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Results for “White matter structural connectivity”

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At least 19 recordsLinked to original sources

PubMed2025

Causal relationship between white matter structural connectivity and epilepsy.

White matter structural connectivity has recently been linked to epilepsy pathogenesis, yet its causal role remains unclear. This study used Mendelian randomization (MR) to investigate the causal relationship between white matter structural connectivity and epilepsy. GWAS summary statistics for white matter structural connectivity were sourced from the UK Biobank, while epilepsy data were obtained from FinnGen R10 and the International League Against Epilepsy (ILAE). Our MR analysis revealed significant causal links between white matter structural connectivity and epilepsy risk. Increased connectivity between the right hemisphere visual and salience/ventral attention networks (RH Vis to RH Sal/VentAttn WMSC) was associated with higher epilepsy risk in FinnGen_R10_FE_STRICT (OR = 2.25, 95 % CI = 1.43-3.56, p < 0.01, FDR P = 0.019). Conversely, increased connectivity between left and right hemisphere salience/ventral attention networks (LH Sal/VentAttn to RH Sal/VentAttn WMSC) was linked to reduced epilepsy risk in FinnGen_R10_GE_STRICT (OR = 0.17, 95 % CI = 0.07-0.46, p < 0.01, FDR P = 0.033). A total of 15 nominally significant associations were identified across datasets. These findings suggest a causal relationship between white matter structural connectivity and epilepsy, offering insights into disease mechanisms and potential therapeutic targets.

Humans↗

PubMed2001

Structural connectivity in white matter using the projected diffusion-tensor distance.

Diffusion tensor imaging (DTI) has become a powerful tool for analyzing the structure of white matter. We have proposed a method for detecting nerve fiber bundles in white matter using diffusion tensor images and have applied the method to in vivo brain measurements. Although there are many methods to investigate the connectivity of white matter that are based on principal eigenvector or full tensor propagation. In the proposed method, we use directional diffusion measurements to infer regional white matter connectivity. To assess the connectivity, we compose the map based on the projected tensor distance, then we put a label on the constructed map and segment regionally connected white matter using labels. The purpose of this study is to obtain a quantitative map of white matter connectivity in vivo using diffusion tensor properties.

Algorithms↗

PubMed2004

Geometric strategies for neuroanatomic analysis from MRI.

In this paper, we describe ongoing work in the Image Processing and Analysis Group (IPAG) at Yale University specifically aimed at the analysis of structural information as represented within magnetic resonance images (MRI) of the human brain. Specifically, we will describe our applied mathematical approaches to the segmentation of cortical and subcortical structure, the analysis of white matter fiber tracks using diffusion tensor imaging (DTI), and the intersubject registration of neuroanatomical (aMRI) data sets. Many of our methods rally around the use of geometric constraints, statistical (MAP) estimation, and the use of level set evolution strategies. The analysis of gray matter structure and connecting white matter paths combined with the ability to bring all information into a common space via intersubject registration should provide us with a rich set of data to investigate structure and variation in the human brain in neuropsychiatric disorders, as well as provide a basis for current work in the development of integrated brain function-structure analysis.

Algorithms↗

PubMed2005

Knowledge-based classification of neuronal fibers in entire brain.

This work presents a framework driven by parcellation of brain gray matter in standard normalized space to classify the neuronal fibers obtained from diffusion tensor imaging (DTI) in entire human brain. Classification of fiber bundles into groups is an important step for the interpretation of DTI data in terms of functional correlates of white matter structures. Connections between anatomically delineated brain regions that are considered to form functional units, such as a short-term memory network, are identified by first clustering fibers based on their terminations in anatomically defined zones of gray matter according to Talairach Atlas, and then refining these groups based on geometric similarity criteria. Fiber groups identified this way can then be interpreted in terms of their functional properties using knowledge of functional neuroanatomy of individual brain regions specified in standard anatomical space, as provided by functional neuroimaging and brain lesion studies.

Algorithms↗

PubMed2002

The neuroanatomy of attention.

Attention is a complex neurobehavioral domain that is essential for all higher functions. Large areas of the brain are devoted to attention, reflecting its importance in the entire range of mental operations. Currently, two major distributed neural networks are recognized as mediating complementary aspects of attentional function. One is a diffuse system that distributes attention globally. This attentional system is subserved by a widespread network of thalamic and bihemispheric structures in which the frontal lobes are particularly important. The second network, a focal system that distributes attention to salient aspects of spatial experience, is lateralized to frontal and parietal regions of the right hemisphere. Both attentional networks are comprised of cortical and subcortical gray matter structures, as well as connecting white matter tracts that integrate these regions into functional ensembles. Neurological disorders frequently produce dramatic syndromes reflecting dysfunction of these networks. Among these syndromes are the acute confusional state, which results from disturbance of the diffuse system, and left neglect, which follows disruption of the right hemisphere system. The neuroanatomy of attention is crucial for understanding important neurobehavioral syndromes and their treatment.

Acute Disease↗

PubMed2006

[Diffusion tensor imaging (DTI) and its importance for exploration of normal or pathological brain development].

Diffusion tensor MR imaging (DTI) can provide in vivo unique information on integrity of white matter structures (anisotropy) and connectivity (fiber tracking) in the human brain. This is made possible by means of non-invasive MR-based technique. The purpose of this article is to review the method and the current applications of diffusion tensor MR imaging. Studies of the past decade featuring relevant neuropsychiatric disorders as well as disorders in child psychiatry are reviewed. Furthermore, this report offers a summary of DTI-studies in children and adolescents showing alterations in brain or CNS structures including neurological, traumatological and oncological investigations. In particular, it focuses on the importance of this method with respect to exploration of normal and pathological brain development.

Anisotropy↗

PubMed2005

Cognitive correlates of cerebral white matter lesions and water diffusion tensor parameters in community-dwelling older people.

BACKGROUND: The biological basis of cognitive ageing is unknown. One underlying process might be disruption of white matter tracts connecting cortical regions. White matter lesions (WML) seen on structural MRI may disrupt cortical connections, but diffusion tensor MRI (DT-MRI) parameters - mean diffusivity ( ) and fractional anisotropy (FA) - may reflect more subtle changes in white matter integrity. Here the relationships between WML load, DT-MRI parameters and cognition in a large cohort of elderly subjects with a very narrow age range were investigated. METHODS: 105 community-dwelling volunteers underwent MRI and neuropsychological assessment. Seventy-two (68.6%) were female, and their mean age was 78.4 (SD 1.5) years. Scans were rated for WML load. and FA were measured from regions of interest in normal-appearing frontal and occipital white matter, and centrum semiovale. RESULTS: and FA differed significantly among the three brain regions studied (p << 0.01). increased with age (r = 0.22 to 0.35, p < 0.03), and was negatively correlated with FA (r = -0.20 to -0.51, p < 0.05) in all three regions. There was a trend towards increased WML load correlating with poorer cognitive function, and this was statistically significant for the Mini-Mental State Examination (rho = -0.23, p = 0.02). was generally negatively correlated with cognitive test score, and FA was positively correlated. This pattern was more consistent for than for FA, and particularly for verbal fluency ( : r = -0.22 to -0.27, p < 0.03), which measures executive function. CONCLUSIONS: DT-MRI parameters, in particular , are sensitive to early ultrastructural changes underlying cognitive ageing. Executive function may be the cognitive domain most sensitive to age-related decline in white matter tract integrity.

Aged↗

PubMed2005

An automated approach to connectivity-based partitioning of brain structures.

We present an automated approach to the problem of connectivity-based partitioning of brain structures using diffusion imaging. White-matter fibres connect different areas of the brain, allowing them to interact with each other. Diffusion-tensor MRI measures the orientation of white-matter fibres in vivo, allowing us to perform connectivity-based partitioning non-invasively. Our new approach leverages atlas-based segmentation to automate anatomical labeling of the cortex. White-matter connectivities are inferred using a probabilistic tractography algorithm that models crossing pathways explicitly. The method is demonstrated with the partitioning of the corpus callosum of eight healthy subjects.

Algorithms↗

PubMed2005

Validation of q-ball imaging with a diffusion fibre-crossing phantom on a clinical scanner.

Magnetic resonance (MR) diffusion imaging provides a valuable tool used for inferring structural anisotropy of brain white matter connectivity from diffusion tensor imaging. Recently, several high angular resolution diffusion models were introduced in order to overcome the inadequacy of the tensor model for describing fibre crossing within a single voxel. Among them, q-ball imaging (QBI), inherited from the q-space method, relies on a spherical Radon transform providing a direct relationship between the diffusion-weighted MR signal and the orientation distribution function (ODF). Experimental validation of these methods in a model system is necessary to determine the accuracy of the methods and to optimize them. A diffusion phantom made up of two textile rayon fibre (comparable in diameter to axons) bundles, crossing at 90 degrees , was designed and dedicated to ex vivo q-ball validation on a clinical scanner. Normalized ODFs were calculated inside regions of interest corresponding to monomodal and bimodal configurations of underlying structures. Three-dimensional renderings of ODFs revealed monomodal shapes for voxels containing single-fibre population and bimodal patterns for voxels located within the crossing area. Principal orientations were estimated from ODFs and were compared with a priori structural fibre directions, validating efficiency of QBI for depicting fibre crossing. In the homogeneous regions, QBI detected the fibre angle with an accuracy of 19 degrees and in the fibre-crossing region with an accuracy of 30 degrees .

Anisotropy↗

PubMed2005

Bilateral limbic diffusion abnormalities in unilateral temporal lobe epilepsy.

Diffusion tensor magnetic resonance imaging can acquire quantitative information on the microstructural integrity of white matter structures and depict brain connectivity in vivo based on the behavior of water diffusion. Diffusion tensor imaging-derived tractography has been used for virtual dissection of the fornix and cingulum in healthy subjects, but not in patients with temporal lobe epilepsy (TLE). Eight patients with medically intractable TLE and unilateral mesial temporal sclerosis and nine healthy control subjects were imaged using diffusion tensor imaging. Fiber tracking was performed to delineate the fornix and cingulum, which were quantitatively analyzed. Bilateral symmetrical reduction in fractional anisotropy was observed in the fornix of patients with TLE, together with an increase in water mobility perpendicular to the axis of the fibers. The findings in the cingulum are similar to those of the fornix with the exception of significantly increased bulk diffusivity in the latter. We observed strikingly symmetrical bilateral abnormalities of axonal integrity in the fornix and cingulum in a series of patients with unilateral mesial temporal sclerosis. Our findings suggest that TLE with unilateral mesial temporal sclerosis is associated with bilateral limbic system pathology.

Adult↗

PubMed2001

A quantitative MR measure of the fornix in schizophrenia.

Some cognitive disturbances accompanying schizophrenia may be due to abnormalities in the thalamus and components of the limbic system. The fornix is an important white-matter relay pathway connecting these structures and is likely to be affected in schizophrenia as well.Magnetic resonance images of the fornix were analyzed in 15 schizophrenic patients and 15 matched comparison group subjects. Fornix volume was compared between the two groups and was also correlated with the volumes of other neuroanatomical structures, as well as with illness presentation, clinical status, and cognitive/psychological measures. There was no significant difference in fornix volume between the two groups. Of note, fornix volume correlated significantly with the volumes of the hippocampus, parahippocampus, and the superior temporal gyrus in the schizophrenic subjects, but not in the controls. Moreover, the correlation between fornix and parahippocampal gyrus volumes differed significantly between the two groups. No association was found between fornix volume and illness presentation or between fornix and cognitive/clinical measures.Results suggest that there are no marked changes in fornix volume in schizophrenia by MRI. The fornix, however, may be part of a network of structures affected in schizophrenia, as indicated by correlated volumetric changes.

Adult↗

PubMed2003

The scaling of white matter to gray matter in cerebellum and neocortex.

It is known that the white matter of neocortex increases disproportionately with brain size. However, relatively few measurements have been made of white matter/gray matter scaling in the cerebellum. We present data on the volumes of white and gray matter in both structures, taken from 45 species of mammals. We find a scaling exponent of 1.13 for cerebellum and 1.28 for neocortex. The 95% confidence intervals for our estimates of these two exponents do not overlap. This difference likely reflects differences in the connectivity and/or micro-structure of white matter in the two regions.

Animals↗

PubMed2004

Increase of white matter string vessels in Alzheimer's disease.

String vessels are collagenous structures connected to capillaries. They have no endothelial cells or lumen. We assessed collagen IV-labeled string vessels in the white matter (WM) of subjects with Alzheimer's disease (AD) (n = 12) and non-AD controls (n = 11) using 100 microm celloidin sections. Ten standard fields were digitally captured and the number and length of normal vessels and string vessels were quantified by computerized image analysis. The WM of the AD-diagnosed individuals contained more strings per mm2 (3.95 +/- 0.49) than comparable WM from controls (1.36 +/- 0.39) (p = 0.0005) and had increased total string vessel length in mm/mm2 (AD = 0.29 +/- 0.04; control = 0.10 +/- 0.03; p = 0.0015). There was a 25% increase (not statistically significant) in vessel density in mm/mm2 in AD subjects (AD = 11.88 +/- 0.87; control = 9.53 +/- 0.78; p = 0.06), presumably due to brain atrophy in the white matter. Although vessel length was slightly increased in AD subjects, they still had more than double the string length per total vessel length (AD = 2.88 +/- 0.38) compared to controls (1.36 +/- 0.27) (p = 0.0057). This increase in string vessels in the white matter of AD subjects suggests a decrease in vascular supply in this disease.

Aged↗

PubMedDate not supplied

White matter reorganization after surgical resection of brain tumors and vascular malformations.

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) and white matter tractography (WMT) are promising techniques for estimating the course, extent, and connectivity patterns of the white matter (WM) structures in the human brain. In this study, DTI and WMT were used to evaluate WM tract reorganization after the surgical resection of brain tumors and vascular malformations. METHODS: Pre- and postoperative DTI data were obtained in 6 patients undergoing surgical resection of brain lesions. WMT using a tensor deflection algorithm was used to reconstruct WM tracts adjacent to the lesions. Reconstructed tracts included corticospinal tracts, the corona radiata, superior longitudinal and inferior fronto-occipital fasciculi, cingulum bundles, and the corpus callosum. RESULTS: WMT revealed a series of tract alteration patterns including deviation, deformation, infiltration, and apparent tract interruption. In general, the organization of WM tracts appeared more similar to normal anatomy after resection, with either disappearance or reduction of the deviation, deformation, or infiltration present preoperatively. In patients whose lesions were associated with corticospinal tract involvement, the WMT reconstructions showed that the tract was preserved during surgery and improved in position and appearance, and this finding correlated with improvement or preservation of motor function as determined by clinical assessment. CONCLUSION: WMT is useful for appreciating the complex relationships between specific WM structures and the anatomic distortions created by brain lesions. Further studies with intraoperative correlation are necessary to confirm these initial findings and to determine WMT utility for presurgical planning and evaluation of surgical treatments.

Adolescent↗

PubMed1996

Maldistribution of interstitial neurons in prefrontal white matter of the brains of schizophrenic patients.

BACKGROUND: The cortical subplate is a transitory structure involved in the formation of connections in developing cerebral cortex. Interstitial neurons, normally present in subcortical white matter (WM) of the adult brain, have escaped the programmed cell death that eliminates most subplate neurons. Previous investigations indicated a maldistribution of one population of interstitial neurons in the WM of brains of schizophrenic patients, suggesting a defect of the subplate during brain development. METHODS: Three histochemically or immunocytochemically defined neuronal populations were studied in WM beneath the middle frontal gyrus of 20 schizophrenic patients and 20 matched control subjects. RESULTS: Brains of schizophrenic patients showed significant changes in the distribution of the three neuronal populations: microtubule-associated protein 2 and nonphosphorylated neurofilament-immunoreactive neurons showed a decreased density in superficial WM and an increased density in deeper WM. Nicotinamide adenine dinucleotide phosphate-diaphorase neurons were reduced in superficial WM and showed variable densities in deeper WM. Thirty-five percent of the brains of schizophrenic patients but no brains of the control subjects showed a maldistribution of neurons toward deeper WM with at least two of the three markers. Changes in neuronal distribution were not linked to age, gender, autolysis time, or subtype of schizophrenia. CONCLUSIONS: Selective displacement of interstitial WM neurons in the frontal lobe of brains of schizophrenic patients may indicate alteration in the migration of subplate neurons or in the pattern of programmed cell death. Both could lead to defective cortical circuitry in the brains of schizophrenic patients.

Adult↗

PubMed2006

Functional magnetic resonance imaging and cognition at the very early stage of MS.

Dysfunction of high controlled information processing is present in patients with multiple sclerosis (MS) right at the beginning of the disease. One hypothesis is that disruption of communication inside large-scale cortical networks, occurring as a consequence of white matter damage, may constitute the anatomical substrate of cognitive impairment at the very early stage of MS. Disturbance of interregional synchronization might be the main pathogenic factor in controlled information processing deficiency in early MS. Preliminary functional MRI studies (fMRI) have provided important clues to corroborate the connectivity hypotheses. First, brain connectivity assessed by fMRI has brought new data about the influence of diffuse white matter damage on connectivity efficiency inside large-scale networks. These studies have suggested that connectivity disturbances occur inside the working memory network in patients at the very early stage of MS and appear related to the extent of structural white matter damage. Also, fMRI studies have suggested that patients may partially compensate for connectivity impairment by a greater cognitive control. Such a compensatory mechanism could limit the determinant functional impact of diffuse white matter damage on high controlled information processing.

Age of Onset↗

PubMed2002

[Interstitial cells of subcortical white matter, their connections, neurochemical specialization, and the role in histogenesis of the cortex].

The literature data and the results of authors' own investigations are presented describing development, structure and neurochemical specialization of interstitial cells of white matter (ICWM) of mammalian animal and human brain. ICWM are derivatives of embryonic subplate and they are conserved in ontogenesis as the residual cellular population of primordial plexiform layer. Main regularities of corticogenesis are considered: neurogenetic "inside-outside" gradient, "radial units" hypothesis, "protomap" model and "handshake" principle of thalamocortical connections formation. Morphogenesis of ICWM is associated with cortical neurons differentiation, modular architectonics and interneuronal connections development. Postnatally these cells form distant connections with neurons of gray matter, express NO-synthase and neuropeptide Y. Alteration of ICWM is associated with the pathogenesis of some neurodegenerative disorders, schisophrenia and Alzheimer's disease. The data obtained support the point of view that permits to consider ICWM as the local cortical interneurons.

Animals↗

PubMed1997

Creating connected representations of cortical gray matter for functional MRI visualization.

We describe a system that is being used to segment gray matter from magnetic resonance imaging (MRI) and to create connected cortical representations for functional MRI visualization (fMRI). The method exploits knowledge of the anatomy of the cortex and incorporates structural constraints into the segmentation. First, the white matter and cerebral spinal fluid (CSF) regions in the MR volume are segmented using a novel techniques of posterior anisotropic diffusion. Then, the user selects the cortical white matter component of interest, and its structure is verified by checking for cavities and handles. After this, a connected representation of the gray matter is created by a constrained growing-out from the white matter boundary. Because the connectivity is computed, the segmentation can be used as input to several methods of visualizing the spatial pattern of cortical activity within gray matter. In our case, the connected representation of gray matter is used to create a flattened representation of the cortex. Then, fMRI measurements are overlaid on the flattened representation, yielding a representation of the volumetric data within a single image. The software is freely available to the research community.

Cerebral Cortex↗