401
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Petti M, Pichiorri F, Toppi J, Cincotti F, Salinari S, Babiloni F, Mattia D, Astolfi L. Individual cortical connectivity changes after stroke: a resampling approach to enable statistical assessment at single-subject level. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2014; 2014:2785-2788. [PMID: 25570569 DOI: 10.1109/embc.2014.6944201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
One of the main limitations commonly encountered when dealing with the estimation of brain connectivity is the difficulty to perform a statistical assessment of significant changes in brain networks at a single-subject level. This is mainly due to the lack of information about the distribution of the connectivity estimators at different conditions. While group analysis is commonly adopted to perform a statistical comparison between conditions, it may impose major limitations when dealing with the heterogeneity expressed by a given clinical condition in patients. This holds true particularly for stroke when seeking for quantitative measurements of the efficacy of any rehabilitative intervention promoting recovery of function. The need is then evident of an assessment which may account for individual pathological network configuration associated with different level of patients' response to treatment; such network configuration is highly related to the effect that a given brain lesion has on neural networks. In this study we propose a resampling-based approach to the assessment of statistically significant changes in cortical connectivity networks at a single subject level. First, we provide the results of a simulation study testing the performances of the proposed approach under different conditions. Then, to show the sensitivity of the method, we describe its application to electroencephalographic (EEG) data recorded from two post-stroke patients who showed different clinical recovery after a rehabilitative intervention.
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402
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Gratton C, Lee TG, Nomura EM, D'Esposito M. The effect of theta-burst TMS on cognitive control networks measured with resting state fMRI. Front Syst Neurosci 2013; 7:124. [PMID: 24416003 PMCID: PMC3874542 DOI: 10.3389/fnsys.2013.00124] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 12/15/2013] [Indexed: 01/12/2023] Open
Abstract
IT HAS BEEN PROPOSED THAT TWO RELATIVELY INDEPENDENT COGNITIVE CONTROL NETWORKS EXIST IN THE BRAIN: the cingulo-opercular network (CO) and the fronto-parietal network (FP). Past work has shown that chronic brain lesions affect these networks independently. It remains unclear, however, how these two networks are affected by acute brain disruptions. To examine this, we conducted a within-subject theta-burst transcranial magnetic stimulation (TBS) experiment in healthy individuals that targeted left anterior insula/frontal operculum (L aI/fO, a region in the CO network), left dorsolateral prefrontal cortex (L dlPFC, a region in the FP network), or left primary somatosensory cortex (L S1, an experimental control region). Functional connectivity (FC) was measured in resting state fMRI scans collected before and after continuous TBS on each day. We found that TBS was accompanied by generalized increases in network connectivity, especially FP network connectivity, after TBS to either region involved in cognitive control. Whole-brain analyses demonstrated that the L dlPFC and L aI/fO showed increased connectivity with regions in frontal, parietal, and cingulate cortex after TBS to either L dlPFC or L aI/fO, but not to L S1. These results suggest that acute disruption by TBS to cognitive control regions causes widespread changes in network connectivity not limited to the targeted networks.
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Affiliation(s)
- Caterina Gratton
- Helen Wills Neuroscience Institute, University of California Berkeley, CA, USA
| | - Taraz G Lee
- Helen Wills Neuroscience Institute, University of California Berkeley, CA, USA ; Department of Psychology, University of California Berkeley, CA, USA
| | - Emi M Nomura
- Helen Wills Neuroscience Institute, University of California Berkeley, CA, USA
| | - Mark D'Esposito
- Helen Wills Neuroscience Institute, University of California Berkeley, CA, USA ; Department of Psychology, University of California Berkeley, CA, USA
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403
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Li W, Huang Y, Li Y, Chen X. Brain network evolution after stroke based on computational experiments. PLoS One 2013; 8:e82845. [PMID: 24376592 PMCID: PMC3869721 DOI: 10.1371/journal.pone.0082845] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/28/2013] [Indexed: 12/31/2022] Open
Abstract
Stroke is a frequently-occurring disease threatening the human nervous system. As a serious debilitation affecting a large-scale, hierarchical, and vastly complex electrochemical system, stroke remains relatively misunderstood. Rehabilitation mechanisms and means have suffered from this lack of systematic understanding. Here we propose an evolution model to simulate the dynamic actual evolvement process of functional brain networks computationally in an effort to address current shortcomings in the state of the field. According to simulation results, we conclude that the brain networks of patients following acute stroke were characterized by lower small worldness and lower quantity of long-distance connections compared with the healthy condition. Moreover, distance penalization may be used to describe the general mechanism of brain network evolution in the acute period after stroke.
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Affiliation(s)
- Wei Li
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, P. R. China
- Department of Intelligent Science and Technology, College of Automation, Huazhong University of Science and Technology, Wuhan, P. R. China
| | - Yue Huang
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, P. R. China
- Department of Intelligent Science and Technology, College of Automation, Huazhong University of Science and Technology, Wuhan, P. R. China
| | - Yapeng Li
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, P. R. China
- Department of Intelligent Science and Technology, College of Automation, Huazhong University of Science and Technology, Wuhan, P. R. China
| | - Xi Chen
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, P. R. China
- Department of Systems Science and Engineering, College of Automation, Huazhong University of Science and Technology, Wuhan, P. R. China
- * E-mail:
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404
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Motor execution and motor imagery: a comparison of functional connectivity patterns based on graph theory. Neuroscience 2013; 261:184-94. [PMID: 24333970 DOI: 10.1016/j.neuroscience.2013.12.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 12/01/2013] [Accepted: 12/03/2013] [Indexed: 11/20/2022]
Abstract
Motor execution and imagery (ME and MI), as the basic abilities of human beings, have been considered to be effective strategies in motor skill learning and motor abilities rehabilitation. Neuroimaging studies have revealed several critical regions from functional activation for ME as well as MI. Recently, investigations have probed into functional connectivity of ME; however, few explorations compared the functional connectivity between the two tasks. With betweenness centrality (BC) of graph theory, we explored and compared the functional connectivity between two finger tapping tasks of ME and MI. Our results showed that using BC, the key node for the ME task mainly focused on the supplementary motor area, while the key node for the MI task mainly located in the right premotor area. These results characterized the connectivity patterns of ME and MI and may provide new insights into the neural mechanism underlying motor execution and imagination of movements.
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405
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Shi L, Wang D, Chu WCW, Liu S, Xiong Y, Wang Y, Wang Y, Wong LKS, Mok VCT. Abnormal organization of white matter network in patients with no dementia after ischemic stroke. PLoS One 2013; 8:e81388. [PMID: 24349063 PMCID: PMC3862493 DOI: 10.1371/journal.pone.0081388] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 10/12/2013] [Indexed: 01/07/2023] Open
Abstract
Structural changes after ischemic stroke could affect information communication extensively in the brain network. It is likely that the defects in the white matter (WM) network play a key role in information interchange. In this study, we used graph theoretical analysis to examine potential organization alteration in the WM network architecture derived from diffusion tensor images from subjects with no dementia and experienced stroke in the past 5.4-14.8 months (N = 47, Mini-Mental Screening Examination, MMSE range 18-30), compared with a normal control group with 44 age and gender-matched healthy volunteers (MMSE range 26-30). Region-wise connectivity was derived from fiber connection density of 90 different cortical and subcortical parcellations across the whole brain. Both normal controls and patients with chronic stroke exhibited efficient small-world properties in their WM structural networks. Compared with normal controls, topological efficiency was basically unaltered in the patients with chronic stroke, as reflected by unchanged local and global clustering coefficient, characteristic path length, and regional efficiency. No significant difference in hub distribution was found between normal control and patient groups. Patients with chronic stroke, however, were found to have reduced betweenness centrality and predominantly located in the orbitofrontal cortex, whereas increased betweenness centrality and vulnerability were observed in parietal-occipital cortex. The National Institutes of Health Stroke Scale (NIHSS) score of patient is correlated with the betweenness centrality of right pallidum and local clustering coefficient of left superior occipital gyrus. Our findings suggest that patients with chronic stroke still exhibit efficient small-world organization and unaltered topological efficiency, with altered topology at orbitofrontal cortex and parietal-occipital cortex in the overall structural network. Findings from this study could help in understanding the mechanism of cognitive impairment and functional compensation occurred in patients with chronic stroke.
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Affiliation(s)
- Lin Shi
- Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Defeng Wang
- Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
- CUHK Shenzhen Research Institute, Shenzhen, China
- * E-mail: (DW); (VCTM)
| | - Winnie C. W. Chu
- Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Shangping Liu
- Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yunyun Xiong
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yilong Wang
- Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Yongjun Wang
- Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Lawrence K. S. Wong
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Vincent C. T. Mok
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
- * E-mail: (DW); (VCTM)
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406
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Yin D, Song F, Xu D, Sun L, Men W, Zang L, Yan X, Fan M. Altered topological properties of the cortical motor-related network in patients with subcortical stroke revealed by graph theoretical analysis. Hum Brain Mapp 2013; 35:3343-59. [PMID: 24222337 DOI: 10.1002/hbm.22406] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/27/2013] [Accepted: 09/09/2013] [Indexed: 11/10/2022] Open
Abstract
Cerebral neuroplasticity after stroke has been elucidated by functional neuroimaging. However, little is known concerning how topological properties of the cortical motor-related network evolved following subcortical stroke. In the present study, we investigated 24 subcortical stroke patients with only left motor pathway damaged and 24 matched healthy controls. A cortical motor-related network consisting of 20 brain regions remote from the primary lesion was constructed using resting-state functional MRI datasets. We subsequently used graph theoretical approaches to analyze the topological properties of this network in both stroke patients and healthy controls. In addition, we divided the stroke patients into two subgroups according to their outcomes in hand function to explore relationships between topological properties of this network and outcomes in hand function. Although we observed that the cortical motor-related network in both healthy controls and stroke patients exhibited small-world topology, the local efficiency of this network in stroke patients is higher than and global efficiency is lower than those in healthy controls. In addition, striking alterations in the betweenness centrality of regions were found in stroke patients, including the contralesional supplementary motor area, dorsolateral premotor cortex, and anterior inferior cerebellum. Moreover, we observed significant correlations between betweenness centrality of regions and Fugl-Meyer assessment scores. A tendency for the cortical motor-related network to be close to a regular configuration and altered betweenness centrality of regions were demonstrated in patients with subcortical stroke. This study provided insight into functional organization after subcortical stroke from the viewpoint of network topology.
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Affiliation(s)
- Dazhi Yin
- Shanghai Key Laboratory of Magnetic Resonance, Key Laboratory of Brain Function Genomics, East China Normal University, Shanghai, China
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407
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Haller S, Kopel R, Jhooti P, Haas T, Scharnowski F, Lovblad KO, Scheffler K, Van De Ville D. Dynamic reconfiguration of human brain functional networks through neurofeedback. Neuroimage 2013; 81:243-252. [DOI: 10.1016/j.neuroimage.2013.05.019] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 04/29/2013] [Accepted: 05/05/2013] [Indexed: 11/24/2022] Open
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408
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Yan J, Sun J, Guo X, Jin Z, Li Y, Li Z, Tong S. Motor imagery cognitive network after left ischemic stroke: study of the patients during mental rotation task. PLoS One 2013; 8:e77325. [PMID: 24167569 PMCID: PMC3805593 DOI: 10.1371/journal.pone.0077325] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 09/09/2013] [Indexed: 11/18/2022] Open
Abstract
Although motor imagery could improve motor rehabilitation, the detailed neural mechanisms of motor imagery cognitive process of stroke patients, particularly from functional network perspective, remain unclear. This study investigated functional brain network properties in each cognitive sub-stage of motor imagery of stroke patients with ischemic lesion in left hemisphere to reveal the impact of stroke on the cognition of motor imagery. Both stroke patients and control subjects participated in mental rotation task, which includes three cognitive sub-stages: visual stimulus perception, mental rotation and response cognitive process. Event-related electroencephalograph was recorded and interdependence between two different cortical areas was assessed by phase synchronization. Both global and nodal properties of functional networks in three sub-stages were statistically analyzed. Phase synchronization of stroke patients significantly reduced in mental rotation sub-stage. Longer characteristic path length and smaller global clustering coefficient of functional network were observed in patients in mental rotation sub-stage which implied the impaired segregation and integration. Larger nodal clustering coefficient and betweenness in contralesional occipitoparietal and frontal area respectively were observed in patients in all sub-stages. In addition, patients also showed smaller betweenness in ipsilesional central-parietal area in response sub-stage. The compensatory effects on local connectedness and centrality indicated the neuroplasticity in contralesional hemisphere. The functional brain networks of stroke patients demonstrated significant alterations and compensatory effects during motor imagery.
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Affiliation(s)
- Jing Yan
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Junfeng Sun
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
- Med-X Research Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoli Guo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zheng Jin
- Department of Neurology, The Fifth People’s Hospital of Shanghai, Shanghai, China
| | - Yao Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
- Med-X Research Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Zhijun Li
- Department of Automation, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Shanbao Tong
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
- Med-X Research Institute, Shanghai Jiao Tong University, Shanghai, China
- * E-mail:
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409
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Vukelić M, Bauer R, Naros G, Naros I, Braun C, Gharabaghi A. Lateralized alpha-band cortical networks regulate volitional modulation of beta-band sensorimotor oscillations. Neuroimage 2013; 87:147-53. [PMID: 24121086 DOI: 10.1016/j.neuroimage.2013.10.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 01/21/2023] Open
Abstract
Sensorimotor rhythms (SMRs) are oscillatory brain activities in the α- and β-bands across the sensorimotor regions of the brain. Each frequency band has its own specific function. The α-band oscillations are closely related to intrinsic cortical networks, whereas oscillations in the β-band are relevant for the information transfer between the cortex and periphery, as well as for visual and proprioceptive feedback. This study aimed to investigate the interaction between these two frequency bands, under the premise that the regional modulation of β-band power is linked to a cortical network in the α-band. We therefore designed a procedure to maximize the modulation of β-band activity over the sensorimotor cortex by combining kinesthetic motor-imagery with closed-loop haptic feedback. The cortical network activity during this procedure was estimated via the phase slope index in electroencephalographic recordings. Analysis of effective connectivity within the α-band network revealed an information flow between the precentral (premotor and primary motor), postcentral (primary somatosensory) and parietal cortical areas. The range of β-modulation was connected to a reduction of an ipsilateral sensorimotor and parietal α-network and, consequently, to a lateralization of this network to the contralateral side. These results showed that regional sensorimotor oscillatory activity in the β-band was regulated by cortical coupling of distant areas in the α-band.
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Affiliation(s)
- Mathias Vukelić
- Division of Translational Neurosurgery and Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, and Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
| | - Robert Bauer
- Division of Translational Neurosurgery and Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, and Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
| | - Georgios Naros
- Division of Translational Neurosurgery and Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, and Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
| | - Ilias Naros
- Division of Translational Neurosurgery and Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, and Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
| | - Christoph Braun
- MEG Center, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
| | - Alireza Gharabaghi
- Division of Translational Neurosurgery and Division of Functional and Restorative Neurosurgery, Department of Neurosurgery, and Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany.
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410
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Dang C, Liu G, Xing S, Xie C, Peng K, Li C, Li J, Zhang J, Chen L, Pei Z, Zeng J. Longitudinal Cortical Volume Changes Correlate With Motor Recovery in Patients After Acute Local Subcortical Infarction. Stroke 2013; 44:2795-801. [PMID: 23929747 DOI: 10.1161/strokeaha.113.000971] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Secondary changes in the volume of motor-related cortical regions and the relationship with functional recovery during the acute stage after cerebral infarction have not been determined. In the present study, we quantified changes in gray matter (GM) volume in motor-related cortical regions and analyzed their correlations to clinical scores in patients with focal cerebral infarct.
Methods—
Fifteen patients with acute subcortical infarct underwent longitudinal high-resolution structural MRI and clinical assessment 3 times during a 12-week period (weeks 1, 4, and 12). Fourteen age- and sex-matched controls underwent MRI examination. Voxel-based morphometry was used to quantify changes in global GM volume; in addition, relationships between GM volume changes in volumes of interest and clinical scores were analyzed.
Results—
In patients with cerebral infarction, GM volumes detected by voxel-based morphometry both decreased and increased significantly in diffuse cortical regions during the observation period (
P
<0.001). GM volumes within volumes of interest decreased significantly in the ipsilateral supplementary motor area and contralateral insula, but they increased in the contralateral supplementary motor area over time (all
P
<0.017). The changes of GM volumes in the ipsilesional and contralesional supplementary motor area correlated with the changes in the Fugl–Meyer scale scores (ipsilesional,
r
s
=0.52;
P
=0.048; contralesional,
r
s
=0.74;
P
=0.002) and Barthel Index (ipsilesional,
r
s
=0.56;
P
=0.030; contralesional,
r
s
=0.65;
P
=0.009).
Conclusions—
These results suggest that secondary GM changes occur in diffuse areas and structural changes in some specific motor-related cortex may inhibit or promote functional recovery after an acute subcortical cerebral infarct.
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Affiliation(s)
- Chao Dang
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Gang Liu
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Shihui Xing
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Chuanmiao Xie
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Kangqiang Peng
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Chuo Li
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Jingjing Li
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Jian Zhang
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Li Chen
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Zhong Pei
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
| | - Jinsheng Zeng
- From the Department of Neurology and Stroke Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China (C.D., G.L., S.X., J.L., J.Z., L.C., Z.P., J.Z.); State Key Laboratory of Oncology in Southern China, Imaging Diagnosis and Interventional Center, Cancer Center, Sun Yat-Sen University, Guangzhou, China (C.X., K.P.); and Department of Internal Medicine, Eighth People’s Hospital, Guangzhou, China (C.L.)
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411
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Li Y, Qin Y, Chen X, Li W. Exploring the functional brain network of Alzheimer's disease: based on the computational experiment. PLoS One 2013; 8:e73186. [PMID: 24019905 PMCID: PMC3760893 DOI: 10.1371/journal.pone.0073186] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 07/17/2013] [Indexed: 12/19/2022] Open
Abstract
The purpose of this study is to explore the changes in functional brain networks of AD patients using complex network theory. In this study, resting-state fMRI datasets of 10 AD patients and 11 healthy controls were collected. Time series of 90 brain regions were extracted from the fMRI datasets after preprocessing. Pearson correlation method was used to calculate the correlation coefficient between any two time series. Then, a wide threshold range was selected to transform the adjacency matrix to a binary matrix under a different threshold. The topology parameters of each binary network were calculated, and all of them were then averaged within a group. During the evolution, node betweenness and the Euclidean distance between the nodes were set as control factors. Each binary network of healthy controls underwent evolution of 100 steps in accordance with the evolution rules. Then, the topology parameters of the evolution network were calculated. Finally, support vector machine (SVM) was used to classify the network topology parameters of the evolution network and to determine whether evolution results matched the datasets from AD patients. We found there were differing degrees of decline in global efficiency, clustering coefficient, number of edges and transitivity in AD patients compared with healthy controls. The topology parameters of the evolution network tended toward those of the AD group. The results of SVM classification of the evolution network show that the evolution network had a greater probability to be classified as an AD patients group. A new biological marker for diagnosis of AD was provided through comparison of topology parameters between AD patients and healthy controls. The study of network evolution strategies enriched the method of brain network evolution. The use of SVM to classify the results of network evolution provides an objective criteria for determining evolution results.
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Affiliation(s)
- YaPeng Li
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, China
- Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Yuanyuan Qin
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xi Chen
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, China
- Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Wei Li
- Image Processing and Intelligent Control Key Laboratory of Education Ministry of China, Wuhan, China
- Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
- * E-mail:
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412
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Carey LM, Seitz RJ, Parsons M, Levi C, Farquharson S, Tournier JD, Palmer S, Connelly A. Beyond the lesion: neuroimaging foundations for post-stroke recovery. FUTURE NEUROLOGY 2013. [DOI: 10.2217/fnl.13.39] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A shift is emerging in the way in which we view post-stroke recovery. This shift, supported by evidence from neuroimaging studies, encourages us to look beyond the lesion and to identify viable brain networks with capacity for plasticity. In this article, the authors review current advances in neuroimaging techniques and the new insights that they have contributed. The ability to quantify salvageable tissue, evidence of changes in remote networks, changes of functional and structural connectivity, and alterations in cortical thickness are reviewed in the context of their impact on post-stroke recovery. The value of monitoring spared structural connections and functional connectivity of brain networks within and across hemispheres is highlighted.
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Affiliation(s)
- Leeanne M Carey
- Department of Occupational Therapy, La Trobe University, Bundoora, Australia
| | - Rüdiger J Seitz
- Centre of Neurology & Neuropsychiatry, LVR-Klinikum Düsseldorf, Germany
- Department of Neurology, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf; Bergische Landstrasse 2, 40629 Düsseldorf, Germany
| | - Mark Parsons
- Stroke Program, Centre for Translational Neuroscience & Mental Health Research, University of Newcastle, Newcastle, Australia
- Hunter Medical Research Institute, Department of Neurology, John Hunter Hospital, Lookout Road, New Lambton, NSW, 2305, Australia
| | - Christopher Levi
- Stroke Program, Centre for Translational Neuroscience & Mental Health Research, University of Newcastle, Newcastle, Australia
- Hunter Medical Research Institute, Department of Neurology, John Hunter Hospital, Lookout Road, New Lambton, NSW, 2305, Australia
| | - Shawna Farquharson
- Imaging Division, The Florey Institute of Neuroscience & Mental Health, Melbourne Brain Centre, 245 Burgundy Street, Heidelberg, 3084, Australia
- Department of Medical Imaging & Radiation Science, Monash University, Melbourne, Australia
| | - Jacques-Donald Tournier
- Imaging Division, The Florey Institute of Neuroscience & Mental Health, Melbourne Brain Centre, 245 Burgundy Street, Heidelberg, 3084, Australia
| | - Susan Palmer
- Neurorehabilitation & Recovery, Stroke Division, The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Melbourne Brain Centre, Austin Campus, 245 Burgundy Street, Heidelberg, Victoria, 3084, Australia
| | - Alan Connelly
- Imaging Division, The Florey Institute of Neuroscience & Mental Health, Melbourne Brain Centre, 245 Burgundy Street, Heidelberg, 3084, Australia
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413
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Li S, Wang B, Xu P, Lin Q, Gong G, Peng X, Fan Y, He Y, Huang R. Increased global and local efficiency of human brain anatomical networks detected with FLAIR-DTI compared to non-FLAIR-DTI. PLoS One 2013; 8:e71229. [PMID: 23967170 PMCID: PMC3742791 DOI: 10.1371/journal.pone.0071229] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 06/30/2013] [Indexed: 11/30/2022] Open
Abstract
Diffusion-weighted MRI (DW-MRI), the only non-invasive technique for probing human brain white matter structures in vivo, has been widely used in both fundamental studies and clinical applications. Many studies have utilized diffusion tensor imaging (DTI) and tractography approaches to explore the topological properties of human brain anatomical networks by using the single tensor model, the basic model to quantify DTI indices and tractography. However, the conventional DTI technique does not take into account contamination by the cerebrospinal fluid (CSF), which has been known to affect the estimated DTI measures and tractography in the single tensor model. Previous studies have shown that the Fluid-Attenuated Inversion Recovery (FLAIR) technique can suppress the contribution of the CSF to the DW-MRI signal. We acquired DTI datasets from twenty-two subjects using both FLAIR-DTI and conventional DTI (non-FLAIR-DTI) techniques, constructed brain anatomical networks using deterministic tractography, and compared the topological properties of the anatomical networks derived from the two types of DTI techniques. Although the brain anatomical networks derived from both types of DTI datasets showed small-world properties, we found that the brain anatomical networks derived from the FLAIR-DTI showed significantly increased global and local network efficiency compared with those derived from the conventional DTI. The increases in the network regional topological properties derived from the FLAIR-DTI technique were observed in CSF-filled regions, including the postcentral gyrus, periventricular regions, inferior frontal and temporal gyri, and regions in the visual cortex. Because brain anatomical networks derived from conventional DTI datasets with tractography have been widely used in many studies, our findings may have important implications for studying human brain anatomical networks derived from DW-MRI data and tractography.
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Affiliation(s)
- Shumei Li
- Center for the Study of Applied Psychology, Key Laboratory of Mental Health and Cognitive Science of Guangdong Province, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Bin Wang
- Center for the Study of Applied Psychology, Key Laboratory of Mental Health and Cognitive Science of Guangdong Province, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Pengfei Xu
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, P. R. China
| | - Qixiang Lin
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, P. R. China
| | - Gaolang Gong
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, P. R. China
| | - Xiaoling Peng
- Center for the Study of Applied Psychology, Key Laboratory of Mental Health and Cognitive Science of Guangdong Province, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Yuanyuan Fan
- Center for the Study of Applied Psychology, Key Laboratory of Mental Health and Cognitive Science of Guangdong Province, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Yong He
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, P. R. China
| | - Ruiwang Huang
- Center for the Study of Applied Psychology, Key Laboratory of Mental Health and Cognitive Science of Guangdong Province, School of Psychology, South China Normal University, Guangzhou, P. R. China
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414
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Iturria-Medina Y. Anatomical brain networks on the prediction of abnormal brain states. Brain Connect 2013; 3:1-21. [PMID: 23249224 DOI: 10.1089/brain.2012.0122] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Graph-based brain anatomical network analysis models the brain as a graph whose nodes represent structural/functional regions, whereas the links between them represent nervous fiber connections. Initial studies of brain anatomical networks using this approach were devoted to describe the key organizational principles of the normal brain, while current trends seem to be more focused on detecting network alterations associated to specific brain disorders. Anatomical networks reconstructed using diffusion-weighed magnetic resonance-imaging techniques can be particularly useful in predicting abnormal brain states in which the white matter structure and, subsequently, the interconnections between gray matter regions are altered (e.g., due to the presence of diseases such as schizophrenia, stroke, multiple sclerosis, and dementia). This article offers an overview from early gross connectional anatomy explorations until more recent advances on anatomical brain network reconstruction approaches, with a specific focus on how the latter move toward the prediction of abnormal brain states. While anatomical graph-based predictor approaches are still at an early stage, they bear promising implications for individualized clinical diagnosis of neurological and psychiatric disorders, as well as for neurodevelopmental evaluations and subsequent assisted creation of educational strategies related to specific cognitive disorders.
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415
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Cheng L, Wu Z, Fu Y, Miao F, Sun J, Tong S. Reorganization of functional brain networks during the recovery of stroke: a functional MRI study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:4132-5. [PMID: 23366837 DOI: 10.1109/embc.2012.6346876] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Studies have demonstrated that reorganization of the cortex after stroke contributed to the recovery of motor function. However, these studies paid much more attention to the reorganization of motor-related brain regions and motor executive network which only contained tens of brain regions, ignoring the change in brain-wide network during the restoration of motor function. Based on this consideration, this paper investigated the functional reorganization of brain-wide network during the recovery after stroke from the perspective of graph theory. At four time points (less than 10 days, around 2 weeks, 1 month and 3 months) after stroke onset, we obtained the functional MRI (fMRI) data of stroke patients when they were doing finger tapping task. Based on the fMRI data, we constructed the brain-wide functional network which consisted of 264 putative functional areas for each subject at each time point. Then the topological parameters (e.g., characteristic path length and cluster coefficient) of these brain networks were examined. Results showed that the brain networks shifted towards a non-optimal topological configuration with low small-worldness during the process of recovery. And this finding may broaden our knowledge about the reorganization of brain function during recovery after stroke.
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Affiliation(s)
- Lin Cheng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China.
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416
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Longitudinal effects of lesions on functional networks after stroke. J Cereb Blood Flow Metab 2013; 33:1279-85. [PMID: 23715061 PMCID: PMC3734780 DOI: 10.1038/jcbfm.2013.80] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/19/2013] [Accepted: 04/26/2013] [Indexed: 11/08/2022]
Abstract
While ischemic stroke reflects focal damage determined by the affected vascular territory, clinical symptoms are often more complex and may be better explained by additional indirect effects of the focal lesion. Assumed to be structurally underpinned by anatomical connections, supporting evidence has been found using alterations in the functional connectivity of resting-state functional magnetic resonance imaging (fMRI) data in both sensorimotor and attention networks. To assess the generalizability of this phenomenon in a stroke population with heterogeneous lesions, we investigated the distal effects of lesions on a global level. Longitudinal resting-state fMRI scans were acquired at three consecutive time points, beginning during the acute phase (days 1, 7, and 90 post-stroke) in 12 patients after ischemic stroke. We found a preferential functional change in affected networks (i.e., networks containing lesions changed more during recovery when compared with unaffected networks). This change in connectivity was significantly correlated with clinical changes assessed with the National Institute of Health Stroke Scale. Our results provide evidence that the functional architecture of large-scale networks is critical to understanding the clinical effect and trajectory of post-stroke recovery.
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417
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Jin SH, Jeong W, Seol J, Kwon J, Chung CK. Functional cortical hubs in the eyes-closed resting human brain from an electrophysiological perspective using magnetoencephalography. PLoS One 2013; 8:e68192. [PMID: 23874535 PMCID: PMC3706585 DOI: 10.1371/journal.pone.0068192] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Accepted: 05/27/2013] [Indexed: 11/19/2022] Open
Abstract
It is not clear whether specific brain areas act as hubs in the eyes-closed (EC) resting state, which is an unconstrained state free from any passive or active tasks. Here, we used electrophysiological magnetoencephalography (MEG) signals to study functional cortical hubs in 88 participants. We identified several multispectral cortical hubs. Although cortical hubs vary slightly with different applied measures and frequency bands, the most consistent hubs were observed in the medial and posterior cingulate cortex, the left dorsolateral superior frontal cortex, and the left pole of the middle temporal cortex. Hubs were characterized as connector nodes integrating EC resting state functional networks. Hubs in the gamma band were more likely to include midline structures. Our results confirm the existence of multispectral cortical cores in EC resting state functional networks based on MEG and imply the existence of optimized functional networks in the resting brain.
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Affiliation(s)
- Seung-Hyun Jin
- MEG center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
- Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
- Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea
| | - Woorim Jeong
- MEG center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
| | - Jaeho Seol
- MEG center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
| | - Jiyeon Kwon
- MEG center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
- Seoul National University College of Medicine, Seoul, Korea
| | - Chun Kee Chung
- MEG center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
- Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
- Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea
- Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea
- * E-mail:
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418
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Eyes-Open/Eyes-Closed Dataset Sharing for Reproducibility Evaluation of Resting State fMRI Data Analysis Methods. Neuroinformatics 2013; 11:469-76. [DOI: 10.1007/s12021-013-9187-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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419
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De Vico Fallani F, Pichiorri F, Morone G, Molinari M, Babiloni F, Cincotti F, Mattia D. Multiscale topological properties of functional brain networks during motor imagery after stroke. Neuroimage 2013; 83:438-49. [PMID: 23791916 DOI: 10.1016/j.neuroimage.2013.06.039] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 06/10/2013] [Accepted: 06/11/2013] [Indexed: 12/21/2022] Open
Abstract
In recent years, network analyses have been used to evaluate brain reorganization following stroke. However, many studies have often focused on single topological scales, leading to an incomplete model of how focal brain lesions affect multiple network properties simultaneously and how changes on smaller scales influence those on larger scales. In an EEG-based experiment on the performance of hand motor imagery (MI) in 20 patients with unilateral stroke, we observed that the anatomic lesion affects the functional brain network on multiple levels. In the beta (13-30 Hz) frequency band, the MI of the affected hand (Ahand) elicited a significantly lower smallworldness and local efficiency (Eloc) versus the unaffected hand (Uhand). Notably, the abnormal reduction in Eloc significantly depended on the increase in interhemispheric connectivity, which was in turn determined primarily by the rise of regional connectivity in the parieto-occipital sites of the affected hemisphere. Further, in contrast to the Uhand MI, in which significantly high connectivity was observed for the contralateral sensorimotor regions of the unaffected hemisphere, the regions with increased connectivity during the Ahand MI lay in the frontal and parietal regions of the contralaterally affected hemisphere. Finally, the overall sensorimotor function of our patients, as measured by Fugl-Meyer Assessment (FMA) index, was significantly predicted by the connectivity of their affected hemisphere. These results improve on our understanding of stroke-induced alterations in functional brain networks.
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Affiliation(s)
- Fabrizio De Vico Fallani
- Brain and Spine Institute (CRICM), UPMC/Inserm UMR_S975/CNRS UMR7225, Paris, France; Neuroelectrical Imaging and BCI Laboratory, IRCCS Fondazione Santa Lucia, Rome, Italy; Department of Physiology and Pharmacology, University Sapienza, Rome, Italy.
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420
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Altered functional connectivity of cognitive-related cerebellar subregions in well-recovered stroke patients. Neural Plast 2013; 2013:452439. [PMID: 23862075 PMCID: PMC3703724 DOI: 10.1155/2013/452439] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 06/03/2013] [Accepted: 06/04/2013] [Indexed: 12/02/2022] Open
Abstract
The cerebellum contains several cognitive-related subregions that are involved in different functional networks. The cerebellar crus II is correlated with the frontoparietal network (FPN), whereas the cerebellar IX is associated with the default-mode network (DMN). These two networks are anticorrelated and cooperatively implicated in cognitive control, which may facilitate the motor recovery in stroke patients. In the present study, we aimed to investigate the resting-state functional connectivity (rsFC) changes in 25 subcortical ischemic stroke patients with well-recovered global motor function. Consistent with previous studies, the crus II was correlated with the FPN, including the dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex, and the cerebellar IX was correlated with the DMN, including the posterior cingulate cortex/precuneus (PCC/Pcu), medial prefrontal cortex (MPFC), DLPFC, lateral parietal cortices, and anterior temporal cortices. No significantly increased rsFCs of these cerebellar subregions were found in stroke patients, suggesting that the rsFCs of the cognitive-related cerebellar subregions are not the critical factors contributing to the recovery of motor function in stroke patients. The finding of the disconnection in the cerebellar-related cognitive control networks may possibly explain the deficits in cognitive control function even in stroke patients with well-recovered global motor function.
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421
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Grefkes C, Ward NS. Cortical reorganization after stroke: how much and how functional? Neuroscientist 2013; 20:56-70. [PMID: 23774218 DOI: 10.1177/1073858413491147] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The brain has an intrinsic capacity to compensate for structural damage through reorganizing of surviving networks. These processes are fundamental for recovery of function after many forms of brain injury, including stroke. Functional neuroimaging techniques have allowed the investigation of these processes in vivo. Here, we review key advances over the past two decades that have shed light on the neural mechanisms enabling recovery of motor function after stroke. We first provide an overview on invasive stroke models in non-human primates that provided insights into lesion-induced changes in the cortical representations of the upper limb. We then present key findings from neuroimaging studies in human stroke patients, which suggest that the role of contralesional motor hemisphere in supporting recovered function depends on factors such as time since stroke, lesion location and anatomical region. More recently, research has been directed at understanding how surviving brain regions influence one another during movement. It appears that it is not only the corticospinal tract but also brainstem pathways and interhemispheric connections that affect cortical reorganization patterns and functional recovery. In summary, neuroimaging opens the way for greater understanding of the mechanisms of recovery and potentially improves our ability to deliver effective restorative therapy.
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Affiliation(s)
- Christian Grefkes
- 1Department of Neurology, Cologne University Hospital, Cologne, Germany
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422
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Küper M, Döring K, Spangenberg C, Konczak J, Gizewski ER, Schoch B, Timmann D. Location and restoration of function after cerebellar tumor removal-a longitudinal study of children and adolescents. THE CEREBELLUM 2013; 12:48-58. [PMID: 22562748 DOI: 10.1007/s12311-012-0389-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Sequelae in children following cerebellar tumor removal surgery are well defined, and predictors for poor recovery include lesions of the cerebellar nuclei and the inferior vermis. Dynamic reorganization is thought to promote functional recovery in particular within the first year after surgery. Yet, the time course and mechanisms of recovery within this critical time frame are elusive and longitudinal studies are missing. Thus, a group of children and adolescents (n = 12, range 6-17 years) were followed longitudinally after cerebellar surgery and compared to age- and gender-matched controls (n = 11). Patients were examined (1) within the first days, (2) 3 months, and (3) 1 year after surgery. Each time behavioral tests of balance and upper limb motor function, ataxia rating, and a MRI scan were performed. Data were used for subsequent lesion-symptom mapping of cerebellar function. Behavioral improvements continued beyond 3 months, but were not complete in all patients after 1 year. At that time, remaining deficits were mild. Within the first 3 months, cerebellar lesion volumes were notably reduced by vanishing edema. Reduction in edema affecting the deep cerebellar nuclei but not reduction of total cerebellar lesion volume was a major predictor of early functional recovery. Persistent impairment in balance and upper limb function was linked to permanent lesions of the inferior vermis and the deep cerebellar nuclei.
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Affiliation(s)
- M Küper
- Department of Neurology, University of Duisburg-Essen, Hufelandstr. 55, 45122, Essen, Germany.
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423
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Wei W, Bai L, Wang J, Dai R, Tong RKY, Zhang Y, Song Z, Jiang W, Shi C, Li M, Ai L, Tian J. A longitudinal study of hand motor recovery after sub-acute stroke: a study combined FMRI with diffusion tensor imaging. PLoS One 2013; 8:e64154. [PMID: 23724030 PMCID: PMC3665895 DOI: 10.1371/journal.pone.0064154] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 04/08/2013] [Indexed: 11/18/2022] Open
Abstract
Previous studies have shown that motor recovery of stroke can be assessed by the cortical activity and the structural integrity of the corticospinal tract (CST), but little is known about the relation between the cortical activity and the structural integrity during motor recovery. In the present study, we investigated the changes in brain activities evoked by twenty days’ functional electrical stimulation (FES) training in twelve sub-acute stroke patients with unilateral upper-limb disability. We compared cortex activity evoked by wrist movement of eleven stroke patients to that of eleven age-matched healthy subjects to figure out how cortex activity changed after stroke. We also measured the structural integrity represented by the fractional anisotropy (FA) asymmetry of the posterior limb of the internal capsule (PLIC) to find the relationship between the brain activity and the structure integrity. In our study, we found that patients with sub-acute stroke have shown greater activity in the contralesional primary motor cortex (M1) during the affected hand’s movement compared with healthy group, while the activity in ipsilesional M1 was decreased after the therapy compared to that before therapy, and the contralesional non-primary motor cortex showed greater activity after therapy. At the baseline we found that the positive correlation between the FA asymmetry of PLIC and the contralesional non-primary motor cortex activity showed that the greater damaged CST, the greater contralesional non-primary motor cortex recruited. While the negative correlation between them after the FES training indicates that after recovery the non-primary motor cortex plays different role in different stroke phases. Our study demonstrates that functional organization of a residual distributed motor system is related to the degree of disruption to the CST, and the non-primary motor areas plays an important role in motor recovery.
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Affiliation(s)
- Wenjuan Wei
- Key Laboratory of Molecular Imaging and Functional Imaging, Institute of Automation, Chinese Academy of Sciences, Beijing, China
| | - Lijun Bai
- Key Laboratory of Molecular Imaging and Functional Imaging, Institute of Automation, Chinese Academy of Sciences, Beijing, China
| | - Jun Wang
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China
| | - Ruwei Dai
- Key Laboratory of Molecular Imaging and Functional Imaging, Institute of Automation, Chinese Academy of Sciences, Beijing, China
| | - Raymond Kai-yu Tong
- Department of Health Technology and Informatics, Hong Kong Polytechnic University, Beijing, China
| | - Yumei Zhang
- Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Zheng Song
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China
| | - Wen Jiang
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Chuanying Shi
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Mengyuan Li
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Lin Ai
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
- * E-mail: (JT); (LA)
| | - Jie Tian
- Key Laboratory of Molecular Imaging and Functional Imaging, Institute of Automation, Chinese Academy of Sciences, Beijing, China
- * E-mail: (JT); (LA)
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424
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Interhemispheric functional connectivity following prenatal or perinatal brain injury predicts receptive language outcome. J Neurosci 2013; 33:5612-25. [PMID: 23536076 DOI: 10.1523/jneurosci.2851-12.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Early brain injury alters both structural and functional connectivity between the cerebral hemispheres. Despite increasing knowledge on the individual hemispheric contributions to recovery from such injury, we know very little about how their interactions affect this process. In the present study, we related interhemispheric structural and functional connectivity to receptive language outcome following early left hemisphere stroke. We used functional magnetic resonance imaging to study 14 people with neonatal brain injury, and 25 age-matched controls during passive story comprehension. With respect to structural connectivity, we found that increased volume of the corpus callosum predicted good receptive language outcome, but that this is not specific to people with injury. In contrast, we found that increased posterior superior temporal gyrus interhemispheric functional connectivity during story comprehension predicted better receptive language performance in people with early brain injury, but worse performance in typical controls. This suggests that interhemispheric functional connectivity is one potential compensatory mechanism following early injury. Further, this pattern of results suggests refinement of the prevailing notion that better language outcome following early left hemisphere injury relies on the contribution of the contralesional hemisphere (i.e., the "right-hemisphere-take-over" theory). This pattern of results was also regionally specific; connectivity of the angular gyrus predicted poorer performance in both groups, independent of brain injury. These results present a complex picture of recovery, and in some cases, such recovery relies on increased cooperation between the injured hemisphere and homologous regions in the contralesional hemisphere, but in other cases, the opposite appears to hold.
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425
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Brain connectivity plasticity in the motor network after ischemic stroke. Neural Plast 2013; 2013:924192. [PMID: 23738150 PMCID: PMC3655657 DOI: 10.1155/2013/924192] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 04/07/2013] [Indexed: 01/06/2023] Open
Abstract
The motor function is controlled by the motor system that comprises a series of cortical and subcortical areas interacting via anatomical connections. The motor function will be disturbed when the stroke lesion impairs either any of these areas or their connections. More and more evidence indicates that the reorganization of the motor network including both areas and their anatomical and functional connectivity might contribute to the motor recovery after stroke. Here, we review recent studies employing models of anatomical, functional, and effective connectivity on neuroimaging data to investigate how ischemic stroke influences the connectivity of motor areas and how changes in connectivity relate to impaired function and functional recovery. We suggest that connectivity changes constitute an important pathophysiological aspect of motor impairment after stroke and important mechanisms of motor recovery. We also demonstrate that therapeutic interventions may facilitate motor recovery after stroke by modulating the connectivity among the motor areas. In conclusion, connectivity analyses improved our understanding of the mechanisms of motor recovery after stroke and may help to design hypothesis-driven treatment strategies and sensitive measures for outcome prediction in stroke patients.
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426
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Jang SH, Chang CH, Lee J, Kim CS, Seo JP, Yeo SS. Functional Role of the Corticoreticular Pathway in Chronic Stroke Patients. Stroke 2013; 44:1099-104. [DOI: 10.1161/strokeaha.111.000269] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Sung Ho Jang
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
| | - Chul Hoon Chang
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
| | - Jun Lee
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
| | - Chung Sun Kim
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
| | - Jeong Pyo Seo
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
| | - Sang Seok Yeo
- From the Department of Physical Medicine and Rehabilitation (S.H.J., J.P.S., S.S.Y.), Department of Neurosurgery (C.H.C.), Department of Neurology (J.L.), College of Medicine, Yeungnam University, Daemyungdong, Namku, Taegu, Republic of Korea; and Department of Physical Therapy, College of Rehabilitation Science, Daegu University, Jillyang, Gyeongsan, Gyeongbuk, Republic of Korea (C.S.K.)
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427
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Varsou O, Macleod MJ, Schwarzbauer C. Functional Connectivity Magnetic Resonance Imaging in Stroke: An Evidence-Based Clinical Review. Int J Stroke 2013; 9:191-8. [DOI: 10.1111/ijs.12033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Stroke is a common condition that may lead to various degrees of neurological deficit and long-term disability. It has become increasingly recognized that cortical reorganization of neuronal networks plays a significant role in regaining function following a focal brain injury. However, the mechanisms involved in this process are still not fully understood. Resting-state functional connectivity magnetic resonance imaging is a rapidly evolving scanning technique that has the potential to shed light into this neuronal rearrangement. A better understanding of the underlying neurological pathways may contribute to the development of targeted treatment that will promote repair and reduce poststroke deficit. The aim of this review is to provide an up-to-date summary of the available scientific data evaluating the clinical application of functional connectivity magnetic resonance imaging among stroke survivors.
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Affiliation(s)
- Ourania Varsou
- Aberdeen Biomedical Imaging Centre, The University of Aberdeen, Aberdeen, UK
| | - Mary Joan Macleod
- Department of Medicine and Therapeutics, The University of Aberdeen, Aberdeen, UK
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428
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Wang L, Li H, Liang Y, Zhang J, Li X, Shu N, Wang YY, Zhang Z. Amnestic mild cognitive impairment: topological reorganization of the default-mode network. Radiology 2013; 268:501-14. [PMID: 23481166 DOI: 10.1148/radiol.13121573] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To investigate the topologic reorganization of the default-mode network (DMN) in patients with mild cognitive impairment (MCI) and whether, relative to healthy control subjects, patients with MCI would be more likely to show disrupted functional connectivity and altered topological configuration of the DMN during the memory task compared with that observed during the resting state. MATERIALS AND METHODS This study was approved by the institutional review board of Beijing Normal University Imaging Center for Brain Research. Written informed consent was obtained from each participant. Healthy control subjects (n = 26) and patients with amnestic MCI (aMCI) (n = 25) performed an episodic memory task and also rested while undergoing functional magnetic resonance imaging. Task-induced deactivations were identified and parcellated into different regions associated with the DMN. Functional connectivity across all pairs of regions was computed to construct the DMN architecture. Graph theoretical approaches were used to characterize topological properties of this network. RESULTS Patients with aMCI showed similar deactivation in the DMN to that observed in healthy control subjects (P > .05) but showed significantly decreased anterior-to-posterior functional connectivity only during the task (P < .05). Significant increases in local efficiency (P < .05), but not in global efficiency (P > .05), were observed in aMCI only during the task. Decreased functional connectivity was predictive of increased local efficiency (r = -0.35, P = .015). Significant correlations between these network measures and cognitive performance (P < .05) indicated their potential use as early markers to assess the risk of Alzheimer disease (AD). CONCLUSION This study suggests the early onset functional reorganization of the DMN toward a nonoptimized regularity configuration in aMCI and expands the understanding of dynamic functional reorganization in brain networks along the continuum from normal aging to AD dementia.
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Affiliation(s)
- Liang Wang
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, 19 Xinjiekouwai St, Beijing 100875, P.R. China
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429
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Wu T, Hallett M. The cerebellum in Parkinson's disease. Brain 2013; 136:696-709. [PMID: 23404337 PMCID: PMC7273201 DOI: 10.1093/brain/aws360] [Citation(s) in RCA: 574] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/24/2012] [Accepted: 11/06/2012] [Indexed: 11/30/2022] Open
Abstract
Parkinson's disease is a chronic progressive neurodegenerative disorder characterized by resting tremor, slowness of movements, rigidity, gait disturbance and postural instability. Most investigations on Parkinson's disease focused on the basal ganglia, whereas the cerebellum has often been overlooked. However, increasing evidence suggests that the cerebellum may have certain roles in the pathophysiology of Parkinson's disease. Anatomical studies identified reciprocal connections between the basal ganglia and cerebellum. There are Parkinson's disease-related pathological changes in the cerebellum. Functional or morphological modulations in the cerebellum were detected related to akinesia/rigidity, tremor, gait disturbance, dyskinesia and some non-motor symptoms. It is likely that the major roles of the cerebellum in Parkinson's disease include pathological and compensatory effects. Pathological changes in the cerebellum might be induced by dopaminergic degeneration, abnormal drives from the basal ganglia and dopaminergic treatment, and may account for some clinical symptoms in Parkinson's disease. The compensatory effect may help maintain better motor and non-motor functions. The cerebellum is also a potential target for some parkinsonian symptoms. Our knowledge about the roles of the cerebellum in Parkinson's disease remains limited, and further attention to the cerebellum is warranted.
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Affiliation(s)
- Tao Wu
- Department of Neurobiology, Key Laboratory on Neurodegenerative Disorders of Ministry of Education, Beijing Institute of Geriatrics, Xuanwu Hospital, Capital Medical University, Beijing 100053, China.
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430
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Transcranial direct current stimulation in stroke rehabilitation: a review of recent advancements. Stroke Res Treat 2013; 2013:170256. [PMID: 23533955 PMCID: PMC3600193 DOI: 10.1155/2013/170256] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 12/17/2012] [Accepted: 01/14/2013] [Indexed: 01/25/2023] Open
Abstract
Transcranial direct current stimulation (tDCS) is a promising technique to treat a wide range of neurological conditions including stroke. The pathological processes following stroke may provide an exemplary system to investigate how tDCS promotes neuronal plasticity and functional recovery. Changes in synaptic function after stroke, such as reduced excitability, formation of aberrant connections, and deregulated plastic modifications, have been postulated to impede recovery from stroke. However, if tDCS could counteract these negative changes by influencing the system's neurophysiology, it would contribute to the formation of functionally meaningful connections and the maintenance of existing pathways. This paper is aimed at providing a review of underlying mechanisms of tDCS and its application to stroke. In addition, to maximize the effectiveness of tDCS in stroke rehabilitation, future research needs to determine the optimal stimulation protocols and parameters. We discuss how stimulation parameters could be optimized based on electrophysiological activity. In particular, we propose that cortical synchrony may represent a biomarker of tDCS efficacy to indicate communication between affected areas. Understanding the mechanisms by which tDCS affects the neural substrate after stroke and finding ways to optimize tDCS for each patient are key to effective rehabilitation approaches.
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431
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Electrophysiological low-frequency coherence and cross-frequency coupling contribute to BOLD connectivity. Neuron 2013; 76:1010-20. [PMID: 23217748 DOI: 10.1016/j.neuron.2012.09.033] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2012] [Indexed: 01/08/2023]
Abstract
Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma-band (30-100 Hz) neural activity contributes to local BOLD signals, the neural basis of interareal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from interareal BOLD correlations during a fixation task, task-free state, and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low-frequency oscillations (<20 Hz), and not gamma activity, predominantly contributed to interareal BOLD correlations. The low-frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks.
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432
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Xia M, He Y. Magnetic resonance imaging and graph theoretical analysis of complex brain networks in neuropsychiatric disorders. Brain Connect 2013; 1:349-65. [PMID: 22432450 DOI: 10.1089/brain.2011.0062] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Neurological and psychiatric disorders disturb higher cognitive functions and are accompanied by aberrant cortico-cortical axonal pathways or synchronizations of neural activity. A large proportion of neuroimaging studies have focused on examining the focal morphological abnormalities of various gray and white matter structures or the functional activities of brain areas during goal-directed tasks or the resting state, which provides vast quantities of information on both the structural and functional alterations in the patients' brain. However, these studies often ignore the interactions among multiple brain regions that constitute complex brain networks underlying higher cognitive function. Information derived from recent advances of noninvasive magnetic resonance imaging (MRI) techniques and computational methodologies such as graph theory have allowed researchers to explore the patterns of structural and functional connectivity of healthy and diseased brains in vivo. In this article, we summarize the recent advances made in the studies of both structural (gray matter morphology and white matter fibers) and functional (synchronized neural activity) brain networks based on human MRI data pertaining to neuropsychiatric disorders. These studies bring a systems-level perspective to the alterations of the topological organization of complex brain networks and the underlying pathophysiological mechanisms. Specifically, noninvasive imaging of structural and functional brain networks and follow-up graph-theoretical analyses demonstrate the potential to establish systems-level biomarkers for clinical diagnosis, progression monitoring, and treatment effects evaluation for neuropsychiatric disorders.
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Affiliation(s)
- Mingrui Xia
- State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China
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433
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Chen G, Chen G, Xie C, Li SJ. Negative functional connectivity and its dependence on the shortest path length of positive network in the resting-state human brain. Brain Connect 2013; 1:195-206. [PMID: 22433048 DOI: 10.1089/brain.2011.0025] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
It is suggested that structurally segregated and functionally specialized brain regions are mediated by synchrony over large-scale networks in order to provide the formation of dynamic links and integration functions. The existence of negative synchrony, or negative functional connectivity (NFC), however, has been a subject of debate in terms of its origin, interpretation, relationship with structural connectivity, and possible neurophysiological function. The present study, which incorporated 20 cognitively healthy elderly human subjects, focused on testing the hypothesis that NFC significantly correlates with the shortest path length (SPL) in the human brain network. Our theoretical calculation, simulated data, and human study results support this hypothesis. In the human study, we find that (1) the percentage of NFC connections among all connections between brain regions significantly correlates with spatial Euclidian distance; (2) the strength of the NFC between the right amygdala and the left dorsolateral prefrontal cortex is significantly correlated with the SPL across the 20 human subjects; (3) such a significant relationship between the NFC and SPL exists in all the NFC connections in the whole brain; and (4) the correlations between the NFC and SPL also are frequency bandwidth dependent. These results suggest that an accumulated phased delay gives rise to the NFC, along the shortest path in the large-scale brain functional network. It is suggested that our study can be extended to examine a variety of neurological diseases and psychiatric disorders by measuring the changes of SPL and functional reorganization in the brain.
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Affiliation(s)
- Guangyu Chen
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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434
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Zhang D, Liu B, Chen J, Peng X, Liu X, Fan Y, Liu M, Huang R. Determination of vascular dementia brain in distinct frequency bands with whole brain functional connectivity patterns. PLoS One 2013; 8:e54512. [PMID: 23359801 PMCID: PMC3554744 DOI: 10.1371/journal.pone.0054512] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 12/12/2012] [Indexed: 11/18/2022] Open
Abstract
Recent studies have shown that multivariate pattern analysis (MVPA) can be useful for distinguishing brain disorders into categories. Such analyses can substantially enrich and facilitate clinical diagnoses. Using MPVA methods, whole brain functional networks, especially those derived using different frequency windows, can be applied to detect brain states. We constructed whole brain functional networks for groups of vascular dementia (VaD) patients and controls using resting state BOLD-fMRI (rsfMRI) data from three frequency bands - slow-5 (0.01 ≈ 0.027 Hz), slow-4 (0.027∼0.073 Hz), and whole-band (0.01 ≈ 0.073 Hz). Then we used the support vector machine (SVM), a type of MVPA classifier, to determine the patterns of functional connectivity. Our results showed that the brain functional networks derived from rsfMRI data (19 VaD patients and 20 controls) in these three frequency bands appear to reflect neurobiological changes in VaD patients. Such differences could be used to differentiate the brain states of VaD patients from those of healthy individuals. We also found that the functional connectivity patterns of the human brain in the three frequency bands differed, as did their ability to differentiate brain states. Specifically, the ability of the functional connectivity pattern to differentiate VaD brains from healthy ones was more efficient in the slow-5 (0.01 ≈ 0.027 Hz) band than in the other two frequency bands. Our findings suggest that the MVPA approach could be used to detect abnormalities in the functional connectivity of VaD patients in distinct frequency bands. Identifying such abnormalities may contribute to our understanding of the pathogenesis of VaD.
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Affiliation(s)
- Delong Zhang
- Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Bo Liu
- Department of Radiology, Guangdong Province Hospital of Traditional Chinese Medicine, Guangzhou, P. R. China
| | - Jun Chen
- Department of Radiology, Guangdong Province Hospital of Traditional Chinese Medicine, Guangzhou, P. R. China
| | - Xiaoling Peng
- Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Xian Liu
- Department of Radiology, Guangdong Province Hospital of Traditional Chinese Medicine, Guangzhou, P. R. China
| | - Yuanyuan Fan
- Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Ming Liu
- Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, P. R. China
| | - Ruiwang Huang
- Center for Studies of Psychological Application, Guangdong Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, P. R. China
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435
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Abstract
Stroke is the major cause of long-term disability worldwide, with impaired manual dexterity being a common feature. In the past few years, noninvasive brain stimulation (NIBS) techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), have been investigated as adjuvant strategies to neurorehabilitative interventions. These NIBS techniques can be used to modulate cortical excitability during and for several minutes after the end of the stimulation period. Depending on the stimulation parameters, cortical excitability can be reduced (inhibition) or enhanced (facilitation). Differential modulation of cortical excitability in the affected and unaffected hemisphere of patients with stroke may induce plastic changes within neural networks active during functional recovery. The aims of this chapter are to describe results from these proof-of-principle trials and discuss possible putative mechanisms underlying such effects. Neurophysiological and neuroimaging changes induced by application of NIBS are reviewed briefly.
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436
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EEG in ischaemic stroke: Quantitative EEG can uniquely inform (sub-)acute prognoses and clinical management. Clin Neurophysiol 2013; 124:10-9. [DOI: 10.1016/j.clinph.2012.07.003] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/13/2012] [Accepted: 07/03/2012] [Indexed: 11/22/2022]
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437
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Motor control and neural plasticity through interhemispheric interactions. Neural Plast 2012; 2012:823285. [PMID: 23326685 PMCID: PMC3541646 DOI: 10.1155/2012/823285] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 11/16/2012] [Accepted: 12/03/2012] [Indexed: 11/18/2022] Open
Abstract
The corpus callosum, which is the largest white matter structure in the human brain, connects the 2 cerebral hemispheres. It plays a crucial role in maintaining the independent processing of the hemispheres and in integrating information between both hemispheres. The functional integrity of interhemispheric interactions can be tested electrophysiologically in humans by using transcranial magnetic stimulation, electroencephalography, and functional magnetic resonance imaging. As a brain structural imaging, diffusion tensor imaging has revealed the microstructural connectivity underlying interhemispheric interactions. Sex, age, and motor training in addition to the size of the corpus callosum influence interhemispheric interactions. Several neurological disorders change hemispheric asymmetry directly by impairing the corpus callosum. Moreover, stroke lesions and unilateral peripheral impairments such as amputation alter interhemispheric interactions indirectly. Noninvasive brain stimulation changes the interhemispheric interactions between both motor cortices. Recently, these brain stimulation techniques were applied in the clinical rehabilitation of patients with stroke by ameliorating the deteriorated modulation of interhemispheric interactions. Here, we review the interhemispheric interactions and mechanisms underlying the pathogenesis of these interactions and propose rehabilitative approaches for appropriate cortical reorganization.
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438
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Yin D, Song F, Xu D, Peterson BS, Sun L, Men W, Yan X, Fan M. Patterns in cortical connectivity for determining outcomes in hand function after subcortical stroke. PLoS One 2012; 7:e52727. [PMID: 23285171 PMCID: PMC3527607 DOI: 10.1371/journal.pone.0052727] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 11/21/2012] [Indexed: 11/18/2022] Open
Abstract
Background and Purpose Previous studies have noted changes in resting-state functional connectivity during motor recovery following stroke. However, these studies always uncover various patterns of motor recovery. Moreover, subgroups of stroke patients with different outcomes in hand function have rarely been studied. Materials and Methods We selected 24 patients who had a subcortical stroke in the left motor pathway and displayed only motor deficits. The patients were divided into two subgroups: completely paralyzed hands (CPH) (12 patients) and partially paralyzed hands (PPH) (12 patients). Twenty-four healthy controls (HC) were also recruited. We performed functional connectivity analysis in both the ipsilesional and contralesional primary motor cortex (M1) to explore the differences in the patterns between each pair of the three diagnostic groups. Results Compared with the HC, the PPH group displays reduced connectivity of both the ipsilesional and contralesional M1 with bilateral prefrontal gyrus and contralesional cerebellum posterior lobe. The connectivity of both the ipsilesional and contralesional M1 with contralateral primary sensorimotor cortex was reduced in the CPH group. Additionally, the connectivity of the ipsilesional M1 with contralesional postcentral gyrus, superior parietal lobule and ipsilesional inferior parietal lobule was reduced in the CPH group compared with the PPH group. Moreover, the connectivity of these regions was positively correlated with the Fugl-Meyer Assessment scores (hand+wrist) across all stroke patients. Conclusions Patterns in cortical connectivity may serve as a potential biomarker for the neural substratum associated with outcomes in hand function after subcortical stroke.
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Affiliation(s)
- Dazhi Yin
- Shanghai Key Laboratory of Magnetic Resonance, Key Laboratory of Brain Function Genomics, East China Normal University, Shanghai, China
| | - Fan Song
- Department of Rehabilitation Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Dongrong Xu
- MRI Unit, Department of Psychiatry, New York State Psychiatric Institute and Columbia University, New York, New York, United States of America
- * E-mail: (MF); (DX)
| | - Bradley S. Peterson
- MRI Unit, Department of Psychiatry, New York State Psychiatric Institute and Columbia University, New York, New York, United States of America
| | - Limin Sun
- Department of Rehabilitation Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Weiwei Men
- Shanghai Key Laboratory of Magnetic Resonance, Key Laboratory of Brain Function Genomics, East China Normal University, Shanghai, China
| | - Xu Yan
- Shanghai Key Laboratory of Magnetic Resonance, Key Laboratory of Brain Function Genomics, East China Normal University, Shanghai, China
| | - Mingxia Fan
- Shanghai Key Laboratory of Magnetic Resonance, Key Laboratory of Brain Function Genomics, East China Normal University, Shanghai, China
- * E-mail: (MF); (DX)
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439
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Rehme AK, Eickhoff SB, Grefkes C. State-dependent differences between functional and effective connectivity of the human cortical motor system. Neuroimage 2012. [PMID: 23201364 DOI: 10.1016/j.neuroimage.2012.11.027] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Neural processing is based on interactions between functionally specialized areas that can be described in terms of functional or effective connectivity. Functional connectivity is often assessed by task-free, resting-state functional magnetic resonance imaging (fMRI), whereas effective connectivity is usually estimated from task-based fMRI time-series. To investigate whether different connectivity approaches assess similar network topologies in the same subjects, we scanned 36 right-handed volunteers with resting-state fMRI followed by active-state fMRI involving a hand movement task. Time-series information was extracted from identical locations defined from individual activation maxima derived from the motor task. Dynamic causal modeling (DCM) was applied to the motor task time-series to estimate endogenous and context-dependent effective connectivity. In addition, functional connectivity was computed for both the rest and the motor task condition by means of inter-regional time-series correlations. At the group-level, we found strong interactions between the motor areas of interest in all three connectivity analyses. However, although the sample size warranted 90% power to detect correlations of medium effect size, resting-state functional connectivity was only weakly correlated with both task-based functional and task-based effective connectivity estimates for corresponding region-pairs. By contrast, task-based functional connectivity showed strong positive correlations with DCM effective connectivity parameters. In conclusion, resting-state and task-based connectivity reflect different components of functional integration that particularly depend on the functional state in which the subject is being scanned. Therefore, resting-state fMRI and DCM should be used as complementary measures when assessing functional brain networks.
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Affiliation(s)
- Anne K Rehme
- Max Planck Institute for Neurological Research, Neuromodulation & Neurorehabilitation, Cologne, Germany.
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440
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Jang SH, Kwon YH, Lee MY, Lee DY, Hong JH. Difference of neural connectivity for motor function in chronic hemiparetic stroke patients with intracerebral hemorrhage. Neurosci Lett 2012; 531:80-5. [PMID: 23123782 DOI: 10.1016/j.neulet.2012.10.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 10/16/2012] [Accepted: 10/19/2012] [Indexed: 11/16/2022]
Abstract
Difference of neural connectivity for motor function had been studied by observation of neural activity within gray matter and nucleus using functional neuroimaging techniques. Diffusion tensor imaging (DTI) by a probabilistic tracking is useful for exploration of structural connectivity in the brain. We attempted to investigate difference of neural connectivity for motor function of the affected hand in chronic hemiparetic patients with intracerebral hemorrhage (ICH). Forty-four patients with ICH and 31 normal control subjects were recruited. Diffusion tensor imaging was acquired using a sensitivity-encoding head coil at 1.5 T. Motor function was evaluated using the motricity index (MI) for hand and Modified Brunnstrom Classification (MBC). The presence or absence of a connection was confirmed between the precentral knob of the affected hemisphere and seven areas. Compared with healthy subjects, the patient group showed lower connectivity to the contralesional primary motor cortex, ipsilesional basal ganglia, ipsilesional thalamus, contralesional cerebellum, and ipsilesional medullary pyramid in the affected hemisphere (p<0.05). Connections to the ipsilesional basal ganglia, ipsilesional thalamus, and ipsilesional medullary pyramid showed positive correlation with MI and MBC (p<0.05). We found difference of neural connectivity for motor function between chronic hemiparetic patients with ICH and control subjects. Our results suggest that the motor function of the stroke patient is related to neural connectivity between the ipsilesional M1 and the ipsilesional medullary pyramid, ipsilesional basal ganglia, and ipsilesional thalamus.
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Affiliation(s)
- Sung Ho Jang
- Department of Physical Medicine and Rehabilitation, College of Medicine, Yeungnam University, Republic of Korea
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441
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Rehme AK, Grefkes C. Cerebral network disorders after stroke: evidence from imaging-based connectivity analyses of active and resting brain states in humans. J Physiol 2012; 591:17-31. [PMID: 23090951 DOI: 10.1113/jphysiol.2012.243469] [Citation(s) in RCA: 198] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Stroke causes a sudden disruption of physiological brain function which leads to impairments of functional brain networks involved in voluntary movements. In some cases, the brain has the intrinsic capacity to reorganize itself, thereby compensating for the disruption of motor networks. In humans, such reorganization can be investigated in vivo using neuroimaging. Recent developments in connectivity analyses based on functional neuroimaging data have provided new insights into the network pathophysiology underlying neurological symptoms. Here we review recent neuroimaging studies using functional resting-state correlations, effective connectivity models or graph theoretical analyses to investigate changes in neural motor networks and recovery after stroke. The data demonstrate that network disturbances after stroke occur not only in the vicinity of the lesion but also between remote cortical areas in the affected and unaffected hemisphere. The reorganization of motor networks encompasses a restoration of interhemispheric functional coherence in the resting state, particularly between the primary motor cortices. Furthermore, reorganized neural networks feature strong excitatory interactions between fronto-parietal areas and primary motor cortex in the affected hemisphere, suggesting that greater top-down control over primary motor areas facilitates motor execution in the lesioned brain. In addition, there is evidence that motor recovery is accompanied by a more random network topology with reduced local information processing. In conclusion, Stroke induces changes in functional and effective connectivity within and across hemispheres which relate to motor impairments and recovery thereof. Connectivity analyses may hence provide new insights into the pathophysiology underlying neurological deficits and may be further used to develop novel, neurobiologically informed treatment strategies.
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Affiliation(s)
- Anne K Rehme
- Max Planck Institute for Neurological Research, Gleueler Str. 50, 50931 Cologne, Germany
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442
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Chen HJ, Jiao Y, Zhu XQ, Zhang HY, Liu JC, Wen S, Teng GJ. Brain dysfunction primarily related to previous overt hepatic encephalopathy compared with minimal hepatic encephalopathy: resting-state functional MR imaging demonstration. Radiology 2012; 266:261-70. [PMID: 23047839 DOI: 10.1148/radiol.12120026] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE To investigate whether resting-state brain functional connectivity (FC) differed among cirrhotic patients without overt hepatic encephalopathy (HE) (OHE), those who currently had minimal HE (MHE), or those who had recovered from previous OHE and to investigate whether previous bouts of OHE rather than current MHE predominantly contributed to brain dysfunction in patients without current OHE. MATERIALS AND METHODS This study was approved by the institutional ethics committee, and informed consent was obtained. Resting-state functional magnetic resonance (MR) data were compared between healthy controls and the following groups of cirrhotic patients: (a) patients without MHE and without previous OHE, (b) patients with current MHE and without previous OHE, and (c) patients with previous OHE. Independent component analysis was applied to identify the best-fit component for the default-mode network (DMN). One-way analysis of variance was performed to detect different FC among groups. Pearson correlation analyses were conducted to determine the relationships between FC and neurocognitive performance. RESULTS Two important regions within the DMN, including the precuneus and posterior cingulate cortex and left medial frontal gyrus, showed significantly different FC among the four groups. A trend of gradually reduced FC in two regions was observed from controls, to patients without HE, and to patients with current MHE, while patients with previous OHE showed remarkably reduced FC in these two regions. Significant correlations were found between FC and neurocognitive performance in cirrhotic patients. CONCLUSION The reduced resting-state FC within DMN was associated with neurocognitive impairments in MHE and after clinical resolution of OHE. Previous OHE rather than current MHE might be primarily related to brain dysfunction in patients with latent OHE. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120026/-/DC1.
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Affiliation(s)
- Hua-Jun Chen
- Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School of Southeast University, 87 Dingjiaqiao Rd, Nanjing 210009, China
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443
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Carter AR, Shulman GL, Corbetta M. Why use a connectivity-based approach to study stroke and recovery of function? Neuroimage 2012; 62:2271-80. [PMID: 22414990 PMCID: PMC3733251 DOI: 10.1016/j.neuroimage.2012.02.070] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 12/27/2011] [Accepted: 02/24/2012] [Indexed: 01/19/2023] Open
Abstract
The brain is organized into a set of widely distributed networks. Therefore, although structural damage from stroke is focal, remote dysfunction can occur in regions connected to the area of lesion. Historically, neuroscience has focused on local processing due in part to the absence of tools to study the function of distributed networks. In this article we discuss how a more comprehensive understanding of the effects of stroke can be attained using resting state functional connectivity BOLD magnetic resonance imaging (resting state fcMRI). Resting state fcMRI has a number of advantages over task-evoked fMRI for studying brain network reorganization in response to stroke, including the ability to image subjects with a broad range of impairments and the ability to study multiple networks simultaneously. We describe our rationale for using resting state connectivity as a tool for investigating the neural substrates of stroke recovery in a heterogeneous population of stroke patients and discuss the main questions we hope to answer, in particular whether resting state fcMRI measures in the acute phase of stroke can predict subsequent recovery. Early results suggest that disruption of inter-hemispheric connectivity in the somatomotor network and the dorsal attention network is more strongly associated with behavioral impairment in those domains than is intra-hemispheric connectivity within either the lesioned or unaffected hemisphere. We also observe in the somatomotor network an interesting interaction between corticospinal tract damage and decreased inter-hemispheric connectivity that suggests that both processes combine to contribute to neuromotor impairment after stroke. A connectivity-based approach will provide greater insight into network reorganization in the acute and chronic phases after stroke and will contribute to improving prognostic ability and the development of therapeutic interventions.
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Affiliation(s)
- Alex R Carter
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
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444
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Dean PJA, Seiss E, Sterr A. Motor planning in chronic upper-limb hemiparesis: evidence from movement-related potentials. PLoS One 2012; 7:e44558. [PMID: 23049676 PMCID: PMC3462178 DOI: 10.1371/journal.pone.0044558] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 08/06/2012] [Indexed: 11/17/2022] Open
Abstract
Background Chronic hemiplegia is a common long-term consequence of stroke, and subsequent motor recovery is often incomplete. Neurophysiological studies have focused on motor execution deficits in relatively high functioning patients. Much less is known about the influence exerted by processes related to motor preparation, particularly in patients with poor motor recovery. Methodology/Principal Findings The current study investigates motor preparation using a modified response-priming experiment in a large sample of patients (n = 50) with moderate-to-severe chronic hemiparesis. The behavioural results revealed that hemiparetic patients had an increased response-priming effect compared to controls, but that their response times were markedly slower for both hands. Patients also demonstrated significantly enhanced midline late contingent negative variation (CNV) during paretic hand preparation, despite the absence of overall group differences when compared to controls. Furthermore, increased amplitude of the midline CNV correlated with a greater response-priming effect. We propose that these changes might reflect greater anticipated effort to respond in patients, and consequently that advance cueing of motor responses may be of benefit in these individuals. We further observed significantly reduced CNV amplitudes over the lesioned hemisphere in hemiparetic patients compared to controls during non-paretic hand preparation, preparation of both hands and no hand preparation. Two potential explanations for these CNV reductions are discussed: alterations in anticipatory attention or state changes in motor processing, for example an imbalance in inter-hemispheric inhibition. Conclusions/Significance Overall, this study provides evidence that movement preparation could play a crucial role in hemiparetic motor deficits, and that advance motor cueing may be of benefit in future therapeutic interventions. In addition, it demonstrates the importance of monitoring both the non-paretic and paretic hand after stroke and during therapeutic intervention.
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445
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Longitudinal Evaluation of Resting-State fMRI After Acute Stroke With Hemiparesis. Neurorehabil Neural Repair 2012; 27:153-63. [DOI: 10.1177/1545968312457827] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background. Functional magnetic resonance imaging (fMRI) of motor impairment after stroke strongly depends on patient effort and capacity to make a movement. Hence fMRI has had limited use in clinical management. Alternatively, resting-state fMRI (ie, with no task) can elucidate the brain’s functional connections by determining temporal synchrony between brain regions. Objective. The authors examined whether resting-state fMRI can elucidate the disruption of functional connections within hours of ischemic stroke as well as during recovery. Methods. A total of 51 ischemic stroke patients—31 with mild-to-moderate hand deficits (National Institutes of Health Stroke Scale [NIHSS] motor score ≥1) and 20 with NIHSS score of 0—underwent resting-state fMRI at <24 hours, 7 days, and 90 days poststroke; 15 age-matched healthy individuals participated in 1 session. Using the resting-state fMRI signal from the ipsilesional motor cortex, the strength of functional connections with the contralesional motor cortex was computed. Whole-brain maps of the resting-state motor network were also generated and compared between groups and sessions. Results. Within hours poststroke, patients with motor deficits exhibited significantly lower connectivity than controls ( P = .02) and patients with no motor impairment ( P = .03). Connectivity was reestablished after 7 days in recovered (ie, NIHSS score = 0) participants. After 90 days, recovered patients exhibited normal motor connectivity; however, reduced connectivity with subcortical regions associated with effort and cognitive processing remained. Conclusion. Resting-state fMRI within hours of ischemic stroke can demonstrate the impact of stroke on functional connections throughout the brain. This tool has the potential to help select appropriate stroke therapies in an acute imaging setting and to monitor the efficacy of rehabilitation.
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446
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Esslinger C, Schüler N, Sauer C, Gass D, Mier D, Braun U, Ochs E, Schulze TG, Rietschel M, Kirsch P, Meyer-Lindenberg A. Induction and quantification of prefrontal cortical network plasticity using 5 Hz rTMS and fMRI. Hum Brain Mapp 2012; 35:140-51. [PMID: 22965696 DOI: 10.1002/hbm.22165] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 06/16/2012] [Accepted: 06/18/2012] [Indexed: 01/08/2023] Open
Abstract
Neuronal plasticity is crucial for flexible interaction with a changing environment and its disruption is thought to contribute to psychiatric diseases like schizophrenia. High-frequency repetitive transcranial magnetic stimulation (rTMS) is a noninvasive tool to increase local excitability of neurons and induce short-time functional reorganization of cortical networks. While this has been shown for the motor system, little is known about the short-term plasticity of networks for executive cognition in humans. We examined 12 healthy control subjects in a crossover study with fMRI after real and sham 5 Hz rTMS to the right dorsolateral prefrontal cortex (DLPFC). During scanning, subjects performed an n-back working memory (WM) task and a flanker task engaging cognitive control. Reaction times during the n-back task were significantly shorter after rTMS than after sham stimulation. RTMS compared with sham stimulation caused no activation changes at the stimulation site (right DLPFC) itself, but significantly increased connectivity within the WM network during n-back and reduced activation in the anterior cingulate cortex during the flanker task. Reduced reaction times after real stimulation support an excitatory effect of high-frequency rTMS. Our findings identified plastic changes in prefrontally connected networks downstream of the stimulation site as the substrate of this behavioral effect. Using a multimodal fMRI-rTMS approach, we could demonstrate changes in cortical plasticity in humans during executive cognition. In further studies this approach could be used to study pharmacological, genetic and disease-related alterations.
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Affiliation(s)
- Christine Esslinger
- Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, University of Heidelberg, Mannheim, Germany
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447
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Abstract
We reviewed the literature on walking recovery of stroke patients as it relates to the following subjects:epidemiology of walking dysfunction, recovery course of walking, and recovery mechanism of walking (neural control of normal walking, the evaluation methods for leg motor function, and motor recovery mechanism of leg).The recovery of walking is one of the primary goals in stroke patients, along with the recovery of hand function and cognition. Walking function has greater potential for recovery than hand function because motor function of the leg is less dependent on the lateral corticospinal tract than that of hand function. This suggests that detailed knowledge of walking can be used to increase the likelihood that stroke patients recover their ability to walk. Therefore, we suggest that further research should focus on these topics, especially, on the neural control mechanism of walking and motor recovery mechanisms of the leg in stroke patients.
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448
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Hill ES, Vasireddi SK, Bruno AM, Wang J, Frost WN. Variable neuronal participation in stereotypic motor programs. PLoS One 2012; 7:e40579. [PMID: 22815768 PMCID: PMC3398049 DOI: 10.1371/journal.pone.0040579] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Accepted: 06/10/2012] [Indexed: 11/19/2022] Open
Abstract
To what extent are motor networks underlying rhythmic behaviors rigidly hard-wired versus fluid and dynamic entities? Do the members of motor networks change from moment-to-moment or from motor program episode-to-episode? These are questions that can only be addressed in systems where it is possible to monitor the spiking activity of networks of neurons during the production of motor programs. We used large-scale voltage-sensitive dye (VSD) imaging followed by Independent Component Analysis spike-sorting to examine the extent to which the neuronal network underlying the escape swim behavior of Tritonia diomedea is hard-wired versus fluid from a moment-to-moment perspective. We found that while most neurons were dedicated to the swim network, a small but significant proportion of neurons participated in a surprisingly variable manner. These neurons joined the swim motor program late, left early, burst only on some cycles or skipped cycles of the motor program. We confirmed that this variable neuronal participation was not due to effects of the VSD by finding such neurons with intracellular recording in dye-free saline. Further, these neurons markedly varied their level of participation in the network from swim episode-to-episode. The generality of such unreliably bursting neurons was confirmed by their presence in the rhythmic escape networks of two other molluscan species, Tritonia festiva and Aplysia californica. Our observations support a view that neuronal networks, even those underlying rhythmic and stereotyped motor programs, may be more variable in structure than widely appreciated.
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Affiliation(s)
- Evan S Hill
- Department of Cell Biology and Anatomy, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
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449
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Resting state α-band functional connectivity and recovery after stroke. Exp Neurol 2012; 237:160-9. [PMID: 22750324 DOI: 10.1016/j.expneurol.2012.06.020] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/08/2012] [Accepted: 06/20/2012] [Indexed: 11/23/2022]
Abstract
After cerebral ischemia, disruption and subsequent reorganization of functional connections occur both locally and remote to the lesion. However, the unpredictable timing and extent of sensorimotor recovery reflects a gap in understanding of these underlying neural mechanisms. We aimed to identify the plasticity of alpha-band functional neural connections within the perilesional area and the predictive value of functional connectivity with respect to motor recovery of the upper extremity after stroke. Our results show improvements in upper extremity motor recovery in relation to distributed changes in MEG-based alpha band functional connectivity, both in the perilesional area and contralesional cortex. Motor recovery was found to be predicted by increased connectivity at baseline in the ipsilesional somatosensory area, supplementary motor area, and cerebellum, contrasted with reduced connectivity of contralesional motor regions, after controlling for age, stroke onset-time and lesion size. These findings support plasticity within a widely distributed neural network and define brain regions in which the extent of network participation predicts post-stroke recovery potential.
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450
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Ivković M, Kuceyeski A, Raj A. Statistics of weighted brain networks reveal hierarchical organization and Gaussian degree distribution. PLoS One 2012; 7:e35029. [PMID: 22761649 PMCID: PMC3382201 DOI: 10.1371/journal.pone.0035029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 10/20/2010] [Indexed: 11/30/2022] Open
Abstract
Whole brain weighted connectivity networks were extracted from high resolution diffusion MRI data of 14 healthy volunteers. A statistically robust technique was proposed for the removal of questionable connections. Unlike most previous studies our methods are completely adapted for networks with arbitrary weights. Conventional statistics of these weighted networks were computed and found to be comparable to existing reports. After a robust fitting procedure using multiple parametric distributions it was found that the weighted node degree of our networks is best described by the normal distribution, in contrast to previous reports which have proposed heavy tailed distributions. We show that post-processing of the connectivity weights, such as thresholding, can influence the weighted degree asymptotics. The clustering coefficients were found to be distributed either as gamma or power-law distribution, depending on the formula used. We proposed a new hierarchical graph clustering approach, which revealed that the brain network is divided into a regular base-2 hierarchical tree. Connections within and across this hierarchy were found to be uncommonly ordered. The combined weight of our results supports a hierarchically ordered view of the brain, whose connections have heavy tails, but whose weighted node degrees are comparable.
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Affiliation(s)
- Miloš Ivković
- Weill Cornell Medical College, New York, New York, United States of America.
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