Multiscale entropy in a 10-minute vigilance task.

Research has shown multiscale entropy, brain signal behavior across time scales, to reliably increase at lower time scales with time-on-task fatigue. However, multiscale entropy has not been examined in short vigilance tasks (i.e., ≤ 10 min). Addressing this gap, we examine multiscale entropy during a 10-minute Psychomotor Vigilance Test (PVT). Thirty-four participants provided neural data while completing the PVT. We compared the first 2 min of the task to the 7th and 8th minutes to avoid end-spurt effects. Results suggested increased multiscale entropy at lower time scales later compared to earlier in the task, suggesting multiscale entropy is a strong marker of time-on-task fatigue onset during short vigils. Separate analyses for Fast and Slow performers reveal differential entropy patterns, particularly over visual cortices. Here, observed brain-behavior linkage between entropy and reaction time for slow performers suggests that entropy assays over sensory cortices might have predictive value for fatigue onset or shifts from on- to off-task states.

Gamma Power as an Index of Sustained Attention in Simulated Vigilance Tasks.

Performance on the psychomotor vigilance test (PVT; Dinges & Powell, 1985)-a common index of sustained attention-is affected by the opposing forces of fatigue and sustained effort, where reaction times and error rates typically increase across trials and are sometimes offset by additional efforts deployed toward the end of the task (i.e., an "end-spurt"; cf. Bergum & Klein, 1961). In ACT-R (Adaptive Control of Thought-Rational; Anderson et al., 2004), these influences on task performance have been modeled as latent variables that are inferred from performance (e.g., Jongman, 1998; Veksler & Gunzelmann, 2018) without connections to directly observable variables. We propose the use of frontal gamma (γ) spectral power as a direct measure of vigilant effort and demonstrate its efficacy in modeling performance on the PVT in both the aggregate and in individuals.

Silver Lining Study: Missileer Fatigue Mitigation During 2020 Coronavirus Pandemic.

INTRODUCTION: The U.S. Air Force's Intercontinental Ballistic Missile (ICBM) force stands ready to launch weapons 365 days per year. Since its inception, missileers vigilantly operate launch consoles on a 3-day cycle: minimum 24-hour alert-shift/24-hour travel-admin/24-hour off, leading to concerns that health, morale, and alertness are chronically impacted. In 2020, a Missileer Occupational Health Assessment (OHA) revealed 76% of respondents struggle with being rested for duty and 29% of respondents never feel adequately rested for duty. Later that year, 20th Air Force initiated long-duration operations to safeguard from the SARS CoV-2 (COVID-19) Pandemic, resulting in increased operations tempo, and exacerbating crew fatigue.341st Operations Group and 341st Medical Group at Malmstrom Air Force Base enacted interventions to mitigate crew fatigue and support continued readiness during pandemic operations. They recorded, analyzed, and compiled findings in this report, including recommendations for long-term ICBM operations at Missile Wings. MATERIALS AND METHODS: All participants were Nuclear and Missile Operations Officers, or missileers, were continuously evaluated with qualitative and quantitative measures to ensure safety of the force during a period of unprecedented change. Interventions implemented and evaluated during the 9-month period included: environmental modifications, scheduling changes, and crew education on fatigue management, nutrition, anticipatory sleep preparation, and fitness. Most notably, the 341st Operations Group examined various 3-person and 4-person shift-length and alert duration schedules. Psychomotor vigilance testing results validated safety of operators and delta between pre- and post-shift measurements. Crew force readiness trends were analyzed for force-health awareness. Pre- and post-OHA results were compared for subjective changes. Fatigue and health-related outcomes were collected from a safety monitoring effort during standard and COVID-19 operations at 341st Missile Wing. RESULTS: Findings from qualitative and quantitative data indicate the optimal schedule is a 3-week cycle:7-day alert/7-day recovery/7-day training-administrative utilizing 4-member or 3-member crews for low tempo operations. Crews experimented with shift-lengths of 24hrs-on/24hrs-off, 16hrs-on/8hrs-off, and 12hrs-on/12hrs-off. Maximum safe alert duration is 7 days due to task fatigue onset between 8 and 10 days. Short and long duration Duties Not to Include Flight (DNIF) (also known as Duties Not to Include Alert (DNIA) among missileers) rates decreased from the first to last month of the period by 74.6% and 79.2%, respectively. The number of alerts missed per month decreased 86% from baseline. The 2021 OHA found a 7% decline in members seeking separation, and absence of sleep, fatigue, and physical or mental health as missileer concerns. CONCLUSIONS: This analysis has identified a sustainable alert rotation of 7/7/7 with emphasis on protected recovery and training time and has been continued after concluding pandemic operations, creating consistent schedule stability where there once was none. If executed properly, this alert rotation, regardless of shift-length selected, has potential to improve trust between crews and leadership, provides adequate recovery time between alerts to maintain health, and improves wellness, family stability, morale, unit cohesion, and crew force retention. Notably, all Air Force Global Strike Missile Operations Groups adjusted scheduling practices to align with these findings.

Profiling cognitive workload in an unmanned vehicle control task with cognitive models and physiological metrics.

In the present study, we use Cognitive Metrics Profiling (CMP) to capture variance in cognitive load within a complex unmanned vehicle control task. We aim to demonstrate convergent validity with existing workload measurement methods, and to decompose workload into constituent cognitive resources to aid in diagnosing causes of workload. A cognitive model of the task was developed and examined to determine the extent to which it could predict behavioral performance, subjective workload, and validated physiological workload metrics. We also examined model activity to draw insights regarding loaded cognitive capacities. We found that composite workload from the model predicted physiological metrics, performance, and subjective workload. Moreover, the model indicates that differences in workload were driven largely by procedural, declarative, and temporal memory demands. We have found preliminary evidence of correspondence between workload predictions of a CMP model and physiological measures of workload. This suggests our approach captures interesting aspects of workload in a complex task environment and may provide a theoretical link between behavioral, physiological, and subjective metrics. This approach may provide a means to design effective workload mitigation interventions and improve decision-making about personnel tasking and automation.

Effects of Sleep Deprivation on Performance during a Change Signal Task with Adaptive Dynamics.

Augmented cognition, which refers to real-time modifications to a human-system interface to improve performance and includes dynamic task environments with automated adaptations, can serve to protect against performance impairment under challenging work conditions. However, the effectiveness of augmented cognition as a countermeasure for performance impairment due to sleep loss is unknown. Here, in a controlled laboratory study, an adaptive version of a Change Signal task was administered repeatedly to healthy adults randomized to 62 h of total sleep deprivation (TSD) or a rested control condition. In the computerized task, a left- or right-facing arrow was presented to start each trial. In a subset of trials, a second arrow facing the opposite direction was presented after a delay. Subjects were to respond within 1000 ms of the trial start by pressing the arrow key corresponding to the single arrow (Go trials) or to the second arrow when present (Change trials). The Change Signal Delay (CSD)-i.e., the delay between the appearance of the first and second arrows-was shortened following incorrect responses and lengthened following correct responses so that subsequent Change trials became easier or harder, respectively. The task featured two distinct CSD dynamics, which produced relatively stable low and high error rates when subjects were rested (Low and High Error Likelihood trials, respectively). During TSD, the High Error Likelihood trials produced the same, relatively high error rate, but the Low Error Likelihood trials produced a higher error rate than in the rested condition. Thus, sleep loss altered the effectiveness of the adaptive dynamics in the Change Signal task. A principal component analysis revealed that while subjects varied in their performance of the task along a single dominant dimension when rested, a second inter-individual differences dimension emerged during TSD. These findings suggest a need for further investigation of the interaction between augmented cognition approaches and sleep deprivation in order to determine whether and how augmented cognition can be relied upon as a countermeasure to performance impairment in operational settings with sleep loss.

Vigilance end-spurt patterns in event-related potentials.

The end-spurt effect, where performance declines with time-on-task and then increases toward the end of a task, has garnered little attention in the vigilance literature. Researchers have suggested the performance enhancement is due to increased motivation or arousal with knowledge of the end of the vigil. However, recent examination of neural signature patterns during a simultaneous discrimination task, where task length was unknown, provided preliminary support that the end-spurt reflects pacing of resources. The current effort expands this previous work to an additional simultaneous task and to a successive discrimination task across two sessions, one where task length was not known and one where task length was known. Twenty-eight (Study 1) and a separate 24 (Study 2) participants completed a Simultaneous Radar task (Study 1) in one session and Simultaneous and Successive Lines tasks (Study 2) across two sessions while neural data was collected. Several event-related potentials exhibited non-monotonic patterns during the vigilance tasks, in some cases reflecting end-spurt patterns, but more commonly reflecting higher-order polynomial patterns. These patterns were more prevalent in anterior regions as opposed to posterior regions. Of note, the N1 anterior exhibited consistent general patterns across all the vigilance tasks and across sessions. Importantly, even when participants had knowledge of session length, some ERPs still exhibited higher-order polynomial trends, suggesting pacing rather than an end-spurt from motivation or arousal as the vigil ends. These insights can help inform predictive modeling of vigilance performance and the implementation of mitigation efforts to allay the vigilance decrement.

Aircrew Actual vs. Prescriptive Sleep Schedules and Resulting Fatigue Estimates.

BACKGROUND: Fatigue is an insidious and costly occurrence in the aviation community, commonly a consequence of insufficient sleep. Some organizations use scheduling tools to generate prescriptive sleep schedules to help aircrew manage their fatigue. It is important to examine whether aircrew follow these prescriptive schedules, especially in very dynamic environments. The current study compares aircrew sleep during missions to prescriptive sleep schedules generated by a mission scheduling tool. METHODS: Participating in the study were 44 volunteers (Mage= 28.23, SDage= 4.23; Proportionmale= 77.27%) from a C-17 mobility squadron providing 25 instances of sleep and mission data (80 flights total). Aircrew wore actigraph watches to measure sleep during missions and prescriptive sleep schedules were collected. Actual and prescriptive sleep was compared with calculated performance effectiveness values per minute across mission flights. RESULTS: Prescriptive schedules generally overestimated effectiveness during missions relative to estimated actual sleep, potentially causing shifts in effectiveness to ranges of increased risk requiring elevated fatigue mitigation efforts. Actual and prescriptive effectiveness estimates tended to increasingly diverge over the course of missions, which magnifies differences on longer missions. DISCUSSION: The current study suggests that aircrew sleep during missions often does not align with prescriptive sleep schedules generated by mission planning software, resulting in effectiveness estimates that are generally lower than predicted. This might discourage aircrew from using mission effectiveness graphs as a fatigue mitigation tool. Additionally, because fatigue estimates factor into overall operational risk management processes, these schedules might underestimate risks to safety, performance, and health. Morris MB, Veksler BZ, Krusmark MA, Gaines AR, Jantscher HL, Gunzelmann G. Aircrew actual vs. prescriptive sleep schedules and resulting fatigue estimates. Aerosp Med Hum Perform. 2021; 92(10):806814.

Aircrew Fatigue Perceptions, Fatigue Mitigation Strategies, and Circadian Typology.

BACKGROUND: Human fatigue is an important factor within aviation, leading organizations to develop strategies to assess and mitigate associated risks. The U.S. Air Force's Air Mobility Command (AMC) conducted the current pilot study to assess fatigue-related risks and issues in mobility operations. Specifically, we examined the relationship among fatigue perceptions, fatigue mitigation strategies, performance effectiveness graph reference, and circadian typology.METHODS: There were 21 volunteers from the Joint Base Charleston C-17 pilot community (Mage = 28.67; SDage = 2.11; Proportionmale = 85.71%) who completed a survey. Items referred to fatigue perceptions, fatigue mitigation strategies, performance effectiveness graph reference, and circadian typology. We examined descriptive statistics, correlations among the variables of interest, and possible moderation effects of circadian typology.RESULTS: Overall, aircrew perceived fatigue to be a serious safety of flight concern. Personal fatigue concerns and perceptions of pressure to continue missions despite fatigue were associated with increased use of the strategy of limiting light exposure during sleep episodes (r = 0.49 and 0.47). Fatigue perceptions were not directly associated with performance effectiveness graph usage. Results suggested that morning type participants might be more likely to utilize specific fatigue mitigation strategies when there are concerns of fatigue compared to evening types.DISCUSSION: Despite organizational efforts, fatigue continues to be a serious concern for the mobility community. This pilot study suggests that circadian typology might affect the relationship between fatigue perceptions and fatigue mitigation strategies and resource use. Future research should further examine these relationships and their impact within fatigue risk management (FRM) programs.Morris MB, Howland JP, Amaddio KM, Gunzelmann G. Aircrew fatigue perceptions, fatigue mitigation strategies, and circadian typology. Aerosp Med Hum Perform. 2020; 91(4):363-368.

Fatigue-Related Aviation Mishaps.

INTRODUCTION: Fatigue is a critical safety issue to U.S. Air Force (USAF) flight and ground crew. Nearly 15 yr of mishap reports were analyzed to determine how fatigue affects USAF operations with the goal of improving fatigue risk management policies and tools.METHODS: Summary data for 19,920 aviation mishap reports dating back to 2003 were collected from the Air Force Safety Automated System (AFSAS). Fatigue-related mishaps were identified based on designations provided within AFSAS. Other metrics examined were characteristics such as timing, cost, and aircraft metrics, among others. Contingency tables built from these metrics were used to assess fatigue-related trends across the aviation community.RESULTS: While only 3.88% of all mishaps were identified as fatigue-related, they are associated with 2.1 billion of medical expenses and property damage, or 18% of the 11.7 billion total cost of all mishaps included in the study. Nearly a quarter of the fatigue-related mishaps fall into the most severe mishap category and more than half occurred between 0100 and 0700, local time. Fatigue-related mishaps tended to be more common for Remotely Piloted Aircraft (RPA) and ground operations.DISCUSSION: Fatigue is very costly to the USAF despite the relatively low incidence rate of fatigue-related mishaps. This is because larger proportions of severe mishaps were found to be fatigue-related. RPA and ground maintenance operators might be especially susceptible to fatigue and potentially lack adequate fatigue mitigation support and training tailored to their unique operational environment, suggesting a need to improve upon fatigue mitigation tools and strategies.Gaines AR, Morris MB, Gunzelmann G. Fatigue-related aviation mishaps. Aerosp Med Hum Perform. 2020; 91(5):440447.

Fatigue Incident Antecedents, Consequences, and Aviation Operational Risk Management Resources.

BACKGROUND: Flight crew fatigue is an important factor in aviation, leading organizations to implement fatigue risk management programs to reduce risk. The U.S. Air Force Air Mobility Command (AMC) has implemented the Aviation Operational Risk Management (AvORM) program to aid mission schedulers and flight crews in mitigating flight risks and identifying appropriate levels of risk. The AvORM program uses a scheduling tool and underpinning biomathematical fatigue model. This study examined self-reported fatigue-related incidents within AMC, which provides some indirect and anecdotal evidence as to the effectiveness of the scheduling tool. METHODS: Archival data from the AMC Aviation Safety Action Program (ASAP) Safety Reporting System was examined. Report content themes were created through an inductive approach in terms of fatigue prevalence, antecedents, and consequences. RESULTS: Fatigue was estimated as a factor in 4% of the reports. The two most commonly referenced fatigue antecedents were associated with mission/duty length and mission scheduling/planning factors. Factors associated with aircraft operation violations were the most cited consequences of fatigue. Fatigue was almost twice as likely to be reported as a secondary rather than primary contributing factor. Aircrew reported both positive and negative aspects of AvORM resources in mission planning and fatigue mitigation. DISCUSSION: Examination of ASAP reports suggests that fatigue is a contributing factor to safety incidents. Although the AvORM program highlights potential flight risks by utilizing a scheduling tool built upon an underlying biomathematical fatigue model, human fatigue continues to impact safety, suggesting an ongoing need for improved fatigue risk management and mitigation.Morris MB, Wiedbusch MD, Gunzelmann G. Fatigue incident antecedents, consequences, and aviation operational risk management resources. Aerosp Med Hum Perform. 2018; 89(8):708-716.