The effects of time of day and circadian rhythm on performance during variable levels of cognitive workload

The present study examined the effects of time of day of testing on a simulated aviation task. The tasks required the participants to engage in multitasking while electroencephalogram (EEG) data was collected to objectively measure participants’ workload. Task demands were altered throughout the testing period to expose participants to both high and low workload conditions. Additionally, individual differences in circadian rhythm were explored by assessing participants’ circadian typology. No significant differences in performance were found resulting from time of day differences. However, performance and EEG differences were found based on phase of testing and workload manipulations. Subjective workload measures were influenced by time of day, with a moderating effect of circadian typology. Implications are discussed

Measuring aviator workload using EEG: an individualized approach to workload manipulation

IntroductionMeasuring an operator's physiological state and using that data to predict future performance decrements has been an ongoing goal in many areas of transportation. Regarding Army aviation, the realization of such an endeavor could lead to the development of an adaptive automation system which adapts to the needs of the operator. However, reaching this end state requires the use of experimental scenarios similar to real-life settings in order to induce the state of interest that are able to account for individual differences in experience, exposure, and perception to workload manipulations. In the present study, we used an individualized approach to manipulating workload in order to account for individual differences in response to workload manipulations, while still providing an operationally relevant flight experience.MethodsEight Army aviators participated in the study, where they completed two visits to the laboratory. The first visit served the purpose of identifying individual workload thresholds, with the second visit resulting in flights with individualized workload manipulations. EEG data was collected throughout both flights, along with subjective ratings of workload and flight performance.ResultsBoth EEG data and workload ratings suggested a high workload. Subjective ratings were higher during the high workload flight compared to the low workload flight (p < 0.001). Regarding EEG, frontal alpha (p = 0.04) and theta (p = 0.01) values were lower and a ratio of beta/(alpha+theta) (p = 0.02) were higher in the baseline flight scenario compared to the high workload scenario. Furthermore, the data were compared to that collected in previous studies which used a group-based approach to manipulating workload.DiscussionThe individualized method demonstrated higher effect sizes in both EEG and subjective ratings, suggesting the use of this method may provide a more reliable way of producing high workload in aviators

Limitations associated with transcranial direct current stimulation for enhancement: considerations of performance tradeoffs in active-duty Soldiers

IntroductionTranscranial direct current stimulation (tDCS) is a non-invasive brain stimulation method, popular due to its low cost, ease-of-application, and portability. As such, it has gained traction in examining its potential for cognitive enhancement in a diverse range of populations, including active-duty military. However, current literature presents mixed results regarding its efficacy and limited evaluations of possible undesirable side-effects (such as degradation to cognitive processes).MethodsTo further examine its potential for enhancing cognition, a double-blind, randomized, sham-controlled, within-subjects design, was used to evaluate both online active-anodal and -cathodal on several cognitive tasks administered. Potential undesirable side effects related to mood, sleepiness, and cognitive performance, were also assessed. Active tDCS was applied for 30 min, using 2 mA, to the left dorsolateral prefrontal cortex with an extracephalic reference placed on the contralateral arm of 27 (14 males) active-duty Soldiers.ResultsWe report mixed results. Specifically, we found improvements in sustained attention (active-anodal) for males in reaction time (p = 0.024, ηp2 = 0.16) and for sensitivity index in females (p = 0.013, ηp2 = 0.18). In addition, we found faster reaction time (p = 0.034, ηp2 = 0.15) and increased accuracy (p = 0.029, ηp2 = 0.16) associated with executive function (active-anodal and -cathodal), and worsened working memory performance (active-cathodal; p = 0.008, ηp2 = 0.18). Additionally, we found increased risk-taking with active-anodal (p = 0.001, ηp2 = 0.33).DiscussiontDCS may hold promise as a method for cognitive enhancement, as evidenced by our findings related to sustained attention and executive function. However, we caution that further study is required to better understand additional parameters and limitations that may explain results, as our study only focused on anode vs. cathode stimulation. Risk-taking was examined secondary to our main interests which warrants further experimental investigation isolating potential tradeoffs that may be associated with tDCS simulation

Neuroenhancement in Military Personnel::Conceptual and Methodological Promises and Challenges

Military personnel face harsh conditions that strain their physical and mental well-being, depleting resources necessary for sustained operational performance. Future operations will impose even greater demands on soldiers in austere environments with limited support, and new training and technological approaches are essential. This report highlights the progress in cognitive neuroenhancement research, exploring techniques such as neuromodulation and neurofeedback, and emphasizes the inherent challenges and future directions in the field of cognitive neuroenhancement for selection, training, operations, and recovery

Swarm Observations of Dawn/Dusk Asymmetries Between Pedersen Conductance in Upward and Downward Field-Aligned Current Regions

The locations of region 1 and 2 field-aligned current systems were determined using fluxgate magnetometer measurements from 875 dawn-dusk passes of the Swarm A satellite. Within each field-aligned current region, the ionospheric Pedersen conductance was derived from the newly corrected Swarm electric and magnetic field measurements. The Pedersen conductances are generally consistent with photoionization models. However, we show that the in situ method of determining Pedersen conductance allows for a more complete description of magnetosphere-ionosphere coupling and should be used in future studies when possible. We show that, overall, the Pedersen conductance is larger in the upward current region than in the downward region by ∼0.6 S on the dawn side of the Earth. Meanwhile, the dusk side Pedersen conductance is equivalent in both current regions. We attribute this asymmetry to dawn side energetic electron precipitation, commonly associated with substorm electron injections from the magnetotail

Neuroenhancement in Military Personnel: Conceptual and Methodological Promises and Challenges

Military personnel are subjected to prolonged operations in harsh and undesirable conditions characterized by severe environmental exposures, resource scarcity, and physical and mental encumbrance. Prolonged military operations under these conditions can degrade the already limited perceptual, cognitive, and emotional resources necessary to sustain performance on mission-related tasks. The complex multi-domain operations of the future battlespace are expected to further increase demands at even the lowest levels of the military echelon. These demands will be characterized with increasingly prolonged operations of small units in austere environments with limited resupply and degraded technological capabilities. It is therefore critical to identify new training and technological approaches to enable sustained, optimized, and/or enhanced performance of military personnel. Research in the international defence science community, academia, and industry has developed several promising neuroscientific strategies for pursuing this goal, including neuromodulatory and neurofeedback techniques. The present paper reviews the state of the art in cognitive neuroenhancement research and development from six participating nations: Canada, Germany, Italy, The Netherlands, United Kingdom, and the United States of America. Six neuromodulation techniques are reviewed, including transcranial magnetic stimulation (TMS), transcranial focused ultrasound stimulation (tFUS), transcranial electrical stimulation (tES), transcutaneous peripheral nerve stimulation (tPNS), photobiomodulation, and cranial electrotherapy stimulation (CES). Three neurofeedback techniques are considered, including the use of electroencephalography (EEG), functional magnetic resonance imaging (fMRI), and functional near-infrared spectroscopy (fNIRS) for monitoring brain states, with feedback loops enabled through machine learning and artificial intelligence. Participating nations summarize basic and applied research leveraging one or more of these neuromodulation and neurofeedback technologies for the purposes of enhancing Warfighter cognitive performance. The report continues by detailing the inherent methodological challenges of cognitive neuroenhancement and other considerations for conducting research, development, and engineering in this domain. The report concludes with a discussion of promising future directions in neuroenhancement, including biosensing, improved mechanistic and predictive modelling and software tools, developing non-invasive forms of deep-brain stimulation, testing emerging theoretical models of brain and behavior, and developing closed-loop neuroenhancement and humanmachine teaming methods. Emphasis is placed on the conceptual and methodological promises and challenges associated with planning, executing, and interpreting neuroenhancement research and development efforts in the context of Warfighter selection, training, operations, and recovery

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