Transcranial Direct Current Stimulation and Aviator Performance During Simulated Flight.

INTRODUCTION: Transcranial direct current stimulation (tDCS) is a promising method for maintaining cognitive performance. Anticipated changes in rotary-wing aircraft are expected to alter aviator performance.METHODS: A single-blind, randomized, sham-controlled study evaluated effects of 2-mA anodal tDCS to the right posterior parietal cortex on aviator performance within a Black Hawk simulator. A mixed design with one between-subjects factor was assessed: stimulation prior to flight (20 constant min) and during flight (two timepoints for 10 min each). The within-subjects factor included active vs. sham stimulation. Randomly assigned to each stimulation group were 22 aviators. Aircraft state metrics derived from the simulator were used to evaluate performance. Subjects completed two flights (active stimulation and sham stimulation) with an in-flight emergency introduced at the end to assess whether the timing of tDCS application (prior or during flight) affected the ability to maintain attention and respond to an unexpected event.RESULTS: Results found active stimulation during flight produced statistically significant improvements in performance during the approach following the in-flight emergency. Subjects maintained a more precise approach path with glideslope values closer to zero (M = 0.05) compared to the prior-to-flight group (M = 0.15). The same was found for localizer values (during flight, M = 0.07; prior to flight, M = 0.17). There were no statistically significant differences between groups on secondary outcome measures.DISCUSSION: These findings suggest stimulation during flight may assist in maintaining cognitive resources necessary to respond to an unexpected in-flight emergency. Moreover, blinding efficacy was supported with 32% of subjects correctly guessing when active stimulation was being delivered (52% correctly guessed the sham condition).Feltman KA, Kelley AM. Transcranial direct current stimulation and aviator performance during simulated flight. Aerosp Med Hum Perform. 2024; 95(1):5-15.

What Is Targeted When We Train Working Memory? Evidence From a Meta-Analysis of the Neural Correlates of Working Memory Training Using Activation Likelihood Estimation.

Working memory (WM) is the system responsible for maintaining and manipulating information, in the face of ongoing distraction. In turn, WM span is perceived to be an individual-differences construct reflecting the limited capacity of this system. Recently, however, there has been some evidence to suggest that WM capacity can increase through training, raising the possibility that training can functionally alter the neural structures supporting WM. To address the hypothesis that the neural substrates underlying WM are targeted by training, we conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of WM training using Activation Likelihood Estimation (ALE). Our results demonstrate that WM training is associated exclusively with decreases in blood oxygenation level-dependent (BOLD) responses in clusters within the fronto-parietal system that underlie WM, including the bilateral inferior parietal lobule (BA 39/40), middle (BA 9) and superior (BA 6) frontal gyri, and medial frontal gyrus bordering on the cingulate gyrus (BA 8/32). We discuss the various psychological and physiological mechanisms that could be responsible for the observed reductions in the BOLD signal in relation to WM training, and consider their implications for the construct of WM span as a limited resource.

A new approach to manipulating aviator workload: A case for individualizing workload manipulations.

The present study sought to manipulate workload individually for participants to evaluate whether individual manipulations of workload produces similar subjective ratings and performance changes across participants. Participants included eight Army-rated rotary-wing aviators who presented to the laboratory for two separate visits. During the first visit, individual responses to workload were determined, and during the second visit, individually manipulated high workload flights were completed. Outcome measures included flight performance and subjective workload ratings. Data were examined at the group and individual level. Subjective ratings of workload endorsed the individual workload manipulations, while performance data provided some additional support. By taking an individualized approach such as this, researchers and practitioners may be better able to control for individual differences influencing workload. This has important implications for system design and testing, development of new intervention technologies, and assessing methods for operator monitoring.

Aircrew Performance and Safety While Using Protective Masks in Response to Coronavirus Disease.

INTRODUCTION: In response to the urgent need for safe aircrew respiratory protection due to the COVID-19 pandemic, three small descriptive evaluations were conducted with aircrew and air traffic controllers (ATC) that assessed the impact of mask use on safety and performance onboard rotary wing aircraft.METHODS: A series of evaluations assessed aircrew performance using the 3MTM Model 1860 N95 respiratory protection mask, two aviation-specific cloth mask prototypes, and a commercial off-the-shelf aviation-specific cloth mask. The series of evaluations included different sets of subjects consisting of up to five Black Hawk helicopter aircrew members, air traffic control (ATC), and 12 CH-47 aircrew members. The Modified Rhyme Test was used to measure speech intelligibility and was administered in the UH-60 among crewmembers of the same aircraft, between pilots of different aircraft, and between the pilots and ATC. Measures of workload, usability, comfort, and pulse oximetry were also administered.RESULTS: Results from the Modified Rhyme Test indicated that all subjects scored greater than 80% accuracy given the proper microphone positioning relative to the mask. With respect to workload, NASA-TLX total scores for the perform radio communications task was 50.83.DISCUSSION: Despite an elevated perceived degree of workload on the communications flight task, results from the speech intelligibility test indicated that performance was maintained within the acceptable range as defined by MIL-STD-1474E, Design Criteria Standard Noise Limit. This abbreviated evaluation suggests that the face masks tested are safe for use by helicopter aircrew under the conditions tested.Cave KM, Kelley AM, Feltman KA, Gerstner JA, Stewart JL, Crowley JS. Aircrew performance and safety while using protective masks in response to coronavirus disease. Aerosp Med Hum Perform. 2021; 92(4):274280.

Measuring the Domain Specificity of Workload Using EEG: Auditory and Visual Domains in Rotary-Wing Simulated Flight.

OBJECTIVE: The overarching objective was to evaluate whether workload sensory-domain specificity could be identified through electroencephalogram (EEG) recordings during simulated rotary-wing operations. BACKGROUND: Rotary-wing aviators experience workload from different sensory domains, although predominantly through auditory and visual domains. Development of real-time monitoring tools using psychophysiological indices, such as EEG recordings, could enable identification of aviator overload in real time. METHOD: Two studies were completed, both of which recorded EEG, task performance, and self-report data. In Study 1, 16 individuals completed a basic auditory and a basic visual laboratory task where workload was manipulated. In Study 2, 23 Army aviators completed simulated aviation flights where workload was manipulated within auditory and visual sensory domains. RESULTS: Results from Study 1 found differences in frontal alpha activity during the auditory task, and that alpha and beta activities were associated with perceived workload. Frontal theta activity was found to differ during the visual task while frontal alpha was associated with perceived workload. Study 2 found support for frontal beta activity and the ratio of beta to alpha + theta to differentiate level of workload within the auditory domain. CONCLUSION: There is likely a role of frontal alpha and beta activities in response to workload manipulations within the auditory domain; however, this role becomes more equivocal when examined in a multifaceted flight scenario. APPLICATION: Results from this study provide a basis for understanding changes in EEG activity when workload is manipulated in sensory domains that can be used in furthering the development of real-time monitoring tools.

Viability of tDCS in Military Environments for Performance Enhancement: A Systematic Review.

INTRODUCTION: Transcranial electrical stimulation (tES) as a method of cognitive enhancement in both diseased and healthy individuals has gained popularity. Its potential for enhancing cognition in healthy individuals has gained the interest of the military. However, before it being implemented into military training or operational settings, further work is needed to determine its efficacy and safety. Although a considerable amount of literature exists, few studies have specifically evaluated its use in enhancing cognition relative to operational, military tasks. Therefore, in a first step to evaluate its efficacy, we completed a systematic literature review of studies using transcranial direct current stimulation (tDCS), a type of tES, to enhance cognitive processes in healthy individuals. METHODS: A systematic literature review was conducted to identify literature published between 2008 and 2018 that used a method of tES for cognitive enhancement. As part of a larger literature review effort, 282 articles were initially retrieved. These were then screened to identify articles meeting predetermined criteria, to include those using various methods of tES, resulting in 44 articles. Next, the articles were screened for those using tDCS or high-definition tDCS, resulting in 34 articles for review and information extraction. RESULTS: Of the 34 articles reviewed, 28 reported some degree of enhancement (eg, improved accuracy on tasks and reduced reaction times). Areas of cognitive enhancements included executive functioning, creativity/cognitive flexibility, attention/perception, decision-making, memory, and working memory. However, the precise outcomes of enhancement varied given the range in tasks that were used to assess the constructs. Additionally, the stimulation parameters in terms of intensity applied, duration of stimulation, and brain region targeted for stimulation varied. CONCLUSIONS: The conclusions to be drawn from this systematic literature review include the identification of a brain region for targeting with stimulation to enhance a broad range of cognitive constructs applicable to military tasks, as well as stimulation parameters for duration and intensity. The dorsolateral prefrontal cortex was most frequently targeted in the studies that found enhanced performance across several cognitive constructs. Stimulation intensities of 2 mA and durations of 20 minutes or longer appeared frequently as well. Although several parameters were identified, further work is required before this type of technology can be recommended for operational use.

Rest and Activity Patterns of Army Aviators in Routine and Operational Training Environments.

INTRODUCTION: Fatigue continues to be a leading cause of military aviation mishaps. Several factors, including reversed shift missions, can negatively affect sleep patterns and increase the risk of fatigue due to sleep restriction. Currently, there is a lack of objective data regarding the current rest and activity patterns of military aviators across multiple operational conditions. The purpose of this descriptive study was to document the rest and activity patterns of U.S. Army aviators in operational training and garrison (routine) environments using wrist-worn actigraphy devices.METHODS: Actigraphy data were collected from U.S. Army aviators in training (N = 20) and garrison (N = 77) environments for a period of 1 wk.RESULTS: Results from this study indicate that 90% of subjects in the training environment, even after accounting for small sleep bouts during the day, averaged less than the recommended 8 h of sleep daily across the recording week. Approximately half of subjects in garrison averaged less than 8 h of sleep daily after accounting for smaller sleep bouts. Sleep efficiency was relatively high and similar in both groups (∼84%). Subjects in the training group averaged significantly more time awake and less time sleeping than those in the routine garrison group. Moreover, subjects in training were exposed to more light during sleep than those in garrison.DISCUSSION: Training environments that are representative of deployed conditions restrict aviator restorative sleep. These results highlight the importance of continued research on aviator sleep and fatigue mitigation in operational environments.Bernhardt KA, Kelley AM, Feltman KA, Curry IP. Rest and activity patterns of Army aviators in routine and operational training environments. Aerosp Med Hum Perform. 2019; 90(1):48-52.

Army Aviators' Perceptions of Advanced Cockpit Aircraft.

BACKGROUND: Perceptions of features of automation, such as its safety and effects on basic flying skills, can shape how someone uses automation and accepts newly developed technology. The purpose of the present study was to evaluate current U.S. Army rotary-wing aviators' perspectives of cockpit automation in terms of safety features and effects on the retention of basic flying skills. In doing so, future lines of research can utilize this information to develop programs for the transitioning and training of advanced aircraft into the Army.METHODS: An anonymous, 125-item questionnaire was completed by 214 U.S. Army aviators. A subset of five items related to perceptions of automation were examined based on experience level and are reported here. The majority of subjects were male aviators with a mean age of 33 yr.RESULTS: Results suggest a difference in perceptions of some of the safety features, with 8 and 12% more of the experienced pilots reporting safety concerns on two items. A 13% difference in the perceptions of effects of automation on skills retention items were found based on experience level. More experienced aviators' responses identified possible distrust of several automation features.DISCUSSION: The findings of this survey identified perspectives of automation which differed based on experience level. Specifically, more experienced individuals indicated some distrust of automation features and a possible overconfidence in basic flying skills. This can be used to further develop research aimed at the transition of advanced technology to aviators.Feltman KA, Kelley AM, Curry IP. Army aviators' perceptions of advanced cockpit aircraft. Aerosp Med Hum Perform. 2018; 89(12):1080-1084.

A Survey of Fatigue in Army Aviators.

INTRODUCTION: Fatigue plays a critical role in mission success due to its effect on a number of performance variables. The purpose of this study was to gauge the extent to which U.S. Army aviators experience subjective fatigue on a regular basis presently as well as their perceptions of their own sleep quality, quantity, and daytime sleepiness. This information is valuable for prioritizing future research lines with respect to injury prevention and fatigue management as well as updating policy. METHODS: An anonymous, 125-item questionnaire was completed by 214 U.S. Army aviators. A subset of those items (15 questions related to fatigue) are reported in this study. Subjects were primarily male and the mean age was 33 yr. RESULTS: Results suggest that the majority of subjects sleep less than the recommended 8 h per night and nearly half of them report sleeping less than their own preferred amount of sleep. Approximately 40% of the sample indicated that they believed fatigue to be a widespread problem in the U.S. Army aviation community. DISCUSSION: Overall, the findings identified factors contributing to fatigue and performance degradation currently experienced by those sampled in this study. Specifically, inconsistent shiftwork, less than optimal levels of rest, and poor sleep quality in the field were identified. Compared to past research, the extent to which fatigue is perceived to be a widespread problem is significantly lower than reported 15 yr prior.Kelley AM, Feltman KA, Curry IP. A survey of fatigue in army aviators. Aerosp Med Hum Perform. 2018; 89(5):464-468.