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

2019 ◽  
Author(s):  
Guido I. Guberman ◽  
Jean-Christophe Houde ◽  
Alain Ptito ◽  
Isabelle Gagnon ◽  
Maxime Descoteaux
Keyword(s):  
Working Memory ◽  
White Matter ◽  
Memory Function ◽  
Diffusion Imaging ◽  
Free Water ◽  
Anterior Cingulate ◽  
High Angular Resolution ◽  
Axonal Loss ◽  
Water Fraction ◽  
The Right

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

scholarly journals Q -ball imaging of macaque white matter architecture

2005 ◽  
Vol 360 (1457) ◽  
pp. 869-879 ◽  
Author(s):  
David S Tuch ◽  
Jonathan J Wisco ◽  
Mark H Khachaturian ◽  
Leeland B Ekstrom ◽  
Rolf Kötter ◽  
...  
Keyword(s):  
White Matter ◽  
Magnetic Resonance ◽  
Diffusion Imaging ◽  
Large Body ◽  
Macaque Monkey ◽  
High Angular Resolution ◽  
Imaging Method ◽  
Diffusion Tractography ◽  
Axonal Projections ◽  
Histological Validation

Diffusion-weighted magnetic resonance imaging holds substantial promise as a technique for non-invasive imaging of white matter (WM) axonal projections. For diffusion imaging to be capable of providing new insight into the connectional neuroanatomy of the human brain, it will be necessary to histologically validate the technique against established tracer methods such as horseradish peroxidase and biocytin histochemistry. The macaque monkey provides an ideal model for histological validation of the diffusion imaging method due to the phylogenetic proximity between humans and macaques, the gyrencephalic structure of the macaque cortex, the large body of knowledge on the neuroanatomic connectivity of the macaque brain and the ability to use comparable magnetic resonance acquisition protocols in both species. Recently, it has been shown that high angular resolution diffusion imaging (HARDI) can resolve multiple axon orientations within an individual imaging voxel in human WM. This capability promises to boost the accuracy of tract reconstructions from diffusion imaging. If the macaque is to serve as a model for histological validation of the diffusion tractography method, it will be necessary to show that HARDI can also resolve intravoxel architecture in macaque WM. The present study therefore sought to test whether the technique can resolve intravoxel structure in macaque WM. Using a HARDI method called q -ball imaging (QBI) it was possible to resolve composite intravoxel architecture in a number of anatomic regions. QBI resolved intravoxel structure in, for example, the dorsolateral convexity, the pontine decussation, the pulvinar and temporal subcortical WM. The paper concludes by reviewing remaining challenges for the diffusion tractography project.

scholarly journals Anatomy and white matter connections of the orbitofrontal gyrus

2018 ◽  
Vol 128 (6) ◽  
pp. 1865-1872 ◽  
Author(s):  
Joshua D. Burks ◽  
Andrew K. Conner ◽  
Phillip A. Bonney ◽  
Chad A. Glenn ◽  
Cordell M. Baker ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Diffusion Imaging ◽  
Internal Capsule ◽  
Ground Truth ◽  
Outcome Evaluation ◽  
Anterior Cingulate ◽  
Anatomical Dissection ◽  
Visual Spatial ◽  
Human Connectome Project

OBJECTIVEThe orbitofrontal cortex (OFC) is understood to have a role in outcome evaluation and risk assessment and is commonly involved with infiltrative tumors. A detailed understanding of the exact location and nature of associated white matter tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging–based fiber tracking validated by gross anatomical dissection as ground truth, the authors have characterized these connections based on relationships to other well-known structures.METHODSDiffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. The OFC was evaluated as a whole based on connectivity with other regions. All OFC tracts were mapped in both hemispheres, and a lateralization index was calculated with resultant tract volumes. Ten postmortem dissections were then performed using a modified Klingler technique to demonstrate the location of major tracts.RESULTSThe authors identified 3 major connections of the OFC: a bundle to the thalamus and anterior cingulate gyrus, passing inferior to the caudate and medial to the vertical fibers of the thalamic projections; a bundle to the brainstem, traveling lateral to the caudate and medial to the internal capsule; and radiations to the parietal and occipital lobes traveling with the inferior fronto-occipital fasciculus.CONCLUSIONSThe OFC is an important center for processing visual, spatial, and emotional information. Subtle differences in executive functioning following surgery for frontal lobe tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.

Changes in mild cognitive impairment and its subtypes as seen on diffusion tensor imaging

2012 ◽  
Vol 24 (9) ◽  
pp. 1483-1493 ◽  
Author(s):  
Senthil Thillainadesan ◽  
Wei Wen ◽  
Lin Zhuang ◽  
John Crawford ◽  
Nicole Kochan ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
White Matter ◽  
Multiple Testing ◽  
Diffusion Tensor ◽  
Internal Capsule ◽  
Anterior Cingulate ◽  
Corona Radiata ◽  
Amnestic Mci ◽  
Subcortical Regions ◽  
The Right

ABSTRACTBackground: Previous studies using diffusion tensor imaging (DTI) have observed microstructural abnormalities in white matter regions in both Alzheimer's disease and mild cognitive impairment (MCI). The aim of this work was to examine the abnormalities in white matter and subcortical regions of MCI and its subtypes in a large, community-dwelling older aged cohortMethods: A community-based sample of 396 individuals without dementia underwent medical assessment, neuropsychiatric testing, and neuroimaging. Of these, 158 subjects were classified as MCI and 238 as cognitively normal (controls) based on international MCI consensus criteria. Regional fractional anisotropy (FA) and mean diffusivity (MD) measures were calculated from the DTI and compared between groups. The false discovery rate correction was applied for multiple testing.Results: Subjects with MCI did not have significant differences in FA compared with controls after correction for multiple testing, but had increased MD in the right putamen, right anterior limb of the internal capsule, genu and splenium of the corpus callosum, right posterior cingulate gyrus, left superior frontal gyrus, and right and left corona radiata. When compared with controls, changes in left anterior cingulate, left superior frontal gyrus, and right corona radiata were associated with amnestic MCI (aMCI), whereas changes in the right putamen, right anterior limb of the internal capsule, and the right corona radiata were associated with non-amnestic MCI (naMCI). On logistic regression, the FA values in the left superior gyrus and MD values in the anterior cingulate distinguished aMCI from naMCI.Conclusions: MCI is associated with changes in white matter and subcortical regions as seen on DTI. Changes in some anterior brain regions distinguish aMCI from naMCI.

scholarly journals Stress-induced anatomical changes in white and gray matter: a review of literature

2020 ◽  
Vol 76 (06) ◽  
pp. 6400-2020
Author(s):  
IWONA ŁUSZCZEWSKA-SIERAKOWSKA ◽  
KAMIL JONAK
Keyword(s):  
White Matter ◽  
Gray Matter ◽  
Traumatic Event ◽  
Gray Matter Volume ◽  
Hippocampal Neurogenesis ◽  
Anterior Cingulate ◽  
Total Brain Volume ◽  
Extreme Stress ◽  
Mri Morphometry ◽  
The Right

Post traumatic stress disorder (PTSD) is a psychiatric abnormality caused by a drastic traumatic event or extreme stress, that exceeds the capability to adapt. There are many papers reporting anatomical brain changes induced by trauma and extreme stress, not only in white matter but in gray matter as well. Extreme stress and trauma are connected with elevation of cortisol level, which may cause damage to the hippocampus and may interfere with the anatomy of the hippocampus as well as its microstructure and cell number. Stress may inhibit the hippocampal neuroregeneration as well as hippocampal neurogenesis and even induce neuronal death within the hippocampus. Diffusor tensor imaging (DTI) is a powerful method enabling the visualization of the microstructure integrity of white matter, to evaluate the changes (rate and directionality) of water diffusion within myelin tracts and provide enhanced images of white matter tracts compared to traditional MRI morphometry images. One can evaluate the differences in white matter using fractional anisotropy (FA), which is a scalar metric of the degree of anisotropy and diffusion direction of water molecules, indicating fiber density, mylination and axon diameter. Many studies report reduced gray matter volume caused by extreme stress or trauma in people both with the diagnosis of PTSD as well as stress-exposed non PTSD in comparison to healthy controls. Studies have revealed reduced volume mostly in the hippocampus but also in regions such as anterior cingulate, corpus callosum, insula, septum pellucidum, subcallosal cortex, amygdala, prefrontal cortex and total brain volume. The right hippocampus may be prone to the effect of stress much more than the left hippocampus. Moreover, comparing trauma-exposed non-PTSD and PTSD participants, they have found volumetric abnormalities only within the right hippocampus among the PTSD group. They suggest an additional pathological process underlying PTSD, connected with the right hippocampus volume.

scholarly journals O5.6. ADVANCED DIFFUSION IMAGING IN PSYCHOSIS RISK: A CROSS-SECTIONAL AND LONGITUDINAL STUDY OF WHITE MATTER DEVELOPMENT

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S13-S13
Author(s):  
Maria Di Biase ◽  
Suheyla Cetin Karayumak ◽  
Andrew Zalesky ◽  
Marek Kubicki ◽  
Yogesh Rathi ◽  
...  
Keyword(s):  
Longitudinal Study ◽  
White Matter ◽  
High Risk ◽  
Diffusion Imaging ◽  
Free Water ◽  
Brain Atlas ◽  
Clinical High Risk ◽  
Cross Sectional ◽  
Rate Of Increase ◽  
Total P

Abstract Background Studies in individuals at clinical high risk (CHR) for psychosis provide a powerful means to predict outcomes and inform putative mechanisms underlying conversion to psychosis. In previous work, we applied advanced diffusion imaging methods to reveal that white matter pathology in a CHR population is characterized by cellular-specific changes in white matter, suggesting a preexisting neurodevelopmental anomaly. However, it remains unknown whether these deficits relate to clinical symptoms and/or conversion to frank psychosis. To address this gap, we examined cross-sectional and longitudinal white matter maturation in the largest imaging population of CHR individuals to date, obtained from the North American Prodrome Longitudinal Study (NAPLS-3). Methods Multi-shell diffusion magnetic resonance imaging (MRI) data were collected across multiple timepoints (1–6 at ~2 month intervals) in 286 subjects (age range=12–32 years). These were 230 unmedicated CHR subjects, including 11% (n=25) who transitioned to psychosis (CHR-converters), as well as 56 age and sex-matched healthy controls. Raw diffusion signals were harmonized to remove scanner/site-induced effects, yielding a unified imaging dataset. Fractional anisotropy of cellular tissue (FAt) and the volume fraction of extracellular free-water (FW) were assessed in 12 major tracts from the IIT Human Brain Atlas (v.5.0). Linear mixed effects (LME) models were fitted to infer developmental trajectories of FAt and FW across age for CHR-converters, CHR-nonconverters and control groups, while accounting for the repeated measurements on each individual. Results The rate at which FAt changed with age significantly differed between the three groups across commissural and association tracts (5 in total; p<0.05). In these tracts, FAt increased with age in controls (0.002% change per year) and in CHR-nonconverters, albeit at a slower rate (0.00074% per year). In contrast, FAt declined with age in CHR-converters at a rate that was significantly faster (-3.944% per year) than the rate of increase in the other two groups. By 25 years of age, FAt was significantly lower in both CHR groups compared to controls (p<0.05). With regard to FW, the rate of change significantly differed between CHR-converters and controls across the forceps major and the left inferior longitudinal and fronto-occipital fasciculi (IFOF; 3 tracts in total; p<0.05). This was due to increased FW with age in the CHR-converters (0.0024% change per year) relative to controls (-0.0002% per year). Consequently, FW was significantly higher in CHR-converters compared to controls by 20 years of age (p<.05). With regard to symptoms, there was a significant impact of IFOF FW on positive symptom severity across CHR subjects, regardless of conversion status (t=2.37, p<0.05). Discussion Our results revealed that clinical high-risk for psychosis is associated with cellular-specific alterations in white matter, regardless of conversion status. Only converters showed excess extracellular free-water, which involved tracts connecting occipital, posterior temporal, and orbito-frontal areas. We also demonstrate a direct impact of free-water on positive symptomatology, collectively, suggesting that excess free-water may signal acute psychosis and its onset. This marker may be useful for patient selection for clinical trials and assessment of individuals with prodromal psychosis.

scholarly journals Computational Representation of White Matter Fiber Orientations

2013 ◽  
Vol 2013 ◽  
pp. 1-12
Author(s):  
Adelino R. Ferreira da Silva
Keyword(s):  
White Matter ◽  
Angular Resolution ◽  
Diffusion Imaging ◽  
Real Data ◽  
Orientation Distribution ◽  
Directional Data ◽  
High Angular Resolution ◽  
Clustering Data ◽  
Von Mises ◽  
Computational Representation

We present a new methodology based on directional data clustering to represent white matter fiber orientations in magnetic resonance analyses for high angular resolution diffusion imaging. A probabilistic methodology is proposed for estimating intravoxel principal fiber directions, based on clustering directional data arising from orientation distribution function (ODF) profiles. ODF reconstructions are used to estimate intravoxel fiber directions using mixtures of von Mises-Fisher distributions. The method focuses on clustering data on the unit sphere, where complexity arises from representing ODF profiles as directional data. The proposed method is validated on synthetic simulations, as well as on a real data experiment. Based on experiments, we show that by clustering profile data using mixtures of von Mises-Fisher distributions it is possible to estimate multiple fiber configurations in a more robust manner than currently used approaches, without recourse to regularization or sharpening procedures. The method holds promise to support robust tractographic methodologies and to build realistic models of white matter tracts in the human brain.

White-matter microstructure in previously drug-naive patients with schizophrenia after 6 weeks of treatment

2013 ◽  
Vol 43 (11) ◽  
pp. 2301-2309 ◽  
Author(s):  
Q. Wang ◽  
C. Cheung ◽  
W. Deng ◽  
M. Li ◽  
C. Huang ◽  
...  
Keyword(s):  
White Matter ◽  
Early Phase ◽  
Clinical Symptoms ◽  
Diffusion Tensor ◽  
Disease Process ◽  
Anterior Cingulate ◽  
First Episode ◽  
Drug Naïve ◽  
The Right ◽  
First Episode Schizophrenia

BackgroundIt is not clear whether the progressive changes in brain microstructural deficits documented in previous longitudinal magnetic resonance imaging (MRI) studies might be due to the disease process or to other factors such as medication. It is important to explore the longitudinal alterations in white-matter (WM) microstructure in antipsychotic-naive patients with first-episode schizophrenia during the very early phase of treatment when relatively ‘free’ from chronicity.MethodThirty-five patients with first-episode schizophrenia and 22 healthy volunteers were recruited. High-resolution diffusion tensor imaging (DTI) was obtained from participants at baseline and after 6 weeks of treatment. A ‘difference map’ for each individual was calculated from the 6-week follow-up fractional anisotropy (FA) of DTI minus the baseline FA. Differences in Positive and Negative Syndrome Scale (PANSS) scores and Global Assessment of Functioning (GAF) scores between baseline and 6 weeks were also evaluated and expressed as a 6-week/baseline ratio.ResultsCompared to healthy controls, there was a significant decrease in absolute FA of WM around the bilateral anterior cingulate gyrus and the right anterior corona radiata of the frontal lobe in first-episode drug-naive patients with schizophrenia following 6 weeks of treatment. Clinical symptoms improved during this period but the change in FA did not correlate with the changes in clinical symptoms or the dose of antipsychotic medication.ConclusionsDuring the early phase of treatment, there is an acute reduction in WM FA that may be due to the effects of antipsychotic medications. However, it is not possible to entirely exclude the effects of underlying progression of illness.

scholarly journals Genetic risk of dementia modifies the impact of obesity on limbic white matter and spatial navigation behavior in cognitively healthy adults

2019 ◽  
Author(s):  
Jilu P. Mole ◽  
Fabrizio Fasano ◽  
John Evans ◽  
Rebecca Sims ◽  
Derek A. Hamilton ◽  
...  
Keyword(s):  
Risk Factors ◽  
White Matter ◽  
Genetic Risk ◽  
Magnetization Transfer ◽  
Spatial Navigation ◽  
Diffusion Imaging ◽  
Axon Density ◽  
Asymptomatic Individuals ◽  
The Right ◽  
The Impact

AbstractA family history (FH) of dementia, APOE-ε4 genotype, and obesity are major risk factors for developing Alzheimer’s disease but their combined effects on the brain and cognition remain elusive. We tested the hypothesis that these risk factors affect apparent white matter (WM) myelin and cognition including spatial navigation and processing speed in 166 asymptomatic individuals (38-71 years). Microstructure in temporal [fornix, parahippocampal cingulum, uncinate fasciculus], motor and whole-brain WM was assessed with myelin-sensitive indices from quantitative magnetization transfer [macromolecular proton fraction (MPF)] and axon density from diffusion imaging. Individuals with the highest genetic risk (FH+ and APOE-ε4) compared to those with FH+ alone showed obesity-related reductions in MPF and axon density in the right parahippocampal cingulum. No effects were present for those without FH. Furthermore, FH modulated obesity-related effects on spatial navigation behaviour. In summary, an individual’s genetic dementia risk influenced the impact of obesity on WM myelin and cognition.

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