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Altered gray matter morphometry and resting-state functional and structural connectivity in social anxiety disorder

LIAO, Wei; XU, Qiang; MANTINI, Dante; DING, Jurong; MACHADO-DE-SOUSA, Joao Paulo; HALLAK, Jaime E. C.; TRZESNIAK, Clarissa; QIU, Changjian; ZENG, Ling; ZHANG, Wei; CRIPPA, Jose Alexandre S.; GONG, Qiyong; CHEN, Huafu
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.41%
In social anxiety disorder (SAD), impairments in limbic/paralimbic structures are associated with emotional dysregulation and inhibition of the medial prefrontal cortex (MPFq. Little is known, however, about alterations in limbic and frontal regions associated with the integrated morphometric, functional, and structural architecture of SAD. Whether altered gray matter volume is associated with altered functional and structural connectivity in SAD. Three techniques were used with 18 SAD patients and 18 healthy controls: voxel-based morphometry; resting-state functional connectivity analysis; and diffusion tensor imaging tractography. SAD patients exhibited significantly decreased gray matter volumes in the right posterior inferior temporal gyrus (ITG) and right parahippocampal/hippocampal gyrus (PHG/HIP). Gray matter volumes in these two regions negatively correlated with the fear factor of the Liebowitz Social Anxiety Scale. In addition, we found increased functional connectivity in SAD patients between the right posterior ITG and the left inferior occipital gyrus, and between the right PHF/HIP and left middle temporal gyms. SAD patients had increased right MPFC volume, along with enhanced structural connectivity in the genu of the corpus callosum. Reduced limbic/paralimbic volume...

Functional and Structural Connectivity Between the Perigenual Anterior Cingulate and Amygdala in Bipolar Disorder

WANG, Fei; KALMAR, Jessica H.; HE, Yong; JACKOWSKI, Marcel; CHEPENIK, Lara G.; EDMISTON, Erin E.; TIE, Karen; GONG, Gaolang; SHAH, Maulik P.; JONES, Monique; UDERMAN, Jodi; CONSTABLE, R. Todd; BLUMBERG, Hilary P.
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.31%
Objective: Abnormalities in the morphology and function of two gray matter structures central to emotional processing, the perigenual anterior cingulate cortex (pACC) and amygdala, have consistently been reported in bipolar disorder (BD). Evidence implicates abnormalities in their connectivity in BD. This study investigates the potential disruptions in pACC-amygdala functional connectivity and associated abnormalities in white matter that provides structural connections between the two brain regions in BD. Methods: Thirty-three individuals with BD and 31 healthy comparison subjects (HC) participated in a scanning session during which functional magnetic resonance imaging (fMRI) during processing of face stimuli and diffusion tensor imaging (DTI) were performed. The strength of pACC-amygdala functional connections was compared between BD and HC groups, and associations between these functional connectivity measures from the fMRI scans and regional fractional anisotropy (FA) from the DTI scans were assessed. Results: Functional connectivity was decreased between the pACC and amygdala in the BD group compared with HC group, during the processing of fearful and happy faces (p < .005). Moreover, a significant positive association between pACC-amygdala functional coupling and FA in ventrofrontal white matter...

Conectividade estrutural do cérebro: diferenças entre um cérebro normal e um cérebro com patologia

Ferra, Carmen; Ferreira, Hugo Alexandre; Gonçalves Pereira, Pedro; Manaças, Rui; Andrade, Alexandre
Fonte: Escola Superior de Tecnologia da Saúde de Lisboa Publicador: Escola Superior de Tecnologia da Saúde de Lisboa
Tipo: Artigo de Revista Científica
Publicado em /06/2014 POR
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46.36%
Perceber a rede estrutural formada pelos neurónios no cérebro a nível da macro escala é um desafio atual na área das neurociências. Neste estudo analisou-se a conectividade estrutural do cérebro em 22 indivíduos saudáveis e em dois doentes com epilepsia pós-traumática. Avaliaram-se as diferenças entre estes dois grupos. Também se pesquisaram diferenças a nível do género e idade no grupo de indivíduos saudáveis e os que têm valores médios mais elevados nas métricas de caracterização da rede. Para tal, desenvolveu-se um protocolo de análise recorrendo a diversos softwares especializados e usaram-se métricas da Teoria dos Grafos para a caracterização da conectividade estrutural entre 118 regiões encefálicas distintas. Dentro do grupo dos indivíduos saudáveis concluiu-se que os homens, no geral, são os que têm média mais alta para as métricas de caracterização da rede estrutural. Contudo, não se observaram diferenças significativas em relação ao género nas métricas de caracterização global do cérebro. Relativamente à idade, esta correlaciona-se negativamente, no geral, com as métricas de caracterização da rede estrutural. As regiões onde se observaram as diferenças mais importantes entre indivíduos saudáveis e doentes são: o sulco rolândico...

Combining Structural Connectivity and Response Latencies to Model the Structure of the Visual System

Capalbo, Michael; Postma, Eric; Goebel, Rainer
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.35%
Several approaches exist to ascertain the connectivity of the brain, and these approaches lead to markedly different topologies, often incompatible with each other. Specifically, recent single-cell recording results seem incompatible with current structural connectivity models. We present a novel method that combines anatomical and temporal constraints to generate biologically plausible connectivity patterns of the visual system of the macaque monkey. Our method takes structural connectivity data from the CoCoMac database and recent single-cell recording data as input and employs an optimization technique to arrive at a new connectivity pattern of the visual system that is in agreement with both types of experimental data. The new connectivity pattern yields a revised model that has fewer levels than current models. In addition, it introduces subcortical–cortical connections. We show that these connections are essential for explaining latency data, are consistent with our current knowledge of the structural connectivity of the visual system, and might explain recent functional imaging results in humans. Furthermore we show that the revised model is not underconstrained like previous models and can be extended to include newer data and other kinds of data. We conclude that the revised model of the connectivity of the visual system reflects current knowledge on the structure and function of the visual system and addresses some of the limitations of previous models.

Resting-State Functional Connectivity Reflects Structural Connectivity in the Default Mode Network

Greicius, Michael D.; Supekar, Kaustubh; Menon, Vinod; Dougherty, Robert F.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.37%
Resting-state functional connectivity magnetic resonance imaging (fcMRI) studies constitute a growing proportion of functional brain imaging publications. This approach detects temporal correlations in spontaneous blood oxygen level–dependent (BOLD) signal oscillations while subjects rest quietly in the scanner. Although distinct resting-state networks related to vision, language, executive processing, and other sensory and cognitive domains have been identified, considerable skepticism remains as to whether resting-state functional connectivity maps reflect neural connectivity or simply track BOLD signal correlations driven by nonneural artifact. Here we combine diffusion tensor imaging (DTI) tractography with resting-state fcMRI to test the hypothesis that resting-state functional connectivity reflects structural connectivity. These 2 modalities were used to investigate connectivity within the default mode network, a set of brain regions—including medial prefrontal cortex (MPFC), medial temporal lobes (MTLs), and posterior cingulate cortex (PCC)/retropslenial cortex (RSC)—implicated in episodic memory processing. Using seed regions from the functional connectivity maps, the DTI analysis revealed robust structural connections between the MTLs and the retrosplenial cortex whereas tracts from the MPFC contacted the PCC (just rostral to the RSC). The results demonstrate that resting-state functional connectivity reflects structural connectivity and that combining modalities can enrich our understanding of these canonical brain networks.

Disturbed Structural Connectivity in Schizophrenia—Primary Factor in Pathology or Epiphenomenon?

Konrad, Andreas; Winterer, Georg
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.31%
Indirect evidence for disturbed structural connectivity of subcortical fiber tracts in schizophrenia has been obtained from functional neuroimaging and electrophysiologic studies. During the past few years, new structural imaging methods have become available. Diffusion tensor imaging and magnetization transfer imaging (MTI) have been used to investigate directly whether fiber tract abnormalities are indeed present in schizophrenia. To date, findings are inconsistent that may express problems related to methodological issues and sample size. Also, pathological processes detectable with these new techniques are not yet well understood. Nevertheless, with growing evidence of disturbed structural connectivity, myelination has been in the focus of postmortem investigations. Several studies have shown a significant reduction of oligodendroglial cells and ultrastructural alterations of myelin sheats in schizophrenia. There is also growing evidence for abnormal expression of myelin-related genes in schizophrenia: Neuregulin (NRG1) is important for oligodendrocyte development and function, and altered expression of erbB3, one of the NRG1 receptors, has been shown in schizophrenia patients. This is consistent with recent genetic studies suggesting that NRG1 may contribute to the genetic risk for schizophrenia. In conclusion...

Predicting human resting-state functional connectivity from structural connectivity

Honey, C. J.; Sporns, O.; Cammoun, L.; Gigandet, X.; Thiran, J. P.; Meuli, R.; Hagmann, P.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.44%
In the cerebral cortex, the activity levels of neuronal populations are continuously fluctuating. When neuronal activity, as measured using functional MRI (fMRI), is temporally coherent across 2 populations, those populations are said to be functionally connected. Functional connectivity has previously been shown to correlate with structural (anatomical) connectivity patterns at an aggregate level. In the present study we investigate, with the aid of computational modeling, whether systems-level properties of functional networks—including their spatial statistics and their persistence across time—can be accounted for by properties of the underlying anatomical network. We measured resting state functional connectivity (using fMRI) and structural connectivity (using diffusion spectrum imaging tractography) in the same individuals at high resolution. Structural connectivity then provided the couplings for a model of macroscopic cortical dynamics. In both model and data, we observed (i) that strong functional connections commonly exist between regions with no direct structural connection, rendering the inference of structural connectivity from functional connectivity impractical; (ii) that indirect connections and interregional distance accounted for some of the variance in functional connectivity that was unexplained by direct structural connectivity; and (iii) that resting-state functional connectivity exhibits variability within and across both scanning sessions and model runs. These empirical and modeling results demonstrate that although resting state functional connectivity is variable and is frequently present between regions without direct structural linkage...

White matter maturation reshapes structural connectivity in the late developing human brain

Hagmann, P.; Sporns, O.; Madan, N.; Cammoun, L.; Pienaar, R.; Wedeen, V. J.; Meuli, R.; Thiran, J.-P.; Grant, P. E.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.34%
From toddler to late teenager, the macroscopic pattern of axonal projections in the human brain remains largely unchanged while undergoing dramatic functional modifications that lead to network refinement. These functional modifications are mediated by increasing myelination and changes in axonal diameter and synaptic density, as well as changes in neurochemical mediators. Here we explore the contribution of white matter maturation to the development of connectivity between ages 2 and 18 y using high b-value diffusion MRI tractography and connectivity analysis. We measured changes in connection efficacy as the inverse of the average diffusivity along a fiber tract. We observed significant refinement in specific metrics of network topology, including a significant increase in node strength and efficiency along with a decrease in clustering. Major structural modules and hubs were in place by 2 y of age, and they continued to strengthen their profile during subsequent development. Recording resting-state functional MRI from a subset of subjects, we confirmed a positive correlation between structural and functional connectivity, and in addition observed that this relationship strengthened with age. Continuously increasing integration and decreasing segregation of structural connectivity with age suggests that network refinement mediated by white matter maturation promotes increased global efficiency. In addition...

Development of functional and structural connectivity within the default mode network in young children

Supekar, Kaustubh; Uddin, Lucina Q.; Prater, Katherine; Amin, Hitha; Greicius, Michael D.; Menon, Vinod
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.42%
Functional and structural maturation of networks comprised of discrete regions is an important aspect of brain development. The default-mode network (DMN) is a prominent network which includes the posterior cingulate cortex (PCC), medial prefrontal cortex (mPFC), medial temporal lobes (MTL), and angular gyrus (AG). Despite increasing interest in DMN function, little is known about its maturation from childhood to adulthood. Here we examine developmental changes in DMN connectivity using a multimodal imaging approach by combining resting-state fMRI, voxel-based morphometry and diffusion tensor imaging-based tractography. We found that the DMN undergoes significant developmental changes in functional and structural connectivity, but these changes are not uniform across all DMN nodes. Convergent structural and functional connectivity analyses suggest that PCC-mPFC connectivity along the cingulum bundle is the most immature link in the DMN of children. Both PCC and mPFC also showed gray matter volume differences, as well as prominent macrostructural and microstructural differences in the dorsal cingulum bundle linking these regions. Notably, structural connectivity between PCC and left MTL was either weak or non-existent in children, even though functional connectivity did not differ from that of adults. These results imply that functional connectivity in children can reach adult-like levels despite weak structural connectivity. We propose that maturation of PCC-mPFC structural connectivity plays an important role in the development of self-related and social-cognitive functions that emerge during adolescence. More generally...

Altered Functional and Structural Connectivity Networks in Psychogenic Non-Epileptic Seizures

Ding, Ju-Rong; An, Dongmei; Liao, Wei; Li, Jinmei; Wu, Guo-Rong; Xu, Qiang; Long, Zhiliang; Gong, Qiyong; Zhou, Dong; Sporns, Olaf; Chen, Huafu
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 22/05/2013 EN
Relevância na Pesquisa
46.43%
Psychogenic non-epileptic seizures (PNES) are paroxysmal behaviors that resemble epileptic seizures but lack abnormal electrical activity. Recent studies suggest aberrant functional connectivity involving specific brain regions in PNES. Little is known, however, about alterations of topological organization of whole-brain functional and structural connectivity networks in PNES. We constructed functional connectivity networks from resting-state functional MRI signal correlations and structural connectivity networks from diffusion tensor imaging tractography in 17 PNES patients and 20 healthy controls. Graph theoretical analysis was employed to compute network properties. Moreover, we investigated the relationship between functional and structural connectivity networks. We found that PNES patients exhibited altered small-worldness in both functional and structural networks and shifted towards a more regular (lattice-like) organization, which could serve as a potential imaging biomarker for PNES. In addition, many regional characteristics were altered in structural connectivity network, involving attention, sensorimotor, subcortical and default-mode networks. These regions with altered nodal characteristics likely reflect disease-specific pathophysiology in PNES. Importantly...

Altered intrahemispheric structural connectivity in Gilles de la Tourette syndrome☆☆☆

Cheng, Bastian; Braass, Hanna; Ganos, Christos; Treszl, Andras; Biermann-Ruben, Katja; Hummel, Friedhelm C.; Müller-Vahl, Kirsten; Schnitzler, Alfons; Gerloff, Christian; Münchau, Alexander; Thomalla, Götz
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 07/12/2013 EN
Relevância na Pesquisa
46.38%
Gilles de la Tourette syndrome (GTS) is a common developmental neuropsychiatric disorder characterized by tics and frequent psychiatric comorbidities, often causing significant disability. Tic generation has been linked to disturbed networks of brain areas involved in planning, controlling and execution of actions, particularly structural and functional disorders in the striatum and cortico–striato–thalamo–cortical loops. We therefore applied structural diffusion tensor imaging (DTI) to characterize changes in intrahemispheric white matter connectivity in cortico-subcortical circuits engaged in motor control in 15 GTS patients without psychiatric comorbidities. White matter connectivity was analyzed by probabilistic fiber tractography between 12 predefined cortical and subcortical regions of interest. Connectivity values were combined with measures of clinical severity rated by the Yale Global Tic Severity Scale (YGTSS). GTS patients showed widespread structural connectivity deficits. Lower connectivity values were found specifically in tracts connecting the supplementary motor areas (SMA) with basal ganglia (pre-SMA–putamen, SMA–putamen) and in frontal cortico-cortical circuits. There was an overall trend towards negative correlations between structural connectivity in these tracts and YGTSS scores. Structural connectivity of frontal brain networks involved in planning...

A multimodal approach for determining brain networks by jointly modeling functional and structural connectivity

Xue, Wenqiong; Bowman, F. DuBois; Pileggi, Anthony V.; Mayer, Andrew R.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 20/02/2015 EN
Relevância na Pesquisa
46.3%
Recent innovations in neuroimaging technology have provided opportunities for researchers to investigate connectivity in the human brain by examining the anatomical circuitry as well as functional relationships between brain regions. Existing statistical approaches for connectivity generally examine resting-state or task-related functional connectivity (FC) between brain regions or separately examine structural linkages. As a means to determine brain networks, we present a unified Bayesian framework for analyzing FC utilizing the knowledge of associated structural connections, which extends an approach by Patel et al. (2006a) that considers only functional data. We introduce an FC measure that rests upon assessments of functional coherence between regional brain activity identified from functional magnetic resonance imaging (fMRI) data. Our structural connectivity (SC) information is drawn from diffusion tensor imaging (DTI) data, which is used to quantify probabilities of SC between brain regions. We formulate a prior distribution for FC that depends upon the probability of SC between brain regions, with this dependence adhering to structural-functional links revealed by our fMRI and DTI data. We further characterize the functional hierarchy of functionally connected brain regions by defining an ascendancy measure that compares the marginal probabilities of elevated activity between regions. In addition...

A Constraint Handling Strategy for Bit-Array Representation GA in Structural Topology Optimization

Wang, Shengyin; Tai, Kang
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 197914 bytes; application/pdf
EN_US
Relevância na Pesquisa
56.24%
In this study, an improved bit-array representation method for structural topology optimization using the Genetic Algorithm (GA) is proposed. The issue of representation degeneracy is fully addressed and the importance of structural connectivity in a design is further emphasized. To evaluate the constrained objective function, Deb's constraint handling approach is further developed to ensure that feasible individuals are always better than infeasible ones in the population to improve the efficiency of the GA. A hierarchical violation penalty method is proposed to drive the GA search towards the topologies with higher structural performance, less unusable material and fewer separate objects in the design domain in a hierarchical manner. Numerical results of structural topology optimization problems of minimum weight and minimum compliance designs show the success of this novel bit-array representation method and suggest that the GA performance can be significantly improved by handling the design connectivity properly.; Singapore-MIT Alliance (SMA)

Exploratory graphical models of functional and structural connectivity patterns for Alzheimer's Disease diagnosis

Ortiz, Andrés; Munilla, Jorge; Álvarez-Illán, Ignacio; Górriz, Juan M.; Ramírez, Javier;
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 03/11/2015 EN
Relevância na Pesquisa
46.31%
Alzheimer's Disease (AD) is the most common neurodegenerative disease in elderly people. Its development has been shown to be closely related to changes in the brain connectivity network and in the brain activation patterns along with structural changes caused by the neurodegenerative process. Methods to infer dependence between brain regions are usually derived from the analysis of covariance between activation levels in the different areas. However, these covariance-based methods are not able to estimate conditional independence between variables to factor out the influence of other regions. Conversely, models based on the inverse covariance, or precision matrix, such as Sparse Gaussian Graphical Models allow revealing conditional independence between regions by estimating the covariance between two variables given the rest as constant. This paper uses Sparse Inverse Covariance Estimation (SICE) methods to learn undirected graphs in order to derive functional and structural connectivity patterns from Fludeoxyglucose (18F-FDG) Position Emission Tomography (PET) data and segmented Magnetic Resonance images (MRI), drawn from the ADNI database, for Control, MCI (Mild Cognitive Impairment Subjects), and AD subjects. Sparse computation fits perfectly here as brain regions usually only interact with a few other areas. The models clearly show different metabolic covariation patters between subject groups...

Functional and structural connectivity of frontostriatal circuitry in Autism Spectrum Disorder

Delmonte, Sonja; Gallagher, Louise; O'Hanlon, Erik; McGrath, Jane; Balsters, Joshua H.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 06/08/2013 EN
Relevância na Pesquisa
46.38%
Abnormalities in frontostriatal circuitry potentially underlie the two core deficits in Autism Spectrum Disorder (ASD); social interaction and communication difficulties and restricted interests and repetitive behaviors. Whilst a few studies have examined connectivity within this circuitry in ASD, no previous study has examined both functional and structural connectivity within the same population. The present study provides the first exploration of both functional and structural frontostriatal connectivity in ASD. Twenty-eight right-handed Caucasian male ASD (17.28 ± 3.57 years) and 27 right-handed male, age and IQ matched controls (17.15 ± 3.64 years) took part in the study. Resting state functional connectivity was carried out on 21 ASD and control participants, and tractography was carried out on 22 ASD and 24 control participants, after excluding subjects for excessive motion and poor data quality. Functional connectivity analysis was carried out between the frontal cortex and striatum after which tractography was performed between regions that showed significant group differences in functional connectivity. The ASD group showed increased functional connectivity between regions in the frontal cortex [anterior cingulate cortex (ACC)...

An Integrated Framework for High Angular Resolution Diffusion Imaging–Based Investigation of Structural Connectivity

Bloy, Luke; Ingalhalikar, Madhura; Batmanghelich, Nematollah K.; Schultz, Robert T.; Roberts, Timothy P.L.; Verma, Ragini
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
Publicado em /04/2012 EN
Relevância na Pesquisa
46.42%
Structural connectivity models hold great promise for expanding what is known about the ways information travels throughout the brain. The physiologic interpretability of structural connectivity models depends heavily on how the connections between regions are quantified. This article presents an integrated structural connectivity framework designed around such an interpretation. The framework provides three measures to characterize the structural connectivity of a subject: (1) the structural connectivity matrix describing the proportion of connections between pairs of nodes, (2) the nodal connection distribution (nCD) characterizing the proportion of connections that terminate in each node, and (3) the connection density image, which presents the density of connections as they traverse through white matter (WM). Individually, each possesses different information concerning the structural connectivity of the individual and could potentially be useful for a variety of tasks, ranging from characterizing and localizing group differences to identifying novel parcellations of the cortex. The efficiency of the proposed framework allows the determination of large structural connectivity networks, consisting of many small nodal regions, providing a more detailed description of a subject's connectivity. The nCD provides a gray matter contrast that can potentially aid in investigating local cytoarchitecture and connectivity. Similarly...

Structural Connectivity is Differently Altered in Dementia with Lewy Body and Alzheimer’s Disease

Delli Pizzi, Stefano; Franciotti, Raffaella; Taylor, John-Paul; Esposito, Roberto; Tartaro, Armando; Thomas, Astrid; Onofrj, Marco; Bonanni, Laura
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 02/11/2015 EN
Relevância na Pesquisa
46.35%
The structural connectivity within cortical areas and between cortical and subcortical structures was investigated in dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD). We hypothesized that white matter (WM) tracts, which are linked to visual, attentional, and mnemonic functions, would be differentially and selectively affected in DLB as compared to AD and age-matched control subjects. Structural tensor imaging and diffusion tensor imaging (DTI) were performed on 14 DLB patients, 14 AD patients, and 15 controls. DTI metrics related to WM damage were assessed within tracts reconstructed by FreeSurfer’s TRActs Constrained by UnderLying Anatomy pipeline. Correlation analysis between WM and gray matter (GM) metrics was performed to assess whether the structural connectivity alteration in AD and DLB could be secondary to GM neuronal loss or a consequence of direct WM injury. Anterior thalamic radiation (ATR) and cingulum-cingulate gyrus were altered in DLB, whereas cingulum-angular bundle (CAB) was disrupted in AD. In DLB patients, secondary axonal degeneration within ATR was found in relation to microstructural damage within medio-dorsal thalamus, whereas axonal degeneration within CAB was related to precuneus thinning. WM alteration within the uncinate fasciculus was present in both groups of patients and was related to frontal and to temporal thinning in DLB and AD...

The Structural Connectivity Pattern of the Default Mode Network and Its Association with Memory and Anxiety

Tao, Yan; Liu, Bing; Zhang, Xiaolong; Li, Jin; Qin, Wen; Yu, Chunshui; Jiang, Tianzi
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 26/11/2015 EN
Relevância na Pesquisa
46.34%
The default mode network (DMN) is one of the most widely studied resting state functional networks. The structural basis for the DMN is of particular interest and has been studied by several researchers using diffusion tensor imaging (DTI). Most of these previous studies focused on a few regions or white matter tracts of the DMN so that the global structural connectivity pattern and network properties of the DMN remain unclear. Moreover, evidences indicate that the DMN is involved in both memory and emotion, but how the DMN regulates memory and anxiety from the perspective of the whole DMN structural network remains unknown. We used multimodal neuroimaging methods to investigate the structural connectivity pattern of the DMN and the association of its network properties with memory and anxiety in 205 young healthy subjects with age ranging from 18 to 29 years old. The Group ICA method was used to extract the DMN component from functional magnetic resonance imaging (fMRI) data and a probabilistic fiber tractography technique based on DTI data was applied to construct the global structural connectivity pattern of the DMN. Then we used the graph theory method to analyze the DMN structural network and found that memory quotient (MQ) score was significantly positively correlated with the global and local efficiency of the DMN whereas anxiety was found to be negatively correlated with the efficiency. The strong structural connectivity between multiple brain regions within DMN may reflect that the DMN has certain structural basis. Meanwhile...

On inferring structural connectivity from brain functional-MRI data

Sarkar, Somwrita; Chawla, Sanjay; Xu, Donna
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/02/2015
Relevância na Pesquisa
46.32%
The anatomical structure of the brain can be observed via non-invasive techniques such as diffusion imaging. However, these are imperfect because they miss connections that are actually known to exist, especially long range inter-hemispheric ones. In this paper we formulate the inverse problem of inferring the structural connectivity of brain networks from experimentally observed functional connectivity via functional Magnetic Resonance Imaging (fMRI), by formulating it as a convex optimization problem. We show that structural connectivity can be modeled as an optimal sparse representation derived from the much denser functional connectivity in the human brain. Using only the functional connectivity data as input, we present (a) an optimization problem that models constraints based on known physiological observations, and (b) an ADMM algorithm for solving it. The algorithm not only recovers the known structural connectivity of the brain, but is also able to robustly predict the long range inter-hemispheric connections missed by DSI or DTI, including a very good match with experimentally observed quantitative distributions of the weights/strength of anatomical connections. We demonstrate results on both synthetic model data and a fine-scale 998 node cortical dataset...

Structural connectivity based on diffusion Kurtosis imaging

Loução, Ricardo Sérgio Gomes Almeida
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /09/2015 ENG
Relevância na Pesquisa
66.24%
Structural connectivity models based on Diffusion Tensor Imaging (DTI) are strongly affected by the technique’s inability to resolve crossing fibres, either intra- or inter-hemispherical connections. Several models have been proposed to address this issue, including an algorithm aiming to resolve crossing fibres which is based on Diffusion Kurtosis Imaging (DKI). This technique is clinically feasible, even when multi-band acquisitions are not available, and compatible with multi-shell acquisition schemes. DKI is an extension of DTI enabling the estimation of diffusion tensor and diffusion kurtosis metrics. In this study we compare the performance of DKI and DTI in performing structural brain connectivity. Six healthy subjects were recruited, aged between 25 and 35 (three females). The MRI experiments were performed using a 3T Siemens Trio with a 32-channel head coil. The scans included a T1-weighted sequence (1mm3), and a DWI with b-values 0, 1000 and 2000 s:mm