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1. Impaired visual working memory and reduced connectivity in undergraduates with a history of mild traumatic brain injury

   https://doi.org/10.1038/s41598-021-80995-1  

   Arciniega, Hector ; Shires, Jorja ; Furlong, Sarah ; Kilgore-Gomez, Alexandrea ; Cerreta, Adelle ; Murray, Nicholas G. ; Berryhill, Marian E. ( December 2021 , Scientific Reports)

   null (Ed.)

   Abstract Mild traumatic brain injury (mTBI), or concussion, accounts for 85% of all TBIs. Yet survivors anticipate full cognitive recovery within several months of injury, if not sooner, dependent upon the specific outcome/measure. Recovery is variable and deficits in executive function, e.g., working memory (WM) can persist years post-mTBI. We tested whether cognitive deficits persist in otherwise healthy undergraduates, as a conservative indicator for mTBI survivors at large. We collected WM performance (change detection, n-back tasks) using various stimuli (shapes, locations, letters; aurally presented numbers and letters), and wide-ranging cognitive assessments (e.g., RBANS). We replicated the observation of a general visual WM deficit, with preserved auditory WM. Surprisingly, visual WM deficits were equivalent in participants with a history of mTBI (mean 4.3 years post-injury) and in undergraduates with recent sports-related mTBI (mean 17 days post-injury). In seeking the underlying mechanism of these behavioral deficits, we collected resting state fMRI (rsfMRI) and EEG (rsEEG). RsfMRI revealed significantly reduced connectivity within WM-relevant networks (default mode, central executive, dorsal attention, salience), whereas rsEEG identified no differences (modularity, global efficiency, local efficiency). In summary, otherwise healthy current undergraduates with a history of mTBI present behavioral deficits with evidence of persistent disconnection long after full recovery is expected. 

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2. The Effects of Concussion Can Be Long-Lasting

   https://doi.org/10.3389/frym2020.00057  

   Alexandrea Kilgore-Gomez, Hector Arciniega ( April 2020 , Frontiers for young minds)

   null (Ed.)

   Have you ever felt “groggy” after hitting your head? We are learning more about how important it is to protect your brain from injuries, such as concussion. Concussion is also called mild traumatic brain injury (mTBI). After an mTBI, most people think patients recover within a few weeks. We noticed that some college students who had had an mTBI were struggling to remember information for a few seconds. This ability is called working memory and we need it for most thinking jobs, like remembering the name of someone you just met, or what you wanted to get from the fridge. In our experiments, we tested different groups of students to see if they could remember things for 1 s, like the color of squares. Participants with a history of mTBI (on average, more than 4 years after injury) performed worse than students without a history of mTBI. The take-home message is that there can be lasting effects of mTBI, even years after it happens. 

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3. Effective connectivity in the default mode network after paediatric traumatic brain injury

   https://doi.org/10.1111/ejn.15546  

   Vaughn, Kelly A. ; DeMaster, Dana ; Kook, Jeong Hwan ; Vannucci, Marina ; Ewing‐Cobbs, Linda ( December 2021 , European Journal of Neuroscience)

   Children who experience a traumatic brain injury (TBI) are at elevated risk for a range of negative cognitive and neuropsychological outcomes. Identifying which children are at greatest risk for negative outcomes can be difficult due to the heterogeneity of TBI. To address this barrier, the current study applied a novel method of characterizing brain connectivity networks, Bayesian multi‐subject vector autoregressive modelling (BVAR‐connect), which used white matter integrity as priors to evaluate effective connectivity—the time‐dependent relationship in functional magnetic resonance imaging (fMRI) activity between two brain regions—within the default mode network (DMN). In a prospective longitudinal study, children ages 8–15 years with mild to severe TBI underwent diffusion tensor imaging and resting state fMRI 7 weeks after injury; post‐concussion and anxiety symptoms were assessed 7 months after injury. The goals of this study were to (1) characterize differences in positive effective connectivity of resting‐state DMN circuitry between healthy controls and children with TBI, (2) determine if severity of TBI was associated with differences in DMN connectivity and (3) evaluate whether patterns of DMN effective connectivity predicted persistent post‐concussion symptoms and anxiety. Healthy controls had unique positive connectivity that mostly emerged from the inferior temporal lobes. In contrast, children with TBI had unique effective connectivity among orbitofrontal and parietal regions. These positive orbitofrontal‐parietal DMN effective connectivity patterns also differed by TBI severity and were associated with persisting behavioural outcomes. Effective connectivity may be a sensitive neuroimaging marker of TBI severity as well as a predictor of chronic post‐concussion symptoms and anxiety.

    

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4. Blood biomarkers for mild traumatic brain injury: a selective review of unresolved issues

   https://doi.org/10.1186/s40364-021-00325-5  

   Hier, Daniel B. ; Obafemi-Ajayi, Tayo ; Thimgan, Matthew S. ; Olbricht, Gayla R. ; Azizi, Sima ; Allen, Blaine ; Hadi, Bassam A. ; Wunsch, II, Donald C. ( September 2021 , Biomarker Research)

   The use of blood biomarkers after mild traumatic brain injury (mTBI) has been widely studied. We have identified eight unresolved issues related to the use of five commonly investigated blood biomarkers: neurofilament light chain, ubiquitin carboxy-terminal hydrolase-L1, tau, S100B, and glial acidic fibrillary protein. We conducted a focused literature review of unresolved issues in three areas: mode of entry into and exit from the blood, kinetics of blood biomarkers in the blood, and predictive capacity of the blood biomarkers after mTBI.

   Although a disruption of the blood brain barrier has been demonstrated in mild and severe traumatic brain injury, biomarkers can enter the blood through pathways that do not require a breach in this barrier. A definitive accounting for the pathways that biomarkers follow from the brain to the blood after mTBI has not been performed. Although preliminary investigations of blood biomarkers kinetics after TBI are available, our current knowledge is incomplete and definitive studies are needed. Optimal sampling times for biomarkers after mTBI have not been established. Kinetic models of blood biomarkers can be informative, but more precise estimates of kinetic parameters are needed. Confounding factors for blood biomarker levels have been identified, but corrections for these factors are not routinely made. Little evidence has emerged to date to suggest that blood biomarker levels correlate with clinical measures of mTBI severity. The significance of elevated biomarker levels thirty or more days following mTBI is uncertain. Blood biomarkers have shown a modest but not definitive ability to distinguish concussed from non-concussed subjects, to detect sub-concussive hits to the head, and to predict recovery from mTBI. Blood biomarkers have performed best at distinguishing CT scan positive from CT scan negative subjects after mTBI.

    

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5. Use of Brain Biomechanical Models for Monitoring Impact Exposure in Contact Sports

   https://doi.org/10.1007/s10439-022-02999-w  

   Ji, Songbai ; Ghajari, Mazdak ; Mao, Haojie ; Kraft, Reuben H. ; Hajiaghamemar, Marzieh ; Panzer, Matthew B. ; Willinger, Remy ; Gilchrist, Michael D. ; Kleiven, Svein ; Stitzel, Joel D. ( November 2022 , Annals of Biomedical Engineering)

   Abstract Head acceleration measurement sensors are now widely deployed in the field to monitor head kinematic exposure in contact sports. The wealth of impact kinematics data provides valuable, yet challenging, opportunities to study the biomechanical basis of mild traumatic brain injury (mTBI) and subconcussive kinematic exposure. Head impact kinematics are translated into brain mechanical responses through physics-based computational simulations using validated brain models to study the mechanisms of injury. First, this article reviews representative legacy and contemporary brain biomechanical models primarily used for blunt impact simulation. Then, it summarizes perspectives regarding the development and validation of these models, and discusses how simulation results can be interpreted to facilitate injury risk assessment and head acceleration exposure monitoring in the context of contact sports. Recommendations and consensus statements are presented on the use of validated brain models in conjunction with kinematic sensor data to understand the biomechanics of mTBI and subconcussion. Mainly, there is general consensus that validated brain models have strong potential to improve injury prediction and interpretation of subconcussive kinematic exposure over global head kinematics alone. Nevertheless, a major roadblock to this capability is the lack of sufficient data encompassing different sports, sex, age and other factors. The authors recommend further integration of sensor data and simulations with modern data science techniques to generate large datasets of exposures and predicted brain responses along with associated clinical findings. These efforts are anticipated to help better understand the biomechanical basis of mTBI and improve the effectiveness in monitoring kinematic exposure in contact sports for risk and injury mitigation purposes. 

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