Task Progress:
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In Year 2 of this project, we have made substantial progress in our human subject evaluations at both experimental sites, as well as implementation steps towards future experiments. Programmatically, we have had intermittent virtual team meetings to discuss integrating project objectives, protocol choices, and planned analyses. The bulk of the effort has been on implementing, refining, and performing our human subject testing protocols to evaluate countermeasures effectiveness for mitigating motion sickness. We have also begun initial data visualization and analysis for these complex datasets. Further, we have made substantial progress in integrating hardware and software for later experimental efforts in Year 3. Finally, we have successfully onboarded new trainees, who are becoming/have become more familiar with this research domain.
At the University of Colorado-Boulder, we have performed safety testing on two separate human-rated motion devices, enabling testing on real human subjects. We have safety tested the “wave-like” motion profiles on the Tilt-Translation Sled housed in our laboratory. These profiles are representative of buoy data near potential water landing sites in terms of frequency content, amplitudes, and coherence of tilt motion versus lateral translation. On our other device, the Human Eccentric Rotator Device (HERD), we have finished designing and now assembling a new centrifuge arm that positions the subject far off-axis in order to produce substantial and sustained centrifugal acceleration. We then performed a series of safety tests on this new hardware, spinning for our 1+ hour exposure of hyper-gravity, enacting the “sickness induced by centrifugation” (SIC) paradigm that mimics a gravity transition relevant for spaceflight. We iterated upon our design for how the participant was configured based upon pilot tests, transitioning from a “seated” posture to a “supine” or laying down posture, which we found to be more comfortable for participants during sustained x-axis centrifugation (i.e., “eyeballs in” g-forces).
Next, we performed extensive preliminary testing for each of these paradigms in isolation. We tested 7 subjects that experienced just the “wave-like” motion, the Tilt-Translation Sled, in order to assess the propensity for our motion profile to induce motion sickness symptoms. This further allows us to capture the relative contribution toward motion sickness of the wave-like motion in isolation, as compared to conjointly with the SIC gravity transition analog paradigm. In summary, we found that while the majority of subjects were able to tolerate the entire wave-like motion exposure, the majority also experienced substantial levels of motion sickness. This is important to quantify as we proceed with evaluating countermeasures aimed to help mitigate/reduce motion sickness. This dataset will serve as a control condition for future experimental conditions. We then performed pilot testing with just the SIC gravity transition analog, as performed on our HERD human-rated motion device. We found in our pilot testing that the SIC paradigm was tolerable, and further, that immediately following, when the centrifuge was stopped, subjects reported illusory sensations, unsteadiness, and early symptoms of motion sickness (e.g., nausea). This is consistent with previous studies that have used the SIC paradigm on other centrifuges and suggests that we are able to mimic some of the motion sickness related to gravity transitions relevant for spaceflight.
In one of our planned countermeasure conditions, we intend to provide congruent visual orientation cues to the subject during wave-like motion. The team decided to use a virtual reality head-mounted display to provide these cues, for ease of use in the laboratory, but also operational feasibility in a capsule (low mass, power, and volume). To do this in our experiments, we had to integrate our virtual reality headset into the Tilt-Translation Sled (including integration/modification with the head restraint). Previously, we developed and implemented software enhancements for the Tilt-Translation Sled to enable communication and provide motion information to the head mounted display programmed in Unity. In the last year, we have enhanced our implementation of the congruent visual cues in the virtual reality headset within the Tilt-Translation Sled. Specifically, our approach for driving the visual cues now allow for head-free motion within the Tilt-Translation Sled. This will be critically important for our “postural control” countermeasure condition, where the participant will be instructed to voluntarily move their head/body to remain aligned with perceived upright. These head/body movements are sensed in real-time and the visual cues in the virtual reality headset congruently depicts self-motion derived from both participant active head/body motions and wave-like whole-body passive motions. Finally, we preformed validation tests to confirm that the visual and inertial motion cues were precisely synchronized. Thus, we are now prepared to perform testing in each of our various countermeasure conditions (the control condition, visual cues, postural control, and the combination of both visual cues and postural control).
With all of the technical implementation progress, we have proceeded with formal human subject testing of both the control condition and the visual cueing countermeasure condition. As of the time of writing this report, we have completed testing on 8 subjects (4 in the control condition and 4 in the visual cueing countermeasure condition). (We are testing 2-3 subjects per week, so our subject pool is changing rapidly). In brief, while subjects tend to become increasingly motion sick during the wave-like motion exposure, and then gradually recover after the wave-like motion ceases, the subjects which experience the visual cueing countermeasure appear to become less motion sick than subjects in the control group. Further, balance was substantially impaired in some of the control subjects after the wave-like motion but was unaffected in our subjects to date that were provided the visual cueing countermeasure.
Pilot testing of additional countermeasure conditions is beginning. Specifically, we are exploring providing visual cues that are predictive of upcoming motions and their associated sensory signals. We hypothesize that this will enable the brain to produce between expectations of sensory cues, reducing sensory conflict and the associated motion sickness. Further, we are preparing to test the postural control countermeasure group, in which subjects are instructed to keep themselves upright, evoking postural control mechanisms that may be important for reducing motion sickness through active control.
The Brandeis arm of this project employs a virtual rendition of the visual reorientation levitation illusion introduced by Howard (2000) to partially simulate orbital microgravity, and a six-degree-of-freedom Stewart motion platform to simulate a water landing sea state analog (heave ±42 cm centered on 0.17 Hz and roll ±10 degrees centered on 0.4 Hz). Pilot studies confirmed the validity of the microgravity (n=5) and sea state (n=5) analogs. Data collection is about 70% complete for three within-subject counterbalanced treatment conditions, with a target sample size of 15. All three sessions begin with the microgravity analog for 1 hour in which supine subjects make paced roll head movements in a fully articulated virtual room pitched back 90 degrees, followed by an immediate transition to the sea state analog of reorientation to the upright with head restraint and the onset of platform oscillation. For the next hour, subjects view either 1) a completely dark field (n=12), 2) a head-fixed single fixation point in a dark field (n=12), or 3) a virtual spatially stabilized horizon line (n=7). Motion sickness and anxiety self-ratings are prompted regularly through the entire session, and postural stability (stand on narrow beam eyes open/closed) is measured at the beginning and end. Preliminary statistics show the water landing simulation exacerbates motion sickness significantly more with a head-fixed target than in darkness.
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Abstracts for Journals and Proceedings
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Clark TK, Lonner T, Allred A, Drecksler S, Poole N, Oman CM, Lawson BD, Groen E, Lackner J, DiZio P "Development of a Countermeasure Suite for Motion Sickness Induced by Post-Flight Water Landings" 2022 NASA Human Research Program Investigator's Workshop, Virtual, February 7-11, 2022. Abstracts. 2022 NASA Human Research Program Investigators' Workshop, Virtual, February 7-11, 2020. , Feb-2022
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Abstracts for Journals and Proceedings
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Lonner TL and Clark TK "Evaluating Virtual Reality as a Countermeasure for Astronaut Motion Sickness during Post-Flight Water Landings" 2022 NASA Human Research Program Investigator's Workshop, Virtual, February 7-11, 2022. Abstracts. 2022 NASA Human Research Program Investigators' Workshop, Virtual, February 7-11, 2020., Feb-2022 , Feb-2022
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