Impaired Attentional Processing During Parabolic Flight

Effects of repeated gravity changes during parabolic flight: Evidence of the need to assist space tourists to outer space

In the era of space tourism, walking in the steps of Neil Armstrong has never been more real. Future space tourists will have to face the harshness of the environment, especially the travel, and adapt quickly for their own safety. This issue raises both the question of preparation and the impact of such a journey on novice populations who have not been selected for their physical and cognitive abilities. The objectives of the study are (1) to investigate the impact of space travel on psychophysiological and sensory responses during a parabolic flight experience; (2) to assess recovery from this experience one week later; and (3) to evaluate the relevance of high parasympathetic functioning at baseline as a biomarker of adaptation. Seventeen healthy participants were enrolled in the 79th ESA Parabolic Flight Campaign on board the Airbus A310. Psychological, physiological, and sensory responses were measured at different times from the day before the 3h-flight (baseline) to one week after the flight (recovery). Labels were allocated to two groups according to their parasympathetic functioning at baseline: high parasympathetic (HP) profile and low parasympathetic (LP) profile. At the psychological level, those with an HP profile have a higher coping acceptation and a higher level of interoceptive awareness than the LP profile, except for sleep quality. At the physiological and exteroceptive level, they have a higher heart rate variability, preserved identification of odors and a predisposition to a more adaptive postural response postflight. Nevertheless, postural stability is affected in both profiles, particularly during visual deprivation, while their heart rate variability is increased in both linear and non-linear components. Nevertheless, our results reveal that the recovery constitutes a critical period. Flyers have a decrease of interoceptive awareness and emotions, especially the HP profile. Although the LP profile reported a better subjective sleep quality, both profiles decreased their sleep quality. These results raise the question of the risks that may be induced by space tourism. They highlight two major outcomes: (1) travel of future space tourists does not seem to be at risk as long as the individuals are qualified and fit for the flight and adaptation may be improved by targeting parasympathetic functioning; (2) level of experience has no impact on the psychophysiological and sensory responses. The results highlight the need to monitor the crews over several days and/or to include in the preparation a module allowing them to be prepared for the postflight period and the return to life on Earth. Beyond this, these results contribute to enriching our knowledge of the human challenge of confronting space travel constraints.

Is sleep affected after microgravity and hypergravity exposure? A pilot study

Sleep is known to be affected in space travel and in residents of the international space station. But little is known about the direct effects of gravity changes on sleep, if other factors, such as sleep conditions, are kept constant. Here, as a first exploration, we investigated sleep before and after exposure to short bouts of microgravity and hypergravity during parabolic flights. Sleep was measured through actigraphy and self-report questionnaires in 20 healthy men and women before and after parabolic flight. Higher sleep fragmentation and more awakenings were found in the night after the flight as compared with the night before, which was discrepant from participants' reports showing better and longer sleep after the parabolic flight. Variable levels of experience with parabolic flights did not affect the results, nor did levels of scopolamine, a medication typically taken against motion sickness. Pre-existing sleep problems were related to sleep fragmentation and wake after sleep onset by a quadratic function such that participants with more sleep problems showed lower levels of sleep fragmentation and nighttime awakenings than those with few sleep problems. These novel findings, though preliminary, have important implications for future research, directed at prevention and treatment of sleep problems and their daytime consequences in situations of altered gravity, and possibly in the context of other daytime vestibular challenges as well.

Cognitive performance in ISS astronauts on 6-month low earth orbit missions

Introduction

Current and future astronauts will endure prolonged exposure to spaceflight hazards and environmental stressors that could compromise cognitive functioning, yet cognitive performance in current missions to the International Space Station remains critically under-characterized. We systematically assessed cognitive performance across 10 cognitive domains in astronauts on 6-month missions to the ISS.

Methods

Twenty-five professional astronauts were administered the Cognition Battery as part of National Aeronautics and Space Administration (NASA) Human Research Program Standard Measures Cross-Cutting Project. Cognitive performance data were collected at five mission phases: pre-flight, early flight, late flight, early post-flight, and late post-flight. We calculated speed and accuracy scores, corrected for practice effects, and derived z-scores to represent deviations in cognitive performance across mission phases from the sample's mean baseline (i.e., pre-flight) performance. Linear mixed models with random subject intercepts and pairwise comparisons examined the relationships between mission phase and cognitive performance.

Results

Cognitive performance was generally stable over time with some differences observed across mission phases for specific subtests. There was slowed performance observed in early flight on tasks of processing speed, visual working memory, and sustained attention. We observed a decrease in risk-taking propensity during late flight and post-flight mission phases. Beyond examining group differences, we inspected scores that represented a significant shift from the sample's mean baseline score, revealing that 11.8% of all flight and post-flight scores were at or below 1.5 standard deviations below the sample's baseline mean. Finally, exploratory analyses yielded no clear pattern of associations between cognitive performance and either sleep or ratings of alertness.

Conclusion

There was no evidence for a systematic decline in cognitive performance for astronauts on a 6-month missions to the ISS. Some differences were observed for specific subtests at specific mission phases, suggesting that processing speed, visual working memory, sustained attention, and risk-taking propensity may be the cognitive domains most susceptible to change in Low Earth Orbit for high performing, professional astronauts. We provide descriptive statistics of pre-flight cognitive performance from 25 astronauts, the largest published preliminary normative database of its kind to date, to help identify significant performance decrements in future samples.

The effect of inherent and incidental constraints on bimanual force control in simulated Martian gravity

The ability to coordinate actions between the limbs is important for many operationally relevant tasks associated with space exploration. A future milestone in space exploration is sending humans to Mars. Therefore, an experiment was designed to examine the influence of inherent and incidental constraints on the stability characteristics associated with the bimanual control of force in simulated Martian gravity. A head-up tilt (HUT)/head-down tilt (HDT) paradigm was used to simulate gravity on Mars (22.3° HUT). Right limb dominant participants (N = 11) were required to rhythmically coordinate patterns of isometric forces in 1:1 in-phase and 1:2 multifrequency patterns by exerting force with their right and left limbs. Lissajous displays were provided to guide task performance. Participants performed 14 twenty-second practice trials at 90° HUT (Earth). Following a 30-min rest period, participants performed 2 test trials for each coordination pattern in both Earth and Mars conditions. Performance during the test trials were compared. Results indicated very effective temporal performance of the goal coordination tasks in both gravity conditions. However, results indicated differences associated with the production of force between Earth and Mars. In general, participants produced less force in simulated Martian gravity than in the Earth condition. In addition, force production was more harmonic in Martian gravity than Earth gravity for both limbs, indicating that less force distortions (adjustments, hesitations, and/or perturbations) occurred in the Mars condition than in the Earth condition. The force coherence analysis indicated significantly higher coherence in the 1:1 task than in the 1:2 task for all force frequency bands, with the highest level of coherence in the 1-4 Hz frequency band for both gravity conditions. High coherence in the 1-4 Hz frequency band is associated with a common neural drive that activates the two arms simultaneously and is consistent with the requirements of the two tasks. The results also support the notion that neural crosstalk stabilizes the performance of the 1:1 in-phase task. In addition, significantly higher coherence in the 8-12 Hz frequency bands were observed for the Earth condition than the Mars condition. Force coherence in the 8-12 Hz bands is associated with the processing of sensorimotor information, suggesting that participants were better at integrating visual, proprioceptive, and/or tactile feedback in Earth than for the Mars condition. Overall, the results indicate less neural interference in Martian gravity; however, participants appear to be more effective at using the Lissajous displays to guide performance under Earth's gravity.

Astronauts eye-head coordination dysfunction over the course of twenty space shuttle flights

BACKGROUND

Coordination of motor activity is adapted to Earth's gravity (1 g). However, during space flight the gravity level changes from Earth gravity to hypergravity during launch, and to microgravity (0 g) in orbit. This transition between gravity levels may alter the coordination between eye and head movements in gaze performance.

OBJECTIVE

We explored how weightlessness during space flight altered the astronauts' eye-head coordination (EHC) with respect to flight day and target eccentricity.

METHODS

Thirty-four astronauts of 20 Space Shuttle missions had to acquire visual targets with angular offsets of 20°, 30°, and 49°.

RESULTS

Measurements of eye, head, and gaze positions collected before and during flight days 1 to 15 indicated changes during target acquisition that varied as a function of flight days and target eccentricity.

CONCLUSIONS

The in-flight alterations in EHC were presumably the result of a combination of several factors, including a transfer from allocentric to egocentric reference for spatial orientation in absence of a gravitational reference, the generation of slower head movements to attenuate motion sickness, and a decrease in smooth pursuit and vestibulo-ocular reflex performance. These results confirm that humans have several strategies for gaze behavior, between which they switch depending on the environmental conditions.

The Influence of Altered-Gravity on Bimanual Coordination: Retention and Transfer

Many of the activities associated with spaceflight require individuals to coordinate actions between the limbs (e.g., controlling a rover, landing a spacecraft). However, research investigating the influence of gravity on bimanual coordination has been limited. The current experiment was designed to determine an individual's ability to adapt to altered-gravity when performing a complex bimanual force coordination task, and to identify constraints that influence coordination dynamics in altered-gravity. A tilt table was used to simulate gravity on Earth [90° head-up tilt (HUT)] and microgravity [6° head-down tilt (HDT)]. Right limb dominant participants (N = 12) were required to produce 1:1 in-phase and 1:2 multi-frequency force patterns. Lissajous information was provided to guide performance. Participants performed 14, 20 s trials at 90° HUT (Earth). Following a 30-min rest period, participants performed, for each coordination pattern, two retention trials (Earth) followed by two transfer trials in simulated microgravity (6° HDT). Results indicated that participants were able to transfer their training performance during the Earth condition to the microgravity condition with no additional training. No differences between gravity conditions for measures associated with timing (interpeak interval ratio, phase angle slope ratio) were observed. However, despite the effective timing of the force pulses, there were differences in measures associated with force production (peak force, STD of peak force mean force). The results of this study suggest that Lissajous displays may help counteract manual control decrements observed during microgravity. Future work should continue to explore constraints that can facilitate or interfere with bimanual control performance in altered-gravity environments.