Motion capture technology and Magnetic Resonance Imaging with Diffusion Tensor Imaging (MRI-DTI) were used in this work to detect subtle abnormalities in patients with mild traumatic brain injury (MTBI). A new concept, termed dynamic variability, is introduced in this work to quantify and localize gait variability. Three chronic MTBI patients were recruited from the Veterans Affair Medical Center in Iowa City, IA, and three healthy controls with height, weight, and gender matched to the patients were recruited from the Reserve Officers' Training Corps in Iowa City, IA. Kinematic and kinetic data of the subjects were collected during the performance of three gait testing scenarios. The first test involved single-task walking and was used as a baseline. The second and third tests were dual tasks that involved walking while performing a cognitive or motor task and were designed to magnify gait abnormalities. The results showed that MTBI patients had reduced gait velocity, shortened stride length, and larger step width; findings that are consistent with those published in the literature. The new dynamic variability factor found that, as compared to controls, MTBI patients had more variability in their hip and ankle joint moments. MRI-DTI has been used to detect dysfunction of the major white matter tracts in chronic MTBI patients; although, the sample size of this study was too small to detect a difference between the MTBI and control subjects. The imaging and gait abnormalities are suggestive of frontal lobe-white matter tracts dysfunction.

L’inflammation est un processus essentiel à prendre en compte dans la pratique clinique. Nous avons montré durant cette thèse que le statut (neuro)inflammatoire précédant la survenue d’une pathologie cérébrale est à prendre en compte nécessairement puisqu’il modifie drastiquement la réponse inflammatoire suite à un deuxième stimulus comme la survenue d’un AVC. Il est d’autant plus important que 90% des AVC sont associés à des comorbidités comme l’hypertension artérielle, le diabète ou la consommation chronique d’alcool, qui ont d’ores et déjà été décrites comme des maladies avec une composante inflammatoire. Nous avons caractérisé ce statut neuroinflammatoire silencieux, aussi appelé priming, dans le cadre de la consommation chronique d’alcool et dans le traumatisme crânien léger. De plus, nous avons identifié les macrophages périvasculaires comme participants à l’effet aggravateur du priming inflammatoire sur les lésions ischémiques. Ils semblent alors être une cible thérapeutique de choix et feront l’objet de futures études. Il est donc nécessaire de trouver des techniques d’imagerie non invasives pour détecter le priming. L’autoradiographie ciblant le TSPO nous a permis de révéler le priming inflammatoire dans le cadre du traumatisme crânien léger. Nous proposons, au vu de nos résultats obtenus durant cette thèse, la tomographie par émission de positons pour la détection de la neuroinflammation invisible dans les atteintes cérébrales aigüe(s) et chronique(s). / Inflammation is an essential process to be considered in clinical practice. We have shown during this thesis that the (neuro)inflammatory status preceding the occurrence of a cerebral pathology must necessarily be taken into account since it drastically modifies the inflammatory response following a second stimulus such as stroke. This is even more important given that 90% of strokes are associated with comorbidities such as chronic hypertension, diabetes or chronic alcohol consumption, for which inflammation is an important pathophysiological feature. We have characterized this silent inflammatory status, also called priming, in the context of chronic alcohol consumption and in mild traumatic brain injury. We have identified perivascular macrophages (PVM) as mediators of the aggravating effect of inflammatory priming on ischemic stroke. PVM appear to be potential therapeutic targets and will be the subject of future investigations. It is therefore necessary to find non-invasive imaging techniques to detect inflammatory priming. We show that autoradiography targeting TSPO reveals the inflammatory priming provoked by a single mild traumatic brain injury. We propose, in light of the results obtained during this thesis, the positron emission tomography imaging to detect the invisible neuroinflammation in acute and chronic brain diseases.

Traumatic brain injury (TBI) effects a large number of individuals, both civilians and military personnel, every year. The neuroinflammatory response mounted in the brain following a head injury continues long after the effects of initial subside. While it was initially thought to only occur in moderate or severe TBI, the deleterious effects of this cascade have recently been identified in patients with mild TBI (mTBI). Hypopituitarism is an often underreported condition and can result from TBI of all severity. The long-term sequelae of TBI can manifest in or exacerbate many other comorbidities of brain injury, such as neuroendocrine dysfunction or mental health conditions. Both TBI and hypopituitarism can present with symptoms similar to some psychiatric disorders, or exacerbation comorbid conditions. Veteran patients presenting to their primary care providers with symptoms of irritability, depression, anxiety, or cognitive and behavioral changes may meet criteria to receive diagnoses of psychiatric illnesses prevalent in the military population, while not being evaluated for pituitary dysfunction, and thus receive inadequate treatment. The proposed study aims to identify the prevalence of patients that are receiving psychiatric treatment that have both a history of mTBI and reduced levels of pituitary hormones on serum assays. By identifying a significant portion of this population, future studies can assess the impact that hormonal replacement has on success of psychotherapy, resolution of symptoms, and impact on functional status, among other factors.

Blast-related mild traumatic brain injury (mTBI) is a common injury among Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) veterans due to the frequent use of improvised explosive devices (IEDs). A significant minority of veterans with blast-related mTBI complain of postconcussion symptoms (PCS) and cognitive difficulties, even years after the injury. Studies have suggested that these behavioral sequelae are primarily linked to mental health disorders such as posttraumatic stress disorder (PTSD). However, mTBI is associated with neural changes and the impact of these changes on behavioral sequelae is unclear. As such, this dissertation had three goals. First, this dissertation assessed whether the severity of PCS in blast-exposed individuals is associated with the extent of mTBI-related neural injury. Results revealed that individuals with mTBI with loss of consciousness (LOC) had significantly more white matter abnormalities than no-TBI controls and that these white matter abnormalities were spatially variable across individuals. Importantly, the extent of white matter abnormality was associated with physical PCS severity and mediated the relationship between mTBI with LOC and physical PCS. Second, this dissertation examined whether these white matter abnormalities were also associated with overall cognitive impairment. In light of the observed variability in white matter injury, a measure of overall cognitive status that takes into account heterogeneity of cognitive impairment was used. Results showed that the extent of white matter abnormality was associated with cognitive status and mediated the relationship between mTBI with LOC and cognitive impairment. Third, this dissertation examined performance and brain function in the context of an experimental measure of cognitive control known to be sensitive to residual effects of mTBI. Results revealed that although behavioral performance was similar across groups, the mTBI group had enhanced functional connectivity between brain networks important for task performance, suggesting a potential compensatory mechanism in mTBI. Together, the findings of this dissertation suggest that mTBI is associated with structural and functional connectivity alterations years after the injury. Further, this dissertation suggests that whereas structural connectivity changes may have negative behavioral consequences, changes in functional connectivity may serve as a compensatory mechanism for successful performance.

Indiana University-Purdue University Indianapolis (IUPUI) / Social support is a powerful therapeutic against fear and anxiety and is utilized in many psychotherapies. The concept that a familiar or friendly presence helps a person learn to overcome anxiety has been well-known for decades, yet, the basic neural mechanisms that regulate this psychosocial learning remain unknown. A first step towards elucidating these basic mechanisms is the development of a valid preclinical animal model. However, preclinical behavioral models exploring the use of a social presence in reducing anxiety have not been fully characterized. Therefore, it was our goal to identify a useful way in which to study the mechanisms of how a social presence can induce anxiolysis (the reduction of anxiety). We accomplished this goal by characterizing and validating a preclinical model, as well as demonstrating that the model was capable of measuring deficits in rats given a mild traumatic brain injury. To this end, we identified an existing, but uncharacterized model, the social interaction-habituation model, as an effective model of social familiarity-induced anxiolysis (SoFiA), which demonstrates socially enhanced safety learning, or psychosocial learning. We find that as social familiarity develops across time, anxiolysis develops. We identified that the use of a Bright Light Challenge is a useful anxiogenic stimulus to use during SI-habituation training. The anxiolysis acquired following SI-habituation testing is partner specific, and can be blocked by an inhibition of the medical prefrontal cortex, while it can be enhanced by D-cycloserine. We found that this model identified deficits in SoFiA acquisition in rodents exposed to a mild traumatic brain injury, which, in humans, has been linked to psychosocial deficits. This work is a step in creating ways in which we can study and better understand the regulatory processes of emotions mediated by social behavior.

No description available.

Purpose: Interdisciplinary research in epidemiology, neurology, neuroscience, and sports medicine commonly highlight the dangerous short- and long-term sequelae of sport-related concussions (SRC). Despite advancements in clinical evaluation and recognition, many SRCs are not properly diagnosed and managed, leaving many athletes in danger of acute and chronic neurological deficits. Epidemiological studies suggest the prevalence of chronic traumatic encephalopathy (CTE) is three times, and Alzheimer's disease is four times greater in former athletes with a history of SRC than non-athletes. The underlying mechanisms linking SRC and contact-sport participation to neurodegeneration are not fully understood. Herein, I hypothesized that transient insufficiency of the lymphatic and glymphatic clearance systems in the central nervous system (CNS) could play a crucial role in the SRC-mediated neurological conditions. Therefore, this study aimed to examine the differences in plasma levels of extracellular vesicles (EV) that are associated with the lymphatic and glymphatic clearance systems of the CNS among athletes following sport-related head impacts. Participants: Plasma EV concentrations were analyzed in collegiate athletes (controls n=29, SRC n=19) with and without SRC. In a parallel study, fourteen college-aged soccer players participated in a laboratory-based, repetitive subconcussion paradigm. All participants provided written informed consent, and the study was approved by institutional review board at Temple University. Methods: We evaluated EVs containing markers associated with the CNS lymphatic and glymphatic systems, including lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1), astrocyte-specific glial fibrillary acidic protein (GFAP), aquaporin 4 (AQP4), and the platelet and endothelial cell adhesion molecule 1(PECAM-1 or CD31). Tetraspanin-28 (CD81) was used as an EV-specific marker. Blood samples from athlete controls were collected once during preseason baseline assessments. Samples from athletes with SRC were collected within 72 hours of injury. Whole blood was double-centrifuged to obtain platelet-poor plasma, snap-frozen in liquid nitrogen, and stored at -80°C until analyzed. Quantification of plasma EVs was performed using spectral flow cytometry. Mann-Whitney U tests were used for group comparisons of single and double-positive EV concentrations, and receiver-operating characteristic curve (ROC) and area under the curve (AUC) analyses assessed diagnostic efficacy. Within-group changes in plasma EVs following repetitive, subconcussive head impacts were assessed with Friedman's test using Dunn's correction for multiple comparisons. Results: Among athletes with SRC, plasma concentrations of LYVE1+EVs and CD31+EVs were significantly elevated within 72 hours of injury compared to controls (LYVE1+EVs, p < 0.0001; CD31+EVs, p = 0.005). ROC analysis revealed plasma concentrations of LYVE1+EVs demonstrated significant diagnostic accuracy to differentiate athletes with SRC from athlete controls (AUC: 0.971, 95% C.I. = 0.933-1.000, p < 0.0001). Notably, concentrations of LYVE1+/CD81+ double-positive EVs, CD31+/CD81+ double-positive EVs, and GFAP+/CD81+ double-positive EVs were significantly higher among athletes with SRC within 72 hours of injury compared to control athletes (p < 0.0001; p = 0.0002; p < 0.0001, respectively). Plasma AQP4+/GFAP+ double-positive EVs and AQP4+/CD81+ double-positive EVs were not. However, plasma concentrations of GFAP+/CD81+ double-positive EVs and AQP4+/GFAP+ double-positive EVs were significantly elevated after repetitive, subconcussive head impacts (p < 0.0001 and p = 0.004, respectively). Conclusion: Plasma concentrations of double-positive EVs, including LYVE1+/CD81+EVs, CD31+/CD81+EVs, and GFAP+/CD81+EVs, may be promising biomarkers for acute SRC. EVs associated with the glymphatic system, GFAP+/CD81+EVs and AQP4+/GFAP+EVs, were significantly elevated after repetitive subconcussive head impacts. The differences observed in EV responses to SRC and subconcussion may provide novel mechanistic insights about sport-associated neurodegeneration for current and future athletes. / Kinesiology

While there has been ample research examining the relationship between an acute concussion on immediate neuropsychological performance, very little research has examined the relationship between lifetime concussion history with current neuropsychological performance. We collected preseason neuropsychological test performance (ImPACT) and a detailed lifetime concussion history questionnaire from 71 UCF football players. Stepwise linear regressions were conducted for each of the five ImPACT domain scores for the 18 participants that reported at least one lifetime concussion. The regressions used the following four concussion history predictors: total number of lifetime concussions, length of time between last concussion and lmPACT testing, severity of worst concussion, and severity of most recent concussion. Results revealed that only one ImpACT domain score had at least one predictor enter the model. For the domain of visual memory, the predictor of length of time between last concussion and ImPACT testing entered the model (and only that predictor),P = 4.07, t(l7) = 2.78,p = .01, R1 = .33, as a shorter length of time between the last concussion and the preseason testing related to lower performance on the visual memory tests. Many athletes and clinicians assume that the cognitive effects of a concussion are relatively brief in duration. However, the results of this study suggest that, at least for visual memory, these effects may last for several years following a concussion. The correlational design of this study precludes drawing conclusions about the causal direction of this relationship, but future longitudinal research may be able to clarify this important preliminary finding.

No description available.

A mild traumatic brain injury (mTBI), commonly referred to as a concussion, is when the brain experiences an abrupt acceleration and/or deceleration that sends shock waves through the brain tissue, upsetting its structure and function. A mTBI is a heterogeneous condition with acute and chronic outcomes for patients. The chronic form of mTBI can lead to a wide range of neurological, behavioral, and cognitive symptoms. Critically, this injury is not defined by a simple process or pathophysiological event but rather biomechanical and neurological brain damage that can trigger highly complex physiological cascades. These further lead to a wide range of cellular, molecular, and functional changes that alter genes and associated metabolites. These changes, if specifically characterized, could be used to predict a patient’s outcome and recovery timeline. Recently, genetic studies showed that specific genotypes could increase an individual’s risk of more severe injury and impaired recovery following mTBI. Consequently, an improved understanding of gene alteration and genetic changes is necessary to develop personalized diagnostic approaches which can guide the design of novel treatments. The current study proposes utilizing bioinformatic tools, biological networks, and databases to identify potential genes and microRNAs associated with the mTBI in order to aid the early diagnosis of mTBI and track recovery for individual patients. With bioinformatic techniques, we were able to identify and compare genetic and epigenetic data associated with mTBI, as well as understand the various aspects of molecular changes after brain injury. Ultimately, we analyzed and cataloged the biological pathways and networks associated with this injury. A critical search of online bioinformatics databases was performed to determine interactions between mTBI-related genes, and relevant molecular processes. The major finding was that APOE, S100B, GFAP, BDNF, AQP4, COMT, MBP, UCHL1, DRD2, ASIC1, and CACNA1A genes were significantly associated with mTBI outcome. Those genes are primarily involved in different neurological tasks and neurological pathways such as neuron projection regeneration, regulation of neuronal synaptic plasticity, cognition, memory function, neuronal cell death and the dopaminergic pathway. This study predicted specific miRNAs linked to mTBI outcomes and candidate genes (hsa-miR-204-5p, hsa-miR-16-5p, hsa-miR-10a-5p, has-miR-218-5p, has-miR-34a-5p), and RNA-seq analysis on the GSE123336 data revealed that one miRNA found (hsa-miR-10a-5p) matched our predictions related to mTBI outcomes. Pathway analysis revealed that the predicted miRNA targets were mainly engaged in nervous system signaling, neuron projection and cell differentiation. These findings may contribute to developing diagnostic procedures and treatments for mTBI patients who are still experiencing symptoms, but validation of these genetic markers for mTBI assessment requires patient participation and correlation with advanced personalized MRI methods that show concussion related changes. / Thesis / Master of Applied Science (MASc) / Traumatic brain injury (TBI) is a highly prevalent neurological injury affecting millions of individuals globally. Mild TBI (mTBI), sometimes called concussion, makes up over 85% of TBI cases. A mTBI is a heterogeneous condition with acute and chronic outcomes for patients and involves complex cascades of cellular and molecular events that can lead to functional changes in genes and associated metabolites. In recent genetic studies, it has been shown that certain genotypes are associated with a higher risk of experiencing a more serious injury and a slower recovery after mTBI. These genes can be utilized as crucial biomarkers to predict how long it will take for a person to recover from a concussion. The purpose of this study was to find potential biomarkers that could help in the early detection of mTBI and the monitoring of individual patients’ recovery. It was hypothesized that genes and miRNAs (and their associated proteins) involved in neuronal body, axonal and myelin integrity and regeneration would be identified as important markers of severity.