Altered caudate connectivity is associated with executive dysfunction after traumatic brain injury

Methylphenidate differentially alters corticostriatal connectivity after traumatic brain injury

Traumatic brain injury commonly impairs attention and executive function and disrupts the large-scale brain networks that support these cognitive functions. Abnormalities of functional connectivity are seen in corticostriatal networks, which are associated with executive dysfunction and damage to neuromodulatory catecholaminergic systems caused by head injury. Methylphenidate, a stimulant medication that increases extracellular dopamine and noradrenaline, can improve cognitive function following traumatic brain injury. In this experimental medicine add-on study to a randomized, double-blind, placebo-controlled clinical trial, we test whether administration of methylphenidate alters corticostriatal network function and influences drug response. Forty-three moderate-severe traumatic brain injury patients received 0.3 mg/kg of methylphenidate or placebo twice a day in 2-week blocks. Twenty-eight patients were included in the neuropsychological and functional imaging analysis (four females, mean age 40.9 ± 12.7 years, range 20-65 years) and underwent functional MRI and neuropsychological assessment after each block. 123I-Ioflupane single-photon emission computed tomography dopamine transporter scans were performed, and specific binding ratios were extracted from caudate subdivisions. Functional connectivity and the relationship to cognition were compared between drug and placebo conditions. Methylphenidate increased caudate to anterior cingulate cortex functional connectivity compared with placebo and decreased connectivity from the caudate to the default mode network. Connectivity within the default mode network was also decreased by methylphenidate administration, and there was a significant relationship between caudate functional connectivity and dopamine transporter binding during methylphenidate administration. Methylphenidate significantly improved executive function in traumatic brain injury patients, and this was associated with alterations in the relationship between executive function and right anterior caudate functional connectivity. Functional connectivity is strengthened to brain regions, including the anterior cingulate, that are activated when attention is focused externally. These results show that methylphenidate alters caudate interactions with cortical brain networks involved in executive control. In contrast, caudate functional connectivity reduces to default mode network regions involved in internally focused attention and that deactivate during tasks that require externally focused attention. These results suggest that the beneficial cognitive effects of methylphenidate might be mediated through its impact on the caudate. Methylphenidate differentially influences how the caudate interacts with large-scale functional brain networks that exhibit co-ordinated but distinct patterns of activity required for attentionally demanding tasks.

Neural network localization in Parkinson's disease with impulse control disorders

Background

There is a huge heterogeneity of magnetic resonance imaging findings in Parkinson's disease (PD) with impulse control disorders (ICDs) studies. Here, we hypothesized that brain regions identified by structural and functional imaging studies of PD with ICDs could be reconciled in a common network.

Methods

In this study, an initial systematic literature review was conducted to collect and evaluate whole-brain functional and structural magnetic resonance imaging studies related to PD with ICDs. We subsequently utilized the Human Connectome Project (HCP) dataset (n = 1,093) and a novel functional connectivity network mapping (FCNM) technique to identify a common brain network affected in PD with ICDs.

Results

A total of 19 studies with 25 contrasts, incorporating 345 individuals with PD and ICDs, and 787 individuals with PD without ICDs were included in the analysis. By using the HCP dataset and a novel FCNM technique, we ultimately identified that the aberrant neural networks predominantly involve the default mode network (middle and inferior temporal gyrus, anterior cingulate cortex, angular gyrus) and subcortical network (caudate nucleus).

Conclusion

This study suggests that the heterogeneous neuroimaging findings in PD with ICDs can be attributed to shared abnormalities in the default mode and subcortical networks. These dysfunctions are associated with impaired self-regulation, decision-making, and heightened impulsivity in PD with ICDs. Our findings integrate diverse neuroimaging results from previous studies, providing a clearer understanding of the neurobiological mechanisms underlying PD with ICDs at a network level.

Association of cortical macrostructural and microstructural changes with cognitive performance and gene expression in subcortical ischemic vascular disease patients with cognitive impairment

OBJECTIVE

Previous researches have demonstrated that patients with subcortical ischemic vascular disease (SIVD) exhibited brain structure abnormalities. However, the cortical macrostructural and microstructural characteristics and their relationship with cognitive scores and gene expression in SIVD patients remain largely unknown.

METHODS

This study collected 3D-T1 and diffusion tensor imaging data from 30 SIVD patients with cognitive impairment (SIVD-CI) and 32 normal controls. The between-group comparative analyses of cortical thickness, area, volume, local gyrification index (LGI), and mean diffusivity (MD) were conducted with a general linear model. Moreover, the associations between the significant neuroimaging values and the cognitive scores and gene expression values from Allen Human Brain Atlas database were evaluated using partial least squares regression and partial correlation analysis.

RESULTS

SIVD-CI patients showed significant decreases in cortical thicknesses across 18 regions, cortical volumes across three regions, and cortical LGI across five regions, as well as significant increases in cortical MD across five regions (P < 0.05). The significantly reduced cortical thicknesses of the right insula, left superior temporal gyrus, left central anterior gyrus, and left caudal anterior cingulate cortex, as well as the significantly reduced cortical LGI in left caudal anterior cingulate cortex, were significantly positively correlated with different cognitive scores (P < 0.05). Furthermore, the abnormal cortical structural indicators were found to be significantly related to nine risk genes (VCAN, APOE, EFEMP1, SALL1, BCAN, KCNK2, EPN2, DENND1B and XKR6) (P < 0.05).

CONCLUSIONS

The specific cortical structural damage may be related to specific cognitive decline and specific risk genes in SIVD-CI patients.

Poor long-term outcomes and abnormal neurodegeneration biomarkers after military traumatic brain injury: the ADVANCE study

BACKGROUND

Traumatic brain injury (TBI) is common in military campaigns and is a risk factor for dementia. ArmeD SerVices TrAuma and RehabilitatioN OutComE-TBI (ADVANCE-TBI) aims to ascertain neurological outcomes in UK military personnel with major battlefield trauma, leveraging advances in quantification of axonal breakdown markers like neurofilament light (NfL), and astroglial marker glial fibrillar acidic protein (GFAP) in blood. We aimed to describe the causes, prevalence and consequences of TBI, and its fluid biomarker associations.

METHODS

TBI history was ascertained in 1145 servicemen and veterans, of whom 579 had been exposed to major trauma. Functional and mental health assessments were administered, and blood samples were collected approximately 8 years postinjury, with plasma biomarkers quantified (n=1125) for NfL, GFAP, total tau, phospho-tau181, amyloid-β 42 and 40. Outcomes were related to neurotrauma exposure.

RESULTS

TBI was present in 16.9% (n=98) of exposed participants, with 46.9% classified as mild-probable and 53.1% classified as moderate to severe. Depression (β=1.65, 95% CI (1.33 to 2.03)), anxiety (β=1.65 (1.34 to 2.03)) and post-traumatic stress disorder (β=1.30 (1.19 to 1.41)) symptoms were more common after TBI, alongside poorer 6 minute walk distance (β=0.79 (0.74 to 0.84)) and quality of life (β=1.27 (1.19 to 1.36), all p<0.001). Plasma GFAP was 11% (95% CI 2 to 21) higher post-TBI (p=0.013), with greater concentrations in moderate-to-severe injuries (47% higher than mild-probable (95% CI 20% to 82%, p<0.001). Unemployment was more common among those with elevated GFAP levels post-TBI, showing a 1.14-fold increase (95% CI 1.03 to 1.27, p<0.001) for every doubling in GFAP concentration.

CONCLUSIONS

TBI affected nearly a fifth of trauma-exposed personnel, related to worse mental health, motor and functional outcomes, as well as elevated plasma GFAP levels 8 years post-injury. This was absent after extracranial trauma, and showed a dose-response relationship with the severity of the injury.

Diffusion Tensor Imaging as Neurologic Predictor in Patients Affected by Traumatic Brain Injury: Scoping Review

Background: Diffusion tensor imaging (DTI), a variant of Diffusion Weighted Imaging (DWI), enables a neuroanatomical microscopic-like examination of the brain, which can detect brain damage using physical parameters. DTI's application to traumatic brain injury (TBI) has the potential to reveal radiological features that can assist in predicting the clinical outcomes of these patients. What is the ongoing role of DTI in detecting brain alterations and predicting neurological outcomes in patients with moderate to severe traumatic brain injury and/or diffuse axonal injury? Methods: A scoping review of the PubMed, Scopus, EMBASE, and Cochrane databases was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The aim was to identify all potentially relevant studies concerning the role of DTI in TBI. From an initial pool of 3527 publications, 26 articles were selected based on relevance. These studies included a total of 729 patients with moderate to severe TBI and/or diffuse axonal injury. DTI parameters were analyzed to determine their relationship with neurological outcomes post-TBI, with assessments of several brain functions and regions. Results: The studies included various DTI parameters, identifying significant relationships between DTI variations and neurological outcomes following TBI. Multiple brain functions and regions were evaluated, demonstrating the capability of DTI to detect brain alterations with higher accuracy, sensitivity, and specificity than MRI alone. Conclusions: DTI is a valuable tool for detecting brain alterations in TBI patients, offering enhanced accuracy, sensitivity, and specificity compared to MRI alone. Recent studies confirm its effectiveness in identifying neurological impairments and predicting outcomes in patients following brain trauma, underscoring its utility in clinical settings for managing TBI.

A Biopsychosocial Framework for Apathy Following Moderate to Severe Traumatic Brain Injury: A Systematic Review and Meta-analysis

Apathy, the deficit of goal-directed behaviour, is well recognised as one of the most debilitating syndromes after moderate-to-severe traumatic brain injury (TBI). However, mechanisms underlying apathy, or at least factors associated with apathy, are sporadically reported. Based on a biopsychosocial framework, this systematic review and meta-analysis synthesised evidence regarding neurobiological, socio-environmental and individual factors associated with apathy. Our searches identified 21 studies satisfying inclusion and exclusion criteria. Results showed that the majority of work has focused on cognitive dysfunction, TBI-related factors, demographic variables and psychological correlates of apathy, while evidence for neural substrates and socio-cultural and premorbid aspects is scant. Overall, the current literature suggests that TBI-related and patient demographic factors did not contribute to apathy after TBI, whereas complex neurocognitive alterations, socio-environmental and cultural factors as well as patients' self-related factors may be important components. The evidence points to the multifaceted interplay of certain biopsychosocial contributors to apathy and suggests future investigations of more complex behavioural traits, cultural elements and pre-injury levels to better characterise the aetiology of this detrimental impairment after TBI.

Clinical and neuroanatomical predictors of post-stroke fatigue

INTRODUCTION

Post-stroke fatigue (PSF) has been described as early exhaustion with tiredness that develops during physical or mental activity and generally does not improve with rest. There are inconsistent findings on the relationship between the characteristics of the ischemic brain lesion and PSF. However, some studies suggest that specific neuroanatomical and neuroplastic changes could explain post-stroke fatigue. The aim was to evaluate the severity of PSF in relation to the location and the size of the ischemic lesion in acute stroke patients to establish possible predictors of PSF.

PATIENTS AND METHODS

We performed a prospective observational study to establish potential early predictors of long-term PSF, which was assessed using the Fatigue Assessment Scale six months after ischemic stroke. After segmenting brain infarcts on Diffusion-Weighted Imaging (DWI) images, we studied the association with PSF using Voxel-Based Lesion-Symptom Mapping (VLSM).

RESULTS

Out of 104 patients, 61 (59 %) reported PSF. Female sex and history of diabetes mellitus were associated with a greater risk of developing PSF. The association of PSF with female sex was confirmed in a replication cohort of 50 patients. The ischemic lesion volume was not associated with PSF, and VBLSM analysis did not identify any specific brain area significantly associated with PSF.

CONCLUSIONS

PSF is frequent in stroke patients, especially women, even after six months. The absence of neuroanatomical correlates of PSF suggests that it is a multifactorial process with biological, psychological, and social risk factors that require further study.

Paediatric traumatic brain injury and attention-deficit/hyperactivity disorder medication in Finland: a nationwide register-based cohort study

BACKGROUND

The association between paediatric traumatic brain injury (pTBI) and post-traumatic attention-deficit/hyperactivity disorder (ADHD) medication usage remains understudied subject.

OBJECTIVE

We aimed to evaluate the association between pTBI and subsequent ADHD medication.

METHODS

A nationwide retrospective cohort study in Finland from 1998 to 2018 included 66 594 patients with pTBI and 61 412 references with distal extremity fractures. ADHD medication data were obtained from the Finnish Social Insurance Institution. The primary outcome was post-traumatic pediatric ADHD medication. A 1-year washout period was applied, and follow-up started 1 year post-pTBI.

FINDINGS

Kaplan-Meier analyses showed higher ADHD medication usage in patients with pTBI, especially post-operatively. Both sex groups exhibited elevated rates compared with the reference group. Over 10 years, cumulative incidence rates were 3.89% (pTBI) vs 1.90% (reference). HR for pTBI was 1.89 (95% CI 1.70 to 2.10) after 4 years and 6.31 (95% CI 2.80 to 14.20) for the operative group after the initial follow-up year. After 10 years, cumulative incidence in females increased to 2.14% (pTBI) vs 1.07% (reference), and in males, to 5.02% (pTBI) vs 2.35% (reference). HR for pTBI was 2.01 (95% CI 1.72 to 2.35) in females and 2.23 (95% CI 2.04 to 2.45) in males over 1-20 years.

CONCLUSIONS

A substantial association between pTBI and post-traumatic ADHD medication was evidenced over a 20-year follow-up period.

CLINICAL IMPLICATIONS

These results stress the need for preventive measures for pTBI and highlight the potential impact of long-term post-traumatic monitoring and psychoeducation.

Disrupted topological organization of functional brain networks in traumatic axonal injury

Traumatic axonal injury (TAI) may result in the disruption of brain functional networks and is strongly associated with cognitive impairment. However, the neural mechanisms affecting the neurocognitive function after TAI remain to be elucidated. We collected the resting-state functional magnetic resonance imaging data from 28 patients with TAI and 28 matched healthy controls. An automated anatomical labeling atlas was used to construct a functional brain connectome. We utilized a graph theoretical approach to investigate the alterations in global and regional network topologies, and network-based statistics analysis was utilized to localize the connected networks more precisely. The current study revealed that patients with TAI and healthy controls both showed a typical small-world topology of the functional brain networks. However, patients with TAI exhibited a significantly lower local efficiency compared to healthy controls, whereas no significant difference emerged in other small-world properties (Cp, Lp, γ, λ, and σ) and global efficiency. Moreover, patients with TAI exhibited aberrant nodal centralities in some regions, including the frontal lobes, parietal lobes, caudate nucleus, and cerebellum bilaterally, and right olfactory cortex. The network-based statistics results showed alterations in the long-distance functional connections in the subnetwork in patients with TAI, involving these brain regions with significantly altered nodal centralities. These alterations suggest that brain networks of individuals with TAI present aberrant topological attributes that are associated with cognitive impairment, which could be potential biomarkers for predicting cognitive dysfunction and help understanding the neuropathological mechanisms in patients with TAI.

Turbulent dynamics and whole-brain modeling: toward new clinical applications for traumatic brain injury

Traumatic Brain Injury (TBI) is a prevalent disorder mostly characterized by persistent impairments in cognitive function that poses a substantial burden on caregivers and the healthcare system worldwide. Crucially, severity classification is primarily based on clinical evaluations, which are non-specific and poorly predictive of long-term disability. In this Mini Review, we first provide a description of our model-free and model-based approaches within the turbulent dynamics framework as well as our vision on how they can potentially contribute to provide new neuroimaging biomarkers for TBI. In addition, we report the main findings of our recent study examining longitudinal changes in moderate-severe TBI (msTBI) patients during a one year spontaneous recovery by applying the turbulent dynamics framework (model-free approach) and the Hopf whole-brain computational model (model-based approach) combined with in silico perturbations. Given the neuroinflammatory response and heightened risk for neurodegeneration after TBI, we also offer future directions to explore the association with genomic information. Moreover, we discuss how whole-brain computational modeling may advance our understanding of the impact of structural disconnection on whole-brain dynamics after msTBI in light of our recent findings. Lastly, we suggest future avenues whereby whole-brain computational modeling may assist the identification of optimal brain targets for deep brain stimulation to promote TBI recovery.

Resting-state functional MRI study of conventional MRI-negative intractable epilepsy in children

Objective

The study aimed at investigating functional connectivity strength (FCS) changes in children with MRI-negative intractable epilepsy (ITE) and evaluating correlations between aberrant FCS and both disease duration and intelligence quotient (IQ).

Methods

Fifteen children with ITE, 24 children with non-intractable epilepsy (nITE) and 25 matched healthy controls (HCs) were subjected to rs-fMRI. IQ was evaluated by neuropsychological assessment. Voxelwise analysis of covariance was conducted in the whole brain, and then pairwise comparisons were made across three groups using Bonferroni corrections.

Results

FCS was significantly different among three groups. Relative to HCs, ITE patients exhibited decreased FCS in right temporal pole of the superior temporal gyrus, middle temporal gyrus, bilateral precuneus, etc and increased FCS values in left triangular part of the inferior frontal gyrus, parahippocampal gyrus, supplementary motor area, caudate and right calcarine fissure and surrounding cortex and midbrain. The nITE patients presented decreased FCS in right orbital superior frontal gyrus, precuneus etc and increased FCS in bilateral fusiform gyri, parahippocampal gyri, etc. In comparison to nITE patients, the ITE patients presented decreased FCS in right medial superior frontal gyrus and left inferior temporal gyrus and increased FCS in right middle temporal gyrus, inferior temporal gyrus and calcarine fissure and surrounding cortex. Correlation analysis indicated that FCS in left caudate demonstrated correlation with verbal IQ (VIQ) and disease duration.

Conclusion

ITE patients demonstrated changed FCS values in the temporal and prefrontal cortices relative to nITE patients, which may be related to drug resistance in epilepsy. FCS in the left caudate nucleus associated with VIQ, suggesting the caudate may become a key target for improving cognitive impairment and seizures in children with ITE.

Methylphenidate Ameliorates Behavioural and Neurobiological Deficits in Executive Function for Patients with Chronic Traumatic Brain Injury

(1) Background: Traumatic brain injury (TBI) often results in cognitive impairments, including in visuospatial planning and executive function. Methylphenidate (MPh) demonstrates potential improvements in several cognitive domains in patients with TBI. The Tower of London (TOL) is a visuospatial planning task used to assess executive function. (2) Methods: Volunteers with a history of TBI (n = 16) participated in a randomised, double-blinded, placebo-controlled, fMRI study to investigate the neurobiological correlates of visuospatial planning and executive function, on and off MPh. (3) Results: Healthy controls (HCs) (n = 18) and patients on placebo (TBI-placebo) differed significantly in reaction time (p < 0.0005) and accuracy (p < 0.0001) when considering all task loads, but especially for high cognitive loads for reaction time (p < 0.001) and accuracy (p < 0.005). Across all task loads, TBI-MPh were more accurate than TBI-placebo (p < 0.05) but remained less accurate than HCs (p < 0.005). TBI-placebo substantially improved in accuracy with MPh administration (TBI-MPh) to a level statistically comparable to HCs at low (p = 0.443) and high (p = 0.175) cognitive loads. Further, individual patients that performed slower on placebo at low cognitive loads were faster with MPh (p < 0.05), while individual patients that performed less accurately on placebo were more accurate with MPh at both high and low cognitive loads (p < 0.005). TBI-placebo showed reduced activity in the bilateral inferior frontal gyri (IFG) and insulae versus HCs. MPh normalised these regional differences. MPh enhanced within-network connectivity (between parietal, striatal, insula, and cerebellar regions) and enhanced beyond-network connectivity (between parietal, thalamic, and cerebellar regions). Finally, individual changes in cerebellar-thalamic (p < 0.005) and cerebellar-parietal (p < 0.05) connectivity with MPh related to individual changes in accuracy with MPh. (4) Conclusions: This work highlights behavioural and neurofunctional differences between HCs and patients with chronic TBI, and that adverse differences may benefit from MPh treatment.

Pomalidomide Improves Motor Behavioral Deficits and Protects Cerebral Cortex and Striatum Against Neurodegeneration Through a Reduction of Oxidative/Nitrosative Damages and Neuroinflammation After Traumatic Brain Injury

Neuronal damage resulting from traumatic brain injury (TBI) causes disruption of neuronal projections and neurotransmission that contribute to behavioral deficits. Cellular generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is an early event following TBI. ROS often damage DNA, lipids, proteins, and carbohydrates while RNS attack proteins. The products of lipid peroxidation 4-hydroxynonenal (4-HNE) and protein nitration 3-nitrotyrosine (3-NT) are often used as indicators of oxidative and nitrosative damages, respectively. Increasing evidence has shown that striatum is vulnerable to damage from TBI with a disturbed dopamine neurotransmission. TBI results in neurodegeneration, oxidative stress, neuroinflammation, neuronal apoptosis, and autophagy in the striatum and contribute to motor or behavioral deficits. Pomalidomide (Pom) is a Food and Drug Administration (FDA)-approved immunomodulatory drug clinically used in treating multiple myeloma. We previously showed that Pom reduces neuroinflammation and neuronal death induced by TBI in rat cerebral cortex. Here, we further compared the effects of Pom in cortex and striatum focusing on neurodegeneration, oxidative and nitrosative damages, as well as neuroinflammation following TBI. Sprague-Dawley rats subjected to a controlled cortical impact were used as the animal model of TBI. Systemic administration of Pom (0.5 mg/kg, intravenous [i.v.]) at 5 h post-injury alleviated motor behavioral deficits, contusion volume at 24 h after TBI. Pom alleviated TBI-induced neurodegeneration stained by Fluoro-Jade C in both cortex and striatum. Notably, Pom treatment reduces oxidative and nitrosative damages in cortex and striatum and is more efficacious in striatum (93% reduction in 4-HNE-positive and 84% reduction in 3-NT-positive neurons) than in cerebral cortex (42% reduction in 4-HNE-positive and 55% reduction in 3-NT-positive neurons). In addition, Pom attenuated microgliosis, astrogliosis, and elevations of proinflammatory cytokines in cortical and striatal tissue. We conclude that Pom may contribute to improved motor behavioral outcomes after TBI through targeting oxidative/nitrosative damages and neuroinflammation.

Thalamic deep brain stimulation in traumatic brain injury: a phase 1, randomized feasibility study

Converging evidence indicates that impairments in executive function and information-processing speed limit quality of life and social reentry after moderate-to-severe traumatic brain injury (msTBI). These deficits reflect dysfunction of frontostriatal networks for which the central lateral (CL) nucleus of the thalamus is a critical node. The primary objective of this feasibility study was to test the safety and efficacy of deep brain stimulation within the CL and the associated medial dorsal tegmental (CL/DTTm) tract.Six participants with msTBI, who were between 3 and 18 years post-injury, underwent surgery with electrode placement guided by imaging and subject-specific biophysical modeling to predict activation of the CL/DTTm tract. The primary efficacy measure was improvement in executive control indexed by processing speed on part B of the trail-making test.All six participants were safely implanted. Five participants completed the study and one was withdrawn for protocol non-compliance. Processing speed on part B of the trail-making test improved 15% to 52% from baseline, exceeding the 10% benchmark for improvement in all five cases.CL/DTTm deep brain stimulation can be safely applied and may improve executive control in patients with msTBI who are in the chronic phase of recovery.ClinicalTrials.gov identifier: NCT02881151 .

Disrupted functional connectivity of the striatum in patients with diffuse axonal injury: a resting-state functional MRI study

Diffuse axonal injury (DAI) disrupts the integrity of white matter microstructure and affects brain functional connectivity, resulting in persistent cognitive, behavioral and affective deficits. Mounting evidence suggests that altered cortical-subcortical connectivity is a major contributor to cognitive dysfunction. The functional integrity of the striatum is particularly vulnerable to DAI, but has received less attention. This study aimed to investigate the alteration patterns of striatal subdivision functional connectivity. Twenty-six patients with DAI and 27 healthy controls underwent resting-state fMRI scans on a 3.0 T scanner. We assessed striatal subdivision functional connectivity using a seed-based analysis in DAI. Furthermore, a partial correlation was used to measure its clinical association. Compared to controls, patients with DAI showed decreased functional connectivity between the right inferior ventral striatum and right inferior frontal gyrus, as well as the right inferior parietal lobule, between the left inferior ventral striatum and right inferior frontal gyrus, between the right superior ventral striatum and bilateral cerebellar posterior lobe, between the bilateral dorsal caudal putamen and right anterior cingulate gyrus, and between the right dorsal caudal putamen and right inferior parietal lobule. Moreover, decreased functional connectivity was observed between the left dorsal caudate and the right cerebellar posterior lobe, while increased functional connectivity was found between the left dorsal caudate and right inferior parietal lobule. Correlation analyses showed that regions with functional connectivity differences in the DAI group correlated with multiple clinical scoring scales, including cognition, motor function, agitated behavior, and anxiety disorders. These findings suggest that abnormalities in cortico-striatal and cerebellar-striatal functional connectivity are observed in patients with DAI, enriching our understanding of the neuropathological mechanisms of post-injury cognitive disorders and providing potential neuroimaging markers for the diagnosis and treatment of DAI.

MRI factors associated with cognitive functioning after acute onset brain injury: Systematic review and meta-analysis

Impairments of memory, attention, and executive functioning are frequently reported after acute onset brain injury. MRI markers hold potential to contribute to identification of patients at risk for cognitive impairments and clarification of mechanisms. The aim of this systematic review was to summarize and value the evidence on MRI markers of memory, attention, and executive functioning after acute onset brain injury. We included ninety-eight studies, on six classes of MRI factors (location and severity of damage (n = 15), volume/atrophy (n = 36), signs of small vessel disease (n = 15), diffusion-weighted imaging measures (n = 36), resting-state functional MRI measures (n = 13), and arterial spin labeling measures (n = 1)). Three measures showed consistent results regarding their association with cognition. Smaller hippocampal volume was associated with worse memory in fourteen studies (pooled correlation 0.58 [95% CI: 0.46-0.68] for whole, 0.11 [95% CI: 0.04-0.19] for left, and 0.34 [95% CI: 0.17-0.49] for right hippocampus). Lower fractional anisotropy in cingulum and fornix was associated with worse memory in six and five studies (pooled correlation 0.20 [95% CI: 0.08-0.32] and 0.29 [95% CI: 0.20-0.37], respectively). Lower functional connectivity within the default-mode network was associated with worse cognition in four studies. In conclusion, hippocampal volume, fractional anisotropy in cingulum and fornix, and functional connectivity within the default-mode network showed consistent associations with cognitive performance in all types of acute onset brain injury. External validation and cut off values for predicting cognitive impairments are needed for clinical implementation.

Propofol disrupts alpha dynamics in functionally distinct thalamocortical networks during loss of consciousness

During propofol-induced general anesthesia, alpha rhythms measured using electroencephalography undergo a striking shift from posterior to anterior, termed anteriorization, where the ubiquitous waking alpha is lost and a frontal alpha emerges. The functional significance of alpha anteriorization and the precise brain regions contributing to the phenomenon are a mystery. While posterior alpha is thought to be generated by thalamocortical circuits connecting nuclei of the sensory thalamus with their cortical partners, the thalamic origins of the propofol-induced alpha remain poorly understood. Here, we used human intracranial recordings to identify regions in sensory cortices where propofol attenuates a coherent alpha network, distinct from those in the frontal cortex where it amplifies coherent alpha and beta activities. We then performed diffusion tractography between these identified regions and individual thalamic nuclei to show that the opposing dynamics of anteriorization occur within two distinct thalamocortical networks. We found that propofol disrupted a posterior alpha network structurally connected with nuclei in the sensory and sensory associational regions of the thalamus. At the same time, propofol induced a coherent alpha oscillation within prefrontal cortical areas that were connected with thalamic nuclei involved in cognition, such as the mediodorsal nucleus. The cortical and thalamic anatomy involved, as well as their known functional roles, suggests multiple means by which propofol dismantles sensory and cognitive processes to achieve loss of consciousness.

Association between Beta Oscillations from Subthalamic Nucleus and Quantitative Susceptibility Mapping in Deep Gray Matter Structures in Parkinson's Disease

This study aimed to investigate the association between beta oscillations and brain iron deposition. Beta oscillations were filtered from the microelectrode recordings of local field potentials (LFP) in the subthalamic nucleus (STN), and the ratio of the power spectral density of beta oscillations (PSDXb) to that of the LFP signals was calculated. Iron deposition in the deep gray matter (DGM) structures was indirectly assessed using quantitative susceptibility mapping (QSM). The Unified Parkinson's Disease Rating Scale (UPDRS), part III, was used to assess the severity of symptoms. Spearman correlation coefficients were applied to assess the associations of PSDXb with QSM values in the DGM structures and the severity of symptoms. PSDXb showed a significant positive correlation with the average QSM values in DGM structures, including caudate and substantia nigra (SN) (p = 0.008 and 0.044). Similarly, the PSDXb showed significant negative correlations with the severity of symptoms, including axial symptoms and the gait in the medicine-off state (p = 0.006 for both). The abnormal iron metabolism in the SN and striatum pathways may be one of the underlying mechanisms for the occurrence of abnormal beta oscillations in the STN, and beta oscillations may serve as important pathophysiological biomarkers of PD.

Incremental Effects of Subsequent Concussions on Cognitive Symptoms in the Sport Concussion Assessment Tool

OBJECTIVE

Patients who are fully recovered from a concussion may still be more vulnerable in the face of subsequent concussions. This study examines symptoms associated with repeated concussions in young and otherwise healthy adults.

DESIGN

Cross sectional.

SETTING

Institutional study at a university setting.

PARTICIPANTS

University students with a history of concussion.

INDEPENDENT VARIABLES

Participants were grouped based on numbers of concussions.

MAIN OUTCOME MEASURES

The impact of incremental concussion on symptom clusters in Sport Concussion Assessment Tools 5 and Spearman ranking correlation coefficients between symptom clusters.

RESULTS

One hundred thirty-five participants reported having had 1 concussion, 63 reported 2 concussions, 50 reported 3 concussions, and 43 reported 4 to 6 concussions. Total severity scores over the range of concussion number (1, 2, 3, and greater than 3) did not show a clear incremental effect. However, average scores of cognitive symptoms rose with each subsequent concussion ( P ≤ 0.05). The largest incremental effect observed was that of second concussions on emotional symptom scores (t = 5.85, P < 0.01). Symptoms in the emotional and cognitive clusters were the most correlated regardless of the number of reported concussions; the correlations were lowest with symptoms associated with sensitivity to light or noise.

CONCLUSIONS

The incremental rise of cognitive symptom scores with each concussion affirms the importance of cognitive impairment in concussion assessment and implies a cumulative brain vulnerability that persists even after symptom resolution. The cognitive-emotional symptom clusters may reflect underlying concussion-induced impairments in the corticostriatothalamocortical (CSTC) networks, although sensitivity symptoms are potentially attributable to different neural correlates.

Cognitive efficacy and neural mechanisms of music-based neurological rehabilitation for traumatic brain injury

Traumatic brain injury (TBI) causes lifelong cognitive deficits, most often in executive function (EF). Both musical training and music-based rehabilitation have been shown to enhance EF and neuroplasticity. Thus far, however, there is little evidence for the potential rehabilitative effects of music for TBI. Here, we review the core findings from our recent cross-over randomized controlled trial in which a 10-week music-based neurological rehabilitation (MBNR) protocol was administered to 40 patients with moderate-to-severe TBI. Neuropsychological testing and structural/functional magnetic resonance imaging were collected at three time points (baseline, 3 months, and 6 months); one group received the MBNR between time points 1 and 2, while a second group received it between time points 2 and 3. We found that both general EF and set shifting improved after the intervention, and this effect was maintained long term. Morphometric analyses revealed therapy-induced gray matter volume changes most consistently in the right inferior frontal gyrus, changes that correlated with better outcomes in set shifting. Finally, we found changes in the between- and within-network functional connectivity of large-scale resting-state networks after MBNR, which also correlated with measures of EF. Taken together, the data provide evidence for concluding that MBNR improves EF in TBI; also, the data show that morphometric and resting-state functional connectivity are sensitive markers with which to monitor the neuroplasticity induced by the MBNR intervention.

Brain volume abnormalities and clinical outcomes following paediatric traumatic brain injury

Long-term outcomes are difficult to predict after paediatric traumatic brain injury. The presence or absence of focal brain injuries often do not explain cognitive, emotional and behavioural disabilities that are common and disabling. In adults, traumatic brain injury produces progressive brain atrophy that can be accurately measured and is associated with cognitive decline. However, the effect of paediatric traumatic brain injury on brain volumes is more challenging to measure because of its interaction with normal brain development. Here we report a robust approach to the individualized estimation of brain volume following paediatric traumatic brain injury and investigate its relationship to clinical outcomes. We first used a large healthy control dataset (n > 1200, age 8-22) to describe the healthy development of white and grey matter regions through adolescence. Individual estimates of grey and white matter regional volume were then generated for a group of moderate/severe traumatic brain injury patients injured in childhood (n = 39, mean age 13.53 ± 1.76, median time since injury = 14 months, range 4-168 months) by comparing brain volumes in patients to age-matched controls. Patients were individually classified as having low or normal brain volume. Neuropsychological and neuropsychiatric outcomes were assessed using standardized testing and parent/carer assessments. Relative to head size, grey matter regions decreased in volume during normal adolescence development whereas white matter tracts increased in volume. Traumatic brain injury disrupted healthy brain development, producing reductions in both grey and white matter brain volumes after correcting for age. Of the 39 patients investigated, 11 (28%) had at least one white matter tract with reduced volume and seven (18%) at least one area of grey matter with reduced volume. Those classified as having low brain volume had slower processing speed compared to healthy controls, emotional impairments, higher levels of apathy, increased anger and learning difficulties. In contrast, the presence of focal brain injury and microbleeds were not associated with an increased risk of these clinical impairments. In summary, we show how brain volume abnormalities after paediatric traumatic brain injury can be robustly calculated from individual T1 MRI using a large normative dataset that allows the effects of healthy brain development to be controlled for. Using this approach, we show that volumetric abnormalities are common after moderate/severe traumatic brain injury in both grey and white matter regions, and are associated with higher levels of cognitive, emotional and behavioural abnormalities that are common after paediatric traumatic brain injury.

The Neurobiological Links between Stress and Traumatic Brain Injury: A Review of Research to Date

Neurological dysfunctions commonly occur after mild or moderate traumatic brain injury (TBI). Although most TBI patients recover from such a dysfunction in a short period of time, some present with persistent neurological deficits. Stress is a potential factor that is involved in recovery from neurological dysfunction after TBI. However, there has been limited research on the effects and mechanisms of stress on neurological dysfunctions due to TBI. In this review, we first investigate the effects of TBI and stress on neurological dysfunctions and different brain regions, such as the prefrontal cortex, hippocampus, amygdala, and hypothalamus. We then explore the neurobiological links and mechanisms between stress and TBI. Finally, we summarize the findings related to stress biomarkers and probe the possible diagnostic and therapeutic significance of stress combined with mild or moderate TBI.

Autonomic dysfunction after moderate-to-severe traumatic brain injury: symptom spectrum and clinical testing outcomes

Background

Survivors of moderate-to-severe traumatic brain injury (msTBI) frequently experience troublesome unexplained somatic symptoms. Autonomic dysfunction may contribute to these symptoms. However, there is no previous study of clinical subjective and objective autonomic dysfunction in msTBI.

Methods

We present results from two groups of patients with msTBI. The first, a case–control comparative study, comprises prospectively recruited msTBI outpatients, in whom we measured burden of autonomic symptoms using the Composite Autonomic Symptom Score (COMPASS31) questionnaire. The second, a descriptive case series, comprises retrospectively identified msTBI outpatients who had formal clinical autonomic function testing at a national referral autonomics unit.

Results

Group 1 comprises 39 patients with msTBI (10F:20M, median age 40 years, range 19–76), median time from injury 19 months (range 6–299) and 44 controls (22F:22M, median age 45, range 25–71). Patients had significantly higher mean weighted total COMPASS-31 score than controls (p<0.001), and higher gastrointestinal, orthostatic and secretomotor subscores (corrected p<0.05). Total COMPASS31 score inversely correlated with subjective rating of general health (p<0.001, r_s=−0.84). Group 2 comprises 18 patients with msTBI (7F:11M, median age 44 years, range 21–64), median time from injury 57.5 months (range 2–416). Clinical autonomic function testing revealed a broad spectrum of autonomic dysfunction in 13/18 patients.

Conclusions

There is clinically relevant autonomic dysfunction after msTBI, even at the chronic stage. We advocate for routine enquiry about potential autonomic symptoms, and demonstrate the utility of formal autonomic testing in providing diagnoses. Larger prospective studies are warranted, which should explore the causes and clinical correlates of post-TBI autonomic dysfunction.

Abnormal Dorsal Caudate Activation Mediated Impaired Cognitive Flexibility in Mild Traumatic Brain Injury

BACKGROUND

Mild traumatic brain injury (mTBI) is an important but less recognized public health concern. Previous studies have demonstrated that patients with mTBI have impaired executive function, which disrupts the performance of daily activities. Few studies have investigated neural mechanisms of cognitive flexibility in mTBI patients using objective tools such as the psychological experiment paradigm. Here, we aimed to examine neural correlates of cognitive flexibility in mTBI.

METHODS

Sixteen mTBI patients and seventeen matched healthy controls (HCs) underwent functional MRI during a rule-based task-switching experimental paradigm. Linear models were used to obtain within-group activation maps and areas of differential activation between the groups. In addition, we conducted mediation analyses to evaluate the indirect effect of abnormal dorsal caudate activation on the association between information processing speed and cognitive flexibility in mTBI.

RESULTS

mTBI patients exhibited significantly longer reaction time in the task switching (TS) condition compared to HCs, reflecting impaired cognitive flexibility. In addition, the patients showed reduced activation in the dorsal caudate (dCau), anterior cingulate cortex, and other frontal regions during the TS condition. Mediation analysis revealed that the reduced dCau activation had a significant effect on the relationship between information processing speed and cognitive flexibility in mTBI.

CONCLUSIONS

Abnormal dorsal caudate activation in mTBI mediates impaired cognitive flexibility, which indicated dorsal caudate might be playing a vital role in the cognitive flexibility of mTBI patients. These findings highlight an alternative target for clinical interventions for the improvement of cognitive functions in mTBI.

The human vestibular cortex: functional anatomy of OP2, its connectivity and the effect of vestibular disease

Area OP2 in the posterior peri-sylvian cortex has been proposed to be the core human vestibular cortex. We investigated the functional anatomy of OP2 and adjacent areas (OP2+) using spatially constrained independent component analysis (ICA) of functional magnetic resonance imaging (fMRI) data from the Human Connectome Project. Ten ICA-derived subregions were identified. OP2+ responses to vestibular and visual motion were analyzed in 17 controls and 17 right-sided vestibular neuritis patients who had previously undergone caloric and optokinetic stimulation during fMRI. In controls, a posterior part of right OP2+ showed: (i) direction-selective responses to visual motion and (ii) activation during caloric stimulation that correlated positively with perceived self-motion, and negatively with visual dependence and peak slow-phase nystagmus velocity. Patients showed abnormal OP2+ activity, with an absence of visual or caloric activation of the healthy ear and no correlations with vertigo or visual dependence-despite normal slow-phase nystagmus responses to caloric stimulation. Activity in a lateral part of right OP2+ correlated with chronic visually induced dizziness in patients. In summary, distinct functional subregions of right OP2+ show strong connectivity to other vestibular areas and a profile of caloric and visual responses, suggesting a central role for vestibular function in health and disease.

Processing speed dysfunction is associated with functional corticostriatal circuit alterations in childhood epilepsy with centrotemporal spikes: a PET and fMRI study

Purpose

Epilepsy with centrotemporal spikes (ECTS) is the most common epilepsy syndrome in children and usually presents with cognitive dysfunctions. However, little is known about the processing speed dysfunction and the associated neuroimaging mechanism in ECTS. This study aims to investigate the brain functional abnormality of processing speed dysfunction in ECTS patients by using the ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and resting-state functional magnetic resonance imaging (rs-fMRI).

Methods

This prospective study recruited twenty-eight ECTS patients who underwent the ¹⁸F-FDG PET, rs-fMRI, and neuropsychological examinations. Twenty children with extracranial tumors were included as PET controls, and 20 healthy children were recruited as MRI controls. The PET image analysis investigated glucose metabolism by determining standardized uptake value ratio (SUVR). The MRI image analysis explored abnormal functional connectivity (FC) within the cortical–striatal circuit through network-based statistical (NBS) analysis. Correlation analysis was performed to explore the relationship between SUVR, FC, and processing speed index (PSI).

Results

Compared with healthy controls, ECTS patients showed normal intelligence quotient but significantly decreased PSI (P = 0.04). PET analysis showed significantly decreased SUVRs within bilateral caudate, putamen, pallidum, left NAc, right rostral middle frontal gyrus, and frontal pole of ECTS patients (P < 0.05). Rs-fMRI analysis showed absolute values of 20 FCs were significantly decreased in ECTS patients compared with MRI controls, which connected 16 distinct ROIs. The average SUVR of right caudate and the average of 20 FCs were positively correlated with PSI in ECTS patients (P = 0.034 and P = 0.005, respectively).

Conclusion

This study indicated that ECTS patients presented significantly reduced PSI, which is closely associated with decreased SUVR and FC of cortical–striatal circuit. Caudate played an important role in processing speed dysfunction.

Clinical trial registration

NCT04954729; registered on July 8, 2021, public site, https://clinicaltrials.gov/ct2/show/NCT04954729

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05740-w.

Lesions in different prefrontal sectors are associated with different types of acquired personality disturbances

"Frontal lobe syndrome" is a term often used to describe a diverse array of personality disturbances following frontal lobe damage. This study's guiding premise was that greater neuroanatomical specificity could be achieved by evaluating specific types of personality disturbances following acquired frontal lobe lesions. We hypothesized that three acquired personality disturbances would be associated with lesion involvement of distinct sectors of the prefrontal cortex (PFC): 1) emotional-social disturbance and ventromedial PFC, 2) hypoemotional disturbance and dorsomedial PFC, and 3) dysexecutive and dorsolateral PFC. In addition, we hypothesized that distressed personality disturbance would not be associated with focal PFC lesions in any sector. Each hypothesis was pre-registered and tested in 182 participants with adult-onset, chronic, focal brain lesions studied with an observational, cross-sectional design. Pre- and postmorbid personality was assessed by informant-rating with the Iowa Scales of Personality Change, completed by a spouse or family member. Two complementary analytic approaches were employed: 1) a hypothesis-driven region-of-interest (ROI) regression analysis examining the associations of lesions in specific PFC sectors with acquired personality disturbances; 2) a data-driven multivariate lesion-behavior mapping analysis, which was not limited to pre-specified regions. Each hypothesis received some support: (i) Emotional/social personality disturbance was most strongly associated with ventromedial PFC lesions in both statistical approaches. (ii) Hypoemotional disturbance was associated with dorsomedial PFC lesions in the ROI analyses, without any significant lesion-symptom mapping associations. (iii) Dysexecutive personality disturbance was associated with bilateral dorsolateral PFC lesions and ventromedial PFC lesions; lesion-symptom mapping showed maximal association of executive dysfunction with damage of the right middle frontal gyrus within the dorsolateral PFC. (iv) Distressed personality disturbance was not associated with lesions in any PFC sector. Altogether, the findings can be interpreted to indicate that damage to different prefrontal sectors may disrupt different anatomical-functional systems and result in distinct personality disturbances.

Abnormal resting-state brain activity and connectivity of brain-bladder control network in overactive bladder syndrome

BACKGROUND

Neuroimaging studies have shown that the brain is involved in the mechanism of overactive bladder disease (OAB).

PURPOSE

To explorer spatial patterns of spontaneous neural activities and functional integration in patients with OAB.

MATERIAL AND METHODS

In total, 28 patients with OAB and 28 matched healthy controls (HC) underwent resting-state functional magnetic resonance imaging and completed questionnaires to assess clinical symptoms. The amplitude of low-frequency fluctuation (ALFF) and ROI-based functional connectivity (FC) within the brain-bladder control network (BBCN) were calculated and compared between the two groups using a two-sample t-test. Pearson correlation analysis was performed to investigate the relationship between ALFF and the clinical score of patients with OAB.

RESULTS

Compared with HCs, patients with OAB exhibited significantly decreased ALFF in the left superior medial middle gyrus (SFGmed) and superior dorsal frontal gyrus (SFGdor), and increased ALFF in the right hippocampus. Furthermore, ALFF values in the left SFGmed were negatively correlated with OABSS scores. FC in patients with OAB was significantly increased between the bilateral caudate nucleus (CAU) and bilateral SFGdor, the bilateral CAU and bilateral supplementary motor area (SMA), the bilateral thalamus and SMA; the left CAU and bilateral SFGmed, the left CAU and bilateral anterior cingulate gyrus, and the left CAU and left insula. Additionally, decreased FC was found between the bilateral amygdala and bilateral SFGmed and the left SMA and left insula.

CONCLUSION

These abnormal activities and connectivities of BBCN may indicate impaired cortical control of micturition in OAB, suggesting a possible neural mechanism of OAB.

Compensatory functional connectome changes in a rat model of traumatic brain injury

Penetrating cortical impact injuries alter neuronal communication beyond the injury epicentre, across regions involved in affective, sensorimotor and cognitive processing. Understanding how traumatic brain injury reorganizes local and brain wide nodal interactions may provide valuable quantitative parameters for monitoring pathological progression and recovery. To this end, we investigated spontaneous fluctuations in the functional MRI signal obtained at 11.1 T in rats sustaining controlled cortical impact and imaged at 2- and 30-days post-injury. Graph theory-based calculations were applied to weighted undirected matrices constructed from 12 879 pairwise correlations between functional MRI signals from 162 regions. Our data indicate that on Days 2 and 30 post-controlled cortical impact there is a significant increase in connectivity strength in nodes located in contralesional cortical, thalamic and basal forebrain areas. Rats imaged on Day 2 post-injury had significantly greater network modularity than controls, with influential nodes (with high eigenvector centrality) contained within the contralesional module and participating less in cross-modular interactions. By Day 30, modularity and cross-modular interactions recover, although a cluster of nodes with low strength and low eigenvector centrality remain in the ipsilateral cortex. Our results suggest that changes in node strength, modularity, eigenvector centrality and participation coefficient track early and late traumatic brain injury effects on brain functional connectivity. We propose that the observed compensatory functional connectivity reorganization in response to controlled cortical impact may be unfavourable to brain wide communication in the early post-injury period.

Altered gray matter structural covariance networks at both acute and chronic stages of mild traumatic brain injury

Cognitive and emotional impairments observed in mild traumatic brain injury (mTBI) patients may reflect variances of brain connectivity within specific networks. Although previous studies found altered functional connectivity (FC) in mTBI patients, the alterations of brain structural properties remain unclear. In the present study, we analyzed structural covariance (SC) for the acute stages of mTBI (amTBI) patients, the chronic stages of mTBI (cmTBI) patients, and healthy controls. We first extracted the mean gray matter volume (GMV) of seed regions that are located in the default-mode network (DMN), executive control network (ECN), salience network (SN), sensorimotor network (SMN), and the visual network (VN). Then we determined and compared the SC for each seed region among the amTBI, the cmTBI and the healthy controls. Compared with healthy controls, the amTBI patients showed lower SC for the ECN, and the cmTBI patients showed higher SC for the both DMN and SN but lower SC for the SMN. The results revealed disrupted ECN in the amTBI patients and disrupted DMN, SN and SMN in the cmTBI patients. These alterations suggest that early disruptions in SC between bilateral insula and the bilateral prefrontal cortices may appear in amTBI and persist into cmTBI, which might be potentially related to the cognitive and emotional impairments.

Neural function during emotion regulation and future depressive symptoms in youth at risk for affective disorders

Affective disorders (AD, including bipolar disorder, BD, and major depressive disorder) are severe recurrent illnesses. Identifying neural markers of processes underlying AD development in at-risk youth can provide objective, "early-warning" signs that may predate onset or worsening of symptoms. Using data (n = 34) from the Bipolar Offspring Study, we examined relationships between neural response in regions supporting executive function, and those supporting self-monitoring, during an emotional n-back task (focusing on the 2-back face distractor versus the 0-back no-face control conditions) and future depressive and hypo/manic symptoms across two groups of youth at familial risk for AD: Offspring of parents with BD (n = 15, age = 14.15) and offspring of parents with non-BD psychopathology (n = 19, age = 13.62). Participants were scanned and assessed twice, approximately 4 years apart. Across groups, less deactivation in the mid-cingulate cortex during emotional regulation (Rate Ratio = 3.07(95% CI:1.09-8.66), χ²(1) = 4.48, p = 0.03) at Time-1, and increases in functional connectivity from Time-1 to 2 (Rate Ratio = 1.45(95% CI:1.15-1.84), χ²(1) = 8.69, p = 0.003) between regions that showed deactivation during emotional regulation and the right caudate, predicted higher depression severity at Time-2. Both effects were robust to sensitivity analyses controlling for clinical characteristics. Decreases in deactivation between Times 1 and 2 in the right putamen tail were associated with increases in hypo/mania at Time-2, but this effect was not robust to sensitivity analyses. Our findings reflect neural mechanisms of risk for worsening affective symptoms, particularly depression, in youth across a range of familial risk for affective disorders. They may serve as potential objective, early-warning signs of AD in youth.

Abnormal dorsal attention network activation in memory impairment after traumatic brain injury

Memory impairment is a common, disabling effect of traumatic brain injury. In healthy individuals, successful memory encoding is associated with activation of the dorsal attention network as well as suppression of the default mode network. Here, in traumatic brain injury patients we examined whether: (i) impairments in memory encoding are associated with abnormal brain activation in these networks; (ii) whether changes in this brain activity predict subsequent memory retrieval; and (iii) whether abnormal white matter integrity underpinning functional networks is associated with impaired subsequent memory. Thirty-five patients with moderate-severe traumatic brain injury aged 23-65 years (74% males) in the post-acute/chronic phase after injury and 16 healthy control subjects underwent functional MRI during performance of an abstract image memory encoding task. Diffusion tensor imaging was used to assess structural abnormalities across patient groups compared to 28 age-matched healthy controls. Successful memory encoding across all participants was associated with activation of the dorsal attention network, the ventral visual stream and medial temporal lobes. Decreased activation was seen in the default mode network. Patients with preserved episodic memory demonstrated increased activation in areas of the dorsal attention network. Patients with impaired memory showed increased left anterior prefrontal activity. White matter microstructure underpinning connectivity between core nodes of the encoding networks was significantly reduced in patients with memory impairment. Our results show for the first time that patients with impaired episodic memory show abnormal activation of key nodes within the dorsal attention network and regions regulating default mode network activity during encoding. Successful encoding was associated with an opposite direction of signal change between patients with and without memory impairment, suggesting that memory encoding mechanisms could be fundamentally altered in this population. We demonstrate a clear relationship between functional networks activated during encoding and underlying abnormalities within the structural connectome in patients with memory impairment. We suggest that encoding failures in this group are likely due to failed control of goal-directed attentional resources.

Detecting axonal injury in individual patients after traumatic brain injury

Poor outcomes after traumatic brain injury (TBI) are common yet remain difficult to predict. Diffuse axonal injury is important for outcomes, but its assessment remains limited in the clinical setting. Currently, axonal injury is diagnosed based on clinical presentation, visible damage to the white matter or via surrogate markers of axonal injury such as microbleeds. These do not accurately quantify axonal injury leading to misdiagnosis in a proportion of patients. Diffusion tensor imaging provides a quantitative measure of axonal injury in vivo, with fractional anisotropy often used as a proxy for white matter damage. Diffusion imaging has been widely used in TBI but is not routinely applied clinically. This is in part because robust analysis methods to diagnose axonal injury at the individual level have not yet been developed. Here, we present a pipeline for diffusion imaging analysis designed to accurately assess the presence of axonal injury in large white matter tracts in individuals. Average fractional anisotropy is calculated from tracts selected on the basis of high test-retest reliability, good anatomical coverage and their association to cognitive and clinical impairments after TBI. We test our pipeline for common methodological issues such as the impact of varying control sample sizes, focal lesions and age-related changes to demonstrate high specificity, sensitivity and test-retest reliability. We assess 92 patients with moderate-severe TBI in the chronic phase (≥6 months post-injury), 25 patients in the subacute phase (10 days to 6 weeks post-injury) with 6-month follow-up and a large control cohort (n = 103). Evidence of axonal injury is identified in 52% of chronic and 28% of subacute patients. Those classified with axonal injury had significantly poorer cognitive and functional outcomes than those without, a difference not seen for focal lesions or microbleeds. Almost a third of patients with unremarkable standard MRIs had evidence of axonal injury, whilst 40% of patients with visible microbleeds had no diffusion evidence of axonal injury. More diffusion abnormality was seen with greater time since injury, across individuals at various chronic injury times and within individuals between subacute and 6-month scans. We provide evidence that this pipeline can be used to diagnose axonal injury in individual patients at subacute and chronic time points, and that diffusion MRI provides a sensitive and complementary measure when compared to susceptibility weighted imaging, which measures diffuse vascular injury. Guidelines for the implementation of this pipeline in a clinical setting are discussed.

Childhood neglect is associated with corticostriatal circuit dysfunction in bipolar disorder adults

Bipolar disorder (BD) is characterized with cognitive impairment, which may be mediated by corticostriatal dysfunction. Here we examined whether history of childhood trauma, a risk factor for BD, was linked to corticostriatal dysfunction in BD patients. Furthermore, the possible associations between childhood trauma and cognitive impairment were examined. Thirty-eight BD participants who met the DSM-IV diagnostic criteria were enrolled. Childhood trauma was identified via the Childhood Trauma Questionnaire (CTQ). Participants completed the Wisconsin Card-Sorting Test (WCST). Resting-state functional magnetic resonance imaging (rsfMRI) was performed in participants using a 3T scanner. Bilateral caudate to whole-brain functional connectivity (FC) were analyzed, and childhood trauma was entered as a regressor of interest when controlling for age. Results showed the level of physical neglect was negatively correlated with left-caudate-seed FC to the frontoparietal network, including the right supramarginal gyrus, left inferior parietal lobule, right middle frontal gyrus, and right superior parietal lobule. The level of physical neglect was also negatively correlated with WCST performance. And the left-caudate-seed FCs to the frontoparietal network were positively correlated with WCST performance. Unequivocally, the specific impacts of physical neglect on brain connectivity and executive function in the BD population merit further investigation.

Distinct patterns of structural damage underlie working memory and reasoning deficits after traumatic brain injury

It is well established that chronic cognitive problems after traumatic brain injury relate to diffuse axonal injury and the consequent widespread disruption of brain connectivity. However, the pattern of diffuse axonal injury varies between patients and they have a correspondingly heterogeneous profile of cognitive deficits. This heterogeneity is poorly understood, presenting a non-trivial challenge for prognostication and treatment. Prominent amongst cognitive problems are deficits in working memory and reasoning. Previous functional MRI in controls has associated these aspects of cognition with distinct, but partially overlapping, networks of brain regions. Based on this, a logical prediction is that differences in the integrity of the white matter tracts that connect these networks should predict variability in the type and severity of cognitive deficits after traumatic brain injury. We use diffusion-weighted imaging, cognitive testing and network analyses to test this prediction. We define functionally distinct subnetworks of the structural connectome by intersecting previously published functional MRI maps of the brain regions that are activated during our working memory and reasoning tasks, with a library of the white matter tracts that connect them. We examine how graph theoretic measures within these subnetworks relate to the performance of the same tasks in a cohort of 92 moderate-severe traumatic brain injury patients. Finally, we use machine learning to determine whether cognitive performance in patients can be predicted using graph theoretic measures from each subnetwork. Principal component analysis of behavioural scores confirm that reasoning and working memory form distinct components of cognitive ability, both of which are vulnerable to traumatic brain injury. Critically, impairments in these abilities after traumatic brain injury correlate in a dissociable manner with the information-processing architecture of the subnetworks that they are associated with. This dissociation is confirmed when examining degree centrality measures of the subnetworks using a canonical correlation analysis. Notably, the dissociation is prevalent across a number of node-centric measures and is asymmetrical: disruption to the working memory subnetwork relates to both working memory and reasoning performance whereas disruption to the reasoning subnetwork relates to reasoning performance selectively. Machine learning analysis further supports this finding by demonstrating that network measures predict cognitive performance in patients in the same asymmetrical manner. These results accord with hierarchical models of working memory, where reasoning is dependent on the ability to first hold task-relevant information in working memory. We propose that this finer grained information may be useful for future applications that attempt to predict long-term outcomes or develop tailored therapies.

The Behavioral Neuroscience of Traumatic Brain Injury

Traumatic brain injury is a calamity of various causes, pathologies, and extremely varied and often complex clinical presentations. Because of its predilection for brain systems underlying cognitive and complex behavioral operations, it may cause chronic and severe psychiatric illness that requires expert management. This is more so for the modern epidemic of athletic and military brain injuries which are dominated by psychiatric symptoms. Past medical, including psychiatric, history, and comorbidities are important and relevant for formulation and management. Traumatic brain injury is a model for other neuropsychiatric disorders and may serve as an incubator of new ideas for neurodegenerative disease.

The heterogeneous functional architecture of the posteromedial cortex is associated with selective functional connectivity differences in Alzheimer's disease

The posteromedial cortex (PMC) is a key region involved in the development and progression of Alzheimer's disease (AD). Previous studies have demonstrated a heterogenous functional architecture of the region that is composed of discrete functional modules reflecting a complex pattern of functional connectivity. However, little is understood about the mechanisms underpinning this complex network architecture in neurodegenerative disease, and the differential vulnerability of connectivity-based subdivisions in the PMC to AD pathogenesis. Using a data-driven approach, we applied a constrained independent component analysis (ICA) on healthy adults from the Human Connectome Project to characterise the local functional connectivity patterns within the PMC, and its unique whole-brain functional connectivity. These distinct connectivity profiles were subsequently quantified in the Alzheimer's Disease Neuroimaging Initiative study, to examine functional connectivity differences in AD patients and cognitively normal (CN) participants, as well as the entire AD pathological spectrum. Our findings revealed decreased functional connectivity in the anterior precuneus, dorsal posterior cingulate cortex (PCC), and the central precuneus in AD patients compared to CN participants. Functional abnormalities in the dorsal PCC and central precuneus were also related to amyloid burden and volumetric hippocampal loss. Across the entire AD spectrum, functional connectivity of the central precuneus was associated with disease severity and specific deficits in memory and executive function. These findings provide new evidence showing that the PMC is selectively impacted in AD, with prominent network failures of the dorsal PCC and central precuneus underpinning the neurodegenerative and cognitive dysfunctions associated with the disease.

DPP-4 inhibitor reduces striatal microglial deramification after sensorimotor cortex injury induced by external force impact

Dipeptidyl peptidase-4 inhibitors (or gliptins), a class of antidiabetic drugs, have recently been shown to have protective actions in the central nervous system. Their cellular and molecular mechanisms responsible for these effects are largely unknown. In the present study, two structurally different gliptins, sitagliptin and vildagliptin, were examined for their therapeutic actions in a controlled cortical impact (CCI) model of moderate traumatic brain injury (TBI) in mice. Early post-CCI treatment with sitagliptin, but not vildagliptin, significantly reduced body asymmetry, locomotor hyperactivity, and brain lesion volume. Sitagliptin attenuated post-CCI microglial deramification in the ipsilateral dorsolateral (DL) striatum, while vildagliptin had no effect. Sitagliptin also reduced striatal expression of galectin-3 and monocyte chemoattractant protein 1(MCP-1), and increased the cortical and striatal levels of the anti-inflammatory cytokine IL-10 on the ipsilateral side. These data support a differential protective effect of sitagliptin against TBI, possibly mediated by an anti-inflammatory effect in striatum to preserve connective network. Both sitagliptin and vildagliptin produced similar increases of active glucagon-like peptide-1 (GLP-1) in blood and brain. Increasing active GLP-1 may not be the sole molecular mechanisms for the neurotherapeutic effect of sitagliptin in TBI.

Improve cognition of depressive patients through the regulation of basal ganglia connectivity: Combined medication using Shuganjieyu capsule

Shuganjieyu capsule (Shugan) is a combined extract of Hypericum perforatum (HP) and Eleutherococcus senticosus (ES). Both HP and ES have been proven effective in the treatment of depression and impaired cognition. However, for mild to moderate depression (MMD), the treatment effect and underlying mechanism by combining both HP and ES are largely unknown. Here, we aim to evaluate the therapeutic effects on impaired cognition using Shugan, a combined medication of HP and ES. Resting-state magnetic resonance imaging (MRI) data and cognitive assessment have been collected from 54 healthy controls and 55 MMD patients that have been undergoing 8-week Shugan-treatment. The functional connectivity (FC) and brain region volume changes of the basal ganglia seeded circuit have been measured, and their relation with the cognitive assessment score was calculated. After that, a literature-based pathway analysis has been conducted to explore the biological relations among Shugan, brain regions, and depression. Compared to healthy controls, MMD patients demonstrated a significantly higher FC (P= 0.0025) between right ventral caudate (vCa) and left orbitofrontal cortex (OFC), which was decreased after the treatment (P < 0.001). A volume of the right caudate, which is increased in MMD, has also been reduced by Shugan treatment (P= 0.017). Importantly, the cognitive scores were strongly correlated with both Shugan treatment and the FC between vCa and OFC (r= 0.321, P= 0.02). Besides, we identified multiple signaling pathways, through which Shugan might improve the cognition of MMD patients. Our results support the therapeutic effects of Shugan on cognition in MMD, which may be realized partly through the regulation within two brain regions, vCa and OFC.

HIF-1α/SDF-1/CXCR4 axis reduces neuronal apoptosis via enhancing the bone marrow-derived mesenchymal stromal cell migration in rats with traumatic brain injury

Mesenchymal stromal injection is a promising therapy for traumatic brain injury (TBI). The aim of this study was to explore the effects of the HIF-1α/SDF-1/CXCR4 axis on neuron repair in TBI rats through improving the bone marrow-derived mesenchymalstromal cells (BMSCs) migration. TBI rat models were established. The rats were treated with exogenous SDF-1, and then the neuronal apoptosis in TBI rats was measured. BMSCs from rats were collected, and the roles of NF-κB p65 expression in nuclei, overexpression of SDF-1 and HIF-1α, as well as downregulation of CXCR4 in BMSC migration were identified. HIF-1α- and SDF-1- treated BMSCs were transplanted into TBI rats, after which the neuronal apoptosis and activity of the HIF-1α/SDF-1/CXCR4 axis were detected. Consequently, we found SDF-1 elevated the HIF-1α/SDF-1/CXCR4 activity and presented protective roles in TBI rat hippocampal neurons with reduced neuronal apoptosis. SDF-1 promoted BMSC migration in vitro, and co-effects of SDF-1 and HIF-1α showed strong promotion, while CXCR4 inhibition suppressed BMSC migration. BMSC transplantation activated the HIF-1α/SDF-1/CXCR4 axis and reduced neuronal apoptosis in TBI rats. To conclude, our study demonstrated that the HIF-1α/SDF-1/CXCR4 axis could enhance BMSC migration and alleviate neuronal damage and apoptosis in TBI rats. This study provided novel options for TBI therapy.

The Effects of Benzodiazepine Use and Abuse on Cognition in the Elders: A Systematic Review and Meta-Analysis of Comparative Studies

OBJECTIVE

Benzodiazepines (BZD) are one of the most frequently prescribed drugs worldwide. However, the cognitive effects of benzodiazepines in the elderly are highly debated. This systematic review and meta-analysis aims to explore the following two questions in the elderly population: (i) Do BZD lead to any impairments in cognitive functions in elderly users? and (ii) Which specific cognitive domains are most affected by BZD use and abuse?

METHODS

First, we performed a literature search following the PRISMA guidelines. Electronic databases, including PubMed, PsycINFO, EMBASE, Cochrane Library, and Web of Science were searched until May 14^th, 2020. After selecting the relevant articles, we integrated the results of the selected studies with a standardized cognitive classification method. Next, we performed meta-analyses with the random-effects model on the cognitive results. Finally, we specifically examined the cognitive impairments of BZD in the abuse subgroup.

RESULTS

Of the included studies, eight of the thirteen had meta-analyzable data. Compared to the controls, elderly BZD users had significantly lower digital symbol test scores (n=253; SMD: -0.61, 95% CI: -0.91 to 0.31, I² = 0%, p < 0.0001). There was no significant difference in Mini-Mental State Examination, Auditory Verbal Learning Test, and Stroop Color and Word Test scores between BZD users and controls. According to the subgroup analyses, BZD abusers performed significantly worse than controls in Mini-Mental State Examination (n=7726; SMD: -0.23, 95% CI: -0.44 to -0.03, I² = 86%, p = 0.02), while there was no significant difference between the regular BZD users and the controls (n=1536; SMD: -0.05, 95% CI: -0.59 to 0.48, I² = 92%, p =0.85).

CONCLUSION

In the elderly population, the processing speed (digital symbol test scores) was significantly impaired in BZD users; global cognition (Mini-Mental State Examination scores) was significantly impaired in BZD abusers but not in BZD regular users. This study provides insight into the factors that interact with BZD cognitive effects, such as aging, testing tools, and abuse. Clinicians should be cautious when prescribing BZD for the elderly.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, identifier CRD42019124711.

Longitudinal change in regional brain volumes with exposure to repetitive head impacts

Objective

This study tests the hypothesis that certain MRI-based regional brain volumes will show reductions over time in a cohort exposed to repetitive head impacts (RHI).

Methods

Participants were drawn from the Professional Fighters Brain Health Study, a longitudinal observational study of professional fighters and controls. Participants underwent annual 3T brain MRI, computerized cognitive testing, and blood sampling for determination of neurofilament light (NfL) and tau levels. Yearly change in regional brain volume was calculated for several predetermined cortical and subcortical brain volumes and the relationship with NfL and tau levels determined.

Results

A total of 204 participants who had at least 2 assessments were included in the analyses. Compared to controls, the active boxers had an average yearly rate of decline in volumes of the left thalamus (102.3 mm³/y [p = 0.0004], mid anterior corpus callosum (10.2 mm³/y [p = 0.018]), and central corpus callosum (16.5 mm³/y [p = <0.0001]). Retired boxers showed the most significant volumetric declines compared to controls in left (32.1 mm³/y [p = 0.002]) and right (30.6 mm³/y [p = 0.008]) amygdala and right hippocampus (33.5 mm³/y [p = 0.01]). Higher baseline NfL levels were associated with greater volumetric decline in left hippocampus and mid anterior corpus callosum.

Conclusion

Volumetric loss in different brain regions may reflect different pathologic processes at different times among individuals exposed to RHI.

Nodal Global Efficiency in Front-Parietal Lobe Mediated Periventricular White Matter Hyperintensity (PWMH)-Related Cognitive Impairment

White matter hyperintensity (WMH) is widely observed in the elderly population and serves as a key indicator of cognitive impairment (CI). However, the underlying mechanism remains to be elucidated. Herein, we investigated the topological patterns of resting state functional networks in WMH subjects and the relationship between the topological measures and CI. A graph theory-based analysis was employed in the resting-state functional magnetic resonance scans of 112 subjects (38 WMH subjects with cognitive impairment without dementia (CIND), 36 WMH subjects with normal cognition and 38 healthy controls (HCs), and we found that WMH-CIND subjects displayed decreased global efficiency at the levels of the whole brain, specific subnetworks [fronto-parietal network (FPN) and cingulo-opercular network (CON)] and certain nodes located in the FPN and CON, as well as decreased local efficiency in subnetworks. Our results demonstrated that nodal global efficiency in frontal and parietal regions mediated the impairment of information processing speed related to periventricular WMH (PWMH). Additionally, we performed support vector machine (SVM) analysis and found that altered functional efficiency can identify WMH-CIND subjects with high accuracy, sensitivity and specificity. These findings suggest impaired functional networks in WMH-CIND individuals and that decreased functional efficiency may be a feature of CI in WMH subjects.

Association Between Connectivity of Hippocampal Sub-Regions and Auditory Verbal Hallucinations in Schizophrenia

Background: Hippocampal dysconnectivity has been detected in schizophrenia patients with auditory verbal hallucinations (AVHs). Neuroanatomical evidence has indicated distinct sub-regions in the hippocampus, but which sub-regions within the hippocampus may emerge dysfunction in the brain network, and the relationship between connection strength and the severity of this debilitating disorder have yet to be revealed. Masked independent component analysis (mICA), i.e., ICA restricted to a defined region of interest, can provide insight into observing local functional connectivity in a particular brain region. We aim to map out the sub-regions in the hippocampus with dysconnectivity linked to AVHs in schizophrenia.

Methods: In this functional magnetic resonance imaging study of schizophrenia patients with (n = 57) and without (n = 83) AVHs, and 71 healthy controls, we first examined hippocampal connectivity using mICA, and then the correlation between connection metric and clinical severity was generated.

Results: As compared with patients without AVHs, mICA showed a group of hyper-connections for the left middle part, as well as another group of hypo-connections for the bilateral antero-lateral and right antero-medial parts in patients with AVHs. Connectivity was linked to the clinical symptoms scores in the sample of patients with AVHs.

Conclusion: These findings demonstrate that the left middle part is more densely connected, but the bilateral antero-lateral and right antero-medial parts are more sparsely connected in schizophrenia patients with AVHs. The findings in the present study show proof of precious location in the hippocampus mediating the neural mechanism behind AVHs in schizophrenia.

Corticostriatal Hyperactivation to Reward Presentation in Individuals With TBI With High Depressive Symptomatology: A Pilot Study

OBJECTIVE

To examine the impact of depression on neural mechanisms associated with outcome processing (rewarding and punishing outcomes) in persons with traumatic brain injury (TBI).

SETTING

Kessler Foundation's Rocco Ortenzio Neuroimaging Center.

PARTICIPANTS

A total of 16 adults with moderate to severe TBI.

MAIN MEASURES

Chicago Multiscale Depression Inventory (CMDI); Behavioral Inhibition/Behavioral Activation Scale (BIS/BAS); functional MRI of the head while performing a gambling task, with a reward (+$1.00) and punishment (-$0.50).

RESULTS

Individuals with TBI reporting high depressive symptomatology exhibited increased activation in the ventromedial prefrontal cortex (VMPFC) and striatum during presentation of rewarding outcomes compared with individuals with TBI reporting low depressive symptomatology. Punishing outcome presentation was not associated with any change in brain activation. No differences in volume of the striatum and VMPFC were observed between groups.

CONCLUSIONS

Current findings provide the first evidence of differences in neural mechanisms underlying outcome processing between individuals with TBI with and without depression. The results suggest that depressive symptomatology might have a different effect on individuals with TBI than what is typically observed in individuals without TBI reporting with depression, with the possibility of rewards becoming more reinforcing as depressive symptomatology increases. Future studies should explore the potential implications of behavioral responses to rewards and punishments in TBI and how they can affect rehabilitation approaches and activities of daily living.

Age-dependent behavioral and biochemical characterization of single APP knock-in mouse (APPNL-G-F/NL-G-F) model of Alzheimer's disease

Saito et al developed a novel amyloid precursor protein (APP) knock-in mouse model (APP^NL-G-F) for Alzheimer's disease (AD) to overcome the problem of overexpression of APP in available transgenic mouse models. However, this new mouse model for AD is not fully characterized age-dependently with respect to behavioral and biochemical changes. Therefore, in the present study, we performed an age-dependent behavioral and biochemical characterization of this newly developed mouse model. Here, we used 3-, 6-, 9-, and 12-month-old APP^NL-G-F and C57BL/6J mice. We used a separate cohort of animals at each age point. Morris water maze, object recognition, and fear-conditioning tests were used for the assessment of learning and memory functions and open-field test to measure the general locomotor activity of mice. After each testing point, we perfused the mice and collected the brain for immunostaining. We performed the immunostaining for amyloid burden (4G8), glial fibrillary acidic protein, choline acetyltransferase, and tyrosine hydroxylase. The results of the present study indicate that APP^NL-G-F mice showed age-dependent memory impairments with maximum impairment at the age of 12 months. These mice showed memory impairment in Morris water maze and fear conditioning tests when they were 6 months old, whereas, in object recognition test, memory deficit was found in 9-month-old mice. APP^NL-G-F mice age dependently showed an increase in amyloid load in different brain regions. However, no amyloid pathology was found in 3-month-old APP^NL-G-F mice. Choline acetyltransferase neurons in medial septum-diagonal band complex and tyrosine hydroxylase neurons in locus coeruleus were decreased significantly in APP^NL-G-F mice. This mouse model also indicated an age-dependent increase in glial fibrillary acidic protein load. It can be concluded from the results that the APP^NL-G-F mouse model may be used to explore the Aβ hypothesis, molecular, and cellular mechanisms involved in AD pathology and to screen the therapeutic potential compounds for the treatment of AD.

Executive functioning: perspectives on neurotrophic activity and pharmacology

Executive functioning is a high-level cognitive ability, regulating other abilities and behaviors to achieve desired goals. A typical executive task can be defined as the capacity to maintain one's attention on the current task, that is, responding only to the correct but not to distractive stimuli. Impairments of executive functions, or executive dysfunctions, have a growing impact on everyday life and academic achievement and are usually an early feature, and one of the core features, in brain injury and memory and behavioral disorders. Furthermore, emerging evidence indicates that memory therapeutics cannot achieve their clinical benefits in cognition if executive dysfunction is not effectively and simultaneously treated. Improvement of executive functions might be achieved through targeting some signaling pathways in the brain, including the brain-derived neurotrophic factor signaling pathways. These agents may be useful either as stand-alone interventions for patients with executive dysfunction and/or psychiatric and memory disorders or as essential adjuncts to drugs that target the underlying pathology in various brain injury and memory and behavioral disorders.

Longitudinal Changes of Caudate-Based Resting State Functional Connectivity in Mild Traumatic Brain Injury

Mild traumatic brain injury (mild TBI) is associated with dysfunctional brain network and accumulating evidence is pointing to the caudate as a vulnerable hub region. However, little is known about the longitudinal changes in the caudate-based resting-state functional connectivity following mild TBI. In the current study, 50 patients with mild TBI received resting-state functional magnetic resonance imaging as well as neuropsychological assessments within 7 days post-injury (acute phase) and 1 month later (subacute phase). Thirty-six age- and gender- matched healthy controls underwent the same protocol. The caudate was segmented into the dorsal and ventral sub-regions based on their related functionally distinct neural circuits and separate functional connectivity was investigated. Results indicated that patients with mild TBI at acute phase exhibited reduced left dorsal caudate-based functional connectivity with ventral lateral prefrontal cortex, dorsal anterior cingulate cortex, and inferior parietal lobule, which mainly distributed in the cognitive control network, and reduced right ventral caudate-based functional connectivity with the dorsal lateral prefrontal cortex, dorsal anterior cingulate cortex (dACC), and bilateral ventral anterior cingulate cortex (vACC), which mainly distributed in the executive network and emotional processing network. Furthermore, patients with mild TBI presented the reduced functional connectivity between the left dorsal caudate and the ventral lateral prefrontal cortex (vlPFC) compared with healthy controls at acute phase while this difference became no significance and return to the normal level following 1 month post-injury subacute phase. Similarly, the functional connectivity between the right ventral caudate and anterior cingulate cortex (both dorsal and ventral part) showed the reduced strength in patients compared with healthy controls only at the acute phase but presented no significant difference at subacute phase following mild TBI. Along the same line, patients with mild TBI presented the impaired performance on the information processing speed and more complaints on the pain impact index at acute phase compared with healthy controls but showed no significant difference at the follow-up 1 month post-injury subacute phase. The longitudinal changes of caudate-based dysfunction connectivity could serve as a neuroimaging biomarker following patients with mild TBI, with the evidence that the abnormal caudate-based functional connectivity at acute phase have returned to the normal level accompanying with the recovery of the neuropsychological syndromes following patients with mild TBI at subacute phase.