; and implications of disturbances to the circadian rhythm and sleep in space. Possible solutions to relevant mentioned cognitive and mental health challenges are also discussed.

Immunological Aspects of Isolation and Confinement.

Beyond all doubts, the exploration of outer space is a strategically important and priority sector of the national economy, scientific and technological development of every and particular country, and of all human civilization in general. A number of stress factors, including a prolonged confinement in a limited hermetically sealed space, influence the human body in space on board the spaceship and during the orbital flight. All these factors predominantly negatively affect various functional systems of the organism, in particular, the astronaut's immunity. These ground-based experiments allow to elucidate the effect of confinement in a limited space on both the activation of the immunity and the changes of the immune status in dynamics. Also, due to simulation of one or another emergency situation, such an approach allows the estimation of the influence of an additional psychological stress on the immunity, particularly, in the context of the reserve capacity of the immune system. A sealed chamber seems a convenient site for working out the additional techniques for crew members selection, as well as the countermeasures for negative changes in the astronauts' immune status. In this review we attempted to collect information describing changes in human immunity during isolation experiments with different conditions including short- and long-term experiments in hermetically closed chambers with artificial environment and during Antarctic winter-over.

Towards the Affective Cognition Approach to Human Performance in Space.

INTRODUCTION: In recent decades, there has been investigation into the effects of microgravity and microgravity-like environments on cognition and emotion separately. Here we highlight the need of focusing on emotion-cognition interactions as a framework for explaining cognitive performance in space. In particular, by referring to the affective cognition hypothesis, the significant interplay between emotional variables and cognitive processing in space is briefly analyzed. Altogether, this approach shows an interesting pattern of data pointing to a dynamic relation that may be sensitive to microgravity. The importance of examining interactions between emotion and cognition for space performance remains fundamental (e.g., stress-related disorders) and deserves further attention. This approach is ultimately interesting considering the potential effects that microgravity may play on human performance during long-term space missions and on return to Earth.Mammarella N. Towards the affective cognition approach to human performance in space. Aerosp Med Hum Perform. 2020; 91(6):532-534.

Spatial Updating Depends on Gravity.

As we move through an environment the positions of surrounding objects relative to our body constantly change. Maintaining orientation requires spatial updating, the continuous monitoring of self-motion cues to update external locations. This ability critically depends on the integration of visual, proprioceptive, kinesthetic, and vestibular information. During weightlessness gravity no longer acts as an essential reference, creating a discrepancy between vestibular, visual and sensorimotor signals. Here, we explore the effects of repeated bouts of microgravity and hypergravity on spatial updating performance during parabolic flight. Ten healthy participants (four women, six men) took part in a parabolic flight campaign that comprised a total of 31 parabolas. Each parabola created about 20-25 s of 0 g, preceded and followed by about 20 s of hypergravity (1.8 g). Participants performed a visual-spatial updating task in seated position during 15 parabolas. The task included two updating conditions simulating virtual forward movements of different lengths (short and long), and a static condition with no movement that served as a control condition. Two trials were performed during each phase of the parabola, i.e., at 1 g before the start of the parabola, at 1.8 g during the acceleration phase of the parabola, and during 0 g. Our data demonstrate that 0 g and 1.8 g impaired pointing performance for long updating trials as indicated by increased variability of pointing errors compared to 1 g. In contrast, we found no support for any changes for short updating and static conditions, suggesting that a certain degree of task complexity is required to affect pointing errors. These findings are important for operational requirements during spaceflight because spatial updating is pivotal for navigation when vision is poor or unreliable and objects go out of sight, for example during extravehicular activities in space or the exploration of unfamiliar environments. Future studies should compare the effects on spatial updating during seated and free-floating conditions, and determine at which g-threshold decrements in spatial updating performance emerge.

Changes of brain DTI in healthy human subjects after 520 days isolation and confinement on a simulated mission to Mars.

INTRODUCTION: Long-term confinement is known to be a stressful experience with multiple psycho-physiological effects. In the MARS500 project, a real-time simulation of a space-flight to Mars conducted in a hermetically isolated habitat, effects of long-term confinement could be investigated in a unique manner. The aim of this study was to evaluate effects of long-term-confinement on brain cytoarchitecture. MATERIAL & METHODS: The participants of the MARS500 project underwent 3T-MR imaging including a dedicated DTI-sequence before the isolation, right after ending of confinement and 6 months after the experiment. Voxelwise statistical analysis of the DTI data was carried out using tract-based-spatial statistics, comparing an age-matched control group. RESULTS: At all three sessions, significant lower fractional anisotropy (FA) than in controls was found in the anterior parts of the callosal body of the participants. Furthermore, after ending of confinement a wide-spread FA reduction could be seen in the right hemisphere culminating in the temporo-parietal-junction-zone. All these areas with decreased FA predominantly showed an elevated radial diffusivity and mean diffusivity while axial diffusivity was less correlated. DISCUSSION: Long-term confinement does have measurable effects on the microstructure of the brain white matter. We assume effects of sensory deprivation to account for the regional FA reductions seen in the right TPJ. The differences in the Corpus callosum were interpreted as due to preliminary conditions, e.g. personality traits or training effects. FA and radial diffusivity were the predominant DTI parameters with significant changes, suggesting underlying processes of myelin plasticity.