The second aim will assess the suitability of a proposed set of sensorimotor assessment tasks, or measures that would be feasible within the limited time, resources, and space of a lunar/Martian lander. The assessment tasks should aid in progressive adaptation to the novel gravitational environment, provide opportunities to develop strategies to recover from off-nominal body positions, and mimic operational tasks such that crew can self-assess their potential ability to complete their missions. We will obtain performance of the sensorimotor assessment tasks at varying levels of the SDA magnitude to map sensorimotor ability to the probability of completion of operational performance measures.

Our third aim involves up to 90 minutes of prolonged +3GX centrifugation to mimic the vestibular alterations observed after gravity transitions. Immediately after egress from the centrifuge, subjects will perform a subset of the sensorimotor assessment tasks followed by the operational performance tasks. We will map performance in sensorimotor assessment tasks to performance in operational performance measures, similar to aim two.

Our fourth aim will utilize the NASA Johnson Space Center (JSC) Active Response Gravity Offload System (ARGOS) to characterize the effects of a reduced gravity load on balance-related exploration and operational measures.

The fifth and final aim will build on the lunar landing simulations that will be developed for the Manual Crew Override study (PI: Wood) and the human lander systems training simulations to support the Flight Operations Directorate for exploration class mission training. The study will involve two pre-test familiarization sessions focused on developing proficiency to perform the landing task through multiple landings with both the full simulator and a Just In Time (JIT) trainer platform. Following a standard duration mission timeline (~6-8 months), subjects will perform the same lunar landing while experiencing sensorimotor disorientation (galvanic vestibular stimulation). Between the familiarization and final test sessions, subjects will undergo 1 of 3 “inflight” training paradigms using the JIT trainer including: 1) no training, 2) consistent training throughout the mission, or 3) training only at the end of mission consistent with current ISS protocols. The outcome of this aim is to characterize the relationship between the performance on the JIT platform with post-disorientation lunar landing performance to inform what performance threshold is required to mitigate risk associated with vertigo and disorientation with manual crew override during landings.

The main deliverables from this project will be recommended sensorimotor assessments for extravehicular activity (EVA) operations that provide a quantitative index of readiness to perform key operational tasks and validation of lunar landing simulations for training manual crew override during landings.

NOTE: Per the Principal Investigator (PI): During the first project year, Aim 1c was removed from the project (Ed., 4/18/23). Aim 1c was to examine a large number of proposed sensorimotor assessment tasks in an effort to reduce the set of tasks to those that are the most sensitive to changes in sensorimotor disruption via the SDA.

This project is in direct response to the baselined Human Research Program (HRP) Path to Risk Reduction milestone of defining sensorimotor assessments that can provide a quantitative index of readiness to perform key exploration tasks. The Flight Operations Directorate has identified the need for better sensorimotor assessment tools that would protect against hazards of performing operational tasks too soon following gravitational transitions. The project outcomes will address this recommendation by providing a validated set of sensorimotor assessment tasks that will 1) allow for self-assessment when communication with ground support may be limited or delayed and 2) provide progressive adaptation to the novel gravitational environment.

For Earth-based benefits: The sensorimotor community has a need for simple assessment tasks that could be used clinically, through telemedicine, or by the patient alone. These tasks could be used to help in self-determination of the patient’s sensorimotor ability to perform daily activities and/or guide recovery of vestibular-impaired patients.

Aims 2 & 3 sought to map performance in the proposed set of sensorimotor assessment tasks with performance during operational analog tasks while experiencing varying levels of sensorimotor disorientation. Aim 2 utilized the validated sensorimotor disorientation analog (SDA) to induce disorientation, while Aim 3 used sustained +3Gx centrifugation. Validation of the proposed set of sensorimotor assessment tasks will ultimately downselect the task set to those that meet the following criteria: 1) have a strong correlation between performance in the sensorimotor assessment tasks with operational analog tasks, and 2) elicit distinct performance groupings across varying levels of sensorimotor disorientation.

Aim 2 Methods Aim 2 Phase 1 was completed with 21 subjects in the previous reporting period. An interim analysis suggested that additional subjects were required to achieve an appropriate statistical power for analyses. Aim 2 Phase 2 was completed on an additional 20 subjects, for a total of 41 subjects. In brief, subjects attended two sessions separated by a minimum of 1 day. The first session provided familiarization to the sensorimotor assessment tasks and operational analog tasks and then baseline data were collected. The second session completed the assessment and operational tasks under two levels of the SDA: 1) high-level replicating crewmember immediate postflight performance (R+0) and 2) low-level replicating R+1 when crewmembers are within the recovery phase yet still have slight sensorimotor disorientation.

Aim 3 Methods Data collection occurred at the KBR Aerospace Environment Protection Lab (AEPL) located in San Antonio, TX. The KBR AEPL centrifuge has a free-swinging gondola at the end of the long arm, resulting in a constant alignment of the gravito-inertial force with the gondola. The subjects were oriented in a supine position in the gondola (feet pointing in the direction of motion) so the resultant force vector was in the naso-occipital direction to minimize orthostatic stress. Moderate 0.1 G/s acceleration and deceleration rate were used. Subjects attended two sessions separated by a minimum of 1 day. A familiarization session was conducted including a 5-min centrifuge exposure to minimize any biases toward prior exposure. The centrifuge profile used was unique to those with prior exposure; therefore, no bias or skew in the data was present. The test session included a pre-centrifuge baseline data collection, followed by the 60-min centrifugation spin, and finally, two post-centrifuge tests separated by ~45 min, mimicking the two postflight time points and SDA levels (R+0/high, R+1/low) from Aims 1 & 2. The second post-centrifuge recovery test performance was not significantly different from pre-centrifuge performance; therefore, the following preliminary results will only include the immediate post-centrifuge data.

Aim 2 & 3 Preliminary Results To aid in down selection of sensorimotor assessment tasks, we first conducted paired t-tests to examine which tasks were most sensitive to change in sensorimotor disruption. For the SDA, significant differences were present for all sensorimotor assessment and operational analogs tasks between the none (baseline) and high level. There were a few significant differences between the low level and either the none or high level. This does indicate that the low level is able to elicit performance differences in between none and high levels; however, it is not consistent across tasks likely due to subject variability in performance and susceptibility to the SDA. For the centrifuge, only four assessment tasks were significantly different between pre- and immediate post-centrifuge testing. These tasks were consistent with the SDA tasks that had significant performance differences across none, low, and high levels. There were no significant differences in performance for the operational analog tasks post-centrifuge. Given that the operational tasks were conducted after the assessment tasks, the impact of +3Gx on the operational tasks was limited due to the quicker-than-expected recovery.

To examine the predictive ability of the sensorimotor assessment tasks to performance in operational analog tasks, preliminary analyses were conducted using the Aim 2 SDA dataset. Pearsons’ correlation r-values were calculated between 1) all assessment tasks and 2) each assessment and operational analog task, across individuals and SDA levels (n = 120). Strong correlations were present between each assessment task (r ≥ 0.59). The two assessment tasks with the strongest correlations to both the operational analog tasks were the fall recovery (r ≥ 0.45) and obstacle turn tasks (r ≥ 0.60). Leave-one-out cross-validation (LOOCV) was conducted with a linear model of assessment tasks selected using stepwise regression. The operational analog predictors were the time to complete the capsule egress and the number of bag transfers completed during the 5-minute EVA traversal. For capsule egress, only the obstacle turn task was included in the model with a mean absolute error (MAE) of 12.8 sec between predicted and observed values (Q2 = 0.35). For the EVA traversal, the fall recovery, obstacle turn, and four-square-step-test were included in the model with an MAE of 6.5 bags (Q2 = 0.53).

These results provide early evidence for the down-selection of assessment tasks that were best able to predict performance in operationally relevant tasks for use in upcoming Artemis missions.

The second aim will assess the suitability of a proposed set of sensorimotor assessment tasks, or measures that would be feasible within the limited time, resources, and space of a lunar/Martian lander. The assessment tasks should aid in progressive adaptation to the novel gravitational environment, provide opportunities to develop strategies to recover from off-nominal body positions, and mimic operational tasks such that crew can self-assess their potential ability to complete their missions. We will obtain performance of the sensorimotor assessment tasks at varying levels of the SDA magnitude to map sensorimotor ability to the probability of completion of operational performance measures.

Our third aim involves up to 90 minutes of prolonged +3GX centrifugation to mimic the vestibular alterations observed after gravity transitions. Immediately after egress from the centrifuge, subjects will perform a subset of the sensorimotor assessment tasks followed by the operational performance tasks. We will map performance in sensorimotor assessment tasks to performance in operational performance measures, similar to aim two.

Our fourth aim will utilize the NASA Johnson Space Center (JSC) Active Response Gravity Offload System (ARGOS) to characterize the effects of a reduced gravity load on balance-related exploration and operational measures.

The fifth and final aim will build on the lunar landing simulations that will be developed for the Manual Crew Override study (PI: Wood) and the human lander systems training simulations to support the Flight Operations Directorate for Artemis mission training. Similar to Aim 1a, this aim anticipates working with experienced crewmembers to satisfy some of the training for generic lunar landing tasks. The study will involve two pre-test familiarization sessions focused on developing proficiency to perform the landing task through multiple landings with both the full simulator and the Just In Time (JIT) trainer platform. Following recommended guidelines for Artemis sustaining mission, crewmembers will then wait 75 days before performing the same lunar landing following a g-state analog (sustained centrifugation). The outcome of this aim is to characterize the relationship between the performance on the JIT platform with post-centrifuge lunar landing performance to inform what performance threshold is required to mitigate risk associated with vertigo and disorientation with manual crew override during landings.

The main deliverables from this project will be recommended sensorimotor assessments for extravehicular activity (EVA) operations that provide a quantitative index of readiness to perform key operational tasks and validation of lunar landing simulations for training manual crew override during landings.

NOTE: Per the Principal Investigator (PI): During the first project year, Aim 1c was removed from the project (Ed., 4/18/23). Aim 1c was to examine a large number of proposed sensorimotor assessment tasks in an effort to reduce the set of tasks to those that are the most sensitive to changes in sensorimotor disruption via the SDA.

This project is in direct response to the baselined Human Research Program (HRP) Path to Risk Reduction milestone of defining sensorimotor assessments that can provide a quantitative index of readiness to perform key exploration tasks. The Flight Operations Directorate has identified the need for better sensorimotor assessment tools that would protect against hazards of performing operational tasks too soon following gravitational transitions. The project outcomes will address this recommendation by providing a validated set of sensorimotor assessment tasks that will 1) allow for self-assessment when communication with ground support may be limited or delayed and 2) provide progressive adaptation to the novel gravitational environment.

For Earth-based benefits: The sensorimotor community has a need for simple assessment tasks that could be used clinically, through telemedicine, or by the patient alone. These tasks could be used to help in self-determination of the patient’s sensorimotor ability to perform daily activities and/or guide recovery of vestibular-impaired patients.

Aim 2 This aim seeks to map performance in a proposed set of sensorimotor assessment tasks with performance in operational analog tasks. Validation of the proposed set of sensorimotor assessment tasks will ultimately down select the task set to those that meet the following criteria: 1) have a strong correlation between performance in the sensorimotor assessment tasks with operational analog tasks, and 2) elicit distinct performance groupings across varying levels of sensorimotor disorientation. Aim 2 is the first validation study in the overall project. The deliverable from this aim is to 1) provide an initial performance prediction model between the sensorimotor assessment tasks and operational analog tasks, and 2) define performance thresholds across a range of sensorimotor disorientation. The model generated from Aim 2 will be further refined utilizing data from Aims 3 and 4. Therefore, it is important to ensure the model is generalizable to new data.

In discussions with the Flight Operations Directorate, feedback from a Technical Interchange Meeting sponsored by the Human Research Program (HRP) Health Human Countermeasures Element, and lessons learned from Apollo Missions, the proposed set of sensorimotor assessment tasks was developed to include the following parameters: 1) mimic body maneuvers such as reaching, bending over, etc., such that crew can self-assess their potential ability to complete operational tasks; 2) provide opportunities to develop strategies to recover from off-nominal body positions; and 3) aid in progressive adaptation to the novel gravitational environment. Operational logistic constraints included: 1) tasks should be completable within a limited space and within the various Human Lander System (HLS) configurations, and 2) complete tasks with minimal to no hardware mass utilizing the available HLS configurations. The sensorimotor assessment tasks were defined and completed in the following order, starting from the least vestibularly provocative movements: postural challenge task, step test (Eymir et al., 2022; Feld et al., 2022; Hong et al., 2012; Mercer et al., 2009), fall recovery task from prone and supine, four square step test (Dite and Temple, 2002; Whitney et al., 2007), an obstacle turn task required 180- and 90-degree turns, kneel-and-turn task, and an augmented reality full body eye-hand coordination task simulating an EVA geological sampling task.

Aim 2 utilized high-fidelity operational analog tasks that were developed to simulate top-hatch capsule egress and early exploration EVA (Egress Fitness, PI: Norcross).

A total of 21 subjects completed Aim 2 Phase 1. Subjects attended two sessions separated by a minimum of 1 day. The first session provided familiarization to the sensorimotor assessment tasks and operational analog tasks and then baseline data were collected. The second session completed the assessment and operational tasks under two levels of sensorimotor disorientation: 1) high-level replicating crewmember immediate postflight performance (R+0), and 2) low-level replicating R+1 when crewmembers are within the recovery phase yet still have slight sensorimotor disorientation. To achieve these levels of disorientation, the validated Sensorimotor Disorientation Analog (SDA) was used (Moudy et al., 2023; Moudy et al., 2024). The SDA is comprised of galvanic vestibular stimulation simulating vestibular disruption (high: peaks reach 3mA, low: peak reach 2mA) and a weighted suit at the chest and distally at the ankles and wrists simulating proprioceptive deconditioning and subjective heaviness (high: 30% added bodyweight, low: 15% bodyweight). A cross-balanced approach was used where half of the subjects experienced the high level first followed by the low level and vice versa for the other half of subjects.

An interim analysis was conducted on the initial sample population of 21 subjects to assess the R-squared value and determine whether the planned sample size was appropriate to achieve a high precision efficiency (PE). PE refers to the ability of a sample-derived prediction equation to extrapolate to future samples (i.e., generalizability), with higher numbers indicating better extrapolation. Mixed linear models were conducted for two operational performance measures individually, which yielded R-squared values of 0.47 (operational task: time to complete capsule egress) and 0.83 (operational task: number of bag passes during EVA traversal task). These values indicated a sufficient level to achieve a high PE. The sample size calculation based on a number of predictors, effect size, and PE indicated a required sample size of 37 to achieve a PE of 0.8, assuming 2 predictors in the model (SDA level and one assessment task) and an R-squared value of 0.47.

The interim analysis secondarily assessed if distinct performance groupings existed across the SDA levels. A repeated measures ANOVA was conducted. All ANOVA tests, except for the time to complete the task board, were significant, indicating that at least two of the groups had different means. Paired t-tests were performed to compare any two groups. These data were also used to conduct a secondary sample size estimation. For the operational capsule egress task, assuming a mean difference of 5 and a standard deviation of 10 to detect a one-side paired difference between groups, a sample size of 38 would be needed to achieve 80% power at an alpha level of 0.0167 (0.05/3). A smaller sample size would be needed if we calculate it based on summary statistics of other variables.

Based on the interim analysis recommendations, an additional 16 subjects (a total of 37 needed minus initial 21) were required to achieve a precision efficiency (PE) of 0.8. Data collection is ongoing for 20 additional subjects (total N: 41 subjects) to allow for any dropouts (conservative 25% attrition rate) to meet sample size estimations required to develop a generalizable prediction model. This Aim 2 Phase 2 is expected to be completed in May 2024. An additional analysis will be completed again to confirm whether we have met the required sample size given the additional datasets.

A second finding of this analysis was the inability of the simulated EVA task board portion to measure relevant sensorimotor changes in performance. No significant differences were found between SDA levels for this task and correlation values to the sensorimotor assessment tasks were weak (Pearson r = 0.35). This was not unexpected as the task has an inherent stabilizing feature where subjects hold onto the umbilicals and task board to complete the task. A light touch has been shown previously to provide enough stabilizing support to compensate for vestibular disruptions (Baldan et al., 2014). As such, and in preparation for future aims where the transportability of operational analog tasks is critical, data collection for the additional 20 subjects is being conducted using updated operational analog tasks. The operational analog tasks include the same simulated capsule egress, and an alternative simulated EVA traversal that replicates the key physiological requirements as the original EVA traversal task.

Aim 3 Similar to Aim 2, Aim 3 is focused on mapping the relationship between performance in the sensorimotor assessment tasks to performance in the operational analog tasks under varying levels of sensorimotor disorientation. Aim 3 will induce sensorimotor disorientation through sustained hypergravity centrifugation which drives vestibular adaptive changes similar to G-transitional effects following spaceflight (Albery and Martin, 1996; Bles et al., 1989; Groen et al., 2008; Nooij et al., 2007). The centrifuge exposure parameters are based largely on the protocol established by Groen and TNO colleagues in Soesterberg, The Netherlands. Based on their work, the optimal exposure is +3Gx for 60 min (Bles et al., 1997; Nooij and Bos, 2007). Data collection will occur at the KBR Aerospace Environment Protection Lab (AEPL) located in San Antonio, TX. The KBR AEPL centrifuge has a free-swinging gondola at the end of the long arm, resulting in a constant alignment of the gravito-inertial force with the gondola. The subject will be oriented in a supine position in the gondola (feet pointing in the direction of motion) so the resultant force vector is in the naso-occipital direction to minimize orthostatic stress. Although the centrifuge is capable of fast G-onset for performance jet training, our profile will utilize a moderate 0.1 G/s acceleration and deceleration rate.

Subjects will attend two sessions separate by a minimum of one day. The first session will be to familiarize the subjects with the tasks and complete a short 5-minute centrifuge exposure to minimize biases toward prior exposure. The centrifuge profile used in this study is unique to the AEPL facility and subject pool, therefore, we do not expect any data skew due to prior exposure. The second session will be the test session to include pre-exposure baseline data collection, followed by a sustained 60-minute exposure, and two post-centrifuge tests separated by 45 minutes. The test session was developed such that the post-centrifuge tests mimic the two postflight time points and SDA levels (R+0/high, R+1/low) from Aims 1 and 2.

References

Albery, W. B., & Martin, E. T. (1996). Development of space motion sickness in a ground-based human centrifuge. Acta Astronautica, 38(9), 721-731.

Baldan, A., Alouche, S., Araujo, I., & Freitas, S. (2014). Effect of light touch on postural sway in individuals with balance problems: a systematic review. Gait & Posture, 40(1), 1-10. Bles, W., Bos, E., Furrer, R., de Graaf, B., Hosman, R. J. A. W., Kortschot, H. W., Krol, J. R., Kuipers, A., Marcus, J. T., Messerschmid, E., Ockels, W. J., Oosterveld, W. J., Smit, J., Wertheim, A. H., & Wientjes, C. J. E. (1989). Space adaptation syndrome induced by a long duration +3Gx centrifuge run (IZF 1989-25).

Bles, W., de Graaf, B., Bos, J. E., Groen, E., & Krol, J. R. (1997). A sustained hyper-g load as a tool to simulate space sickness. Journal of gravitational physiology: a journal of the International Society for Gravitational Physiology, 4(2), P1-4.

Dite, W., & Temple, V. A. (2002). A clinical test of stepping and change of direction to identify multiple falling older adults. Archives of Physical Medicine and Rehabilitation, 83(11), 1566-1571.

Eymir, M., Yuksel, E., Unver, B., & Karatosun, V. (2022). Reliability, validity, and minimal detectable change of the Step Test in patients with total knee arthroplasty. Irish Journal of Medical Science (1971-), 1-6.

Feld, J. A., Goode, A. P., Mercer, V. S., & Plummer, P. (2022). Utility of an obstacle-crossing test to classify future fallers and non-fallers at hospital discharge after stroke: a pilot study. Gait & Posture, 96, 179-184.

Groen, E. L., Nooij, S. A., & Bos, J. E. (2008, June 22-27, 2008). Ground-based research on vestibular adaptation to g-level transitions. Life in Space for Life on Earth, Angers, France.

Hong, S.-J., Goh, E. Y., Chua, S. Y., & Ng, S. S. (2012). Reliability and validity of step test scores in subjects with chronic stroke. Archives of Physical Medicine and Rehabilitation, 93(6), 1065-1071.

Mercer, V. S., Freburger, J. K., Chang, S.-H., & Purser, J. L. (2009). Step test scores are related to measures of activity and participation in the first 6 months after stroke. Physical Therapy, 89(10), 1061-1071.

Moudy, S., Peters, B., Clark, T., Schubert, M., Bishop, M., Young, M., & Wood, S. (2023). Development of a Sensorimotor Ground Analog from Astronaut Postflight Experience. 2023 NASA Human Research Program Investigators’ Workshop.

Moudy, S., Peters, B., Clark, T., Schubert, M., De Dios, Y., Bollinger, A., & Wood, S. (2024). Validation of A Sensorimotor Disorientation Ground Analog. HRP IWS, Nooij, S. A., Bos, J., Groen, E., Bles, W., & Ockels, W. (2007). Space sickness on earth. Microgravity Sci Technol, 19(5-6), 113-117. Nooij, S. A., & Bos, J. E. (2007). Sickness induced by head movements after different centrifugal G x-loads and durations. Journal of Vestibular Research, 17(5-6), 323-332.

Reschke, M. F., Clément, G. R., Thorson, S. L., Mader, T. H., Dudley, A. M., Wood, S. J., Bloomberg, J. J., Mulavara, A. P., Gibson, C. R., & Williams, D. (2016). Neurology. In A. E. Nicogossian, R. S. Williams, C. L. Huntoon, C. R. Doarn, J. D. Polk, & V. S. Schneider (Eds.), Space Physiology and Medicine (4th ed., pp. 245-282). Springer.

Thuro, A., & Stirling, L. (2021). Characterization of the Apollo Astronaut Lunar Extravehicular Activity Falls and Near-Falls 2021 IEEE Aerospace Conference (50100).

Whitney, S. L., Marchetti, G. F., Morris, L. O., & Sparto, P. J. (2007). The reliability and validity of the Four Square Step Test for people with balance deficits secondary to a vestibular disorder. Archives of Physical Medicine and Rehabilitation, 88(1), 99-104.

The second aim will assess the suitability of a proposed set of sensorimotor assessment tasks, or measures that would be feasible within the limited time, resources, and space of a lunar/Martian lander. The assessment tasks should aid in progressive adaptation to the novel gravitational environment, provide opportunities to develop strategies to recover from off-nominal body positions, and mimic operational tasks such that crew can self-assess their potential ability to complete their missions. We will obtain performance of the sensorimotor assessment tasks at varying levels of the SDA magnitude to map sensorimotor ability to the probability of completion of operational performance measures.

Our third aim involves up to 90 minutes of prolonged +3GX centrifugation to mimic the vestibular alterations observed after gravity transitions. Immediately after egress from the centrifuge, subjects will perform a subset of the sensorimotor assessment tasks followed by the operational performance tasks. We will map performance in sensorimotor assessment tasks to performance in operational performance measures, similar to aim two.

Our fourth aim will utilize the NASA Johnson Space Center (JSC) Active Response Gravity Offload System (ARGOS) to characterize the effects of a reduced gravity load on balance-related exploration and operational measures.

The fifth and final aim will build on the lunar landing simulations that will be developed for the Manual Crew Override study (PI: Wood) and the human lander systems training simulations to support the Flight Operations Directorate for Artemis mission training. Similar to Aim 1a, this aim anticipates working with experienced crewmembers to satisfy some of the training for generic lunar landing tasks. The study will involve two pre-test familiarization sessions focused on developing proficiency to perform the landing task through multiple landings with both the full simulator and the Just In Time (JIT) trainer platform. Following recommended guidelines for Artemis sustaining mission, crewmembers will then wait 75 days before performing the same lunar landing following a g-state analog (sustained centrifugation). The outcome of this aim is to characterize the relationship between the performance on the JIT platform with post-centrifuge lunar landing performance to inform what performance threshold is required to mitigate risk associated with vertigo and disorientation with manual crew override during landings.

The main deliverables from this project will be recommended sensorimotor assessments for extravehicular activity (EVA) operations that provide a quantitative index of readiness to perform key operational tasks and validation of lunar landing simulations for training manual crew override during landings.

NOTE: Per the Principal Investigator (PI): During the first project year, Aim 1c was removed from the project (Ed., 4/18/23). Aim 1c was to examine a large number of proposed sensorimotor assessment tasks in an effort to reduce the set of tasks to those that are the most sensitive to changes in sensorimotor disruption via the SDA.

This project is in direct response to the baselined Human Research Program (HRP) Path to Risk Reduction milestone of defining sensorimotor assessments that can provide a quantitative index of readiness to perform key exploration tasks. The Flight Operations Directorate has identified the need for better sensorimotor assessment tools that would protect against hazards of performing operational tasks too soon following gravitational transitions. The project outcomes will address this recommendation by providing a validated set of sensorimotor assessment tasks that will 1) allow for self-assessment when communication with ground support may be limited or delayed and 2) provide progressive adaptation to the novel gravitational environment.

For Earth-based benefits: The sensorimotor community has a need for simple assessment tasks that could be used clinically, through telemedicine, or by the patient alone. These tasks could be used to help in self-determination of the patient’s sensorimotor ability to perform daily activities and/or guide recovery of vestibular-impaired patients.

Aim 1a: We completed an exploratory study to gather subjective feedback from five previously flown astronauts (1 male, 4 females; average time since flight: 377 days) on a Sensorimotor Disorientation Analog (SDA) that would mimic their postflight experience and functional performance following long duration stay in microgravity. We chose to replicate two timepoints during postflight recovery that would encompass a large range of performance decrements: immediately after landing (R+0-4hrs; high level) and post-landing (R+24-48hrs; low level). The SDA consisted of galvanic vestibular stimulation (GVS) to disorient the vestibular system, visual disorientation goggles to disrupt the visual field, and a weighted suit to alter proprioceptive feedback and replicate subjective heaviness. A random sum-of-sines profile between 0-1Hz was used for the GVS with peak amplitudes ranging from 1-4mA (Wood, 2002). GVS was applied independently first at the low (2mA) and high (3mA) levels, followed by the weighted suit alone at the low (20% body weight) and high levels (40% body weight), then combined with the GVS. Last, the disorientation goggles were applied alongside both the GVS and weighted suit at the low (0.07-0.10+ blood alcohol content (BAC)) and high (0.12-0.15+ BAC) levels. Each element of the SDA could be increased or decreased depending on crew feedback to find the disorientation levels that best matched their experience.

Four of the five crewmembers reported that GVS alone replicated ~80-90% of their post-flight performance with the weighted suit fine-tuning the experience to replicate an additional 5-10% of their experience. The fifth crewmember stated the GVS and weighted suit equivalently replicated their experience (50%). Crewmembers did not believe the disorientation goggles represented either the visual disruptions or illusory sensations that they experienced postflight, nor did they believe the goggles impacted their performance in postflight tasks similarly. While the disorientation goggles were not meant to replicate the exact visual disruptions that have been described by crewmembers, the feedback suggested that replicating crewmember experience is important. The final SDA, resulting from crewmember feedback, includes the GVS at the levels described above and the weighted suit at 15% and 30% body weight. The disorientation goggles were removed from the SDA. These results provided a more accurate SDA that can be used to define the sensorimotor assessment thresholds. The results from this exploratory study were presented at the 2023 NASA Human Research Program (HRP) Investigators’ Workshop (Moudy et al., 2023).

Aim 1b: The second study was completed to validate the SDA levels defined in Aim 1a by confirming that 1) three distinct groupings exist in task performance for the three SDA levels, and 2) the range of performance across the three SDA levels replicates the range in postflight performance of crewmembers. Thirty healthy non-astronaut subjects (17 male, 13 female) performed three tasks, termed gold standard measures, that have a wealth of spaceflight data available where the recovery timeline is understood. These tasks included computerized dynamic posturography (CDP), obstacle walk, and tandem walk. CDP is the only neurovestibular medical requirement (MedB 1.5) to quantitatively assess balance recovery in which we have a wealth of data through the Shuttle and International Space Station (ISS) programs. Subjects were asked to maintain upright stance for 20s with eyes closed on an unstable sway-reference platform that pitches in proportion to body sway (EquiTest system; Natus, San Carlos, CA). This was performed with head erect (sensory organization test (SOT)-5) and with head pitch ±20° to an auditory cue (SOT-5M). An equilibrium score (EQ) measured from peak-to-peak anterior posterior sway provided an overall stability score (Wood et al., 2012). Obstacle walk and tandem walk tasks are well-established measures from recent investigations including Field Test and Standard Measures (Clément et al., 2022; Reschke et al., 2020). The obstacle walk is a modified timed-up-and-go task involving a sit-to-stand with 10s quiet stance followed by walking to and around a cone placed 4m away while navigating a 30cm obstacle on the way to the cone and back. The tandem walk involves walking heel-to-toe for approximately 10-12 steps with eyes open and eyes closed. Subjects performed the gold standard measures under each level of the SDA.

As SDA magnitude increased, overall performance outcomes decreased. However, the ability of the SDA to replicate the range of astronaut postflight performance was task dependent. CDP SOT-5 performance across SDA levels closely replicated astronaut performance preflight and postflight at R+0-24hours and R+24-48hours. SOT-5M, however, had minimal performance changes across SDA levels and was unable to replicate astronaut performance potentially due to 1) a learning effect for this complex task that mitigated effects from the SDA, and/or 2) the medial-lateral GVS disruption was mitigated by either out-of-plane head pitch movement or high cognitive effort. The obstacle walk showed performance changes across SDA levels and matched astronaut performance preflight and at R+24-48hrs . Obstacle walk performance when SDA was at the high level (mimicking R+0-4hrs) was reduced in comparison to the low level (R+24-48hrs); however, it was not replicative of astronaut performance immediately after landing. Specifically, crewmembers take longer to turn around the cone and for the turn to sit back in the chair at the end of the task. This specific disruption was unable to be replicated using the SDA modalities. For example, both the GVS and weighted suit are consistent disruptions, whereas crewmembers will feel increased disruption during head movement (such as turning or standing from a chair). Last, tandem walk had distinct groupings of performance across SDA levels and was able to elicit a high level of disorientation consistent with R+0-24 hours postflight performance for eyes open and eyes closed. The low-level SDA for both eyes open and eyes closed was more disruptive than previous crewmember performance at the R+24-48 hours timepoint. These results suggest that the SDA levels are able to elicit distinct performance groupings and, although not able to perfectly replicate R+0-4hrs, the SDA did replicate a large range of performance after return to Earth.

Aim 1c: This sub-aim was removed from the proposal. The initial intent of Aim 1c was to examine a large number of proposed sensorimotor assessment tasks in an effort to reduce the set of tasks to those that are the most sensitive to changes in sensorimotor disruption via the SDA (i.e., vary as a function of SDA magnitude). This reduced set of proposed tasks would then be used in Aim 2 to map performance against operational performance measures and Aims 3-4 under different analog conditions. However, this early reduction of potential sensorimotor assessment tasks was based on changes in performance between SDA levels alone, which may not be reliable for certain types of movements as found in Aim 1b. Further, the ultimate goal of this research is to map sensorimotor assessment performance to operational task performance. Therefore, sensorimotor assessment tasks should only be removed if they do not predict performance in operational tasks. As such, all proposed sensorimotor assessment tasks will be performed under each analog condition in the following aims alongside operational tasks.

Aim 2: This aim seeks to map performance in a proposed set of sensorimotor assessment tasks with performance in operational tasks. In discussions with the NASA Flight Operations Directorate and feedback from a Technical Interchange Meeting sponsored by the HRP Health Human Countermeasures Element, the proposed set of sensorimotor assessment tasks should aid in progressive adaptation to the novel gravitational environment, provide opportunities to develop strategies to recover from off-nominal body positions, and mimic operational tasks such that crewmembers can self-assess their potential ability to complete their missions. This aim will also utilize high-fidelity operational tasks that were developed to simulated capsule egress and early exploration EVA (Egress Fitness, PI: Norcross). (Ed. Note: See "Validation of Fitness for Duty Standards Using Pre- and Post-Flight Capsule Egress and Suited Functional Performance Tasks in Simulated Reduced Gravity", Internal Project, PI: Norcross). Data collection of an initial 20 subjects is currently in progress, at which time interim statistical analysis will be completed to determine the number of additional subjects needed to determine the relationship between task sets.

References Clément, G., Moudy, S. C., Macaulay, T. R., Bishop, M. O., & Wood, S. J. (2022). Missioncritical tasks for assessing risks from vestibular and sensorimotor adaptation during space exploration [Original Research]. Frontiers in Physiology, 13. https://doi.org/10.3389/fphys.2022.1029161

Reschke, M. F., Clément, G. R., Thorson, S. L., Mader, T. H., Dudley, A. M., Wood, S. J., Bloomberg, J. J., Mulavara, A. P., Gibson, C. R., & Williams, D. (2016). Neurology. In A. E. Nicogossian, R. S. Williams, C. L. Huntoon, C. R. Doarn, J. D. Polk, & V. S. Schneider (Eds.), Space Physiology and Medicine (4th ed., pp. 245-282). Springer.

Reschke, M. F., Kozlovskaya, I. B., Lysova, N., Kitov, V., Rukavishnikov, I., Kofman, I. S., Tomilovskaya, E. S., Rosenberg, M. J., Osetsky, N., Fomina, E., Grishin, A., & Wood, S. J. (2020). Joint Russian-USA Field Test: Implications for deconditioned crew following long duration spaceflight. Aerosp Environ Med, 54(6), 94-100.

Wood, S. J. (2002). Human otolith–ocular reflexes during off-vertical axis rotation: effect of frequency on tilt–translation ambiguity and motion sickness, Neuroscience Letters.Elsevier: Neuroscience Letters, 323(1), 41-44.

Wood, S. J., Reschke, M. F., & Owen Black, F. (2012). Continuous equilibrium scores: factoring in the time before a fall. Gait Posture, 36(3), 487-489. https://doi.org/10.1016/j.gaitpost.2012.04.014