Characterizing Relationships Among the Cognitive, Physical, Social-emotional, and Health-related Traits of Military Personnel.

INTRODUCTION: Personnel engaged in high-stakes occupations, such as military personnel, law enforcement, and emergency first responders, must sustain performance through a range of environmental stressors. To maximize the effectiveness of military personnel, an a priori understanding of traits can help predict their physical and cognitive performance under stress and adversity. This work developed and assessed a suite of measures that have the potential to predict performance during operational scenarios. These measures were designed to characterize four specific trait-based domains: cognitive, health, physical, and social-emotional. MATERIALS AND METHODS: One hundred and ninety-one active duty U.S. Army soldiers completed interleaved questionnaire-based, seated task-based, and physical task-based measures over a period of 3-5 days. Redundancy analysis, dimensionality reduction, and network analyses revealed several patterns of interest. RESULTS: First, unique variable analysis revealed a minimally redundant battery of instruments. Second, principal component analysis showed that metrics tended to cluster together in three to five components within each domain. Finally, analyses of cross-domain associations using network analysis illustrated that cognitive, health, physical, and social-emotional domains showed strong construct solidarity. CONCLUSIONS: The present battery of metrics presents a fieldable toolkit that may be used to predict operational performance that can be clustered into separate components or used independently. It will aid predictive algorithm development aimed to identify critical predictors of individual military personnel and small-unit performance outcomes.

Electrophysiological correlates of perceptual prediction error are attenuated in dyslexia.

A perceptual adaptation deficit often accompanies reading difficulty in dyslexia, manifesting in poor perceptual learning of consistent stimuli and reduced neurophysiological adaptation to stimulus repetition. However, it is not known how adaptation deficits relate to differences in feedforward or feedback processes in the brain. Here we used electroencephalography (EEG) to interrogate the feedforward and feedback contributions to neural adaptation as adults with and without dyslexia viewed pairs of faces and words in a paradigm that manipulated whether there was a high probability of stimulus repetition versus a high probability of stimulus change. We measured three neural dependent variables: expectation (the difference between prestimulus EEG power with and without the expectation of stimulus repetition), feedforward repetition (the difference between event-related potentials (ERPs) evoked by an expected change and an unexpected repetition), and feedback-mediated prediction error (the difference between ERPs evoked by an unexpected change and an expected repetition). Expectation significantly modulated prestimulus theta- and alpha-band EEG in both groups. Unexpected repetitions of words, but not faces, also led to significant feedforward repetition effects in the ERPs of both groups. However, neural prediction error when an unexpected change occurred instead of an expected repetition was significantly weaker in dyslexia than the control group for both faces and words. These results suggest that the neural and perceptual adaptation deficits observed in dyslexia reflect the failure to effectively integrate perceptual predictions with feedforward sensory processing. In addition to reducing perceptual efficiency, the attenuation of neural prediction error signals would also be deleterious to the wide range of perceptual and procedural learning abilities that are critical for developing accurate and fluent reading skills.

ERP Mismatch Negativity Amplitude and Asymmetry Reflect Phonological and Rapid Automatized Naming Skills in English-Speaking Kindergartners.

The mismatch negativity (MMN), an electrophysiological response to an oddball auditory stimulus, is related to reading ability in many studies. There are conflicting findings regarding exactly how the MMN relates to risk or actual diagnosis of dyslexia/reading impairment, perhaps due to the heterogeneity of abilities in children with reading impairment. In this study, 166 English-speaking kindergarten children oversampled for dyslexia risk completed behavioral assessments and a speech-syllable MMN paradigm. We examined how early and late MMN mean amplitude and laterality were related to two established predictors of reading ability: phonological awareness (PA) and rapid automatized naming (RAN). In bootstrapped group analyses, late MMN amplitude was significantly greater in children with typical PA ability than low PA ability. In contrast, laterality of the early and late MMN was significantly different in children with low versus typical RAN ability. Continuous analyses controlling for child age, non-verbal IQ, and letter and word identification abilities showed the same associations between late MMN amplitude with PA and late MMN laterality with RAN. These findings suggest that amplitude of the MMN may relate to phonological representations and ability to manipulate them, whereas MMN laterality may reflect differences in brain processes that support automaticity needed for reading.

Load Carriage and Physical Exertion Influence Cognitive Control in Military Scenarios.

INTRODUCTION: Physical exertion has both beneficial and detrimental effects on cognitive performance, particularly cognitive control. Research into physical exertion under conditions of load carriage is particularly important given that military personnel and first responders must perform optimally under such combinatorial physical stressors. The present work sought to characterize cognitive control as a function of physical exertion and load carriage in a military operational scenario. METHODS: Thirty-one active-duty soldiers underwent a 4-h operationally relevant and fatiguing scenario that included two 1-h foot marches under load carriage conditions of 8.8, 47.2, 50.7 kg on each of three separate days. During each foot march, they completed five 5-min blocks of an auditory go/no-go task of response inhibition. RESULTS: Results showed that response inhibition declined with increasing load carriage and physical exertion, as evidenced by lower proportion of correct responses, higher proportion of false alarms, and lower response sensitivity between all three load conditions, particularly upon successive foot marches and time blocks within each foot march. CONCLUSIONS: The results support previous laboratory-based work on load carriage and physical exertion and suggest that deteriorations in cognitive control witnessed in laboratory settings are more pronounced within realistic operational scenarios akin to those encountered by military personnel and first responders.

Exerting cognitive control under threat: Interactive effects of physical and emotional stress.

Individuals with stressful occupations, such as law enforcement and military personnel, are required to operate in high stakes environments that can be simultaneously physically and emotionally demanding. These individuals are tasked with maintaining peak performance under stressful and often unpredictable conditions, exerting high levels of cognitive control to sustain attention and suppress task-irrelevant actions. Previous research has shown that physical and emotional stressors differentially influence such cognitive control processes. For example, physical stress impairs while emotional stress facilitates the ability to inhibit a prepotent response, yet, interactions between the two remain poorly understood. Here we examined whether emotional stress induced by threat of unpredictable electric shock mitigates the effects of physical stress on response inhibition. Participants performed an auditory Go/NoGo task under safe versus threat conditions while cycling at high intensity (84% HRmax) for 50 min. In threat conditions, participants were told they would receive mild electric shocks that were unpredictable and unrelated to task performance. Self-reported anxiety increased under threat versus safe conditions, and perceived exertion increased with exercise duration. As predicted, we observed decrements in response inhibition (increased false alarms) as exertion increased under safe conditions, but improved response inhibition as exertion increased under threat conditions. These findings are consistent with previous work showing that anxiety induced by unpredictable threat promotes adaptive survival mechanisms, such as improved vigilance, threat detection, cautious behavior, and harm avoidance. Here, we suggest that emotional stress induced by unpredictable threat can also mitigate decrements in cognitive performance experienced under physically demanding conditions. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Endurance Exercise Enhances Emotional Valence and Emotion Regulation.

Acute exercise consistently benefits both emotion and cognition, particularly cognitive control. We evaluated acute endurance exercise influences on emotion, domain-general cognitive control and the cognitive control of emotion, specifically cognitive reappraisal. Thirty-six endurance runners, defined as running at least 30 miles per week with one weekly run of at least 9 miles (21 female, age 18-30 years) participated. In a repeated measures design, participants walked at 57% age-adjusted maximum heart rate (HRmax; range 51%-63%) and ran at 70% HRmax (range 64%-76%) for 90 min on two separate days. Participants completed measures of emotional state and the Stroop test of domain-general cognitive control before, every 30 min during and 30 min after exercise. Participants also completed a cognitive reappraisal task (CRT) after exercise. Functional near-infrared spectroscopy (fNIRS) tracked changes in oxygenated and deoxygenated hemoglobin (O2Hb and dHb) levels in the prefrontal cortex (PFC). Results suggest that even at relatively moderate intensities, endurance athletes benefit emotionally from running both during and after exercise and task-related PFC oxygenation reductions do not appear to hinder prefrontal-dependent cognitive control.

Different profiles of decision making and physiology under varying levels of stress in trained military personnel.

Decision making is one of the most vital processes we use every day, ranging from mundane decisions about what to eat to life-threatening choices such as how to avoid a car collision. Thus, the context in which our decisions are made is critical, and our physiology enables adaptive responses that account for how environmental stress influences our performance. The relationship between stress and decision making can additionally be affected by one's expertise in making decisions in high-threat environments, where experts can develop an adaptive response that mitigates the negative impacts of stress. In the present study, 26 male military personnel made friend/foe discriminations in an environment where we manipulated the level of stress. In the high-stress condition, participants received a shock when they incorrectly shot a friend or missed shooting a foe; in the low-stress condition, participants received a vibration for an incorrect decision. We characterized performance using signal detection theory to investigate whether a participant changed their decision criterion to avoid making an error. Results showed that under high-stress, participants made more false alarms, mistaking friends as foes, and this co-occurred with increased high frequency heart rate variability. Finally, we examined the relationship between decision making and physiology, and found that participants exhibited adaptive behavioral and physiological profiles under different stress levels. We interpret this adaptive profile as a marker of an expert's ingrained training that does not require top down control, suggesting a way that expert training in high-stress environments helps to buffer negative impacts of stress on performance.

Habitual exercise is associated with cognitive control and cognitive reappraisal success.

Habitual exercise is associated with enhanced domain-general cognitive control, such as inhibitory control, selective attention, and working memory, all of which rely on the frontal cortex. However, whether regular exercise is associated with more specific aspects of cognitive control, such as the cognitive control of emotion, remains relatively unexplored. The present study employed a correlational design to determine whether level of habitual exercise was related to performance on the Stroop test measuring selective attention and response inhibition, the cognitive reappraisal task measuring cognitive reappraisal success, and associated changes in prefrontal cortex (PFC) oxygenation using functional near-infrared spectroscopy. 74 individuals (24 men, 50 women, age 18-32 years) participated. Higher habitual physical activity was associated with lower Stroop interference (indicating greater inhibitory control) and enhanced cognitive reappraisal success. Higher habitual exercise was also associated with lower oxygenated hemoglobin (O2Hb) in the PFC in response to emotional information. However, NIRS data indicated that exercise was not associated with cognitive control-associated O2Hb in the PFC. Behaviorally, the findings support and extend the previous findings that habitual exercise relates to more successful cognitive control of neutral information and cognitive reappraisal of emotional information. Future research should explore whether habitual exercise exerts causal benefits to cognitive control and PFC oxygenation, as well as isolate specific cognitive control processes sensitive to change through habitual exercise.

Cognitive strategies in the mental rotation task revealed by EEG spectral power.

The classic mental rotation task (MRT; Shepard & Metzler, 1971) is commonly thought to measure mental rotation, a cognitive process involving covert simulation of motor rotation. Yet much research suggests that the MRT recruits both motor simulation and other analytic cognitive strategies that depend on visuospatial representation and visual working memory (WM). In the present study, we investigated cognitive strategies in the MRT using time-frequency analysis of EEG and independent component analysis. We scrutinized sensorimotor mu (µ) power reduction, associated with motor simulation, parietal alpha (pα) power reduction, associated with visuospatial representation, and frontal midline theta (fmθ) power enhancement, associated with WM maintenance and manipulation. µ power increased concomitant with increasing task difficulty, suggesting reduced use of motor simulation, while pα decreased and fmθ power increased, suggesting heightened use of visuospatial representation processing and WM, respectively. These findings suggest that MRT performance involves flexibly trading off between cognitive strategies, namely a motor simulation-based mental rotation strategy and WM-intensive analytic strategies based on task difficulty. Flexible cognitive strategy use may be a domain-general cognitive principle that underlies aptitude and spatial intelligence in a variety of cognitive domains. We close with discussion of the present study's implications as well as future directions.

Development of sensitivity versus specificity for print in the visual word form area.

An area near the left lateral occipito-temporal sulcus that responds preferentially to print has been designated as the visual word form area (VWFA). Research suggests that specialization in this brain region increases as reading expertise is achieved. Here we aimed to characterize that development in terms of sensitivity (response to printed words relative to non-linguistic faces) versus specificity (response to printed words versus line drawings of nameable objects) in typically reading children ages 7-14 versus young adults as measured by functional magnetic resonance imaging (fMRI). Relative to adults, children displayed equivalent sensitivity but reduced specificity. These findings suggest that sensitivity for print relative to non-linguistic stimuli develops relatively early in the VWFA in the course of reading development, but that specificity for printed words in VWFA is still developing through at least age 14.

Masked priming for the comparative evaluation of camouflage conspicuity.

Human observer test and evaluation of camouflage patterns is critical for understanding relative pattern conspicuity against a range of background scenes. However, very few validated methodologies exist for this purpose, and those that do carry several limitations. Five experiments examined whether masked priming with a dot probe could be used to reliably differentiate camouflage patterns. In each experiment, participants were primed with a camouflaged target appearing on the left or right of the screen, and then made a speeded response to a dot probe appearing on the same (congruent) or different (incongruent) side. Across experiments we parametrically varied prime duration between 35, 42, 49, 56, and 63 ms. Results demonstrated that as prime duration increased, a response time disadvantage for incongruent trials emerged with certain camouflage patterns. Interestingly, the most conspicuous patterns showed behavioral differences at a relatively brief (49 ms) prime duration, whereas behavioral differences were only found at longer prime durations for less conspicuous patterns; this overall results pattern matched that predicted by a visual salience model. Together, we demonstrate the viability of masked priming for the test and evaluation of camouflage patterns, and correlated outcomes for saliency models and primed object processing.

Orthographic and phonological processing in developing readers revealed by ERPs.

The development of neurocognitive mechanisms in single word reading was studied in children ages 8-10 years using ERPs combined with priming manipulations aimed at dissociating orthographic and phonological processes. Transposed-letter (TL) priming (barin-BRAIN vs. bosin-BRAIN) was used to assess orthographic processing, and pseudohomophone (PH) priming (brane-BRAIN vs. brant-BRAIN) was used to assess phonological processing. Children showed TL and PH priming effects on both the N250 and N400 ERP components, and the magnitude of TL priming correlated positively with reading ability, with better readers showing larger TL priming effects. Phonological priming, on the other hand, did not correlate with reading ability. The positive correlations between TL priming and reading ability in children points to a key role for flexible sublexical orthographic representations in reading development, in line with their hypothesized role in the efficient mapping of orthographic information onto semantic information in skilled readers.

Pupil diameter changes reflect difficulty and diagnostic accuracy during medical image interpretation.

BACKGROUND: No automated methods exist to objectively monitor and evaluate the diagnostic process while physicians review computerized medical images. The present study tested whether using eye tracking to monitor tonic and phasic pupil dynamics may prove valuable in tracking interpretive difficulty and predicting diagnostic accuracy. METHODS: Pathologists interpreted digitized breast biopsies varying in diagnosis and rated difficulty, while pupil diameter was monitored. Tonic diameter was recorded during the entire duration of interpretation, and phasic diameter was examined when the eyes fixated on a pre-determined diagnostic region during inspection. RESULTS: Tonic pupil diameter was higher with increasing rated difficulty levels of cases. Phasic diameter was interactively influenced by case difficulty and the eventual agreement with consensus diagnosis. More difficult cases produced increases in pupil diameter, but only when the pathologists' diagnoses were ultimately correct. All results were robust after adjusting for the potential impact of screen brightness on pupil diameter. CONCLUSIONS: Results contribute new understandings of the diagnostic process, theoretical positions regarding locus coeruleus-norepinephrine system function, and suggest novel approaches to monitoring, evaluating, and guiding medical image interpretation.

The effect of a brief mindfulness induction on processing of emotional images: an ERP study.

The ability to effectively direct one's attention is an important aspect of regulating emotions and a component of mindfulness. Mindfulness practices have been established as effective interventions for mental and physical illness; however, the underlying neural mechanisms of mindfulness and how they relate to emotional processing have not been explored in depth. The current study used a within-subjects repeated measures design to examine if focused breathing, a brief mindfulness induction, could modulate event-related potentials (ERPs) during emotional image processing relative to a control condition. We related ERP measures of processing positive, negative, and neutral images (the P300 and late positive potential - LPP) to state and trait mindfulness measures. Overall, the brief mindfulness induction condition did not influence ERPs reflecting emotional processing; however, in the brief mindfulness induction condition, those participants who reported feeling more decentered (a subscale of the Toronto Mindfulness Scale) after viewing the images had reduced P300 responses to negative versus neutral images.

Direct current stimulation of the left temporoparietal junction modulates dynamic humor appreciation.

The aim of this study was to evaluate the influence of transcranial direct current stimulation targeting the left temporoparietal junction (TPJ) on humor appreciation during a dynamic video rating task. In a within-participants design, we targeted the left TPJ with anodal, cathodal, or no transcranial direct current stimulation, centered at electrode site C3 using a 4×1 targeted stimulation montage. During stimulation, participants dynamically rated a series of six stand-up comedy videos for perceived humor. We measured event-related (time-locked to crowd laughter) modulation of humor ratings as a function of stimulation condition. Results showed decreases in rated humor during anodal (vs. cathodal or none) stimulation; this pattern was evident for the majority of videos and was only partially predicted by individual differences in humor style. We discuss the possibility that upregulation of neural circuits involved in the theory of mind and empathizing with others may reduce appreciation of aggressive humor. In conclusion, the present data show that neuromodulation of the TPJ can alter the mental processes underlying humor appreciation, suggesting critical involvement of this cortical region in detecting, comprehending, and appreciating humor.

The Effects of Load Carriage and Physical Fatigue on Cognitive Performance.

In the current study, ten participants walked for two hours while carrying no load or a 40 kg load. During the second hour, treadmill grade was manipulated between a constant downhill or changing between flat, uphill, and downhill grades. Throughout the prolonged walk, participants performed two cognitive tasks, an auditory go no/go task and a visual target detection task. The main findings were that the number of false alarms increased over time in the loaded condition relative to the unloaded condition on the go no/go auditory task. There were also shifts in response criterion towards responding yes and decreased sensitivity in responding in the loaded condition compared to the unloaded condition. In the visual target detection there were no reliable effects of load carriage in the overall analysis however, there were slower reaction times in the loaded compared to unloaded condition during the second hour.

Increasing breadth of semantic associations with left frontopolar direct current brain stimulation: a role for individual differences.

The aim of this study was to evaluate the influence of left frontopolar versus auditory (control) cortex transcranial direct current stimulation (tDCS) on the breadth of semantic associations produced in a cued free association task. A within-participants design administered anodal tDCS over the left frontopolar or auditory cortex, centered at electrode site AFZ or T7 using a 4×1 targeted stimulation montage. During stimulation, participants produced free associates in response to cues designed to promote narrow, moderate, or broad semantic associations. We measured the latent semantic associative strength of generated words relative to cues. The cue manipulation produced expected effects on the associative breadth of generated words, but there was no main effect of stimulation site, and calculated Bayes factors showed strong support for the null hypothesis. However, individual differences in creative potential, as assessed by the remote associates test, reliably and positively predicted increases in associative breadth under the frontopolar versus the auditory control condition, but only in response to narrow cues. In conclusion, the present data support neuroimaging studies demonstrating the involvement of left frontopolar cortical regions in generating relatively broad semantic associations. They also provide novel evidence that individual differences in creative potential may modulate the influence of brain stimulation on the breadth of generated semantic associations.

Acute exercise increases oxygenated and deoxygenated hemoglobin in the prefrontal cortex.

Both acute and chronic exercise is consistently associated with a number of benefits to physical and mental health, including cardiovascular function, body weight, mood, and cognition. Near-infrared spectroscopy is an ideal method to measure changes in oxygenated and deoxygenated hemoglobin (O2Hb and dHb) levels in the prefrontal cortex (PFC) during exercise, to better understand the locus of such changes in affective and cognitive processes. The present study tracked time-dependent changes in O2Hb and dHb levels in the PFC as a function of parametrically manipulated target exercise intensity. Near-infrared spectroscopy was conducted as regular exercisers completed a 30-min bout of exercise with one of three target intensities: 52% (low condition), 68% (moderate condition), or 84% (high condition) of age-adjusted maximum heart rate. Heart rate data confirmed that the participants reached their goal intensities immediately, after 10 min, or after 20 min, respectively. Data showed that O2Hb and dHb levels in the PFC increased as a function of both exercise load and duration. An 84%>68%>52% difference was evident after 18 min of cycling for O2Hb and after 23 min of cycling for dHb. The present results add to the growing body of literature showing that at submaximal levels, increasing exercise intensities reliably promote prefrontal cerebral oxygenation.

Direct current brain stimulation enhances navigation efficiency in individuals with low spatial sense of direction.

The aim of this study was to evaluate the influence of right versus left temporal transcranial direct current stimulation (tDCS) on navigation efficiency and spatial memory in individuals with low versus high spatial skills. A mixed design administered low (0.5 mA) versus high (2.0 mA) anodal tDCS (within-participants) over the right or the left temporal lobe (between-participants), centered at electrode site T8 (right) or T7 (left). During stimulation, participants navigated virtual environments in search of specified landmarks, and data were logged in terms of current position and heading over time. Following stimulation, participants completed pointing and map-drawing spatial memory tests. Individual differences in sense of direction reliably and inversely predicted navigation advantages in the 2.0 versus 0.5 mA right hemisphere stimulation condition (R=0.45, P<0.01); in other words, individuals with lower sense of direction showed increased navigation efficiency in the 2.0 versus 0.5 mA condition. Spatial memory tests also showed the development of relatively comprehensive spatial memories: bidimensional regression indicated lower distortion in sketch maps drawn following 2.0 versus 0.5 mA right temporal lobe stimulation (F=8.7, P<0.05). Data provide the first demonstration that right temporal anodal tDCS may hold potential for enhancing navigation efficiency in otherwise poor navigators. Data support neuroimaging studies showing the engagement of right temporal brain regions in developing and applying spatial memories during complex navigation tasks, and uniquely suggest that continuing research may find value in optimizing stimulation parameters (intensity, focality) as a function of individual differences.

Neural correlates of letter reversal in children and adults.

Children often make letter reversal errors when first learning to read and write, even for letters whose reversed forms do not appear in normal print. However, the brain basis of such letter reversal in children learning to read is unknown. The present study compared the neuroanatomical correlates (via functional magnetic resonance imaging) and the electrophysiological correlates (via event-related potentials or ERPs) of this phenomenon in children, ages 5-12, relative to young adults. When viewing reversed letters relative to typically oriented letters, adults exhibited widespread occipital, parietal, and temporal lobe activations, including activation in the functionally localized visual word form area (VWFA) in left occipito-temporal cortex. Adults exhibited significantly greater activation than children in all of these regions; children only exhibited such activation in a limited frontal region. Similarly, on the P1 and N170 ERP components, adults exhibited significantly greater differences between typical and reversed letters than children, who failed to exhibit significant differences between typical and reversed letters. These findings indicate that adults distinguish typical and reversed letters in the early stages of specialized brain processing of print, but that children do not recognize this distinction during the early stages of processing. Specialized brain processes responsible for early stages of letter perception that distinguish between typical and reversed letters may develop slowly and remain immature even in older children who no longer produce letter reversals in their writing.