Cerebral white matter: neuroanatomy, clinical neurology, and neurobehavioral correlates

Are White Matter Tract Integrities Different in Multiple Sclerosis Women With Voiding Dysfunction?

OBJECTIVES

Two white matter tracts (WMTs) are proposed to be involved in bladder function: anterior thalamic radiation and superior longitudinal fasciculus. Multiple sclerosis (MS) patients with voiding dysfunction (VD) may have distinct changes in these 2 WMTs. This study aims to compare the fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor imaging of MS females with and without VD versus healthy controls (HCs).

METHODS

Prospective observational cohorts of 28 female MS patients and 11 HCs were recruited. Multiple sclerosis patients were divided into 2 groups: voiders (patients without VD, n = 14) and VD (patients with VD, n = 14). Diffusion tensor imaging of each subject was obtained, from which FA and MD maps were generated. The mean FA and MD of each WMT on both sides were analyzed using one-way analysis of variance and pairwise comparison with adjusted P values.

RESULTS

Overall MS patients had significantly lower mean FA (loss of coherence) and significantly higher mean MD (increased free diffusion) than HCs in both WMTs, indicating more damage. Furthermore, VD showed a trend of loss of integrity in both WMTs when compared with voiders with lower FA and higher MD.

CONCLUSIONS

There is damage reflected by lower FA and higher MD values in the proposed WMTs involved in bladder function in MS women. Voiding dysfunction in this patient population can be attributed to these damages considering women with VD demonstrated a trend of deterioration in these WMTs compared with women without VD. Future studies with larger sample sizes should be done to further confirm this correlation.

Neural substrates of subcortical aphasia in subacute stroke: Voxel-based lesion symptom mapping study

Subcortical aphasia develops as a result of damage to subcortical brain areas without loss of cortical functions. Although earlier voxel-based lesion-symptom mapping (VLSM) studies have shown possible neural correlates for aphasia, it remains to be clarified which brain regions are associated with subcortical aphasia. The aim of this study was to investigate the neural substrates associated with subcortical aphasia in patients with stroke using VLSM and atlas-based analyses to explore the involvement of white matter tracts and subcortical structures. Fifty patients with subacute subcortical stroke without cortical involvement were retrospectively enrolled: 24 with and 26 without aphasia. We performed VLSM and atlas-based analyses of the patients' fluid-attenuated inversion recovery images and found that the left perisylvian white matter, left fronto-occipital fasciculus, uncinate fasciculus, and forceps minor were significantly more greatly affected in the aphasia than in the non-aphasia group. The left anterior thalamic radiation, cingulum (cingulate gyrus), and superior longitudinal fasciculus also showed higher involvement in this group (marginal significance). Among the subcortical regions, the left caudate and putamen were more greatly involved in the aphasia group. Our findings confirm language processing as one of the integrated sensory-motor processes that occur in the region around the left sylvian fissure. Our atlas-based analysis approach can be used to complement VLSM analyses.

Cognitive profiles in adult-onset neuronal intranuclear inclusion disease: a case series from the memory clinic

OBJECTIVE

This study aimed to analyze the characteristics of cognitive impairment in adult-onset neuronal intranuclear inclusion disease (NIID).

METHODS

Seven patients with adult-onset NIID were collected consecutively from the memory clinic of Xuanwu hospital from February to December 2019. These cases were diagnosed with skin biopsy triggered by DWI high-intensity signals in corticomedullary junction on brain MRI. We used a battery of neuropsychological scales to detect the patient's performance in each cognitive domain, and made a detailed analysis on the characteristics of cognitive impairment.

RESULTS

All seven cases had cognitive impairment, and four of them had met the criteria for dementia. The scores of Montreal Cognitive Assessment and Frontal Assessment Battery were abnormal in all patients. The executive dysfunction was confirmed by the abnormal scores of Trail Making Test (5/7, 71%) and Clock Drawing Test (4/7, 57%). Bad performance in Auditory Verbal Learning Test (6/7, 86%) demonstrated that the memory was also a very commonly impaired cognitive domain. The low score on the animal fluency (4/7, 57%), Boston Naming Test (3/7, 43%), and Pentagon and Cube Copying Test (4/7, 57%) indicated that the language and visuospatial skills were also impaired. Fazekas scores were significantly correlated to the global cognition, executive and language functions (r = 0.788-0.906, P < 0.05).

CONCLUSIONS

There is obvious impairment in multiple cognitive domains in adult-onset NIID, and both the executive dysfunction and memory deficit are very common. Leukoencephalopathy may be the main course of cognitive impairment in adult-onset NIID.

The frontal longitudinal system as revealed through the fiber microdissection technique: structural evidence underpinning the direct connectivity of the prefrontal-premotor circuitry

OBJECTIVE

The purpose of this study was to investigate the morphology, connectivity, and correlative anatomy of the longitudinal group of fibers residing in the frontal area, which resemble the anterior extension of the superior longitudinal fasciculus (SLF) and were previously described as the frontal longitudinal system (FLS).

METHODS

Fifteen normal adult formalin-fixed cerebral hemispheres collected from cadavers were studied using the Klingler microdissection technique. Lateral to medial dissections were performed in a stepwise fashion starting from the frontal area and extending to the temporoparietal regions.

RESULTS

The FLS was consistently identified as a fiber pathway residing just under the superficial U-fibers of the middle frontal gyrus or middle frontal sulcus (when present) and extending as far as the frontal pole. The authors were able to record two different configurations: one consisting of two distinct, parallel, longitudinal fiber chains (13% of cases), and the other consisting of a single stem of fibers (87% of cases). The fiber chains' cortical terminations in the frontal and prefrontal area were also traced. More specifically, the FLS was always recorded to terminate in Brodmann areas 6, 46, 45, and 10 (premotor cortex, dorsolateral prefrontal cortex, pars triangularis, and frontal pole, respectively), whereas terminations in Brodmann areas 4 (primary motor cortex), 47 (pars orbitalis), and 9 were also encountered in some specimens. In relation to the SLF system, the FLS represented its anterior continuation in the majority of the hemispheres, whereas in a few cases it was recorded as a completely distinct tract. Interestingly, the FLS comprised shorter fibers that were recorded to interconnect exclusively frontal areas, thus exhibiting different fiber architecture when compared to the long fibers forming the SLF.

CONCLUSIONS

The current study provides consistent, focused, and robust evidence on the morphology, architecture, and correlative anatomy of the FLS. This fiber system participates in the axonal connectivity of the prefrontal-premotor cortices and allegedly subserves cognitive-motor functions. Based in the SLF hypersegmentation concept that has been advocated by previous authors, the FLS should be approached as a distinct frontal segment within the superior longitudinal system.

Corpus callosum integrity loss predicts cognitive impairment in Leukoaraiosis

Objective

To investigate regional white matter fibers loss in Leukoaraiosis (LA) and its relationship with cognitive impairments.

Methods

Fifty‐six participants with LA and 38 healthy controls underwent clinical evaluations and MR scans. Participants with LA were classified as cognitively normal (LA‐NC, n = 18), vascular cognitive impairment of none dementia (LA‐VCIND, n = 24), and vascular dementia (LA‐VaD, n = 14) by Mini‐Mental State Examination and Clinical Dementia Rating. Cognitive domains including visual‐spatial, naming, attention, language, abstraction, memory, and orientation were assessed. With the use of Tract‐based spatial statistics, mean fractional anisotropy (FA) of major white matter fiber tracts were compared between LA and controls and among LA groups with varying levels of cognitive impairments. Regression analyses were performed to evaluate relationships between FA values and cognitive performance.

Results

Participants showed significant FA reduction in the corpus callosum (CC), bilateral corona radiata, anterior limb of the internal capsule, external capsule, posterior thalamic radiation, and superior longitudinal fasciculus compared to controls and across LA groups. The LA‐VaD group showed consistent damage in the body and genu of CC compared to the LA‐NC and LA‐VCIND groups. A positive correlation between visual‐spatial and FA reduction in right anterior corona radiates in LA‐VCIND and body of CC in LA‐ VaD.

Interpretation

We found regional fiber loss in the CC across the cognitive spectrum in patients with LA and correlations between FA and visuospatial impairment in the anterior corona radiata in patients with LA‐VCIND and in the body of CC in patients with LA‐VaD.

Social Cognition and White Matter: Connectivity and Cooperation

Humans are highly social animals whose survival and well-being depend on their capacity to cooperate in complex social settings. Advances in anthropology and psychology have demonstrated the importance of cooperation for enhancing social cohesion and minimizing conflict. The understanding of social behavior is informed by the notion of social cognition, a set of mental operations including emotion perception, mentalizing, and empathy. The social brain hypothesis posits that the mammalian brain has enlarged over evolution to meet the challenges of social life, culminating in a large human brain well adapted for social cognition. The structures subserving social cognition are mainly located in the frontal and temporal lobes, and although gray matter is critical, social cognition also requires white matter. Whereas the social brain hypothesis assumes that brain enlargement has been driven by neocortical expansion, cerebral white matter has expanded even more robustly than the neocortex, coinciding with the emergence of social cognition. White matter expansion is most evident in the frontal and temporal lobes, where it enhances connectivity between regions critical for social cognition. Myelination has, in turn, conferred adaptive social advantages by enabling prompt empathic concern for offspring and by strengthening networks that support cooperation and the related capacities of altruism and morality. Social cognition deficits related to myelinated tract involvement occur in many disorders, including stroke, Binswanger disease, traumatic brain injury, multiple sclerosis, glioma, and behavioral variant frontotemporal dementia. The contribution of white matter to social cognition can be conceptualized as the enhancement of cooperation through brain connectivity.

Evaluating High Spatial Resolution Diffusion Kurtosis Imaging at 3T: Reproducibility and Quality of Fit

BACKGROUND

Diffusion kurtosis imaging (DKI) quantifies the non-Gaussian diffusion of water within tissue microstructure. However, it has increased fitting parameters and requires higher b-values. Evaluation of DKI reproducibility is important for clinical purposes.

PURPOSE

To assess the reproducibility in whole-brain high-resolution DKI at varying b-values.

STUDY TYPE

Retrospective.

SUBJECTS AND PHANTOMS

In all, 44 individuals from the test-retest Human Connectome Project (HCP) database and 12 3D-printed phantoms.

FIELD STRENGTH/SEQUENCE

Diffusion-weighted multiband echo-planar imaging sequence at 3T and 9.4T. magnetization-prepared rapid acquisition gradient echo at 3T for in vivo structural data only.

ASSESSMENT

From HCP data with b-values = 1000, 2000, 3000 s/mm² (dataset A), two additional datasets with b-values = 1000, 3000 s/mm² (dataset B) and b-values = 1000, 2000 s/mm² (dataset C) were extracted. Estimated DKI metrics from each dataset were used for evaluating reproducibility and fitting quality in white matter (WM) and gray matter (GM) based on whole-brain and regions of interest (ROIs).

STATISTICAL TESTS

DKI reproducibility was assessed using the within-subject coefficient of variation (CoV), fitting residuals to evaluate DKI fitting accuracy and Pearson's correlation to investigate the presence of systematic biases. Repeated measures analysis of variance was used for statistical comparison.

RESULTS

Datasets A and B exhibited lower DKI CoVs (<20%) compared to C (<50%) in both WM and GM ROIs (all P < 0.05). This effect varies between DKI and DTI parameters (P < 0.005). Whole-brain fitting residuals were consistent across datasets (P > 0.05), but lower residuals in dataset B were detected for the WM ROIs (P < 0.001). A similar trend was observed for the phantom data CoVs (<7.5%) at varying fiber orientations for datasets A and B. Finally, dataset C was characterized by higher residuals across the different fiber crossings (P < 0.05).

DATA CONCLUSION

The study demonstrates that high reproducibility can still be achieved within a reasonable scan time, specifically dataset B, supporting the potential of DKI for aiding clinical tools in detecting microstructural changes.

Early microstructure of white matter associated with infant attention

Early infancy is characterized by rapid brain development that occurs alongside, and in response to, the development of cognitive and behavioral functions, including attention. Infants' ability to orient and sustain attention to stimuli develops in concert with refinement of the orienting network in frontoparietal regions of the brain. Infants (n = 97) underwent magnetic resonance imaging at one-month of age and data were fit to a diffusion tensor imaging model to calculate fractional anisotropy (FA) and radial diffusivity (RD), as well as to a neurite orientation dispersion and density imaging model to calculate intracellular volume fraction (νic). Infant attention was assessed at six months of age using a dynamic puppet task (Cuevas and Bell, 2014). Infants with higher FA in the corpus callosum and anterior cingulum showed increased orienting behaviors. Our findings indicate that increased microstructure of the white matter tracts in the orienting network may play a role in the early neurodevelopment of attentional orienting behaviors.

Dynamic analysis of fMRI activation during epileptic spikes can help identify the seizure origin

OBJECTIVE

We use the dynamic electroencephalography-functional magnetic resonance imaging (EEG-fMRI) method to incorporate variability in the amplitude and field of the interictal epileptic discharges (IEDs) into the fMRI analysis. We ask whether IED variability analysis can (a) identify additional activated brain regions during the course of IEDs, not seen in standard analysis; and (b) demonstrate the origin and spread of epileptic activity. We explore whether these functional changes recapitulate the structural connections and propagation of epileptic activity during seizures.

METHODS

Seventeen patients with focal epilepsy and at least 30 IEDs of a single type during simultaneous EEG-fMRI were studied. IED variability and EEG source imaging (ESI) analysis extracted time-varying dynamic changes. General linear modeling (GLM) generated static functional maps. Dynamic maps were compared to static functional maps. The dynamic sequence from IED variability was compared to the ESI results. In a subset of patients, we investigated structural connections between active brain regions using diffusion-based fiber tractography.

RESULTS

IED variability distinguished the origin of epileptic activity from its propagation in 15 of 17 (88%) patients. This included two cases where no result was obtained from the standard GLM analysis. In both of these cases, IED variability revealed activation in line with the presumed epileptic focus. Two cases showed no result from either method. Both had very high spike rates associated with dysplasia in the postcentral gyrus. In all 15 cases with dynamic activation, the observed dynamics were concordant with ESI. Fiber tractography identified specific white matter pathways between brain regions that were active at IED onset and propagation.

SIGNIFICANCE

Dynamic techniques involving IED variability can provide additional power for EEG-fMRI analysis, compared to standard analysis, revealing additional biologically plausible information in cases with no result from the standard analysis and gives insight into the origin and spread of IEDs.

Prefrontal White Matter Abnormalities Associated With Pain Catastrophizing in Patients With Complex Regional Pain Syndrome

OBJECTIVE

To investigate altered prefrontal white matter integrity in complex regional pain syndrome (CRPS) and its relation with the degree of pain catastrophizing.

DESIGN

Cross-sectional study.

SETTING

University hospital.

PARTICIPANTS

Twenty-one CRPS patients and 49 patients without CRPS (N=70).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The fractional anisotropy values within the prefrontal regions reflecting the structural integrity of white matter were measured in CRPS patients and patients without CRPS using diffusion tensor imaging. The degree of pain catastrophizing was also evaluated in CRPS patients.

RESULTS

The structural integrity of the prefrontal white matter was lower in CRPS patients than in patients without CRPS (P=.03). In addition, lower structural integrity in the prefrontal cortex was correlated with a higher degree of pain catastrophizing among CRPS patients (r= -0.54, P=.01).

CONCLUSIONS

Our findings suggest that pain catastrophizing, which is frequently reported in patients with CRPS, may be associated with the dysfunction of the prefrontal white matter.

Establishment of a simple one-step method for oligodendrocyte progenitor cell preparation from rodent brains

BACKGROUND

Oligodendrocytes, which form myelin, enable rapid and efficient nerve conduction. Destruction of myelin causes demyelinating diseases such as multiple sclerosis. Primary oligodendrocyte progenitor cells (OPCs) from postnatal rodents have been utilized to elucidate the developmental mechanism of oligodendrocytes in vitro. However, this process is complicated and takes up to several weeks.

NEW METHOD

We established a method to culture OPCs from neonatal rat brain in DMEM/F-12 with Stem-Pro, bFGF (10 ng/mL), and rhPDGF (30 ng/mL). The culture, without shaking or immunopanning, became OPC-enriched rather than a mixed glial culture.

RESULTS

Immunofluorescent analysis using cell lineage markers suggested that these cells were initially glial progenitors, which gradually changed to OPCs with a few cells further differentiating into oligodendrocytes. Using compounds that promote OPC differentiation, we confirmed that these cells were compatible for high-throughput screening in a 96-well plate format. In co-culture with dorsal root ganglion neuron, OPCs showed myelin sheath-like morphologies. This method was also applicable to mouse OPCs.

COMPARISON WITH EXISTING METHODS

Although the purity of the OPCs was not comparable to that after immunopanning, most cells were of the oligodendrocyte lineage at 8 DIV, while less than 10% were astrocytes. This method requires mediums with only two growth factors without any specific equipment like antibodies or magnet and takes simple procedures.

CONCLUSIONS

The simplicity and high yield of our method make it a good choice when working with oligodendrocytes/OPCs. We believe that this method is an affordable protocol for various biological applications without any special techniques or equipment.

Cortical and Subcortical Control of Swallowing-Can We Use Information From Lesion Locations to Improve Diagnosis and Treatment for Patients With Stroke?

Purpose Swallowing is a complex process, mediated by a broad bilateral neural network that spans from the brainstem to subcortical and cortical brain structures. Although the cortex's role in swallowing was historically neglected, we now understand, especially through clinical observations and research of patients with stroke, that it substantially contributes to swallowing control. Neuroimaging techniques (e.g., magnetic resonance imaging) have helped significantly to elucidate the role of cortical and subcortical brain areas, in general, and the importance of specific areas in swallowing control in healthy individuals and patients with stroke. We will review recent discoveries in cortical and subcortical neuroimaging research studies and their generalizability across patients to discuss their potential implications and translation to dysphagia diagnosis and treatment in clinical practice. Conclusions Stroke lesion locations have been identified that are commonly associated across patients with the occurrence and recovery of dysphagia, suggesting that clinical brain scans provide useful information for improving the diagnosis and treatment of patients with stroke. However, individual differences in brain structure and function limit the generalizability of these relationships and emphasize that the extent of the motor and sensory pathology in swallowing, and how the patient recovers, also depends on a patient's individual brain constitution. The involvement of the damaged brain tissue in swallowing control before the stroke and the health of the residual, undamaged brain tissue are crucial factors that can differ between individuals.

Hemispheric Differences in Functional Interactions Between the Dorsal Lateral Prefrontal Cortex and Ipsilateral Motor Cortex

Background: The dorsolateral prefrontal cortex (DLPFC) in both hemispheres have a central integrative function for motor control and behavior. Understanding the hemispheric difference between DLPFC and ipsilateral motor cortex connection in the resting-state will provide fundamental knowledge to explain the different roles DLPFC plays in motor behavior.

Purpose: The current study tested the interactions between the ipsilateral DLPFC and the primary motor cortex (M1) in each hemisphere at rest. We hypothesized that left DLPFC has a greater inhibitory effect on the ipsilateral M1 compared to the right DLPFC.

Methods: Fourteen right-handed subjects were tested in a dual-coil paired-pulse paradigm using transcranial magnetic stimulation. The conditioning stimulus (CS) was applied to the DLPFC and the test stimulus (TS) was applied to M1. Interstimulus intervals (ISIs) between CS and TS were 2, 4, 6, 8, 10, 15, 20, 25, and 30 ms. The result was expressed as a percentage of the mean peak-to-peak amplitude of the unconditioned test pulse.

Results: There was stronger inhibitory effect for the left compared to the right hemisphere at ISIs of 2 (p = 0.045), 10 (p = 0.006), 15 (p = 0.029) and 20 (p = 0.024) ms. There was no significant inhibition or facilitation at any ISI in the right hemisphere.

Conclusions: The two hemispheres have distinct DLPFC and M1 cortico-cortical connectivity at rest. Left hemisphere DLPFC is dominant in inhibiting ipsilateral M1.

Assessing cognitive control and the reward system in overweight young adults using sensitivity to incentives and white matter integrity

Cognitive control and incentive sensitivity are related to overeating and obesity. Optimal white matter integrity is relevant for an efficient interaction among reward-related brain regions. However, its relationship with sensitivity to incentives remains controversial. The aim of this study was to assess the incentive sensitivity and its relationship to white matter integrity in normal-weight and overweight groups. Seventy-six young adults participated in this study: 31 were normal-weight (body mass index [BMI] 18.5 to < 25.0 kg/m², 14 females) and 45 were overweight (BMI ≥ 25.0 kg/m², 22 females). Incentive sensitivity was assessed using an antisaccade task that evaluates the effect of incentives (neutral, reward, and loss avoidance) on cognitive control performance. Diffusion tensor imaging studies were performed to assess white matter integrity. The relationship between white matter microstructure and incentive sensitivity was investigated through tract-based spatial statistics. Behavioral antisaccade results showed that normal-weight participants presented higher accuracy (78.0 vs. 66.7%, p = 0.01) for loss avoidance incentive compared to overweight participants. Diffusion tensor imaging analysis revealed a positive relationship between fractional anisotropy and loss avoidance accuracy in the normal-weight group (p < 0.05). No relationship reached significance in the overweight group. These results support the hypothesis that white matter integrity is relevant for performance in an incentivized antisaccade task.

Lean mass index is positively associated with white matter volumes in several brain regions in children with overweight/obesity

BACKGROUND

The relationship of obesity with grey and white matter volumes has been examined in several studies, and the results are decidedly mixed.

OBJECTIVE

To investigate the associations of body mass index (BMI), fat mass index (FMI) and lean mass index (LMI) with total and regional grey and white matter volumes.

METHODS

This is a cross-sectional study involving 100 children (60% boys) with overweight/obesity. T1-weighted images were acquired using magnetic resonance imaging. Dual energy X-ray absorptiometry was used to measure body composition. Separate hierarchical regression analyses were performed between predictor variables (BMI, FMI and LMI) and the total brain volumes including sex, years from peak height velocity and parental education as covariates. In addition, FMI was added as a covariate when LMI was the predictor and vice versa. Statistical analyses of imaging data were performed using three whole-brain voxel-wise multiple regression models and adjusted by the same covariates.

RESULTS

LMI was positively associated with white matter in numerous regions and to a lower extent, with grey matter regions. Further, the relationship between LMI, and grey and white matter regions was independent of FMI levels.

CONCLUSIONS

LMI seems to be a positive predictor of regional white matter volumes in children with overweight/obesity.

Dissection of white matter association fasciculi in bovine (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus) brains

The cerebral fasciculi (association, commissural and projection) pass through the cerebral white matter in organized groups connecting regions, hemispheres, gyri, areas and brain lobes to each other. The study can be done in vivo through diffusion tensor imaging (DTI) but presenting some technical problems. The post-mortem study by dissection allows to have a clearer view of its location, path and connections. In this work, we dissect, identify and compare the fasciculi of association of the white matter of the dorsolateral face of bovine hemispheres (Bos taurus), pig hemispheres (Sus scrofa domesticus) and rabbit hemispheres (Oryctolagus cuniculus), applying the Klingler´s technique. In 30 cerebral hemispheres (10 of each species, five right and five left), we applied the Klingler technique to identify and isolate the occipitofrontal fasciculus, uncinate fasciculus, inferior longitudinal fasciculus and superior longitudinal fasciculus; we established its location by fixing landmarks, and determined the difference in its length and width between the right and left hemispheres as well as between species using the statistical tests of t-student and one-way ANOVA. We identify the gyri, sulci and fasciculi of the dorsolateral surface of the cerebral hemispheres of the three species. We found statistically significant differences in several fasciculi between species principally in the occipitofrontal fasciculus. The preparation of the brains through the modified Klingler technique allowed a successful identification of the fascicules of association of the dorsolateral face of the cerebral hemispheres and the empowerment of these animal models for future research work in this field.

Respirator usage protects brain white matter from welding fume exposure: A pilot magnetic resonance imaging study of welders

Welding fume exposure has been associated with structural brain changes and a wide variety of clinical and sub-clinical outcomes including cognitive, behavioral and motor abnormalities. Respirator use has been shown to decrease exposure to welding fumes; however, the associations between respirator use and health outcomes, particularly neurologic health, have been understudied. In this preliminary study, we used diffusion tensor imaging (DTI) to investigate the effectiveness of respirator use in protecting workers' white matter (WM) from the harmful effects related to welding fume exposure. Fractional anisotropy (FA), a common DTI measurement of water diffusion properties, was used as a marker of WM microstructure integrity. We hypothesized that FA in brain regions involved in motor and neurocognitive functions would differ between welders reporting respirator use compared to those not using a respirator. We enrolled a pilot cohort of 19 welders from labor unions in the New York City area. All welders completed questionnaires to assess welding history and occupational health. All completed a DTI acquisition on a 3 T Siemens scanner. Partial least squares discriminant analysis (PLS-DA), a bioinformatic analytical strategy, was used to model the divergence of WM microstructures in 48 regions defined by the ICBM-DTI-81 atlas between respirator users compared to non-users. This yielded an effective discrimination of respirator users from non-users, with the uncinate fasciculus, the cerebellar peduncle and the superior longitudinal fasciculus contributing most to the discrimination of these groups. These white matter tracts are involved in widespread motor and cognitive functions. To our knowledge, this study is the first to suggest a protective effect of respirator on WM microstructure, indicating that the lack of respirator may present unsafe working conditions for welders. These preliminary findings may inform a larger, longitudinal intervention study that would be more appropriate to investigate the potential protective effect of respirator usage on brain white matter in welders.

Revisiting the Functional Anatomy of the Human Brain: Toward a Meta-Networking Theory of Cerebral Functions

For more than one century, brain processing was mainly thought in a localizationist framework, in which one given function was underpinned by a discrete, isolated cortical area, and with a similar cerebral organization across individuals. However, advances in brain mapping techniques in humans have provided new insights into the organizational principles of anatomo-functional architecture. Here, we review recent findings gained from neuroimaging, electrophysiological, as well as lesion studies. Based on these recent data on brain connectome, we challenge the traditional, outdated localizationist view and propose an alternative meta-networking theory. This model holds that complex cognitions and behaviors arise from the spatiotemporal integration of distributed but relatively specialized networks underlying conation and cognition (e.g., language, spatial cognition). Dynamic interactions between such circuits result in a perpetual succession of new equilibrium states, opening the door to considerable interindividual behavioral variability and to neuroplastic phenomena. Indeed, a meta-networking organization underlies the uniquely human propensity to learn complex abilities, and also explains how postlesional reshaping can lead to some degrees of functional compensation in brain-damaged patients. We discuss the major implications of this approach in fundamental neurosciences as well as for clinical developments, especially in neurology, psychiatry, neurorehabilitation, and restorative neurosurgery.

Identifying Schizo-Obsessive Comorbidity by Tract-Based Spatial Statistics and Probabilistic Tractography

A phenomenon in schizophrenia patients that deserves attention is the high comorbidity rate with obsessive-compulsive disorder (OCD). Little is known about the neurobiological basis of schizo-obsessive comorbidity (SOC). We aimed to investigate whether specific changes in white matter exist in patients with SOC and the relationship between such abnormalities and clinical parameters. Twenty-eight patients with SOC, 28 schizophrenia patients, 30 OCD patients, and 30 demographically matched healthy controls were recruited. Using Tract-based Spatial Statistics and Probabilistic Tractography, we examined the pattern of white matter abnormalities in these participants. We also used ANOVA and Support Vector Classification of various white matter indices and structural connection probability to further examine white matter changes among the 4 groups. We found that patients with SOC had decreased fractional anisotropy (FA) and increased radial diffusivity in the right sagittal stratum and the left crescent of the fornix/stria terminalis compared with healthy controls. We also found changed connection probability in the Default Mode Network, the Subcortical Network, the Attention Network, the Task Control Network, the Visual Network, the Somatosensory Network, and the cerebellum in the SOC group compared with the other 3 groups. The classification results further revealed that FA features could differentiate the SOC group from the other 3 groups with an accuracy of .78. These findings highlight the specific white matter abnormalities found in patients with SOC.

Association between Diffusion Tensor Imaging Findings and Cognitive Outcomes Following Mild Traumatic Brain Injury: A PRISMA-Compliant Meta-Analysis

Previous diffusion tensor imaging (DTI) research in mild traumatic brain injury (mTBI) patients only concentrated on a limited number of brain regions and a specific cognitive function. Thus, the study aimed to explore the association between DTI findings and cognitive function following mTBI using a meta-analysis. We conducted a search for articles exploring the associations between DTI findings and cognitive outcomes following mTBI published in English in databases (PubMed, Web of Science, EMBASE, Medline, and Google Scholar) before October 2019. The correlations were computed to explore associations between DTI findings and specific cognitive function. Finally, 9 studies (including 293 mTBI patients) were included in the meta-analysis. The study showed that higher fractional anisotropy (FA) values in the longitudinal fasciculus (LF), sagittal stratum (SS), cerebellum, and internal capsule (IC) were associated with better general cognitive function. However, the study showed that higher FA values in the cerebellar peduncles (CP) were associated with worse general cognitive function. Additionally, the present study showed that higher FA values in the mesencephalon, anterior corona radiata (ACR), forceps major (FM), uncinate fasciculus (UF), cingulum, and genu of corpus callosum (gCC) were related to better memory. Higher FA values in the ACR were associated with worse attention, processing speed, and working memory. The study indicated that higher mean diffusivity (MD)/apparent diffusion coefficient (ADC) values in the external capsule (EC) were associated with worse memory. Additionally, higher MD/ADC values in the UF were associated with worse attention, processing speed, and working memory. The present study showed that better white matter integrity (higher FA, lower MD/ADC) might be associated with better cognitive function following mTBI.

Childhood Adversity and Neural Development: A Systematic Review

An extensive literature on childhood adversity and neurodevelopment has emerged over the past decade. We evaluate two conceptual models of adversity and neurodevelopment-the dimensional model of adversity and stress acceleration model-in a systematic review of 109 studies using MRI-based measures of neural structure and function in children and adolescents. Consistent with the dimensional model, children exposed to threat had reduced amygdala, medial prefrontal cortex (mPFC), and hippocampal volume and heightened amygdala activation to threat in a majority of studies; these patterns were not observed consistently in children exposed to deprivation. In contrast, reduced volume and altered function in frontoparietal regions were observed consistently in children exposed to deprivation but not children exposed to threat. Evidence for accelerated development in amygdala-mPFC circuits was limited but emerged in other metrics of neurodevelopment. Progress in charting neurodevelopmental consequences of adversity requires larger samples, longitudinal designs, and more precise assessments of adversity.

White matter hypointensities and hyperintensities have equivalent correlations with age and CSF β-amyloid in the nondemented elderly

INTRODUCTION

T1- and T2-weighted sequences from MRI often provide useful complementary information about tissue properties. Leukoaraiosis results in signal abnormalities on T1-weighted images, which are automatically quantified by FreeSurfer, but this marker is poorly characterized and is rarely used. We evaluated associations between white matter hyperintensity (WM-hyper) volume from FLAIR and white matter hypointensity (WM-hypo) volume from T1-weighted images and compared their associations with age and cerebrospinal fluid (CSF) β-amyloid and tau.

METHODS

A total of 56 nondemented participants (68-94 years) were recruited and gave informed consent. All participants went through MR imaging on a GE 1.5T scanner and of these 47 underwent lumbar puncture for CSF analysis. WM-hypo was calculated using FreeSurfer analysis of T1 FSPGR 3D, and WM-hyper was calculated with the Lesion Segmentation Toolbox in the SPM software package using T2-FLAIR.

RESULTS

WM-hyper and WM-hypo were strongly correlated (r = .81; parameter estimate (p.e.): 1.53 ± 0.15; p < .0001). Age was significantly associated with both WM-hyper (r = .31, p.e. 0.078 ± 0.030, p = .013) and WM-hypo (r = .42, p.e. 0.055 ± 0.015, p < .001). CSF β-amyloid levels were predicted by WM-hyper (r = .33, p.e. -0.11 ± 0.044, p = .013) and WM-hypo (r = .42, p.e. -0.24 ± 0.073, p = .002). CSF tau levels were not correlated with either WM-hyper (p = .9) or WM-hypo (p = .99).

CONCLUSIONS

Strong correlations between WM-hyper and WM-hypo, and similar associations with age, abnormal β-amyloid, and tau suggest a general equivalence between these two imaging markers. Our work supports the equivalence of white matter hypointensity volumes derived from FreeSurfer for evaluating leukoaraiosis. This may have particular utility when T2-FLAIR is low in quality or absent, enabling analysis of older imaging data sets.

Tractography of the external capsule and cognition: A diffusion MRI study of cholinergic fibers

INTRODUCTION

White matter changes (WMC) in the cholinergic tracts contribute to executive dysfunction in the context of cognitive aging. WMC in the external capsule have been associated with executive dysfunction. The objectives of this study were to: 1) Characterize the lateral cholinergic tracts (LCT) and the superior longitudinal fasciculus (SLF). 2) Evaluate the association between diffusion measures within those tracts and cognitive performance.

METHODS

Neuropsychological testing and high angular resolution diffusion imaging (HARDI) of 34 healthy elderly participants was done, followed by anatomically constrained probabilistic tractography reconstruction robust to crossing fibers. The external capsule was manually segmented on a mean T1 image then merged with an atlas, allowing extraction of the LCT. Diffusion tensor imaging (DTI) and HARDI-based measures were obtained.

RESULTS

Correlations between diffusion measures in the LCT and the time of completion of Stroop (left LCT radial and medial diffusivity), the Symbol Search score (right LCT apparent fiber density) and the motor part of Trail-B (left LCT axial and radial diffusivity) were observed. Correlations were also found with diffusion measures in the SLF. WMC burden was low, and no correlation was found with diffusion measures or cognitive performance.

DISCUSSION

DTI and HARDI, with isolation of strategic white matter tracts for cognitive functions, represent complimentary tools to better understand the complex process of brain aging.

A Connectomic Atlas of the Human Cerebrum-Chapter 12: Tractographic Description of the Middle Longitudinal Fasciculus

The middle longitudinal fasciculus (MdLF) is a small and somewhat controversial white matter tract of the human cerebrum, confined to the posterior superior temporal region from which it courses posteriorly to connect at the occipital-parietal interface. The tract appears to be involved in language processing as well as auditory organization and localization, while sub-serving other higher level cognitive functions that have yet to be fully elucidated. Little is known about the specific, interparcellation connections that integrate to form the MdLF. Utilizing diffusion spectrum magnetic resonance imaging tractography coupled with the human cortex parcellation data presented earlier in this supplement, we aim to describe the macro-connectome of the MdLF in relation to the linked parcellations present within the human cortex. The purpose of this study is to present this information in an indexed, illustrated, and tractographically aided series of figures and tables for anatomic and clinical reference.

A Connectomic Atlas of the Human Cerebrum-Chapter 10: Tractographic Description of the Superior Longitudinal Fasciculus

The superior longitudinal fasciculus/arcuate white matter complex (SLF/AC) is the largest and most complex white matter tract of the human cerebrum with multiple inter-linked connections encompassing multiple cognitive functions such as language, attention, memory, emotion, and visuospatial function. However, little is known regarding the overall connectivity of this complex. Recently, the Human Connectome Project parcellated the human cortex into 180 distinct regions. Utilizing diffusion spectrum magnetic resonance imaging tractography coupled with the human cortex parcellation data presented earlier in this supplement, we aim to describe the macro-connectome of the SLF/AC in relation to the linked parcellations present within the human cortex. The purpose of this study is to present this information in an indexed, illustrated, and tractographically aided series of figures and tables for anatomic and clinical reference.

Quantification of apparent axon density and orientation dispersion in the white matter of youth born with congenital heart disease

BACKGROUND

White matter alterations have previously been demonstrated in adolescents born with congenital heart disease (CHD) using diffusion tensor imaging (DTI). However, due to the non-specific nature of DTI metrics, it is difficult to interpret these findings in terms of their microstructural implications. This study investigated the use of neurite orientation dispersion and density imaging (NODDI), which involves the acquisition of advanced multiple b-value data over two shells and provides proxy measures of apparent axon density and orientation dispersion within white matter, as a complement to classic DTI measures.

STUDY DESIGN

Youth aged 16 to 24 years born with complex CHD and healthy peers underwent brain magnetic resonance imaging. White matter tract volumes and tract-average values of DTI and NODDI metrics were compared between groups. Tract-average DTI and NODDI results were spatially confirmed using tract-based spatial statistics.

RESULTS

There were widespread regions of lower tract-average neurite density index (NDI) in the CHD group as compared to the control group, particularly within long association tracts and in regions of the corpus callosum, accompanied by smaller white matter tract volumes and isolated clusters of lower fractional anisotropy (FA). There were no significant differences in orientation dispersion index (ODI) between groups.

CONCLUSION

Lower apparent density of axonal packing, but not altered axonal orientation, is a key microstructural factor in the white matter abnormalities observed in youth born with CHD. These impairments in axonal packing may be an enduring consequence of early life brain injury and dysmaturation and may explain some of the long-term neuropsychological difficulties experienced by this at-risk group.

Cerebral Damage after Carbon Monoxide Poisoning: A Longitudinal Diffusional Kurtosis Imaging Study

BACKGROUND AND PURPOSE

Previous DTI cross-sectional studies have showed the cerebral damage feature was different in the three clinical stages after carbon monoxide poisoning. Diffusional kurtosis imaging (DKI) is an advanced diffusion imaging model and considered to better provide microstructural contrast in comparison with DTI parameters. The primary aim of this study was to assess microstructural changes in gray and white matter with diffusional kurtosis imaging in the acute, delayed neuropsychiatric, and chronic phases after acute carbon monoxide (CO) poisoning. The secondary aim was to relate diffusional kurtosis imaging measures to neuropsychiatric outcomes of acute carbon monoxide poisoning.

MATERIALS AND METHODS

In all, 17 patients with acute carbon monoxide poisoning and 30 sex- and age-matched healthy volunteers were enrolled in the study. Patients were scanned within 1 week, 3-8 weeks, and 6 months after acute carbon monoxide poisoning. Diffusional kurtosis imaging metrics including mean kurtosis, mean diffusivity, fractional anisotropy, and kurtosis fractional anisotropy were measured in 11 ROIs and then further correlated with neuropsychiatric scores.

RESULTS

In WM, mean kurtosis tended to increase from the acute-to-delayed neuropsychiatric phases and then decrease in the chronic phase, while in GM mean kurtosis showed a constant decline. Contrary to mean kurtosis, mean diffusivity first decreased then tended to increase in WM, while in GM, from the acute to chronic phases, mean diffusivity showed a constant increase. In both WM and GM, the fractional anisotropy and kurtosis fractional anisotropy values progressively declined with time. Kurtosis fractional anisotropy showed the best diagnostic efficiency with an area under the curve of 0.812 (P = .000). Along with neuropsychiatric scores, kurtosis fractional anisotropy of the centrum semiovale and Digit Span Backward were most relevant (r = 0.476, P = .000).

CONCLUSIONS

Longitudinally, microstructural changes were inconsistent in WM and GM with time after acute carbon monoxide poisoning. Diffusional kurtosis imaging metrics provided important complementary information to quantify the damage to cognitive impairment.

Brain microstructural abnormalities in type 2 diabetes mellitus: A systematic review of diffusion tensor imaging studies

Type 2 diabetes mellitus (T2DM) is associated with deficits in the structure and function of the brain. Diffusion tensor imaging (DTI) is a highly sensitive method for characterizing cerebral tissue microstructure. Using PRISMA guidelines, we identified 29 studies which have demonstrated widespread brain microstructural impairment and topological network disorganization in patients with T2DM. Most consistently reported structures with microstructural abnormalities were frontal, temporal, and parietal lobes in the lobar cluster; corpus callosum, cingulum, uncinate fasciculus, corona radiata, and internal and external capsules in the white matter cluster; thalamus in the subcortical cluster; and cerebellum. Microstructural abnormalities were correlated with pathological derangements in the endocrine profile as well as deficits in cognitive performance in the domains of memory, information-processing speed, executive function, and attention. Altogether, the findings suggest that the detrimental effects of T2DM on cognitive functions might be due to microstructural disruptions in the central neural structures.

Altered working memory-related brain responses and white matter microstructure in extremely preterm-born children at school age

Preterm birth poses a risk for neurocognitive and behavioral development. Preterm children, who have not been diagnosed with neurological or cognitive deficits, enter normal schools and are expected to succeed as their term-born peers. Here we tested the hypotheses that despite an uneventful development after preterm birth, these children might exhibit subtle abnormalities in brain function and white-matter microstructure at school-age. We recruited 7.5-year-old children born extremely prematurely (<28 weeks' gestation), and age- and gender-matched term-born controls (≥37 weeks' gestation). We applied fMRI during working-memory (WM) tasks, and investigated white-matter microstructure with diffusion tensor imaging. Compared with controls, preterm-born children performed WM tasks less accurately, had reduced activation in several right prefrontal areas, and weaker deactivation of right temporal lobe areas. The weaker prefrontal activation correlated with poorer WM performance. Preterm-born children had higher fractional anisotropy (FA) and lower diffusivity than controls in several white-matter areas, and in the posterior cerebellum, the higher FA associated with poorer visuospatial test scores. In controls, higher FA and lower diffusivity correlated with faster WM performance. Together these findings demonstrate weaker WM-related brain activations and altered white matter microstructure in children born extremely preterm, who had normal global cognitive ability.

Very preterm children at risk for developmental coordination disorder have brain alterations in motor areas

AIM

Brain alterations in very preterm children at risk for developmental coordination disorder were investigated.

METHODS

Infants born very preterm with gestation age <30 weeks or birthweight <1250 g were recruited from Royal Women's Hospital Melbourne from 2001 to 2003. Volumetric imaging was performed at term equivalent age; at seven years, volumetric imaging and diffusion tensor imaging were performed. At seven years, 53 of 162 children without cerebral palsy had scores ≤16th percentile on the Movement Assessment Battery for Children-Second Edition and were considered at risk for developmental coordination disorder.

RESULTS

At term equivalent age, smaller brain volumes were found for total brain tissue, cortical grey matter, cerebellum, caudate accumbens, pallidum and thalamus in children at risk for developmental coordination disorder (p < 0.05); similar patterns were present at seven years. There was no evidence for catch-up brain growth in at-risk children. At seven years, at-risk children displayed altered microstructural organisation in many white matter tracts (p < 0.05).

CONCLUSION

Infants born very preterm at risk for developmental coordination disorder displayed smaller brain volumes at term equivalent age and seven years, and altered white matter microstructure at seven years, particularly in motor areas. There was no catch-up growth from infancy to seven years.

Altered White Matter Integrity after Mild to Moderate Traumatic Brain Injury

(1) Background: White matter changes among individuals with mild-to-moderate traumatic brain injury (TBI) may be sensitive imaging markers reflecting functional impairment, particularly in the context of post-concussion syndrome. The objective of this study was to examine the altered white matter integrity in mild-to-moderate TBI patients compared with age-matched normal controls. (2) Methods: Diffusion tensor imaging data from 15 individuals with TBI and 15 control subjects were retrospectively obtained. We investigated and compared white matter integrity in both groups, with regard to fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) and examined the relationship with cognitive dysfunction and impaired balance in patients. (3) Results: In comparison with controls, the TBI patients had significantly decreased FA as well as increased RD, in the right corticospinal tract. Decreased RD was observed in the left cerebellar area near the middle cerebellar peduncle. Decreased AD was observed in the left inferior cerebellar peduncle, showing positive correlation with poor balance control. We observed decreased FA and increased AD in the left superior longitudinal fasciculus showing positive and negative correlation, respectively, with cognitive function in the TBI group. (4) Conclusions: Altered white matter integrity in mild-to-moderate TBI cases may be indicative of cognitive dysfunction and impaired balance.

Aging, cognition, and the brain: effects of age-related variation in white matter integrity on neuropsychological function

Alterations in brain structure are viewed as neurobiological indicators which are closely tied to cognitive changes in healthy human aging. The current study used diffusion tensor imaging (DTI) tractography to investigate the relationship between age, brain variation in white matter (WM) integrity, and cognitive function. Sixteen younger adults (aged 20-28 years) and 18 healthy older adults (aged 60-75 years) underwent DTI scanning and a standardized battery of neuropsychological measures. Behaviorally, older adults exhibited poorer performance on multiple cognitive measures compared to younger adults. At the neural level, the effects of aging on theWM integrity were evident within interhemispheric (the anterior portion of corpus callosum) and transverse (the right uncinate fasciculus) fibers of the frontal regions, and the cingulum-angular fibers. Our correlation results showed that age-related WM differentially influenced cognitive function, with increased fractional anisotropy values in both the anterior corpus callosum and the right cingulum/angular fibers positively correlated with performance on the visuospatial task in older adults. Moreover, mediation analysis further revealed that the WM tract integrity of the frontal interhemspheric fibers was a significant mediator of age-visuospatial performance relation in older adults, but not in younger adults. These findings support the vulnerability of the frontal WM fibers to normal aging and push forward our understanding of cognitive aging by providing a more integrative view of the neural basis of linkages among aging, cognition, and brain.

Progressive brain structural changes after the first year of treatment in first-episode treatment-naive patients with deficit or nondeficit schizophrenia

Progressive brain volume atrophy has been reported in patients with schizophrenia. However, whether this progress differs between patients with primary negative symptoms (deficit schizophrenia; DS) and those without such symptoms (nondeficit schizophrenia; NDS) is unknown. Here, we examined grey matter volume (GMV) and white matter volume (WMV) changes over 12 months in 34 first-episode treatment-naive patients with schizophrenia (14 DS and 20 NDS) and 32 healthy controls (HCs) using structural magnetic resonance imaging and voxel-based morphometry. At baseline, compared to HCs, patients with DS but not NDS had less WMV in bilateral posterior limb of the internal capsule (PLIC) and cerebellar tonsil (P < 0.05, FDR corrected) and smaller GMV in the cerebellar culmen (P < 0.05, FWE corrected). At follow-up, NDS group showed WMV reduction in bilateral PLIC (P < 0.05, FDR corrected), while DS group showed no progressive WMV changes. While both patient groups exhibited GMV reduction in the hippocampus and insular cortex, patients with NDS showed additional GMV loss in the frontal and cingulate cortex and a selective increase in GMV in the left thalamus (P < 0.05 FWE corrected). Our study revealed double dissociations in developmental brain volume changes in the first year after clinical contact for psychosis in DS versus NDS patients.

Characterization of White Matter Tracts by Diffusion MR Tractography in Cat and Ferret that Have Similar Gyral Patterns

The developmental relationships between gyral structures and white matter tracts have long been debated, but it is still difficult to discern whether they influence each other's development or are causally related. To explore this topic, this study used cats and ferrets as models for species that share similar gyral folding patterns and imaged with diffusion magnetic resonance imaging to compare white matter innervations in homologous gyri and other brain regions. Adult cat and ferret brains were analyzed via diffusion spectrum imaging tractography and homologous regions of interest were compared. Although similar genetic lineage and gyral structures would suggest analogous white matter tracts, tractography reveals significantly differing white matter connectivity in both the visual and auditory cortices. Similarities in connectivity were concentrated primarily in the highly conserved cerebellar region. These results correlate well with existing histological and functional studies of both species. Our results indicate that, while the 2 species may share similar gyral structures, they utilize different white matter connectivity; suggesting that while species may share similar gyral structures, they can develop different underlying white matter connectivity.

Exploring white matter microstructure and olfaction dysfunction in early parkinson disease: diffusion MRI reveals new insight

Olfaction dysfunction is considered as a robust marker of prodromal Parkinson disease (PD). Measurement of olfaction function as a screening test is unsatisfactory due to long lead time interval and low specificity for detection of PD. Use of imaging markers might yield more accurate predictive values and provide bases for combined use of imaging and clinical markers for early PD. Diffusion MRI connectometry was conducted on 85 de novo PD patients in and 36 healthy controls to find: first, white matter tracts with significant difference in quantitative anisotropy between PD groups with various degrees of olfaction dysfunction and second, second fibers with correlation with University of Pennsylvania Smell Identification Test (UPSIT) score in each group using a multiple regression analysis considering age, sex, GDS and MoCA score. Local connectomes were determined in seven of all the possible comparisons, correcting for false discovery rate (FDR). PD patients with anosmia and normal olfaction had the highest number of fibers with decreased connectivity in left inferior longitudinal fasciculus, bilateral fornix, bilateral middle cerebellar peduncle (MCP), bilateral cingulum, bilateral corticospinal tract (CST) and body, genu and splenium of corpus callosum (CC) (FDR = 0.0013). In multiple regression analysis, connectivity in the body, genu and splenium of CC and bilateral fornix had significant negative correlation (FDR between 0.019 and 0.083), and bilateral cingulum and MCP had significant positive correlation (FDR between 0.022 and 0.092) with UPSIT score. White matter connectivity in healthy controls could not be predicted by UPSIT score using the same model. The results of this study provide compelling evidence that microstructural degenerative changes in these areas underlie the clinical phenotype of prodromal olfaction dysfunction in PD and that diffusion parameters of these areas might be able to serve as signature markers for early detection of PD. This is the first report that confirms a discriminative role for UPSIT score in identifying PD specific changes in white matter microstructure. Our results open a window to identify microstructural signatures of prodromal PD in white matter.

Mild Neonatal Brain Hypoxia-Ischemia in Very Immature Rats Causes Long-Term Behavioral and Cerebellar Abnormalities at Adulthood

Systemic hypoxia-ischemia (HI) often occurs during preterm birth in human. HI induces injuries to hinder brain cells mainly in the ipsilateral forebrain structures. Such HI injuries may cause lifelong disturbances in the distant regions, such as the contralateral side of the cerebellum. We aimed to evaluate behavior associated with the cerebellum, to acquire cerebellar abundant metabolic alterations using in vivo 1H magnetic resonance spectroscopy (1H MRS), and to determine GFAP, NeuN, and MBP protein expression in the left cerebellum, in adult rats after mild early postnatal HI on the right forebrain at day 3 (PND3). From PND45, HI animals exhibited increased locomotion in the open field while there is neither asymmetrical forelimb use nor coordination deficits in the motor tasks. Despite the fact that metabolic differences between two cerebellar hemispheres were noticeable, a global increase in glutamine of HI rats was observed and became significant in the left cerebellum compared to the sham-operated group. Furthermore, increases in glutamate, glycine, the sum of glutamate and glutamine and total choline, only occurred in the left cerebellum of HI rats. Remarkably, there were decreased expression of MBP and NeuN but no detectable reactive astrogliosis in the contralateral side of the cerebellum of HI rats. Taken together, the detected alterations observed in the left cerebellum of HI rats may reflect disequilibrium in the glutamate-glutamine cycle and a delay in the return of glutamine from astrocytes to neurons from hypoxic-ischemic origin. Our data provides in vivo evidence of long-term changes in the corresponding cerebellum following mild neonatal HI in very immature rats, supporting the notion that systemic HI could cause cell death in the cerebellum, a distant region from the expected injury site.

HIGHLIGHTS

-Neonatal hypoxia-ischemia (HI) in very immature rats induces hyperactivity toward adulthood.-1H magnetic resonance spectroscopy detects long-term cerebellar metabolic changes in adult rats after neonatal HI at postnatal day 3.-Substantial decreases of expression of neuronal and myelin markers in adult rats cerebellum after neonatal cortical mild HI.

FTY720 attenuates iron deposition and glial responses in improving delayed lesion and long-term outcomes of collagenase-induced intracerebral hemorrhage

Most intracerebral hemorrhage (ICH) survivors have poor long-term outcomes, such as cognitive deficits and depression. Delayed lesions of ICH include neuron loss and white matter injury and the pathology of the lesions involves iron deposition and glial responses, which contribute to depressive-like behavior and cognitive impairment in animals. This study aimed to investigate the effects of FTY720 (0.3 mg/kg/day for 4 weeks) on iron deposition, glial responses, histological abnormalities and behavioral dysfunction in mice with ICH. The primary adverse long-term outcomes in our study of ICH mice were depressive-like behavior and impaired recognition memory. We found that FTY720 safely ameliorated depressive-like behavior and impaired recognition without affecting recovery of grip function and locomotor activity 28 days post-ICH. Moreover, we measured neuron loss, white matter lesions, lesion volume and iron deposition at day 28, which were attenuated in the FTY720-treated group compared to the ICH-control group, without changing initial hematoma volume on day 1 post-ICH. Long-term elevation of glial responses, including microglia activity and astrogliosis with tumor necrosis factor alpha (TNFα) expression was demonstrated by Western blot and immunofluorescence staining, which we found was attenuated by FTY720 treatment. Hence, FTY720 could become a novel therapeutic agent for improving long-term outcomes after ICH.

Reduced Interhemispheric White Matter Asymmetries in Medial Temporal Lobe Epilepsy With Hippocampal Sclerosis

Mesial temporal lobe epilepsy (MTLE), one of the most common types of refractory focal epilepsy, has shown white matter abnormalities both within and beyond the temporal lobe. In particular, the white matter abnormalities in the ipsilateral hemisphere are more obvious than those in the contralateral hemisphere in MTLE, that is, the abnormalities present asymmetrical characteristics. However, very few studies have characterized the white matter microstructure asymmetry in MTLE patients specifically. Thus, we performed diffusion tensor imaging (DTI) to investigate the white matter microstructure asymmetries of patients with MTLE with unilateral hippocampal sclerosis (MTLE-HS). We enrolled 25 MTLE-HS (left MTLE-HS group, n = 13; right MTLE-HS group, n = 12) and 26 healthy controls (HC). DTI data were analyzed by tract-based spatial statistics (TBSS) to test the hemispheric differences across the entire white matter skeleton. We also conducted a two-sample paired t-test for 21 paired region of interests (ROIs) parceled on the basis of the ICBM-DTI-81 white-matter label atlas of bilateral hemispheres to test the hemispheric differences. An asymmetry index (AI) was calculated to further quantify the differences between the left and right paired-ROIs. It was found that the asymmetries of white matter skeletons were significantly lower in the MTLE-HS groups than in the HC group. In particular, the asymmetry traits were moderately reduced in the RMTLE-HS group and obviously reduced in the LMTLE-HS group. In addition, AI was significantly different in the RMTLE-HS group from the LMTLE-HS or HC group in the limbic system and superior longitudinal fasciculus (SLF). The current study found that the interhemispheric white matter asymmetries were significantly reduced in the MTLE-HS groups than in the HC group. The interhemispheric white matter asymmetries are distinctly affected in left and right MTLE-HS groups. The differences in AI among RMTLE-HS, LMTLE-HS, and HC involved the limbic system and SLF, which may have some pragmatic implications for the diagnosis of MTLE and differentiating LMTLE-HS from RMTLE-HS.

Physical Fitness, White Matter Volume and Academic Performance in Children: Findings From the ActiveBrains and FITKids2 Projects

Objectives: The aims of this study were (i) to examine the association between cardiorespiratory fitness and white matter volume and test whether those associations differ between normal-weight and overweight/obese children (ii) to analyze the association between other physical fitness components (i.e., motor and muscular) and white matter volume, and (iii) to examine whether the fitness-related associations in white matter volume were related to academic performance.

Methods: Data came from two independent projects: ActiveBrains project (n = 100; 10.0 ± 1.1 years; 100% overweight/obese; Spain) and FITKids2 project (n = 242; 8.6 ± 0.5 years; 36% overweight/obese, United States). Cardiorespiratory fitness was assessed in both projects, and motor and muscular fitness were assessed in the ActiveBrains project. T1-weighted images were acquired with a 3.0 T S Magnetom Tim Trio system. Academic performance was assessed by standardized tests.

Results: Cardiorespiratory fitness was associated with greater white matter volume in the ActiveBrain project (P < 0.001, k = 177; inferior fronto-opercular gyrus and inferior temporal gyrus) and in the FITKids project (P < 0.001, k = 117; inferior temporal gyrus, cingulate gyrus, middle occipital gyrus and fusiform gyrus) among overweight/obese children. However, no associations were found among normal-weight children in the FITKids project. In the ActiveBrains project, motor fitness was related to greater white matter volume (P < 0.001, k = 173) in six regions, specifically, insular cortex, caudate, bilateral superior temporal gyrus and bilateral supramarginal gyrus; muscular fitness was associated with greater white matter volumes (P < 0.001, k = 191) in two regions, particularly, the bilateral caudate and bilateral cerebellum IX. The white matter volume of six of these regions were related to academic performance, but after correcting for multiple comparisons, only the insular cortex remained significantly related to math calculations skills (β = 0.258; P < 0.005). In both projects, no brain regions showed a statistically significant negative association between any physical fitness component and white matter volume.

Conclusion: Cardiorespiratory fitness may positively relate to white matter volume in overweight/obese children, and in turn, academic performance. In addition, motor and muscular fitness may also influence white matter volume coupled with better academic performance. From a public health perspective, implementing exercise interventions that combine aerobic, motor and muscular training to enhance physical fitness may benefit brain development and academic success.

A novel radiological classification system for cerebral gliomas: The Brain-Grid

Purpose

Standard radiological/topographical classifications of gliomas often do not reflect the real extension of the tumor within the lobar-cortical anatomy. Furthermore, these systems do not provide information on the relationship between tumor growth and the subcortical white matter architecture. We propose the use of an anatomically standardized grid system (the Brain-Grid) to merge serial morphological magnetic resonance imaging (MRI) scans with a representative tractographic atlas. Two illustrative cases are presented to show the potential advantages of this classification system.

Methods

MRI scans of 39 patients (WHO grade II and III gliomas) were analyzed with a standardized grid created by intersecting longitudinal lines on the axial, sagittal, and coronal planes. The anatomical landmarks were chosen from an average brain, spatially normalized to the Montreal Neurological Institute (MNI) space and the Talairach space. Major white matter pathways were reconstructed with a deterministic tracking algorithm on a reference atlas and analyzed using the Brain-Grid system.

Results

In all, 48 brain grid voxels (areas defined by 3 coordinates, axial (A), coronal (C), sagittal (S) and numbers from 1 to 4) were delineated in each MRI sequence and on the tractographic atlas. The number of grid voxels infiltrated was consistent, also in the MNI space. The sub-cortical insula/basal ganglia (A3-C2-S2) and the fronto-insular region (A3-C2-S1) were most frequently involved. The inferior fronto-occipital fasciculus, anterior thalamic radiation, uncinate fasciculus, and external capsule were the most frequently associated pathways in both hemispheres.

Conclusions

The Brain-Grid based classification system provides an accurate observational tool in all patients with suspected gliomas, based on the comparison of grid voxels on a morphological MRI and segmented white matter atlas. Important biological information on tumor kinetics including extension, speed, and preferential direction of progression can be observed and even predicted with this system. This novel classification can easily be applied to both prospective and retrospective cohorts of patients and increase our comprehension of glioma behavior.

Mapping acute lesion locations to physiological swallow impairments after stroke

Dysphagia is a common deficit after a stroke, and it is frequently associated with pneumonia, malnutrition, dehydration, and poor quality of life. It is not yet fully clear which brain regions are directly related to swallowing, and how lesions affect swallow physiology. This study aimed to assess the statistical relationship between acute stroke lesion locations and impairment of specific aspects of swallow physiology. We performed lesion symptom mapping with 68 retrospectively recruited, acute, first-ever ischemic stroke patients. Lesions were determined on diffusion weighted MRI scans. Post-stroke swallow physiology was determined using the Modified Barium Swallow Study Impairment Profile (MBSImP©™). The relationship between brain lesion location and 17 physiological aspects of swallowing were tested using voxel-based and region-based statistical associations corrected for multiple comparisons using permutation thresholding. We found that laryngeal elevation, anterior hyoid excursion, laryngeal vestibular closure, and pharyngeal residue were associated with lesioned voxels or regions of interests. All components showed distinct and overlapping lesion locations, mostly in the right hemisphere, and including cortical regions (inferior frontal gyrus, pre- and postcentral gyrus, supramarginal gyrus, angular gyrus, superior temporal gyrus, insula), subcortical regions (thalamus, amygdala) and white matter tracts (superior longitudinal fasciculus, corona radiata, internal capsule, external capsule, ansa lenticularis, lenticular fasciculus). Our findings indicate that different aspects of post-stroke swallow physiology are associated with distinct lesion locations, primarily in the right hemisphere, and primarily including sensory-motor integration areas and their corresponding white matter tracts. Future studies are needed to expand on our findings and thus, support the development of a neuroanatomical model of post-stroke swallow physiology and treatment approaches targeting the neurophysiological underpinnings of swallowing post stroke.

•

Different aspects of swallow physiology are associated with distinct stroke lesion locations.

•

Sensory-motor integration areas and white matter tracts are crucial for swallow physiology.

•

Mostly regions in the right and only few in the left hemisphere contribute to swallow physiology.

Girls' internalizing symptoms and white matter tracts in Cortico-Limbic circuitry

Dysfunction in cortico-limbic circuitry is implicated in internalizing disorders (i.e., depressive and anxious disorders), but less is known about whether structural variations precede frank disorder and thus potentially mark risk. We therefore examined associations between white matter (WM) tract microstructure in cortico-limbic circuitry at age 7 and concurrent and longitudinal patterns of internalizing symptoms in 42 typically developing girls using Diffusion Tensor Imaging (DTI). Girls' internalizing symptoms were concurrently associated with reduced fractional anisotropy (FA) in segments of the cingulum bundle (CB) and the uncinate fasciculus (UF), bilaterally. Moreover, latent profile analysis showed that girls with increasing internalizing symptoms, based on assessments at ages 3, 6, 7, and 8, had reduced FA in these segments compared to girls with stably low symptoms. These results point to a putative neural mechanism underlying the course of childhood internalizing symptoms.

Disruptions in White Matter Maturation and Mediation of Cognitive Development in Youths on the Psychosis Spectrum

BACKGROUND

Psychosis onset typically occurs in adolescence, and subclinical psychotic experiences peak in adolescence. Adolescence is also a time of critical neural and cognitive maturation. Using cross-sectional data from the Philadelphia Neurodevelopmental Cohort, we examined whether regional white matter (WM) development is disrupted in youths with psychosis spectrum (PS) features and whether WM maturation mediates the relationship between age and cognition in typically developing (TD) youths and youths with PS features.

METHODS

We examined WM microstructure, as assessed via diffusion tensor imaging, in 670 individuals (age 10-22 years; 499 TD group, 171 PS group) by using tract-based spatial statistics. Multiple regressions were used to evaluate age × group interactions on regional WM indices. Mediation analyses were conducted on four cognitive domains-executive control, complex cognition, episodic memory, and social cognition-using a bootstrapping approach.

RESULTS

There were age × group interactions on fractional anisotropy (FA) in the superior longitudinal fasciculus (SLF) and retrolenticular internal capsule. Follow-up analyses revealed these effects were significant in both hemispheres. Bilateral SLF FA mediated the relationship between age and complex cognition in the TD group, but not the PS group. Regional FA did not mediate the age-associated increase in any of the other cognitive domains.

CONCLUSIONS

Our results showed aberrant age-related effects in SLF and retrolenticular internal capsule FA in youths with PS features. SLF development supports emergence of specific higher-order cognitive functions in TD youths, but not in youths with PS features. Future mechanistic explanations for these relationships could facilitate development of earlier and refined targets for therapeutic interventions.