Blast exposure results in tau and neurofilament light chain changes in peripheral blood.

OBJECTIVES: To evaluate how blast exposure impacts peripheral biomarkers.in military personnel enrolled in 10-day blast training. METHODS: On day 7, 21 military personnel experienced peak overpressure <2 pounds per square inch (psi); while 29 military personnel experienced peak overpressure ≥5 psi. Blood samples were collected each day to measure changes in amyloid beta (Aß), neurofilament light chain (NFL), and tau concentrations. RESULTS: Within 24 hours following exposure ≥5 psi, the ≥5 psi group had lower Aß42 (p = .004) and NFL (p < .001) compared to the <2 psi group and lower Aß42 (9.35%) and NFL (22.01%) compared to baseline. Twenty-four hours after ≥5 psi exposure, the ≥5 psi group had lower tau (p < .001) and NFL (p < .001) compared to the <2 psi group and baseline. Seventy-two hours after exposure ≥5 psi, tau increased in the ≥5 psi group compared to the <2 psi group (p = .02) and baseline. The tau:Aß42 ratio 24 hours after blast (p = .012), and the Aß40:Aß42 ratio 48 hours after blast (p = .04) differed in the ≥5 psi group compared to the <2 psi group. CONCLUSIONS: These findings provide an initial report of acute alterations in biomarker concentrations following blast exposure.

Moderate blast exposure results in increased IL-6 and TNFα in peripheral blood.

A unique cohort of military personnel exposed to isolated blast was studied to explore acute peripheral cytokine levels, with the aim of identifying blast-specific biomarkers. Several cytokines, including interleukin (IL) 6, IL-10 and tumor necrosis factor alpha (TNFα) have been linked to pre-clinical blast exposure, but remained unstudied in clinical blast exposure. To address this gap, blood samples from 62 military personnel were obtained at baseline, and daily, during a 10-day blast-related training program; changes in the peripheral concentrations of IL-6, IL-10 and TNFα were evaluated using an ultrasensitive assay. Two groups of trainees were matched on age, duration of military service, and previous history of blast exposure(s), resulting in moderate blast cases and no/low blast controls. Blast exposures were measured using helmet sensors that determined the average peak pressure in pounds per square inch (psi). Moderate blast cases had significantly elevated concentrations of IL-6 (F1,60=18.81, p<0.01) and TNFα (F1,60=12.03, p<0.01) compared to no/low blast controls; levels rebounded to baseline levels the day after blast. On the day of the moderate blast exposure, the extent of the overpressure (psi) in those exposed correlated with IL-6 (r=0.46, p<0.05) concentrations. These findings indicate that moderate primary blast exposure results in changes, specifically acute and transient increases in peripheral inflammatory markers which may have implications for neuronal health.

Coach-Like Skills for Educators: An Engaging and Applicable Workshop.

Equipping students with coach-like skills is one way to motivate and prepare them as future educators. Herein, we describe an engaging and applicable workshop designed to teach five skills to improve interactions with others. Educators who acquire coach-like skills may positively impact learners and enhance their development.

The Military Medicine Leadership Life Cycle: A Model for Longitudinal Leadership Development in Medicine-Undergraduate and Graduate Medical Education.

Physicians must be leaders more than ever with innumerable challenges. Despite this need, there is a paucity of consistent leadership development (LD) from medical student to staff physician. Military medicine has additional challenges-working within a large health care organization, constant turnover, working in a variety of contexts-that make the need for LD even more pressing. The purpose of this paper is to describe the LD life cycle for military undergraduate and graduate medical education (UME and GME), providing examples for other organizations while identifying steps to meet the future needs in military medicine. The Health Professions Scholarship Program produces over 75% of graduates for military medicine each year. Yet, since learners are dispersed throughout civilian medical schools any LD results in a heterogeneous experience. Uniformed Services University has a 4-year LD program required for all students as well as other opportunities for leadership professional growth. Military GME programs are unique, requiring a military unique curriculum to prepare graduates for their initial assignments. Military unique curriculum vary, but include clinical topics relevant to military medicine as well as leadership. There is no Military Healthcare System-wide leadership curriculum used by everyone at this time. Based on these UME and GME approaches to LD, there have been multiple lessons learned formed on the authors experience and published literature: learners do not typically see themselves as leaders; learners want applicable curriculum with less lecturing and more application and discussion; programs are often siloed from one another and sharing curriculum content does not typically occur; no one-size-fits-all model. On the basis of the lessons learned and the current state of UME and GME leadership education, there are 5 recommendations to enhance UME and GME leadership programs: (1) develop a Health Professions Scholarship Program Leadership Curriculum; (2) develop a MHS GME Leadership Curriculum; (3) integrate UME and GME Leadership Curricula; (4) develop faculty to teach leadership; and (5) conduct research on UME and GME in military and share lessons learned. We suggest a roadmap for strengthening LD within military medicine and civilian institutions.

The evolution of traumatic brain injury in a rat focal contusion model.

Serial MRI facilitates the in vivo analysis of the intra- and intersubject evolution of traumatic brain injury lesions. Despite the availability of MRI, the natural history of experimental focal contusion lesions in the controlled cortical impact (CCI) rat model has not been well described. We performed CCI on rats and MRI during the acute to chronic stages of cerebral injury to investigate the time course of changes in the brain. Female Wistar rats underwent CCI of their left motor cortex with a flat impact tip driven by an electromagnetic piston. In vivo MRI was performed at 7 T serially over 6 weeks post-CCI. The appearances of CCI-induced lesions and lesion-associated cortical volumes were variable on MRI, with the percentage change in cortical volume of the CCI ipsilateral side relative to the contralateral side ranging from 18% within 2 h of injury on day 0 to a peak of 35% on day 1, and a trough of -28% by week 5/6, with an average standard deviation of ± 14% at any given time point. In contrast, the percentage change in cortical volume of the ipsilateral side relative to the contralateral side in control rats was not significant (1 ± 2%). Hemorrhagic conversion within and surrounding the CCI lesion occurred between days 2 and 9 in 45% of rats, with no hemorrhage noted on the initial scan. Furthermore, hemorrhage and hemosiderin within the lesion were positive for Prussian blue and highly autofluorescent on histological examination. Although some variation in injuries may be technique related, the divergence of similar lesions between initial and final scans demonstrates the inherent biological variability of the CCI rat model.

Impact on Faculty's Own Development When Assessing Student Performance.

INTRODUCTION: Assessing learner performance is a primary focus within simulation-based education in order to prepare students with the knowledge and skills they will need going forward in their careers. In order to properly conduct these assessments of learner performance, faculty must be adequately trained on the scenario, expectations, assessment measures, and debriefing. During Operation Bushmaster, a five-day "deployment" for learners, faculty assess students as they rotate through different leadership roles. The faculty development includes online and in-person training that provides them with an understanding of the scenario; what learners know; the framework used at USU to guide curriculum, development, and assessment; how to assess learners; and how to provide feedback to learners. Research has examined the value of receiving assessment and feedback from a student perspective, but the impact of being the assessor and giving feedback has not been researched from the faculty point of view. The purpose of this study, therefore, was to examine the impact of assessing students in simulation scenarios on faculty's own development as an educator and leader. MATERIALS AND METHODS: Through a phenomenological qualitative study, we explored participants' lived experiences as faculty at Operation Bushmaster. Eighteen faculty from a variety of medical specialties and military ranks volunteered to participate. Participants were interviewed in-person using a semi-structured interview. Analyses included individually reading through each transcript; then individually coding and taking notes of terms and phrases used by participants; codes were compiled and organized into categories, which became the themes of our study. RESULTS: The interviews demonstrated the following themes in which providers who serve as faculty of Operation Bushmaster believe they gain from the experience: (1) The experience helps to reground their own thinking; (2) acting as faculty during simulation-based education helps them remain up-to-date on necessary skills; and (3) working with students helps faculty continually develop as an educator and a leader. CONCLUSIONS: This work describes how even when faculty are brought in for learner assessment, they are taking away lessons and experiences that aid in their own development as an educator as well as a leader. Acting as an assessing faculty for students may allow faculty to reground their own thinking, remain up-to-date on necessary skills, and continually develop their skills as an educator and leader. These findings suggest that some faculty involved in simulation events may also gain knowledge, skills, and experiences that can help with their own development even when the focus is on learners.

Leaders, Talent Management, and Allies: The Keys to Successful Integration in the Combat Arms.

Servicewomen enhance the U.S. Military fighting force by bringing diverse perspectives, collaborative and creative problem-solving skills for global peace and security, and innovative, adaptive talent as leaders. Despite servicewomen integrating into combat units over the past decade, a number of barriers remain related to inclusion, promotion, and quality of life, particularly for marginalized women. To eliminate inequities experienced by servicewomen, leaders across all levels of the military play a key role in supporting the successful integration of servicewomen, cultivating an environment of belonging, and guarding against toxicity, which will result in optimized performance and readiness for all servicemembers in defense of the Nation. Herein, we review the original gaps related to leadership and peer behaviors identified by the 2014 Women in Combat Symposium, provide updates in the literature, address the topics that arose at the 2021 Women in Combat Symposium, and finally, outline the remaining barriers and challenges to the successful integration of female servicemembers.

Students' Leadership Development During a High-fidelity Military Medical Field Practicum.

INTRODUCTION: Leadership development is a cornerstone aspect of military medical education. Operation Bushmaster, a medical field practicum (MFP) conducted by the USU, tests fourth-year medical students' clinical skills and leadership acumen in an operational environment. No studies have examined students' perceptions of their own leadership development during this MFP. Therefore, this study explored leadership development from the students' perspectives. MATERIALS AND METHODS: Using a qualitative phenomenological design, we analyzed the reflection papers of 166 military medical students who participated in Operation Bushmaster during the fall of 2021. Our research team coded and categorized the data. Once defined, these categories served as the themes in this study. RESULTS: Three central themes were expressed: (1) the importance of direct and decisive communication, (2) unit cohesion and interpersonal relationships enhance the team's ability to adapt, and (3) followership quality determines leadership outcomes. The students' leadership ability was maximized by established relationships within their unit and well-practiced communication, and a decreased propensity for followership negatively affected leadership. Overall, Operation Bushmaster increased students' appreciation of the importance of leadership development and overall enhanced their leadership outlook as a future military medical officer. CONCLUSIONS: This study provided an introspective vantage from military medical students pertaining to their own leadership development, as participants described how the challenging environment of a military MFP challenged them to hone and develop their leadership skills. As a result, the participants gained a greater appreciation of continued leadership development and realization of their future roles and responsibilities within the military health care system.

Undergraduate Medical Education Leader Performance Predicts Postgraduate Military Leader Performance.

INTRODUCTION: Developing physicians as leaders has gained attention across the United States. Undergraduate medical education (UME) and graduate medical education (GME) leader development programs have increased. During postgraduate years (PGY), graduates bring their leadership education to the bedside; however, associations between leader performance in medical school and GME is largely unknown. It is important to find experiences that can assess leader performance that may be useful to predict future performance. The purpose of this study was to determine if (1) there is a correlation between leader performance during the fourth year of medical school versus leader performance in PGY1 and 3, and (2) leader performance during the fourth year of medical school is associated with military leadership performance in PGY1 and 3s while taking previous academic performance markers into account. METHODS: This study examined overall leader performance of learners (classes of 2016-2018) during the fourth year of medical school and their graduate leader performance post-medical school. Leader performance was assessed by faculty during a medical field practicum (UME leader performance) and graduate leader performance was assessed by program directors at the end of PGY1 (N = 297; 58.3%) and 3 (N = 142; 28.1%). Pearson correlation analysis examined relationships among UME leader performance and between the PGY leader performance items. In addition, stepwise multiple linear regression analyses were conducted to examine the relationship between leader performance at the end of medical school with military leadership performance in PGY1 and 3, while taking into account the academic performance markers. RESULTS: Pearson correlation analyses revealed that the UME leader performance was correlated with 3 of 10 variables at PGY1, and was correlated at PGY3 with 10 out of 10 variables. Results of the stepwise multiple linear regression analysis indicated that leader performance during the fourth year of medical school explained an additional 3.5% of the variance of PGY1 leader performance after controlling for the previous academic performance markers (MCAT total score, USMLE Step 1 score and Step 2 CK score). In contrast, leader performance during the fourth year of medical school alone accounted for an additional 10.9% of the variance of PGY3 leader performance above and beyond the set of academic performance markers. Overall, UME leader performance has more predictive power in PGY leader performance than the MCAT or USMLE Step exams. CONCLUSIONS: The findings of this study indicate that a positive relationship exists between leader performance at the end of medical school and leader performance in PGY1 and 3 years of residency. These correlations were stronger in PGY3 compared to PGY1. During PGY1, learners may be more focused on being a physician and an effective team member compared to PGY3 where they have a deeper understanding of their roles and responsibilities and can take on more leadership roles. Additionally, this study also found that MCAT and USMLE Step exams performance was not predictive of PGY1 or PGY3 leader performance. These findings provide evidence of the power of continued leader development in UME and beyond.

Learning to Lead: 10 Leadership Lessons From Operation Bushmaster.

Medical students at the Uniformed Services University of the Health Sciences participate in a leadership curriculum designed to develop leadership skills. Operation Bushmaster is a 5-day field practicum designed to test these skills. In this article, we describe 10 leadership lessons learned during Operation Bushmaster applicable to all leaders.

A Pilot Study of Whole-Blood Transcriptomic Analysis to Identify Genes Associated with Repetitive Low-Level Blast Exposure in Career Breachers.

Repetitive low-level blast exposure is one of the major occupational health concerns among US military service members and law enforcement. This study seeks to identify gene expression using microRNA and RNA sequencing in whole-blood samples from experienced breachers and unexposed controls. We performed experimental RNA sequencing using Illumina's HiSeq 2500 Sequencing System, and microRNA analysis using NanoString Technology nCounter miRNA expression panel in whole-blood total RNA samples from 15 experienced breachers and 14 age-, sex-, and race-matched unexposed controls. We identified 10 significantly dysregulated genes between experienced breachers and unexposed controls, with FDR corrected <0.05: One upregulated gene, LINC00996 (long intergenic non-protein coding RNA 996); and nine downregulated genes, IGLV3-16 (immunoglobulin lambda variable 3-16), CD200 (CD200 molecule), LILRB5 (leukocyte immunoglobulin-like receptor B5), ZNF667-AS1 (ZNF667 antisense RNA 1), LMOD1 (leiomodin 1), CNTNAP2 (contactin-associated protein 2), EVPL (envoplakin), DPF3 (double PHD fingers 3), and IGHV4-34 (immunoglobulin heavy variable 4-34). The dysregulated gene expressions reported here have been associated with chronic inflammation and immune response, suggesting that these pathways may relate to the risk of lasting neurological symptoms following high exposures to blast over a career.

Neuronally-derived tau is increased in experienced breachers and is associated with neurobehavioral symptoms.

Military and law enforcement breachers are exposed to many low-level blasts during their training and occupational experiences in which they detonate explosives to force entry into secured structures. There is a concern that exposure to these repetitive blast events in career breachers could result in cumulative neurological effects. This study aimed to determine concentrations of neurofilament light (NF-L), tau, and amyloid-beta 42 (Aß42) in serum and in neuronal-derived extracellular vesicles (EVs) in an experienced breacher population, and to examine biomarker associations with neurobehavioral symptoms. Thirty-four participants enrolled in the study: 20 experienced breachers and 14 matched military or civilian law enforcement controls. EV tau concentrations were significantly elevated in experienced breachers (0.3301 ± 0.5225) compared to controls (-0.4279 ± 0.7557; F = 10.43, p = 0.003). No statistically significant changes were observed in EV levels of NF-L or Aß42 or in serum levels of NF-L, tau, or Aß42 (p's > 0.05). Elevated EV tau concentrations correlated with increased Neurobehavioral Symptom Inventory (NSI) score in experienced breachers (r = 0.596, p = 0.015) and predicted higher NSI score (F(1,14) = 7.702, p = 0.015, R2 = 0.355). These findings show that neuronal-derived EV concentrations of tau are significantly elevated and associated with neurobehavioral symptoms in this sample of experienced breachers who have a history of many low-level blast exposures.

Acute and Chronic Molecular Signatures and Associated Symptoms of Blast Exposure in Military Breachers.

Injuries from exposure to explosions rose dramatically during the Iraq and Afghanistan wars, which motivated investigations of blast-related neurotrauma and operational breaching. In this study, military "breachers" were exposed to controlled, low-level blast during a 10-day explosive breaching course. Using an omics approach, we assessed epigenetic, transcriptional, and inflammatory profile changes in blood from operational breaching trainees, with varying levels of lifetime blast exposure, along with daily self-reported symptoms (with tinnitus, headaches, and sleep disturbances as the most frequently reported). Although acute exposure to blast did not confer epigenetic changes, specifically in DNA methylation, differentially methylated regions (DMRs) with coordinated gene expression changes associated with lifetime cumulative blast exposures were identified. The accumulative effect of blast showed increased methylation of PAX8 antisense transcript with coordinated repression of gene expression, which has been associated with sleep disturbance. DNA methylation analyses conducted in conjunction with reported symptoms of tinnitus in the low versus high blast incidents groups identified DMRS in KCNE1 and CYP2E1 genes. KCNE1 and CYP2E1 showed the expected inverse correlation between DNA methylation and gene expression, which have been previously implicated in noise-related hearing loss. Although no significant transcriptional changes were observed in samples obtained at the onset of the training course relative to chronic cumulative blast, we identified a large number of transcriptional perturbations acutely pre- versus post-blast exposure. Acutely, 67 robustly differentially expressed genes (fold change ≥1.5), including UFC1 and YOD1 ubiquitin-related proteins, were identified. Inflammatory analyses of cytokines and chemokines revealed dysregulation of MCP-1, GCSF, HGF, MCSF, and RANTES acutely after blast exposure. These data show the importance of an omics approach, revealing that transcriptional and inflammatory biomarkers capture acute low-level blast overpressure exposure, whereas DNA methylation marks encapsulate chronic long-term symptoms.

A Moderate Blast Exposure Results in Dysregulated Gene Network Activity Related to Cell Death, Survival, Structure, and Metabolism.

Blast exposure is common in military personnel during training and combat operations, yet biological mechanisms related to cell survival and function that coordinate recovery remain poorly understood. This study explored how moderate blast exposure influences gene expression; specifically, gene-network changes following moderate blast exposure. On day 1 (baseline) of a 10-day military training program, blood samples were drawn, and health and demographic information collected. Helmets equipped with bilateral sensors worn throughout training measured overpressure in pounds per square inch (psi). On day 7, some participants experienced moderate blast exposure (peak pressure ≥5 psi). On day 10, 3 days post-exposure, blood was collected and compared to baseline with RNA-sequencing to establish gene expression changes. Based on dysregulation data from RNA-sequencing, followed by top gene networks identified with Ingenuity Pathway Analysis, a subset of genes was validated (NanoString). Five gene networks were dysregulated; specifically, two highly significant networks: (1) Cell Death and Survival (score: 42), including 70 genes, with 50 downregulated and (2) Cell Structure, Function, and Metabolism (score: 41), including 69 genes, with 41 downregulated. Genes related to ubiquitination, including neuronal development and repair: UPF1, RNA Helicase and ATPase (UPF1) was upregulated while UPF3 Regulator of Nonsense Transcripts Homolog B (UPF3B) was downregulated. Genes related to inflammation were upregulated, including AKT serine/threonine kinase 1 (AKT1), a gene coordinating cellular recovery following TBIs. Moderate blast exposure induced significant gene expression changes including gene networks involved in (1) cell death and survival and (2) cellular development and function. The present findings may have implications for understanding blast exposure pathology and subsequent recovery efforts.

Functional and Structural Neuroimaging Correlates of Repetitive Low-Level Blast Exposure in Career Breachers.

Combat military and civilian law enforcement personnel may be exposed to repetitive low-intensity blast events during training and operations. Persons who use explosives to gain entry (i.e., breach) into buildings are known as "breachers" or dynamic entry personnel. Breachers operate under the guidance of established safety protocols, but despite these precautions, breachers who are exposed to low-level blast throughout their careers frequently report performance deficits and symptoms to healthcare providers. Although little is known about the etiology linking blast exposure to clinical symptoms in humans, animal studies demonstrate network-level changes in brain function, alterations in brain morphology, vascular and inflammatory changes, hearing loss, and even alterations in gene expression after repeated blast exposure. To explore whether similar effects occur in humans, we collected a comprehensive data battery from 20 experienced breachers exposed to blast throughout their careers and 14 military and law enforcement controls. This battery included neuropsychological assessments, blood biomarkers, and magnetic resonance imaging measures, including cortical thickness, diffusion tensor imaging of white matter, functional connectivity, and perfusion. To better understand the relationship between repetitive low-level blast exposure and behavioral and imaging differences in humans, we analyzed the data using similarity-driven multi-view linear reconstruction (SiMLR). SiMLR is specifically designed for multiple modality statistical integration using dimensionality-reduction techniques for studies with high-dimensional, yet sparse, data (i.e., low number of subjects and many data per subject). We identify significant group effects in these data spanning brain structure, function, and blood biomarkers.

Hearing Loss and Irritability Reporting Without Vestibular Differences in Explosive Breaching Professionals.

Background: Blast exposure is a potential hazard in modern military operations and training, especially for some military occupations. Helmets, peripheral armor, hearing protection, and eye protection worn by military personnel provide some acute protection from blast effects but may not fully protect personnel against cumulative effects of repeated blast overpressure waves experienced over a career. The current study aimed to characterize the long-term outcomes of repeated exposure to primary blast overpressure in experienced career operators with an emphasis on the assessment of hearing and vestibular outcomes. Methods: Participants included experienced "breachers" (military and law enforcement explosives professionals who gain entry into structures through controlled detonation of charges) and similarly aged and experienced "non-breachers" (non-breaching military and law enforcement personnel). Responses to a clinical interview and performance on audiological and vestibular testing were compared. Results: Hearing loss, ringing in the ears, irritability, and sensitivity to light or noise were more common among breachers than non-breachers. Breachers reported more combat exposure than non-breachers, and subsequently, memory loss and difficulty concentrating were associated with both breaching and combat exposure. Vestibular and ocular motor outcomes were not different between breachers and non-breachers. Conclusion: Hearing-related, irritability, and sensitivity outcomes are associated with a career in breaching. Future studies examining long-term effects of blast exposure should take measures to control for combat exposure.

Sleep extension reduces pain sensitivity.

INTRODUCTION: Insufficient sleep increases pain sensitivity in healthy individuals. Additionally, extending sleep (eg, increasing nocturnal sleep time or adding a mid-day nap) has been shown to restore pain sensitivity to baseline levels in sleep deprived/restricted individuals. Whether sleep extension can reduce pain sensitivity beyond baseline levels in non-sleep restricted/deprived individuals remains unknown. METHODS: In a sample of 27 healthy, pain-free, normally-sleeping individuals (17 males, mean age ∼24 yrs), we examined the impact of five nights of sleep extension on pain sensitivity. Pain threshold (elapsed time until the participant reported pain) and pain tolerance (total time the participant kept the hand submerged in the cold water) were measured using the Cold Pressor Task. Furthermore, we assessed the extent to which self-reported sleep amount in relation to the minimal subjective sleep requirement for adequate performance (sleep credit) was associated with pain sensitivity changes. RESULTS: On average individuals slept almost 2 extra hours per night. Our results indicate that sleep extension increases pain tolerance beyond baseline levels. However, sleep extension did not impact pain threshold. We also found that individuals with a smaller sleep credit (ie, those who habitually obtain less sleep than they feel they need) experienced greater increases in pain tolerance after extending sleep. CONCLUSIONS: The present findings suggest that sleep extension may increase pain tolerance but not pain threshold in healthy individuals who normally sleep the recommended amount. Our findings also support the idea that sleep credit may be a strong indicator of sleep debt in the context of pain sensitivity.

A systematic review and meta-analysis of sleep architecture and chronic traumatic brain injury.

Sleep quality appears to be altered by traumatic brain injury (TBI). However, whether persistent post-injury changes in sleep architecture are present is unknown and relatively unexplored. We conducted a systematic review and meta-analysis to assess the extent to which chronic TBI (>6 months since injury) is characterized by changes to sleep architecture. We also explored the relationship between sleep architecture and TBI severity. In the fourteen included studies, sleep was assessed with at least one night of polysomnography in both chronic TBI participants and controls. Statistical analyses, performed using Comprehensive Meta-Analysis software, revealed that chronic TBI is characterized by relatively increased slow wave sleep (SWS). A meta-regression showed moderate-severe TBI is associated with elevated SWS, reduced stage 2, and reduced sleep efficiency. In contrast, mild TBI was not associated with any significant alteration of sleep architecture. The present findings are consistent with the hypothesis that increased SWS after moderate-severe TBI reflects post-injury cortical reorganization and restructuring. Suggestions for future research are discussed, including adoption of common data elements in future studies to facilitate cross-study comparability, reliability, and replicability, thereby increasing the likelihood that meaningful sleep (and other) biomarkers of TBI will be identified.

Sleep deprivation impairs recognition of specific emotions.

Emotional processing is particularly sensitive to sleep deprivation, but research on the topic has been limited and prior studies have generally evaluated only a circumscribed subset of emotion categories. Here, we evaluated the effects of one night of sleep deprivation and a night of subsequent recovery sleep on the ability to identify the six most widely agreed upon basic emotion categories (happiness, surprise, fear, sadness, disgust, anger). Healthy adults (29 males; 25 females) classified a series of 120 standard facial expressions that were computer morphed with their most highly confusable expression counterparts to create continua of expressions that differed in discriminability between emotion categories (e.g., combining 70% happiness+30% surprise; 90% surprise+10% fear). Accuracy at identifying the dominant emotion for each morph was assessed after a normal night of sleep, again following a night of total sleep deprivation, and finally after a night of recovery sleep. Sleep deprivation was associated with significantly reduced accuracy for identifying the expressions of happiness and sadness in the morphed faces. Gender differences in accuracy were not observed and none of the other emotions showed significant changes as a function of sleep loss. Accuracy returned to baseline after recovery sleep. Findings suggest that sleep deprivation adversely affects the recognition of subtle facial cues of happiness and sadness, the two emotions that are most relevant to highly evolved prosocial interpersonal interactions involving affiliation and empathy, while the recognition of other more primitive survival-oriented emotional face cues may be relatively robust against sleep loss.