NOTE: End date changed to 7/31/2022 per NSSC information (Ed., 7/6/21)

Since Fall 2022 we have been preparing and finalizing all the operational aspects involved in the upcoming parabolic flight campaign. We have worked closely with Novespace during the development of the Experimental Safety Data Package (ESDP) document to ensure that all safety and operational constraints have been accounted for. Safety considerations include physical volume, mass, electricity, fire, vibration, electromagnetic fields, light, odors, and noise considerations, as well as operational considerations such as positioning and stowage. The current experimental design and team readiness reflect a flexibility to adapt to complications such as airsickness among participants or experimenters, hardware and software anomalies, or any changes to the campaign schedule due to unforeseen events such as inclement weather or aircraft maintenance. In addition, to practice our operations during parabolic flight, we have designated floor space in our lab to match the dimensions of our designated area of the Airbus 310 cabin, hardware mounting rails, seats, and baseplates. This has allowed us to iterate our protocol checklists and practice anomaly resolution in as similar an environment as we can without the actual aircraft. Thus, the experimental hardware, software, and the experimental protocol have undergone extensive testing during our weekly rehearsals. Minor bugs have been corrected and optimization adjustments have been made to arrive at a final detailed experimental protocol. Following the submission of this report, we are eagerly anticipating the parabolic flight campaign, scheduled during June 5-17, 2023.

During Year 3, we have also continued our ground experiment efforts. Using a tilt paradigm as an altered-gravity analog, we have completed another experiment on EMG coherence using a bimanual coordination frequency task. Results and conclusions from our previous ground experiments have been updated following generation of dose-response curves. Finally, we have also investigated bimanual coordination performance when exposed to a graded Lower Body Negative Pressure (LBNP) environment. Twenty-four (12M/12F) conducted the same bimanual coordination tasks that we will use in the upcoming parabolic flight when exposed to LBNP. Subjects were required to participate in two experimental sessions scheduled on consecutive days: one session was focused on frequency tasks (1:1 and 1:2), and the other session was focused on scanning tasks (180° and 90°). During the frequency tasks, participants were required to coordinate 1:1 (i.e., in-phase) and 1:2 rhythmical bimanual force production tasks when provided visual feedback in the form of Lissajous templates. For the in-phase or 1:1 bimanual force coordination task, participants were required to use both their left and right limbs to simultaneously produce continuous patterns of forces. The 1:2 task required participants to produce two patterns of force with the right limb for every one pattern of force produced by the left limb. During the scanning tasks, participants were required to coordinate left and right limb movement together in a continuous pattern at 90° and 180° of relative phase angle when provided visual feedback in the form of Lissajous templates. The order of the frequency and scanning sessions was counterbalanced across subjects. In the frequency tasks sessions, subjects were first exposed to -20 mmHg and asked to do four 30-second trials in the following order: 1:1, 1:2, 1:1, 1:2. After a 60-second break, the LBNP level was incremented by 10 mmHg and subjects were asked to repeat the same sequence of frequency tasks. This protocol is repeated, increasing the LBNP at a rate of 10 mmHg every 3 minutes until the LBNP chamber reached -100 mmHg, or early should presyncope develop. A similar protocol was implemented during the scanning tasks sessions in which subjects completed four 30-second trials in the following order: 180°, 90°, 180°, 90°. Both cardiovascular variables (blood pressure, cardiac output, heart rate variability, etc.) and bimanual coordination variables (timing variables, force variables, harmonicity, etc.) were collected continuously. Data collection have just been completed and data analysis is underway.

NOTE: End date changed to 7/31/2022 per NSSC information (Ed., 7/6/21)

During Year 2, we have also conducted experiments in the laboratory environment. We have implemented a tilt table paradigm as a simulated analog environment for hypogravity conditions. In a round of experiments following the previous year’s, 12 subjects conducted a force coordination task using a new tilt platform to simulate five g-levels (0g, 0.25g, 0.50g, 0.75g, and 1g) in a scanning manner, corresponding to the same gravitational loads that will be delivered in the parabolic flight. During the experiments, participants were required to coordinate 1:1 (i.e., in-phase) and 1:2 rhythmical bimanual force production tasks when provided visual feedback in the form of Lissajous templates. For the in-phase, or 1:1 bimanual force coordination task, participants were required to use both their left and right limb to simultaneously produce continuous patterns of forces. The 1:2 task required participants to produce two patterns of force with the right limb for every one pattern of force produced by the left limb. Participants were familiarized with the apparatus but received no formal training on the tasks prior to their first trial. Similar to our first experiment, preliminary results showed very effective timing performance in both coordination tasks (1:1 and 1:2) and all altered-gravity conditions (0g, 0.25g, 0.50g, 0.75g, and 1g) after the very limited training received, supporting the efficacy of Lissajous feedback to increase coordination performance. However, differences were observed between gravity conditions for measures associated with force production (mean and peak force), and force harmonicity. We will continue to explore constraints that facilitate or interfere with bimanual coordination in altered-gravity environments using head-down tilt / head-up tilt (HDT/HUT), parabolic flight, and short-radius centrifugation analogs.

During Year 1, we have also conducted experiments in the laboratory environment. We have implemented a head-down tilt/head-up tilt (HDT/HUT) paradigm as a simulated analog environment for hypogravity conditions. In a first round of experiments, 12 subjects conducted a force coordination task using this tilt platform to simulate microgravity (6° HDT), Moon’s gravity (9.5° HUT), Mars’s gravity (22.3° HUT), and Earth’s Gravity (90° HUT, or upright position). During the experiments, participants were required to coordinate 1:1 (i.e., in-phase) and 1:2 (i.e., anti-phase) rhythmical bimanual force production tasks when provided visual feedback in the form of Lissajous templates. For the in-phase or 1:1 bimanual force coordination task, participants were required to use both their left and right limb to simultaneously produce continuous patterns of forces. The 1:2 or anti-phase task required participants to produce two patterns of force with the right limb for every one pattern of force produced by the left limb. Participants received training in upright position (14 trials in each one of the coordination tasks), and after a 30 min break, they performed a retention test in upright position (2 trials in each one of the coordination tasks), followed by a transfer test (an additional 2 trials in each one of the coordination tasks) in each one of the three simulated altered-gravity environments: Mars, Moon, and microgravity (in counterbalanced order). Preliminary results showed very effective performance in both coordination tasks (1:1 and 1:2) and all altered-gravity conditions (Mars, Moon, microgravity) after the short training received, supporting the efficacity of Lissajous feedback to increase coordination performance. However, differences were observed between gravity conditions for measures associated with force production, specifically during the 1:1 task. Given that 1:1 coordination task is considered to be the brain default coordination mode, differences with gravity suggest that the coordination landscape differs between Earth and altered-gravity environments. We will continue to explore constraints that facilitate or interfere with bimanual coordination in altered-gravity environments using HDT/HUT, parabolic flight, and short-radius centrifugation analogs.