Figure - available from: Frontiers in Physiology
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Time course of salivary cortisol levels. Baseline saliva was collected between 9 am and noon on the day of arrival. Two different patterns could be observed, with the highest measured cortisol either after P30 (High-P30) or before P0 (High-P0). Orange line represents participants of High-P30, violet line represents participants of High-P0, dark blue line shows data of all participants. Data are presented as marginal means ± SE. *P < 0.05, **P < 0.01, ***P < 0.001 compared to baseline, ‡P < 0.05, ‡‡P < 0.001 compared to High-P0.
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Previous studies suggest that altered gravity levels during parabolic flight maneuvers affect spatial updating. Little is known about the impact of the experimental setting and psychological stressors associated with parabolic flight experiments on attentional processes. To address this gap, we investigated the level of alertness, selective and sus...
Citations
... During a typical parabolic flight, participants enter an equipped plane that is subjected to a parabolic manoeuvre, creating a state of weightlessness (microgravity) inside the aircraft for about 22 s, intertwined with states of hypergravity ( Figure 1). As such, results have shown how attentional processing and spatial updating performance deteriorates during gravity changes (Friedl-Werner et al., 2021;Stahn et al., 2020), how instrument control deteriorates during microgravity (Steinberg et al., 2015), how the vestibular system can affect cardiovascular control (Etard et al., 2004), and how intrinsic functional brain connectivity changes after exposure to different gravity conditions . ...
... increased excitation, nervousness or even stress in participants, especially in first-time flyers(Friedl-Werner et al., 2021). However, adding previous parabolic flight experience as an additional factor into the analysis did not have an effect on our main results and, thus, the novelty effect of the event cannot fully explain the findings. ...
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 para-bolic 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 partici-pants' 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 qua-dratic 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.
... As such, Lissajous displays may prove particularly beneficial in altered gravity . However, given the increased cognitive, perceptual, and attentional demands associated with altered gravity, and lack of efficiency in integrating these sensory inputs (Friedl-Werner et al., 2021;Saradjian et al., 2014) Lissajous displays may not be as effective in Martian gravity as in 1 g. ...
... Furthermore, a decrease in the 8-12 Hz frequency band is thought to reflect a lapse in attention and the need to refocus on task performance (Carlsen et al., 2023). Given the increased cognitive, perceptual, and attentional demands associated with altered gravity environments (Friedl-Werner et al., 2021;Saradjian et al., 2014), it is logical that changes in the oscillatory bands associated with attentional focus were observed in the Mars condition. Results are consistent with several studies demonstrating impairments in visuomotor performance (e.g., Heuer & Hegele, 2010;Manzey et al., 2000) and white matter changes in regions of the brain related to visual processing, visual attention, and visuomotor control with exposure to altered gravity environments (see Roy-O'Reilly, Mulavara, & Williams, 2021 for a review). ...
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.
... Above all, it continues to shed light on the mechanisms of human physiology, even during short duration microgravity conditions. Parabolic flights offer a test platform to specifically study physiology or neurology, as cardiovascular adaptation, motor adaptation or environment perception perturbation [11][12][13][14][15][16][17][18][19]. Longer stays in a microgravity environment have effects on the human body that are very similar to those of ageing (loss of bone and muscle mass, degradation of arteries, etc.). ...
... The integrated feedback information provided by the Lissajous plots likely reduced the attentional, cognitive, and/or perceptual constraints associated with task performance . However, given the increased attentional, cognitive, and perceptual demands associated with spaceflight and alteredgravity environments (e.g., Saradjian et al., 2014;Friedl-Werner et al., 2021), it is not clear whether integrated feedback information can be used to perform and learn complex bimanual tasks in microgravity, similar to that observed in normal gravity (1 g). In addition, astronauts train for operational tasks in a 1 g environment; therefore, understanding constraints that influence performance and learning in 1 g environment, and how these constraints transfer to novel gravity environments may have important implications for future training protocols and countermeasures. ...
... Extending this line of research to altered-gravity environments provides further evidence for the robust utility of Lissajous displays in facilitating complex bimanual coordination tasks . Considering the increased attentional, cognitive, and perceptual demands associated with alteredgravity environments (Friedl-Werner et al., 2021), the ability to quickly and effectively produce a complex pattern of force in altered-gravity is particularly impressive. ...
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.
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.
