Differential working memory load effects after mild traumatic brain injury

Prefrontal Cortex Activity During Gait in People With Persistent Symptoms After Concussion

BACKGROUND

Concussions result in transient symptoms stemming from a cortical metabolic energy crisis. Though this metabolic energy crisis typically resolves in a month, symptoms can persist for years. The symptomatic period is associated with gait dysfunction, the cortical underpinnings of which are poorly understood. Quantifying prefrontal cortex (PFC) activity during gait may provide insight into post-concussion gait dysfunction. The purpose of this study was to explore the effects of persisting concussion symptoms on PFC activity during gait. We hypothesized that adults with persisting concussion symptoms would have greater PFC activity during gait than controls. Within the concussed group, we hypothesized that worse symptoms would relate to increased PFC activity during gait, and that increased PFC activity would relate to worse gait characteristics.

METHODS

The Neurobehavior Symptom Inventory (NSI) characterized concussion symptoms. Functional near-infrared spectroscopy quantified PFC activity (relative concentration changes of oxygenated hemoglobin [HbO2]) in 14 people with a concussion and 25 controls. Gait was assessed using six inertial sensors in the concussion group.

RESULTS

Average NSI total score was 26.4 (13.2). HbO2 was significantly higher (P = .007) for the concussed group (0.058 [0.108]) compared to the control group (-0.016 [0.057]). Within the concussion group, HbO2 correlated with NSI total symptom score (ρ = .62; P = .02), sagittal range of motion (r = .79; P = .001), and stride time variability (r = -.54; P = .046).

CONCLUSION

These data suggest PFC activity relates to symptom severity and some gait characteristics in people with persistent concussion symptoms. Identifying the neurophysiological underpinnings to gait deficits post-concussion expands our knowledge of motor behavior deficits in people with persistent concussion symptoms.

Fatigue and cognitive fatigability in patients with chronic pain

OBJECTIVES

Fatigue is common in patients with chronic pain. Still, there is a lack of studies examining objectively measurable cognitive aspects of fatigue: cognitive fatigability (CF). We aimed to investigate the presence of CF in patients with chronic pain and its relation to self-rated fatigue, attention, pain characteristics, sleep disturbance, depression, and anxiety.

METHODS

Two hundred patients with chronic pain and a reference group of 36 healthy subjects underwent a comprehensive neuropsychological test battery, including measurement of CF with the Wechsler Adult Intelligence Scale-III Coding subtest, and self-assessment of trait and state fatigue.

RESULTS

The patients with chronic pain did not show more CF as compared to the reference group. There was an association between CF and processing speed on a test of sustained and selective attention in the chronic pain group, while self-rated fatigue measures and pain characteristics were not associated with CF. Self-rated fatigue measures were highly correlated with self-rated pain intensity, spreading of pain, depression, anxiety, and sleep disturbance.

CONCLUSIONS

The findings highlight the distinction between objective and subjective aspects of fatigue in chronic pain, and that the underlying causes of these different aspects of fatigue need to be studied further.

Evaluating the effects of brain injury, disease and tasks on cognitive fatigue

Because cognitive fatigue (CF) is common and debilitating following brain injury or disease we investigated the relationships among CF, behavioral performance, and cerebral activation within and across populations by combining the data from two cross-sectional studies. Individuals with multiple sclerosis (MS) were included to model CF resulting from neurological disease; individuals who had sustained a traumatic brain injury (TBI) were included to model CF resulting from neurological insult; both groups were compared with a control group (Controls). CF was induced while neuroimaging data was acquired using two different tasks. CF significantly differed between the groups, with the clinical groups reporting more CF than Controls-a difference that was statistically significant for the TBI group and trended towards significance for the MS group. The accrual of CF did not differ across the three groups; and CF ratings were consistent across tasks. Increasing CF was associated with longer response time for all groups. The brain activation in the caudate nucleus and the thalamus was consistently correlated with CF in all three groups, while more dorsally in the caudate, activation differed across the groups. These results suggest the caudate and thalamus to be central to CF while more dorsal aspects of the caudate may be sensitive to damage associated with particular types of insult.

The impact of mindfulness on working memory-related brain activation in breast cancer survivors with cognitive complaints

PURPOSE

Cancer-related cognitive impairment (CRCI) has been associated with altered brain activation after chemotherapy in areas related to working memory. Hence, improving working memory capacity and associated brain activation might aid in the recovery of CRCI. In this study, we investigated the potential of a mindfulness-based intervention (MBI) to impact working memory-related brain activation.

METHODS

Female breast cancer survivors reporting cognitive complaints (N=117) were randomized into a mindfulness (n=43; MBI), physical training (n=36; PT), or waitlist control condition (n=38; WL). Participants completed MRI scans before the intervention, immediately after, and three months post-intervention. Task-based functional MRI was used to measure differences between groups over time in working memory-related brain activation while performing a visual-verbal n-back task.

RESULTS

Data of 83 participants (32/26/25 MBI/PT/WL) was included. Compared to the waitlist group, MBI participants showed reduced task-related activation in the right middle frontal and angular gyrus and increased activation in the right dorsal posterior cingulate cortex over time. Compared to the physical training group, MBI participants showed reduced brain activation in the bilateral superior parietal lobule and right dorsal anterior cingulate cortex over time. No differences between physical training and no intervention were identified.

CONCLUSION

This study showed that an 8-week mindfulness-based intervention can significantly alter brain activation across brain regions involved in working memory, attentional control, and emotion processing during performance of a working memory task. This might aid in the recovery of CRCI.

IMPLICATIONS FOR CANCER SURVIVORS

Mindfulness might alter brain activation patterns while performing a working memory task, which might ultimately aid in restoring higher order cognitive functions.

Hyper-acute effects of sub-concussive soccer headers on brain function and hemodynamics

Introduction

Sub-concussive head impacts in soccer are drawing increasing research attention regarding their acute and long-term effects as players may experience thousands of headers in a single season. During these impacts, the head experiences rapid acceleration similar to what occurs during a concussion, but without the clinical implications. The physical mechanism and response to repetitive impacts are not completely understood. The objective of this work was to examine the immediate functional outcomes of sub-concussive level impacts from soccer heading in a natural, non-laboratory environment.

Methods

Twenty university level soccer athletes were instrumented with sensor-mounted bite bars to record impacts from 10 consecutive soccer headers. Pre- and post-header measurements were collected to determine hyper-acute changes, i.e., within minutes after exposure. This included measuring blood flow velocity using transcranial Doppler (TCD) ultrasound, oxyhemoglobin concentration using functional near infrared spectroscopy imaging (fNIRS), and upper extremity dual-task (UEF) neurocognitive testing.

Results

On average, the athletes experienced 30.7 ± 8.9 g peak linear acceleration and 7.2 ± 3.1 rad/s peak angular velocity, respectively. Results from fNIRS measurements showed an increase in the brain oxygenation for the left prefrontal cortex (PC) (p = 0.002), and the left motor cortex (MC) (p = 0.007) following the soccer headers. Additional analysis of the fNIRS time series demonstrates increased sample entropy of the signal after the headers in the right PC (p = 0.02), right MC (p = 0.004), and left MC (p = 0.04).

Discussion

These combined results reveal some variations in brain oxygenation immediately detected after repetitive headers. Significant changes in balance and neurocognitive function were not observed in this study, indicating a mild level of head impacts. This is the first study to observe hemodynamic changes immediately after sub-concussive impacts using non-invasive portable imaging technology. In combination with head kinematic measurements, this information can give new insights and a framework for immediate monitoring of sub-concussive impacts on the head.

Emotional Regulation and Adolescent Concussion: Overview and Role of Neuroimaging

Emotional dysregulation symptoms following a concussion are associated with an increased risk for emotional dysregulation disorders (e.g., depression and anxiety), especially in adolescents. However, predicting the emergence or worsening of emotional dysregulation symptoms after concussion and the extent to which this predates the onset of subsequent psychiatric morbidity after injury remains challenging. Although advanced neuroimaging techniques, such as functional magnetic resonance imaging and diffusion magnetic resonance imaging, have been used to detect and monitor concussion-related brain abnormalities in research settings, their clinical utility remains limited. In this narrative review, we have performed a comprehensive search of the available literature regarding emotional regulation, adolescent concussion, and advanced neuroimaging techniques in electronic databases (PubMed, Scopus, and Google Scholar). We highlight clinical evidence showing the heightened susceptibility of adolescents to experiencing emotional dysregulation symptoms following a concussion. Furthermore, we describe and provide empirical support for widely used magnetic resonance imaging modalities (i.e., functional and diffusion imaging), which are utilized to detect abnormalities in circuits responsible for emotional regulation. Additionally, we assess how these abnormalities relate to the emotional dysregulation symptoms often reported by adolescents post-injury. Yet, it remains to be determined if a progression of concussion-related abnormalities exists, especially in brain regions that undergo significant developmental changes during adolescence. We conclude that neuroimaging techniques hold potential as clinically useful tools for predicting and, ultimately, monitoring the treatment response to emotional dysregulation in adolescents following a concussion.

Changes in Brain Activation Patterns During Working Memory Tasks in People With Post-COVID Condition and Persistent Neuropsychiatric Symptoms

BACKGROUND AND OBJECTIVES

Post-COVID condition (PCC) is common and often involves neuropsychiatric symptoms. This study aimed to use blood oxygenation level-dependent fMRI (BOLD-fMRI) to assess whether participants with PCC had abnormal brain activation during working memory (WM) and whether the abnormal brain activation could predict cognitive performance, motor function, or psychiatric symptoms.

METHODS

The participants with PCC had documented coronavirus disease 2019 (COVID-19) at least 6 weeks before enrollment. Healthy control participants had no prior history of COVID-19 and negative tests for severe acute respiratory syndrome coronavirus 2. Participants were assessed using 3 NIH Toolbox (NIHTB) batteries for Cognition (NIHTB-CB), Emotion (NIHTB-EB), and Motor function (NIHTB-MB) and selected tests from the Patient-Reported Outcomes Measurement Information System (PROMIS). Each had BOLD-fMRI at 3T, during WM (N-back) tasks with increasing attentional/WM load.

RESULTS

One hundred sixty-nine participants were screened; 50 fulfilled the study criteria and had complete and usable data sets for this cross-sectional cohort study. Twenty-nine participants with PCC were diagnosed with COVID-19 242 ± 156 days earlier; they had similar ages (42 ± 12 vs 41 ± 12 years), gender proportion (65% vs 57%), racial/ethnic distribution, handedness, education, and socioeconomic status, as the 21 uninfected healthy controls. Despite the high prevalence of memory (79%) and concentration (93%) complaints, the PCC group had similar performance on the NIHTB-CB as the controls. However, participants with PCC had greater brain activation than the controls across the network (false discovery rate-corrected p = 0.003, Tmax = 4.17), with greater activation in the right superior frontal gyrus (p = 0.009, Cohen d = 0.81, 95% CI 0.15-1.46) but lesser deactivation in the default mode regions (p = 0.001, d = 1.03, 95% CI 0.61-1.99). Compared with controls, participants with PCC also had poorer dexterity and endurance on the NIHTB-MB, higher T scores for negative affect and perceived stress, but lower T scores for psychological well-being on the NIHTB-EB, as well as more pain symptoms and poorer mental and physical health on measures from the PROMIS. Greater brain activation predicted poorer scores on measures that were abnormal on the NIHTB-EB.

DISCUSSION

Participants with PCC and neuropsychiatric symptoms demonstrated compensatory neural processes with greater usage of alternate brain regions, and reorganized networks, to maintain normal performance during WM tasks. BOLD-fMRI was sensitive for detecting brain abnormalities that correlated with various quantitative neuropsychiatric symptoms.

Plasticity impairment alters community structure but permits successful pattern separation in a hippocampal network model

Patients who suffer from traumatic brain injury (TBI) often complain of learning and memory problems. Their symptoms are principally mediated by the hippocampus and the ability to adapt to stimulus, also known as neural plasticity. Therefore, one plausible injury mechanism is plasticity impairment, which currently lacks comprehensive investigation across TBI research. For these studies, we used a computational network model of the hippocampus that includes the dentate gyrus, CA3, and CA1 with neuron-scale resolution. We simulated mild injury through weakened spike-timing-dependent plasticity (STDP), which modulates synaptic weights according to causal spike timing. In preliminary work, we found functional deficits consisting of decreased firing rate and broadband power in areas CA3 and CA1 after STDP impairment. To address structural changes with these studies, we applied modularity analysis to evaluate how STDP impairment modifies community structure in the hippocampal network. We also studied the emergent function of network-based learning and found that impaired networks could acquire conditioned responses after training, but the magnitude of the response was significantly lower. Furthermore, we examined pattern separation, a prerequisite of learning, by entraining two overlapping patterns. Contrary to our initial hypothesis, impaired networks did not exhibit deficits in pattern separation with either population- or rate-based coding. Collectively, these results demonstrate how a mechanism of injury that operates at the synapse regulates circuit function.

Electrophysiology reveals cognitive-linguistic alterations after concussion

Language deficits and alterations to the N400 ERP are commonly reported in aphasia and moderate-to-severe traumatic brain injury (TBI), but have seldomly been investigated after mild TBI, such as concussion. In the present study, the N400 was recorded from young adults within 1-month after concussion and matched controls during a sentence processing task. The N400 recorded to semantically incongruent sentence-final words was significantly more negative and with a more anterior distribution in the concussion group than control group. Among the concussion group, a weaker N400 was associated with more concussion symptoms, slower response time, and poorer executive functioning. Multiple regression results showed that concussion occurrence and male gender were independently associated with a more negative N400-effect, whereas symptoms were associated with a weaker N400. These findings provide novel evidence that alterations to lexical-semantic networks may occur after concussion and vary based on individual differences in post-concussion symptoms and cognitive function.

Memory retrieval brain-behavior disconnection in mild traumatic brain injury: A magnetoencephalography and diffusion tensor imaging study

Mild traumatic brain (mTBI) injury is often associated with long-term cognitive and behavioral complications, including an increased risk of memory impairment. Current research challenges include a lack of cross-modal convergence regarding the underlying neural-behavioral mechanisms of mTBI, which hinders therapeutics and outcome management for this frequently under-treated and vulnerable population. We used multi-modality imaging methods including magnetoencephalography (MEG) and diffusion tensor imaging (DTI) to investigate brain-behavior impairment in mTBI related to working memory. A total of 41 participants were recruited, including 23 patients with a first-time mTBI imaged within 3 months of injury (all male, age = 29.9, SD = 6.9), and 18 control participants (all male, age = 27.3, SD = 5.3). Whole-brain statistics revealed spatially concomitant functional-structural disruptions in brain-behavior interactions in working memory in the mTBI group compared with the control group. These disruptions are located in the hippocampal-prefrontal region and, additionally, in the amygdala (measured by MEG neural activation and DTI measures of fractional anisotropy in relation to working memory performance; p < .05, two-way ANCOVA, nonparametric permutations, corrected). Impaired brain-behavior connections found in the hippocampal-prefrontal and amygdala circuits indicate brain dysregulation of memory, which may leave mTBI patients vulnerable to increased environmental demands exerting memory resources, leading to related cognitive and emotional psychopathologies. The findings yield clinical implications and highlight a need for early rehabilitation after mTBI, including attention- and sensory-based behavioral exercises.

Multimodal MRI examination of structural and functional brain changes in older women with breast cancer in the first year of antiestrogen hormonal therapy

PURPOSE

Cancer patients are concerned about treatment-related cognitive problems. We examined effects of antiestrogen hormonal therapy on brain imaging metrics in older women with breast cancer.

METHODS

Women aged 60 + treated with hormonal therapy only and matched non-cancer controls (n = 29/group) completed MRI and objective and self-reported cognitive assessment at pre-treatment/enrollment and 12 months later. Gray matter was examined using voxel-based morphometry (VBM), FreeSurfer, and brain age calculations. Functional MRI (fMRI) assessed working memory-related activation. Analyses examined cross-sectional and longitudinal differences and tested associations between brain metrics, cognition, and days on hormonal therapy.

RESULTS

The cancer group showed regional reductions over 12 months in frontal, temporal, and parietal gray matter on VBM, reduced FreeSurfer cortical thickness in prefrontal, parietal, and insular regions, and increased working memory-related fMRI activation in frontal, cingulate, and visual association cortex. Controls showed only reductions in fusiform gyrus on VBM and FreeSurfer temporal and parietal cortex thickness. Women with breast cancer showed higher estimated brain age and lower regional gray matter volume than controls at both time points. The cancer group showed a trend toward lower performance in attention, processing speed, and executive function at follow-up. There were no significant associations between brain imaging metrics and cognition or days on hormonal therapy.

CONCLUSION

Older women with breast cancer showed brain changes in the first year of hormonal therapy. Increased brain activation during working memory processing may be a sign of functional compensation for treatment-related structural changes. This hypothesis should be tested in larger samples over longer time periods.

CLINICALTRIALS

GOV IDENTIFIER

NCT03451383.

Neural alterations in working memory of mild-moderate TBI: An fMRI study in Malaysia

Working memory (WM) encompasses crucial cognitive processes or abilities to retain and manipulate temporary information for immediate execution of complex cognitive tasks in daily functioning such as reasoning and decision-making. The WM of individuals sustaining traumatic brain injury (TBI) was commonly compromised, especially in the domain of WM. The current study investigated the brain responses of WM in a group of participants with mild-moderate TBI compared to their healthy counterparts employing functional magnetic resonance imaging. All consented participants (healthy: n = 26 and TBI: n = 15) performed two variations of the n-back WM task with four load conditions (0-, 1-, 2-, and 3-back). The respective within-group effects showed a right hemisphere-dominance activation and slower reaction in performance for the TBI group. Random-effects analysis revealed activation difference between the two groups in the right occipital lobe in the guided n-back with cues, and in the bilateral occipital lobe, superior parietal region, and cingulate cortices in the n-back without cues. The left middle frontal gyrus was implicated in the load-dependent processing of WM in both groups. Further group analysis identified that the notable activation changes in the frontal gyri and anterior cingulate cortex are according to low and high loads. Though relatively smaller in scale, this study was eminent as it clarified the neural alterations in WM in the mild-moderate TBI group compared to healthy controls. It confirmed the robustness of the phenomenon in TBI with the reproducibility of the results in a heterogeneous non-Western sample.

Abnormal neurite density and orientation dispersion in frontal lobe link to elevated hyperactive/impulsive behaviors in young adults with traumatic brain injury

Traumatic brain injury is a major public health concern. A significant proportion of individuals experience post-traumatic brain injury behavioural impairments, especially in attention and inhibitory control domains. Traditional diffusion-weighted MRI techniques, such as diffusion tensor imaging, have provided tools to assess white matter structural disruptions reflecting the long-term brain tissue alterations associated with traumatic brain injury. The recently developed neurite orientation dispersion and density imaging is a more advanced diffusion MRI modality, which provides more refined characterization of brain tissue microstructures by assessing the neurite orientation dispersion and neurite density properties. In this study, neurite orientation dispersion and density imaging data from 44 young adults with chronic traumatic brain injury (who had no prior-injury diagnoses of any sub-presentation of attention deficits/hyperactivity disorder or experience of severe inattentive and/or hyperactive behaviours) and 45 group-matched normal controls were investigated, to assess the post-injury morphometrical and microstructural brain alterations and their relationships with the behavioural outcomes. Maps of fractional anisotropy, neurite orientation dispersion index and neurite density index were calculated. Vertex-wise and voxel-wise analyses were conducted for grey matter and white matter, respectively. Post hoc region-of-interest-based analyses were also performed. Compared to the controls, the group of traumatic brain injury showed significantly increased orientation dispersion index and significantly decreased neurite density index in various grey matter regions, as well as significantly decreased orientation dispersion index in several white matter regions. Brain–behavioural association analyses indicated that the reduced neurite density index of the left precentral gyrus and the reduced orientation dispersion index of the left superior longitudinal fasciculus were significantly associated with elevated hyperactive/impulsive symptoms in the patients with traumatic brain injury. These findings suggest that post-injury chronical neurite intracellular volume and angular distribution anomalies in the frontal lobe, practically the precentral area, can significantly contribute to the onset of hyperactive/impulsive behaviours in young adults with traumatic brain injury.

Transcranial direct current stimulation modulates working memory and prefrontal-insula connectivity after mild-moderate traumatic brain injury

Background: Persistent posttraumatic symptoms (PPS) may manifest after a mild-moderate traumatic brain injury (mmTBI) even when standard brain imaging appears normal. Transcranial direct current stimulation (tDCS) represents a promising treatment that may ameliorate pathophysiological processes contributing to PPS. Objective/Hypothesis: We hypothesized that in a mmTBI population, active tDCS combined with training would result in greater improvement in executive functions and post-TBI cognitive symptoms and increased resting state connectivity of the stimulated region, i.e., left dorsolateral prefrontal cortex (DLPFC) compared to control tDCS. Methods: Thirty-four subjects with mmTBI underwent baseline assessments of demographics, symptoms, and cognitive function as well as resting state functional magnetic resonance imaging (rsfMRI) in a subset of patients (n = 24). Primary outcome measures included NIH EXAMINER composite scores, and the Neurobehavioral Symptom Inventory (NSI). All participants received 10 daily sessions of 30 min of executive function training coupled with active or control tDCS (2 mA, anode F3, cathode right deltoid). Imaging and assessments were re-obtained after the final training session, and assessments were repeated after 1 month. Mixed-models linear regression and repeated measures analyses of variance were calculated for main effects and interactions. Results: Both active and control groups demonstrated improvements in executive function (EXAMINER composite: p < 0.001) and posttraumatic symptoms (NSI cognitive: p = 0.01) from baseline to 1 month. Active anodal tDCS was associated with greater improvements in working memory reaction time compared to control (p = 0.007). Reaction time improvement correlated significantly with the degree of connectivity change between the right DLPFC and the left anterior insula (p = 0.02). Conclusion: Anodal tDCS improved reaction time on an online working memory task in a mmTBI population, and decreased connectivity between executive network and salience network nodes. These findings generate important hypotheses for the mechanism of recovery from PPS after mild-moderate TBI.

Novel microglia-mediated mechanisms underlying synaptic loss and cognitive impairment after traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of long-term neurological disability in the world. Currently, there are no therapeutics for treating the deleterious consequences of brain trauma; this is in part due to a lack of complete understanding of cellular processes that underlie TBI-related pathologies. Following TBI, microglia, the brain resident immune cells, turn into a "reactive" state characterized by the production of inflammatory mediators that contribute to the development of cognitive deficits. Utilizing multimodal, state-of-the-art techniques that widely span from ultrastructural analysis to optogenetic interrogation of circuit function, we investigated the reactive microglia phenotype one week after injury when learning and memory deficits are also measured. Microglia displayed increased: (i) phagocytic activity in vivo, (ii) synaptic engulfment, (iii) increased neuronal contact, including with dendrites and somata (termed 'satellite microglia'). Functionally, satellite microglia might impact somatic inhibition as demonstrated by the associated reduction in inhibitory synaptic drive. Cumulatively, here we demonstrate novel microglia-mediated mechanisms that may contribute to synaptic loss and cognitive impairment after traumatic brain injury.

Investigating the Effect of Fatigue and Psychological Distress on Information Processing Speed in the Postacute Period After Mild Traumatic Brain Injury in Premorbidly Healthy Adults

Impairments in processing speed under conditions of increasing cognitive load have been reported in individuals with mild traumatic brain injury (mTBI). In other conditions that are also associated with white matter disruption, both psychological distress and fatigue have been shown to underlie this impairment.

OBJECTIVE

the current study aimed to investigate whether slowing of processing abilities under conditions of greater cognitive load is independent of fatigue and psychological status in premorbidly healthy individuals with subacute mTBI.

METHOD

using a prospective observational design, we examined 84 individuals with mTBI approximately 8 weeks after injury and 47 healthy control (HC) participants. They were assessed with the Symbol Digit Modality Test, an n-back task and a rate of gain of information choice reaction time task that conforms to Hick's law. Participants were also assessed with measures of fatigue and psychological status.

RESULTS

as expected, findings revealed no group differences on simple reaction time tasks, but as task complexity increased, the mTBI group performed more slowly than the HC group. This group difference occurred independently of fatigue and psychological distress levels and was associated with a moderate effect size.

CONCLUSIONS

during the subacute period after mTBI, premorbidly healthy individuals demonstrate impairment in their ability to rapidly process information as the cognitive load of the task increases beyond simple reaction time requirements. Examination of whether these changes affect resumption of premorbid roles is warranted.

Sports Related Brain Injury and Neurodegeneration in Athletes

Sports deserve a special place in human life to impart healthy and refreshing wellbeing. However, sports activities, especially contact sports, renders athlete vulnerable to brain injuries. Athletes participating in a contact sport like boxing, rugby, American football, wrestling, and basketball are exposed to traumatic brain injuries (TBI) or concussions. The acute and chronic nature of these heterogeneous injuries provides a spectrum of dysfunctions that alters the neuronal, musculoskeletal, and behavioral responses of an athlete. Many sports-related brain injuries go unreported, but these head impacts trigger neurometabolic disruptions that contribute to long-term neuronal impairment. The pathophysiology of post-concussion and its underlying mechanisms are undergoing intense research. It also shed light on chronic disorders like Parkinson's disease, Alzheimer's disease, and dementia. In this review, we examined post-concussion neurobehavioral changes, tools for early detection of signs, and their impact on the athlete. Further, we discussed the role of nutritional supplements in ameliorating neuropsychiatric diseases in athletes.

CX3CL1/CX3CR1 signaling targets for the treatment of neurodegenerative diseases

Neuroinflammation was initially thought of as a consequence of neurodegenerative disease pathology, but more recently it is becoming clear that it plays a significant role in the development and progression of disease. Thus, neuroinflammation is seen as a realistic and valuable therapeutic target for neurodegeneration. Neuroinflammation can be modulated by neuron-glial signaling through various soluble factors, and one such critical modulator is Fractalkine or C-X3-C Motif Chemokine Ligand 1 (CX3CL1). CX3CL1 is produced in neurons and is a unique chemokine that is initially translated as a transmembrane protein but can be proteolytically processed to generate a soluble chemokine. CX3CL1 has been shown to signal through its sole receptor CX3CR1, which is located on microglial cells within the central nervous system (CNS). Although both the membrane bound and soluble forms of CX3CL1 appear to interact with CX3CR1, they do seem to have different signaling capabilities. It is believed that the predominant function of CX3CL1 within the CNS is to reduce the proinflammatory response and many studies have shown neuroprotective effects. However, in some cases CX3CL1 appears to be promoting neurodegeneration. This review focusses on presenting a comprehensive overview of the complex nature of CX3CL1/CX3CR1 signaling in neurodegeneration and how it may present as a therapeutic in some neurodegenerative diseases but not others. The role of CX3CL1/CXCR1 is reviewed in the context of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), ischemia, retinopathies, spinal cord and neuropathic pain, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, and epilepsy.

Aberrant modulation of brain activity underlies impaired working memory following traumatic brain injury

Impaired working memory is a common and disabling consequence of traumatic brain injury (TBI) that is caused by aberrant brain processing. However, little is known about the extent to which deficits are perpetuated by specific working memory subprocesses. Using a combined functional magnetic resonance imaging (fMRI) and working memory paradigm, we tested the hypothesis that the pattern of brain activation subserving working memory following TBI would interact with both task demands and specific working memory subcomponents: encoding, maintenance, and retrieval. Forty-three patients with moderate-severe TBI, of whom 25 were in the acute phase of recovery (M = 2.16 months, SD = 1.48 months, range = 0.69 - 6.64 months) and 18 in the chronic phase of recovery (M = 23.44 months, SD = 6.76 months, range = 13.35 - 34.82 months), were compared with 38 demographically similar healthy controls. Behaviourally, we found that working memory deficits were confined to the high cognitive load trials in both acute (P = 0.006) and chronic (P = 0.024) cohorts. Furthermore, results for a subset of the sample (18 chronic TBI and 17 healthy controls) who underwent fMRI revealed that the TBI group showed reduced brain activation when simply averaged across all task trials (regardless of cognitive load or subcomponent). However, interrogation of the subcomponents of working memory revealed a more nuanced pattern of activation. When examined more closely, patterns of brain activity following TBI were found to interact with both task demands and the working memory subcomponent: increased activation was observed during encoding in the left inferior occipital gyrus whereas decreased activation was apparent during maintenance in the bilateral cerebellum and left calcarine sulcus. Taken together, findings indicate an inability to appropriately modulate brain activity according to task demand that is specific to working memory encoding and maintenance.

Psycho-affective health, cognition, and neurophysiological functioning following sports-related concussion in symptomatic and asymptomatic athletes, and control athletes

Little is known about the neuropsychiatric and neurophysiological differences that characterize abnormal recovery following a concussion. The present study aimed to investigate the psycho-affective, cognitive, and neurophysiological profiles of symptomatic, slow-to-recover, concussed athletes, asymptomatic concussed athletes, and control athletes. Seventy-eight athletes (26 symptomatic, 26 asymptomatic, 26 control) completed the Beck Depression Inventory-II, Profile of Mood States, and 2-Back task. Additionally, event-related brain potentials were recorded during an experimental three-stimulus visual Oddball paradigm. Compared to asymptomatic and control groups, the symptomatic group reported greater depression symptoms and negatively altered mood states. Symptomatic athletes also exhibited poorer cognitive performance on the 2-Back task, indicated by more errors and slower reaction time. ERP analyses indicated prolonged P3b latency for both symptomatic and asymptomatic groups, but symptomatic athletes also exhibited reduced P3b amplitude compared to both asymptomatic and control groups. For the asymptomatic group, correlations were observed between time since last concussion and functioning, but no relations were observed within the symptomatic group for any measure. The current findings provide valuable information regarding the psycho-affective, cognitive, and neurophysiological profiles of athletes with and without persistent symptoms following a concussion and highlight the need to assess and treat symptomatic, slow-to-recover athletes from a multidimensional and integrative perspective.

Post-exercise cognitive testing to assess persisting alterations in athletes with a history of concussion

Primary Objective: To determine whether a physical exercise protocol could reveal persistent cognitive alterations in university athletes with a history of concussion (HOC). Thirty-four HOC and 34 controls participated in this study.Research Design: Cross-sectional.Methods and Procedures: The exercise protocol consisted of a 20-min bout on a stationary bike at 80% of the theoretical maximal heart rate. Before and after the exercise, participants performed a computerized switch task designed specifically to recruit executive functions. Group × Condition (pre- and post-exercise) repeated measures of ANCOVAs for accuracy, reaction time, and inverse efficiency score on the switch task were conducted. Chi-square tests were run to determine if the proportion of HOC and controls who underperformed (at least 2SD lower than the control group's average score) at rest and post-exercise were similar. Whilst no interaction or main effects were found with ANCOVAs, significantly more HOC athletes (21%) underperformed following exercise than at rest (3%) on the switch task, p = .02. The current results indicate that an acute bout of exercise can reveal persistent alterations that are not present at rest in the protracted phase of concussion. They also highlight the importance of considering inter-individual differences in recovery trajectories.

Moving Toward Accurate Assessment of Working Memory in Adults With Neurogenically Based Communication Disorders

Purpose This article presents a viewpoint highlighting concerns regarding currently available assessments of working memory in adults with neurogenic communication disorders. Additionally, we provide recommendations for improving working memory assessment in this population. Method This viewpoint includes a critique of clinical and experimental working memory tests relevant to speech-language pathologists. We consider the terminology used to describe memory, as well as discuss language demands and test construction. Results Clinical and experimental testing of working memory in adults with neurogenic communication disorders is challenged due to theoretical, methodological, and practical limitations. The major limitations are characterized as linguistic and task demands, presentation and response modality effects, test administration, and scoring parameters. Taking these limitations into consideration, several modifications to working memory testing and their relevance to neurogenic populations are discussed. Conclusions The recommendations provided in this article can better guide clinicians and researchers to advocate for improved tests of working memory in adults with neurogenic communication disorders. Future research should continue to address these concerns and consider our recommendations.

Neural activity during response inhibition in mild traumatic brain injury and posttraumatic stress disorder

Mild traumatic brain injury (mTBI) is often characterized by deficits in response inhibition, which can contribute to marked social and occupational dysfunction. mTBI often occurs in the context of psychologically traumatic events. This can cause posttraumatic stress disorder (PTSD), which also impedes response inhibition. The overlap or distinction in these inhibitory deficits in mTBI and PTSD is unclear. This study aimed to assess behavioral, neurophysiological, and neuroimaging indices of response inhibition in mTBI by also assessing these parameters in healthy controls (HC) and PTSD participants. Participants with mTBI (without PTSD) (n = 46), PTSD (without mTBI) (n = 41), and HC (n = 40) were assessed during a response inhibition task (the Go/NoGo task) during neuropsychological testing and separate functional magnetic imaging and event-related potentials sessions. PTSD symptom severity was assessed with the Clinician-Administered PTSD Scale. Both mTBI and PTSD participants performed more omission errors on the Go/NoGo task and were associated with greater N2 amplitude, greater left inferior parietal activation and reduced connectivity of the left inferior parietal cluster and left angular gyrus compared to HC. There were no differences between mTBI and PTSD on any of these measures. These findings highlight that both mTBI and PTSD contribute to neural dysfunction during response inhibition, and arguably these occur due to distinct mechanisms. In the context of the common comorbidity between these two conditions, strategies to address response inhibition deficits in mTBI may need to consider causative factors underpinning neurological insult of mTBI and psychological effects associated with PTSD.

Brain bases of recovery following cognitive rehabilitation for traumatic brain injury: a preliminary study

Many patients with traumatic brain injury (TBI) have persistent cognitive deficits, including decreased attention and working memory. This preliminary study examined fMRI data from a clinical trial implementing a 4-week virtual reality driving intervention to assess how sustained training can improve deficits related to traumatic brain injury. Previously-reported behavioral findings showed improvements in working memory and processing speed in those who received the intervention; this report explores the brain bases of these effects by comparing neural activity related to working memory (n-back task) and resting state connectivity before and after the intervention. In the baseline visit (n = 24), working memory activity was prominent in bilateral DLPFC and prefrontal cortex, anterior insula, medial superior frontal gyrus, left thalamus, bilateral supramarginal / angular gyrus, precuneus, and left posterior middle temporal gyrus. Following intervention, participants showed less global activation on the n-back task, with regions of activity only in the bilateral middle frontal cortex, posterior middle frontal gyrus, and supramarginal gyrus. Activity related to working memory load was reduced for the group that went through the intervention (n = 7) compared to the waitlist control group (n = 4). These results suggest that successful cognitive rehabilitation of working memory in TBI may be associated with increased efficiency of brain networks, evidenced by reduced activation of brain activity during cognitive processing. These results highlight the importance of examining brain activity related to cognitive rehabilitation of attention and working memory after brain injury.

Effect of blast-related mTBI on the working memory system: a resting state fMRI study

Reduced working memory is frequently reported by Veterans with a history of blast-related mild traumatic brain injury (mTBI), but can be difficult to quantify on neuropsychological measures. This study aimed to improve our understanding of the impact of blast-related mTBI on the working memory system by using resting state functional magnetic resonance imaging (fMRI) to explore differences in functional connectivity between OEF/OIF/OND Veterans with and without a history of mTBI. Participants were twenty-four Veterans with a history of blast-related mTBI and 17 Veterans who were deployed but had no lifetime history of TBI. Working memory ability was evaluated with the Auditory Consonants Trigrams (ACT) task. Resting state fMRI was used to evaluate intrinsic functional connectivity from frontal seed regions that are known components of the working memory network. No significant group differences were found on the ACT, but the imaging analyses revealed widespread hyper-connectivity from the frontal seed regions in the Veterans with a history of mTBI relative to the deployed control group. Further, within the mTBI group, but not the control group, better performance on the ACT was associated with increased functional connectivity to multiple brain regions, including cerebellar components of the working memory network. These results were present after controlling for age, PTSD symptoms, and estimated premorbid IQ, and suggest that long-term alterations in the functional connectivity of the working memory network following blast-related mTBI may reflect a compensatory change that contributes to intact performance on an objective measure of working memory.

Changes in working memory-related cortical responses following pediatric mild traumatic brain injury: A longitudinal fMRI study

Persistent post-concussion symptoms (PPCS) lasting longer than 4 weeks affect 25% of children with mild traumatic brain injury (mTBI) or concussion. Working memory (WM) problems are a common complaint in children with PPCS. Despite normal function on traditional neuropsychological tests, these children exhibit aberrant cortical responses within the dorsolateral prefrontal cortex (dlPFC) and default mode network (DMN) regions – both of which are implicated in WM. Using a prospective, longitudinal cohort study design, we investigated changes in cortical fMRI responses within the dlPFC and DMN during an nback WM task at two timepoints: one and two months post-injury. Across these timepoints, the primary outcome was change in cortical activations (increase in BOLD) and deactivations (decrease in BOLD) of both dlPFC and DMN. Twenty-nine children (mean age 15.49 ± 2.15; 48.3% male) with fMRI scans at both timepoints were included, following data quality control. Student’s t-tests were used to examine cortical activations across time and task difficulty. ANCOVA F-tests examined cortical responses after removal of baseline across time, task difficulty and recovery. Volumes of interest (5 mm sphere) were placed in peak voxel regions of the DMN and dlPFC to compare cortical responses between recovered and unrecovered participants over time (one-way ANOVA). Between one and two months post-injury, we found significant increases in dlPFC activations and significant activations and deactivations in the DMN with increasing task difficulty, alongside improved task performance. Cortical responses of the DMN and bilateral dlPFC displayed increased intensity in recovered participants, together with improved attention and behavioural symptoms. Overall, our findings suggest evidence of neural compensation and ongoing cognitive recovery from pediatric TBI over time between one and two months post injury in children with PPCS. These results highlight the wider and persisting implications of mTBI in children, whose maturing brains are particularly vulnerable to TBI.

Altered Brain Activation in Youth following Concussion: Using a Dual-task Paradigm

A concussion is known as a functional injury affecting brain communication, integration, and processing. There is a need to objectively measure how concussions disrupt brain activation while completing ecologically relevant tasks.The objective of this study was to compare brain activation patterns between concussion and comparison groups (non-concussed youth) during a cognitive-motor single and dual-task paradigm utilizing functional near-infrared spectroscopy (fNIRS) in regions of the frontal-parietal attention network and compared to task performance.Youth with concussion generally exhibited hyperactivation and recruitment of additional brain regions in the dorsal lateral prefrontal (DLPFC), superior (SPC) and inferior parietal cortices (IPC), which are associated with processing, information integration, and response selection. Additionally, hyper- or hypo-activation patterns were associated with slower processing speed on the cognitive task. Our findings corroborate the growing literature suggesting that neural recovery may be delayed compared to the restoration of behavioral performance post-concussion.Concussion, near-infrared spectroscopy, dual-task paradigm, cognitive, motor, brain activation.

Experimental model for the study of traumatic brain injury

Traumatic brain injury (TBI) represents a public healthcare problem and a major economic burden, all over the world. It is estimated that every year, on the globe, there occur about two million severe TBI and over 42 million mild TBI. The main causes of TBI in civil population are fallings, followed by car accidents. In the last decades, the accelerated development of car industry and the poor development of traffic infrastructure in low- and average-income countries led to an increasing number of brain injuries, this becoming a major problem for medical health systems. According to some studies, approximately 1.35 million people die every year because of car accidents. In the last four decades, these types of injuries started to be studied in order to understand the lesion mechanisms for developing new safety equipment that may be installed on vehicles. The device presented by us for causing a TBI in a lab rat (mechanical pendulum) allows the performance of several major types of TBI, according to the kinetic energy, exposure area, contact surface, etc. The impact energies obtained by the device we presented may vary on a large scale, from less than 1 J up to 10 J, according to its weight, launching angle and impact head shape, thus being obtained minor, moderate or severe TBI.

Neuropsychological, Neurocognitive, Vestibular, and Neuroimaging Correlates of Exposure to Repetitive Low-Level Blast Waves: Evidence From Four Nonoverlapping Samples of Canadian Breachers

INTRODUCTION

We assessed the utility of a battery of neuropsychological, neurocognitive, physiological (balance, ataxia, postural tremor), and neuroimaging measures for studying the effects of blast waves in breachers-a population repeatedly exposed to low-level blast during military training and operations.

MATERIALS AND METHODS

Data were collected from four nonoverlapping samples, in the course of similarly structured 4-day breacher training exercises in successive years involving a combination of indoor and outdoor blast events. In all cases, self-report and neuropsychological measures were administered once at baseline (i.e., 1 day before the start of training). In years 1-2, neurocognitive and physiological measures were administered daily before and after training. In years 3-4, neurocognitive data were collected once at baseline. In Year 4, we introduced 3 modifications to our design. First, in addition to breachers, we also collected data from sex-and age-matched military controls at the same time points. Second, we assessed balance, ataxia, and postural tremor immediately following blast exposure "in the field," enabling us to quantify its acute effects. Third, structural magnetic resonance imaging (MRI) scans were acquired before and after the 4-day training exercise to explore differences between breachers and controls at baseline, as well as possible training-related changes using voxel-based morphometry. These design modifications were made to enable us to test additional hypotheses in the context of the same training exercise.

RESULTS

At baseline, scores on the "Rivermead Post Concussion Symptoms Questionnaire," "RAND SF-36" (physical functioning, role limitation due to physical health, social functioning, energy/fatigue, general health), and "Short Musculoskeletal Function Questionnaire" distinguished breachers from controls. Also at baseline, the MRI data revealed that there was greater regional gray matter volume in controls compared to breachers in the right superior frontal gyrus. Balance, ataxia, and postural tremor did not exhibit sensitivity to the acute effects of blast in the field, nor did neurocognitive measures to its cumulative or daily effects.

CONCLUSION

Our exploratory results suggest that self-report neuropsychological measures and structural MRI hold promise as sensitive measures for quantifying the long-term, cumulative effects of blast exposure in breachers. We discuss the limitations of our study and the need for prospective longitudinal data for drawing causal inferences regarding the impact of blast exposure on breachers' health and performance.

A functional MRI study of presurgical cognitive deficits in glioma patients

Background

The main goal of this functional MRI (fMRI) study was to examine whether cognitive deficits in glioma patients prior to treatment are associated with abnormal brain activity in either the central executive network (CEN) or default mode network (DMN).

Methods

Forty-six glioma patients, and 23 group-matched healthy controls (HCs) participated in this fMRI experiment, performing an N-back task. Additionally, cognitive profiles of patients were evaluated outside the scanner. A region of interest–based analysis was used to compare brain activity in CEN and DMN between groups. Post hoc analyses were performed to evaluate differences between low-grade glioma (LGG) and high-grade glioma (HGG) patients.

Results

In-scanner performance was lower in glioma patients compared to HCs. Neuropsychological testing indicated cognitive impairment in LGG as well as HGG patients. fMRI results revealed normal CEN activation in glioma patients, whereas patients showed reduced DMN deactivation compared to HCs. Brain activity levels did not differ between LGG and HGG patients.

Conclusions

Our study suggests that cognitive deficits in glioma patients prior to treatment are associated with reduced responsiveness of the DMN, but not with abnormal CEN activation. These results suggest that cognitive deficits in glioma patients reflect a reduced capacity to achieve a brain state necessary for normal cognitive performance, rather than abnormal functioning of executive brain regions. Solely focusing on increases in brain activity may well be insufficient if we want to understand the underlying brain mechanism of cognitive impairments in patients, as our results indicate the importance of assessing deactivation.

Decoupling of structural and functional connectivity in hubs and cognitive impairment after mild traumatic brain injury

INTRODUCTION

Mild traumatic brain injury (mild TBI) exhibited abnormal brain network topologies associated with cognitive dysfunction. However, it was still unclear which aspects of network organization were critical underlying the key pathology of mild TBI. Here, a multi-imaging strategy was applied to capture dynamic topological features of both structural and functional connectivity networks (SCN and FCN), to provide more sensitive detection of altered FCN from its anatomical backbone and identify novel biomarkers of mild TBI outcomes.

METHODS

62 mild TBI patients (30 subjects as an original sample with 3-12 months follow-up, 32 subjects as independent replicated sample), and 37 healthy controls were recruited. Both diffusion tensor imaging (DTI) and resting-state fMRI were used to create global connectivity matrices in the same individuals. Global and regional network analyses were applied to identify group differences and correlations with clinical assessments.

RESULTS

Most global network properties were conserved in both SCNs and FCNs in subacute mild TBI, whereas SCNs presented decreased global efficiency and characteristic path length at follow-up. Specifically, some hubs in healthy brain networks typically became non-hubs in patients and vice versa, such as the medial prefrontal cortex, superior temporal gyrus, middle frontal gyrus. The relationship between structural and functional connectivity (SC and FC) in patients also showed salient decoupling as a function of time, primarily located in the hubs.

CONCLUSIONS

These results suggested mild TBI influences the relationship between SCN and FCN, and the SC-FC coupling strength may be used as a potential biomarker to predict long-term outcomes after injury.

Mild traumatic brain injury recovery: a growth curve modelling analysis over 2 years

BACKGROUND

An improved understanding of the trajectory of recovery after mild traumatic brain injury is important to be able to understand individual patient outcomes, for longitudinal patient care and to aid the design of clinical trials.

OBJECTIVE

To explore changes in health, well-being and cognition over the 2 years following mTBI using latent growth curve (LGC) modelling.

METHODS

Sixty-one adults with mTBI presenting to a UK Major Trauma Centre completed comprehensive longitudinal assessment at up to five time points after injury: 2 weeks, 3 months, 6 months, 1 year and 2 years.

RESULTS

Persisting problems were seen with neurological symptoms, cognitive issues and poor quality of life measures including 28% reporting incomplete recovery on the Glasgow Outcome Score Extended at 2 years. Harmful drinking, depression, psychological distress, disability, episodic memory and working memory did not improve significantly over the 2 years following injury. For other measures, including the Rivermead Post-Concussion Symptoms and Quality of Life after Brain Injury (QOLIBRI), LGC analysis revealed significant improvement over time with recovery tending to plateau at 3-6 months.

INTERPRETATION

Significant impairment may persist as late as 2 years after mTBI despite some recovery over time. Longitudinal analyses which make use of all available data indicate that recovery from mTBI occurs over a longer timescale than is commonly believed. These findings point to the need for long-term management of mTBI targeting individuals with persisting impairment.

MEG Working Memory N-Back Task Reveals Functional Deficits in Combat-Related Mild Traumatic Brain Injury

Combat-related mild traumatic brain injury (mTBI) is a leading cause of sustained cognitive impairment in military service members and Veterans. However, the mechanism of persistent cognitive deficits including working memory (WM) dysfunction is not fully understood in mTBI. Few studies of WM deficits in mTBI have taken advantage of the temporal and frequency resolution afforded by electromagnetic measurements. Using magnetoencephalography (MEG) and an N-back WM task, we investigated functional abnormalities in combat-related mTBI. Study participants included 25 symptomatic active-duty service members or Veterans with combat-related mTBI and 20 healthy controls with similar combat experiences. MEG source-magnitude images were obtained for alpha (8-12 Hz), beta (15-30 Hz), gamma (30-90 Hz), and low-frequency (1-7 Hz) bands. Compared with healthy combat controls, mTBI participants showed increased MEG signals across frequency bands in frontal pole (FP), ventromedial prefrontal cortex, orbitofrontal cortex (OFC), and anterior dorsolateral prefrontal cortex (dlPFC), but decreased MEG signals in anterior cingulate cortex. Hyperactivations in FP, OFC, and anterior dlPFC were associated with slower reaction times. MEG activations in lateral FP also negatively correlated with performance on tests of letter sequencing, verbal fluency, and digit symbol coding. The profound hyperactivations from FP suggest that FP is particularly vulnerable to combat-related mTBI.

Neuroimaging and Psychometric Assessment of Mild Cognitive Impairment After Traumatic Brain Injury

Traumatic brain injury (TBI) can be serious partly due to the challenges of assessing and treating its neurocognitive and affective sequelae. The effects of a single TBI may persist for years and can limit patients’ activities due to somatic complaints (headaches, vertigo, sleep disturbances, nausea, light or sound sensitivity), affective sequelae (post-traumatic depressive symptoms, anxiety, irritability, emotional instability) and mild cognitive impairment (MCI, including social cognition disturbances, attention deficits, information processing speed decreases, memory degradation and executive dysfunction). Despite a growing amount of research, study comparison and knowledge synthesis in this field are problematic due to TBI heterogeneity and factors like injury mechanism, age at or time since injury. The relative lack of standardization in neuropsychological assessment strategies for quantifying sequelae adds to these challenges, and the proper administration of neuropsychological testing relative to the relationship between TBI, MCI and neuroimaging has not been reviewed satisfactorily. Social cognition impairments after TBI (e.g., disturbed emotion recognition, theory of mind impairment, altered self-awareness) and their neuroimaging correlates have not been explored thoroughly. This review consolidates recent findings on the cognitive and affective consequences of TBI in relation to neuropsychological testing strategies, to neurobiological and neuroimaging correlates, and to patient age at and assessment time after injury. All cognitive domains recognized by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) are reviewed, including social cognition, complex attention, learning and memory, executive function, language and perceptual-motor function. Affect and effort are additionally discussed owing to their relationships to cognition and to their potentially confounding effects. Our findings highlight non-negligible cognitive and affective impairments following TBI, their gravity often increasing with injury severity. Future research should study (A) language, executive and perceptual-motor function (whose evolution post-TBI remains under-explored), (B) the effects of age at and time since injury, and (C) cognitive impairment severity as a function of injury severity. Such efforts should aim to develop and standardize batteries for cognitive subdomains—rather than only domains—with high ecological validity. Additionally, they should utilize multivariate techniques like factor analysis and related methods to clarify which cognitive subdomains or components are indeed measured by standardized tests.

Brain Injury and Dementia in Pakistan: Current Perspectives

Alzheimer's disease (AD) is the most common form of dementia, accounting for 50-75% of all cases, with a greater proportion of individuals affected at older age range. A single moderate or severe traumatic brain injury (TBI) is associated with accelerated aging and increased risk for dementia. The fastest growth in the elderly population is taking place in China, Pakistan, and their south Asian neighbors. Current clinical assessments are based on data collected from Caucasian populations from wealthy backgrounds giving rise to a "diversity" crisis in brain research. Pakistan is a lower-middle income country (LMIC) with an estimated one million people living with dementia. Pakistan also has an amalgamation of risk factors that lead to brain injuries such as lack of road legislations, terrorism, political instability, and domestic and sexual violence. Here, we provide an initial and current assessment of the incidence and management of dementia and TBI in Pakistan. Our review demonstrates the lack of resources in terms of speciality trained clinician staff, medical equipment, research capabilities, educational endeavors, and general awareness in the fields of dementia and TBI. Pakistan also lacks state-of-the-art assessment of dementia and its risk factors, such as neuroimaging of brain injury and aging. We provide recommendations for improvement in this arena that include the recent creation of Pakistan Brain Injury Consortium (PBIC). This consortium will enhance international collaborative efforts leading to capacity building for innovative research, clinician and research training and developing databases to bring Pakistan into the international platform for dementia and TBI research.

A preliminary investigation of cognitive intolerance and neuroimaging among adolescents returning to school after concussion

PRIMARY OBJECTIVE

To introduce the concept of cognitive intolerance. A test is proposed to measure this concept and pilot data are presented to support this measure and future research to develop this concept into a construct. Research design: Three-group comparison to protect larger study blinding. Methods and procedures: Two groups of student athletes (n = 13, n = 13) between 13 and 17 (mean 15.1 ± 1.1 years; 58% male) who sustained a sport-related concussion within 10 days and one group (n = 13) of age-matched healthy controls were recruited for a comparison of correlations between self and observer ratings of cognitive difficulties and DTI fractional anisotropy (FA) using tract-based spatial statistics (TBSS) analysis at two time points. Main outcomes and results: Significant negative only associations (higher cognitive difficulty and lower FA) with DTI FA were found in white matter tracts. These included the anterior corpus callosum, frontal-parietal longitudinal fasciculi, and cortical-subcortical pathways at only the second time point. Several working memory networks would likely involve connections using the above-identified white matter tracts. Conclusions: Cognitive intolerance can be defined as symptom exacerbation from prolonged cognitive activity. Cognitive intolerance could be measured by the n-back working memory task and time to symptom exacerbation.

Methylphenidate improves executive functions in patients with traumatic brain injuries: a feasibility trial via the idiographic approach

Background

Road traffic accidents are known to be the main cause of traumatic brain injury (TBI). TBI is also a leading cause of death and disability. This study, by means of the idiographic approach (single-case experimental designs using multiple-baseline designs), has examined whether methylphenidate (MPH - trade name Ritalin) had a differential effect on cognitive measures among patients with TBI with the sequel of acute and chronic post-concussion syndromes. The effect on gender was also explored.

Methods

In comparison with healthy controls, patients with TBI (acute and chronic) and accompanying mild cognitive impairment (MCI) were screened for their integrity of executive functioning. Twenty-four patients exhibiting executive dysfunction (ED) were then instituted with the pharmacological intervention methylphenidate (MPH). The methylphenidate was administered using an uncontrolled, open label design.

Results

The administration of methylphenidate impacted ED in the TBI group but had no effect on mood. Attenuation of ED was more apparent in the chronic phases of TBI. The effect on gender was not statistically significant with regard to the observed changes.

Conclusions

To our knowledge, this is the first feasibility trial from the Arabian Gulf to report the performance of a TBI population with mild cognitive impairment according to the IQCODE Arabic version. This investigation confirms anecdotal observations of methylphenidate having the potential to attenuate cognitive impairment; particularly those functions that are critically involved in the integrity of executive functioning. The present feasibility trial should be followed by nomothetic studies such as those that adhere to the protocol of the randomized controlled trial. This evidence-based research is the foundation for intervention and future resource allocation by policy- or public health decision-makers.

Contributions of Interleukin-1 Receptor Signaling in Traumatic Brain Injury

Traumatic brain injury (TBI) in various forms affects millions in the United States annually. There are currently no FDA-approved therapies for acute injury or the chronic comorbidities associated with TBI. Acute phases of TBI are characterized by profound neuroinflammation, a process that stimulates the generation and release of proinflammatory cytokines including interleukin-1α (IL-1α) and IL-1β. Both forms of IL-1 initiate signaling by binding with IL-1 receptor type 1 (IL-1R1), a receptor with a natural, endogenous antagonist dubbed IL-1 receptor antagonist (IL-1Ra). The recombinant form of IL-1Ra has gained FDA approval for inflammatory conditions such as rheumatoid arthritis, prompting interest in repurposing these pharmacotherapies for other inflammatory diseases/injury states including TBI. This review summarizes the currently available preclinical and clinical literature regarding the therapeutic potential of inhibiting IL-1-mediated signaling in the context of TBI. Additionally, we propose specific research areas that would provide a greater understanding of the role of IL-1 signaling in TBI and how these data may be beneficial for the development of IL-1-targeted therapies, ushering in the first FDA-approved pharmacotherapy for acute TBI.

Reduced frontopolar brain activation characterizes concussed athletes with balance deficits

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Symptomatic athletes with balance deficits present reduced frontopolar oxygenation during postural control with closed eyes.

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Decreased brain oxygenation in the FPC of symptomatic individuals may characterize the deficit of shifting the focus from visual inputs towards proprioception.

Objectives

Athletes with sport-related concussions (SRC) often demonstrate deficits in postural stability. Lower cerebral blood flow in frontal cortices has been documented in athletes with symptoms after SRC, however, it is unclear if functional brain oxygenation during postural control tasks is reduced in symptomatic athletes after SRC in the same manner. We therefore compared brain oxygenation patterns in frontal cortices of symptomatic and asymptomatic athletes with SRC during postural control tasks with the hypothesis that symptomatic athletes are characterized by reduced functional brain oxygenation during postural control.

Methods

62 concussed athletes (n = 31 symptomatic, n = 31 asymptomatic) were investigated during four postural control tasks with eyes closed versus eyes opened conditions and stable vs. unstable surface conditions. Brain oxygenation was assessed using functional NearInfraRed Spectroscopy (fNIRS) on frontopolar cortices of each hemisphere. Postural sway was measured by the analysis of ground reaction forces.

Results

Symptomatic athletes showed greater postural sway when compared to asymptomatic athletes during postural control, particularly during closed eyes and/or unstable surface conditions. Changes of oxygenated hemoglobin (∆HbO₂) within the left hemispheric frontopolar cortex were significantly reduced in symptomatic athletes when compared to asymptomatic athletes during the eyes closed condition. A stepwise linear regression analysis revealed that self-reported post-concussion symptoms such as headaches and sadness predict decreased brain oxygenation during postural control with closed eyes.

Conclusion

Symptomatic athletes with increased postural sway are characterized by decreased frontopolar brain oxygenation during postural control tasks, particularly during conditions with closed eyes. Because the frontopolar cortex showed to be involved in redistributing executive functions to novel task situations, we conclude that athletes with post-concussion symptoms suffer from a deficit in coordinating postural adjustments to balance control tasks with reduced sensory input.

Structural abnormalities in thalamo-prefrontal tracks revealed by high angular resolution diffusion imaging predict working memory scores in concussed children

Because of their high prevalence, heterogeneous clinical presentation, and wide-ranging sequelae, concussions are a challenging neurological condition, especially in children. Shearing forces transmitted across the brain during concussions often result in white matter damage. The neuropathological impact of concussions has been discerned from animal studies and includes inflammation, demyelination, and axonal loss. These pathologies can overlap during the sub-acute stage of recovery. However, due to the challenges of accurately modeling complex white matter structure, these neuropathologies have not yet been differentiated in children in vivo. In the present study, we leveraged recent advances in diffusion imaging modeling, tractography, and tractometry to better understand the neuropathology underlying working memory problems in concussion. Studying a sample of 16 concussed and 46 healthy youths, we used novel tractography methods to isolate 11 working memory tracks. Along these tracks, we measured fractional anisotropy, diffusivities, track volume, apparent fiber density, and free water fraction. In three tracks connecting the right thalamus to the right dorsolateral prefrontal cortex (DLPFC), we found microstructural differences suggestive of myelin alterations. In another track connecting the left anterior-cingulate cortex with the left DLPFC, we found microstructural changes suggestive of axonal loss. Structural differences and tractography reconstructions were reproduced using test-retest analyses. White matter structure in the three thalamo-prefrontal tracks, but not the cingulo-prefrontal track, appeared to play a key role in working memory function. The present results improve understanding of working memory neuropathology in concussions, which constitutes an important step toward developing neuropathologically informed biomarkers of concussion in children.

Task-related functional magnetic resonance imaging activations in patients with acute and subacute mild traumatic brain injury: A coordinate-based meta-analysis

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ALE meta-analysis revealed functional activation differences in mTBI.

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Reduced activation identified within the right middle frontal gyrus.

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Suggests alteration of prefrontal region, associated with executive functioning.

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Need for addressing subject- and task-specific variation in future studies.

Task-based functional magnetic resonance imaging (fMRI) has been used to examine neuroanatomical and functional changes following mild traumatic brain injury (mTBI). Prior studies have lacked consistency in identifying common regions of altered neural activity during cognitive tasks. This may be partly due to differences in task paradigm, patient heterogeneity, and methods of fMRI analysis. We conducted a meta-analysis using an activation likelihood estimation (ALE) method to identify regions of differential brain activation in patients with mTBI compared to healthy controls. We included experiments that performed scans from acute to subacute time points post-injury. The seven included studies recruited a total sample of 174 patients with mTBIs and 139 control participants. The results of our coordinate based meta-analysis revealed a single cluster of reduced activation within the right middle frontal gyrus (MFG) that differentiated mTBI from healthy controls. We conclude that the cognitive impairments in memory and attention typically reported in mTBI patients may be associated with a deficit in the right MFG, which impacts the recruitment of neural networks important for attentional control.

Electrophysiological Markers of Visuospatial Attention Recovery after Mild Traumatic Brain Injury

Objective: Attentional problems are amongst the most commonly reported complaints following mild traumatic brain injury (mTBI), including difficulties orienting and disengaging attention, sustaining it over time, and dividing attentional resources across multiple simultaneous demands. The objective of this study was to track, using a single novel electrophysiological task, various components associated with the deployment of visuospatial selective attention. Methods: A paradigm was designed to evoke earlier visual evoked potentials (VEPs), as well as attention-related and visuocognitive ERPs. Data from 36 individuals with mTBI (19 subacute, 17 chronic) and 22 uninjured controls are presented. Postconcussion symptoms (PCS), anxiety (BAI), depression (BDI-II) and visual attention (TEA Map Search, DKEFS Trail Making Test) were also assessed. Results: Earlier VEPs (P1, N1), as well as processes related to visuospatial orientation (N2pc) and encoding in visual short-term memory (SPCN), appear comparable in mTBI and control participants. However, there appears to be a disruption in the spatiotemporal dynamics of attention (N2pc-Ptc, P2) in subacute mTBI, which recovers within six months. This is also reflected in altered neuropsychological performance (information processing speed, attentional shifting). Furthermore, orientation of attention (P3a) and working memory processes (P3b) are also affected and remain as such in the chronic post-mTBI period, in co-occurrence with persisting postconcussion symptomatology. Conclusions: This study adds original findings indicating that such a sensitive and rigorous ERP task implemented at diagnostic and follow-up levels could allow for the identification of subtle but complex brain activation and connectivity deficits that can occur following mTBI.

Frontal theta-gamma ratio is a sensitive index of concussion history in athletes on tasks of visuo-motor control

Patients with mTBI often show deficits in executive function and changes in neural activity. Similar changes in those with a history of mTBI (i.e. concussion), however, have not been consistently reported. Frontal theta-to-gamma frequency ratio has shown promise in EEG research in predicting performance on working memory tasks. In the present study we explored the sensitivity of the frontal theta-to-gamma relative power spectral density (PSD) ratio to the history of concussion in 81 youth athletes (18 with a history of concussion, ages 13–18) during the tests of the Nike Sensory Training Station that vary in working memory and processing speed demands and motor output requirements. The results showed that the theta-to-gamma relative PSD ratio was significantly lower in the concussion history group on the tests of target capture, perception span and hand reaction time. A principle component analysis further indicated that this metric reflects an underlying dimension shared by several visuo-motor control tests of the Nike battery. The results suggested persistent deficits in psychomotor ability in the athletes with a history of concussion that may have implications for diagnosis, rehabilitation and athletic training.

An observational study of trait and state fatigue, and their relation to cognitive fatigability and saccade performance

Aim:

Different fatigue measurements and their relation to saccadic functions were investigated in 15 patients with a mild traumatic brain injury (mTBI) and 15 orthopedic controls.

Materials & methods:

State fatigue was measured with the Fatigue Severity Scale and trait fatigue with the question on fatigue in the Rivermead Post Concussion Questionnaire and fatigability as decreased performance over time on a neuropsychological measure.

Results:

Patients with an mTBI scored significantly higher in state fatigue and showed more fatigability compared with the orthopedic controls. Among patients with mTBI, state fatigue correlated with prosaccade latency and cognitive fatigability, while trait fatigue correlated with anxiety and antisaccade latency and variability.

Conclusion:

This pilot study indicates that saccade measurements might, in the future, be useful in the understanding of fatigue and in the search for prognostic factors after mTBI.

Dynamin and reverse-mode sodium calcium exchanger blockade confers neuroprotection from diffuse axonal injury

Mild traumatic brain injury (mTBI) is a frequently overlooked public health concern that is difficult to diagnose and treat. Diffuse axonal injury (DAI) is a common mTBI neuropathology in which axonal shearing and stretching induces breakdown of the cytoskeleton, impaired axonal trafficking, axonal degeneration, and cognitive dysfunction. DAI is becoming recognized as a principal neuropathology of mTBI with supporting evidence from animal model, human pathology, and neuroimaging studies. As mitochondrial dysfunction and calcium overload are critical steps in secondary brain and axonal injury, we investigated changes in protein expression of potential targets following mTBI using an in vivo controlled cortical impact model. We show upregulated expression of sodium calcium exchanger1 (NCX1) in the hippocampus and cortex at distinct time points post-mTBI. Expression of dynamin-related protein1 (Drp1), a GTPase responsible for regulation of mitochondrial fission, also changes differently post-injury in the hippocampus and cortex. Using an in vitro model of DAI previously reported by our group, we tested whether pharmacological inhibition of NCX1 by SN-6 and of dynamin1, dynamin2, and Drp1 by dynasore mitigates secondary damage. Dynasore and SN-6 attenuate stretch injury-induced swelling of axonal varicosities and mitochondrial fragmentation. In addition, we show that dynasore, but not SN-6, protects against H2O2-induced damage in an organotypic oxidative stress model. As there is currently no standard treatment to mitigate cell damage induced by mTBI and DAI, this work highlights two potential therapeutic targets for treatment of DAI in multiple models of mTBI and DAI.