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Bao Z, Zhang T, Pan T, Zhang W, Zhao S, Liu H, Nie B. Automatic method for individual parcellation of manganese-enhanced magnetic resonance imaging of rat brain. Front Neurosci 2022; 16:954237. [PMID: 35968388 PMCID: PMC9365988 DOI: 10.3389/fnins.2022.954237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/05/2022] [Indexed: 11/25/2022] Open
Abstract
Aims To construct an automatic method for individual parcellation of manganese-enhanced magnetic resonance imaging (MEMRI) of rat brain with high accuracy, which could preserve the inherent voxel intensity and Regions of interest (ROI) morphological characteristics simultaneously. Methods and results The transformation relationship from standardized space to individual space was obtained by firstly normalizing individual image to the Paxinos space and then inversely transformed. On the other hand, all the regions defined in the atlas image were separated and resaved as binary mask images. Then, transforming the mask images into individual space via the inverse transformations and reslicing using the 4th B-spline interpolation algorithm. The boundary of these transformed regions was further refined by image erosion and expansion operator, and finally combined together to generate the individual parcellations. Moreover, two groups of MEMRI images were used for evaluation. We found that the individual parcellations were satisfied, and the inherent image intensity was preserved. The statistical significance of case-control comparisons was further optimized. Conclusions We have constructed a new automatic method for individual parcellation of rat brain MEMRI images, which could preserve the inherent voxel intensity and further be beneficial in case-control statistical analyses. This method could also be extended to other imaging modalities, even other experiments species. It would facilitate the accuracy and significance of ROI-based imaging analyses.
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Affiliation(s)
- Zhiguo Bao
- First Affiliated Hospital of Henan University, Kaifeng, China
| | - Tianhao Zhang
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Tingting Pan
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- Physical Science and Technology College, Zhengzhou University, Zhengzhou, China
| | - Wei Zhang
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Shilun Zhao
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Hua Liu
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Binbin Nie
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China
- *Correspondence: Binbin Nie
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2
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Van der Linden A, Hoehn M. Monitoring Neuronal Network Disturbances of Brain Diseases: A Preclinical MRI Approach in the Rodent Brain. Front Cell Neurosci 2022; 15:815552. [PMID: 35046778 PMCID: PMC8761853 DOI: 10.3389/fncel.2021.815552] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/06/2021] [Indexed: 12/20/2022] Open
Abstract
Functional and structural neuronal networks, as recorded by resting-state functional MRI and diffusion MRI-based tractography, gain increasing attention as data driven whole brain imaging methods not limited to the foci of the primary pathology or the known key affected regions but permitting to characterize the entire network response of the brain after disease or injury. Their connectome contents thus provide information on distal brain areas, directly or indirectly affected by and interacting with the primary pathological event or affected regions. From such information, a better understanding of the dynamics of disease progression is expected. Furthermore, observation of the brain's spontaneous or treatment-induced improvement will contribute to unravel the underlying mechanisms of plasticity and recovery across the whole-brain networks. In the present review, we discuss the values of functional and structural network information derived from systematic and controlled experimentation using clinically relevant animal models. We focus on rodent models of the cerebral diseases with high impact on social burdens, namely, neurodegeneration, and stroke.
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Affiliation(s)
- Annemie Van der Linden
- Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
- μNEURO Research Centre of Excellence, University of Antwerp, Antwerp, Belgium
| | - Mathias Hoehn
- Research Center Jülich, Institute 3 for Neuroscience and Medicine, Jülich, Germany
- *Correspondence: Mathias Hoehn
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3
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Pallast N, Diedenhofen M, Blaschke S, Wieters F, Wiedermann D, Hoehn M, Fink GR, Aswendt M. Processing Pipeline for Atlas-Based Imaging Data Analysis of Structural and Functional Mouse Brain MRI (AIDAmri). Front Neuroinform 2019; 13:42. [PMID: 31231202 PMCID: PMC6559195 DOI: 10.3389/fninf.2019.00042] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 05/21/2019] [Indexed: 11/23/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a key technology in multimodal animal studies of brain connectivity and disease pathology. In vivo MRI provides non-invasive, whole brain macroscopic images containing structural and functional information, thereby complementing invasive in vivo high-resolution microscopy and ex vivo molecular techniques. Brain mapping, the correlation of corresponding regions between multiple brains in a standard brain atlas system, is widely used in human MRI. For small animal MRI, however, there is no scientific consensus on pre-processing strategies and atlas-based neuroinformatics. Thus, it remains difficult to compare and validate results from different pre-clinical studies which were processed using custom-made code or individual adjustments of clinical MRI software and without a standard brain reference atlas. Here, we describe AIDAmri, a novel Atlas-based Imaging Data Analysis pipeline to process structural and functional mouse brain data including anatomical MRI, fiber tracking using diffusion tensor imaging (DTI) and functional connectivity analysis using resting-state functional MRI (rs-fMRI). The AIDAmri pipeline includes automated pre-processing steps, such as raw data conversion, skull-stripping and bias-field correction as well as image registration with the Allen Mouse Brain Reference Atlas (ARA). Following a modular structure developed in Python scripting language, the pipeline integrates established and newly developed algorithms. Each processing step was optimized for efficient data processing requiring minimal user-input and user programming skills. The raw data is analyzed and results transferred to the ARA coordinate system in order to allow an efficient and highly-accurate region-based analysis. AIDAmri is intended to fill the gap of a missing open-access and cross-platform toolbox for the most relevant mouse brain MRI sequences thereby facilitating data processing in large cohorts and multi-center studies.
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Affiliation(s)
- Niklas Pallast
- Department of Neurology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Michael Diedenhofen
- In-vivo-NMR Laboratory, Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Stefan Blaschke
- Department of Neurology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Frederique Wieters
- Department of Neurology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Dirk Wiedermann
- In-vivo-NMR Laboratory, Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Mathias Hoehn
- In-vivo-NMR Laboratory, Max Planck Institute for Metabolism Research, Cologne, Germany.,Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Juelich, Juelich, Germany
| | - Gereon R Fink
- Department of Neurology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.,Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Juelich, Juelich, Germany
| | - Markus Aswendt
- Department of Neurology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
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4
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Nunes D, Ianus A, Shemesh N. Layer-specific connectivity revealed by diffusion-weighted functional MRI in the rat thalamocortical pathway. Neuroimage 2019; 184:646-657. [PMID: 30267858 PMCID: PMC6264401 DOI: 10.1016/j.neuroimage.2018.09.050] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 09/17/2018] [Accepted: 09/18/2018] [Indexed: 12/18/2022] Open
Abstract
Investigating neural activity from a global brain perspective in-vivo has been in the domain of functional Magnetic Resonance Imaging (fMRI) over the past few decades. The intricate neurovascular couplings that govern fMRI's blood-oxygenation-level-dependent (BOLD) functional contrast are invaluable in mapping active brain regions, but they also entail significant limitations, such as non-specificity of the signal to active foci. Diffusion-weighted functional MRI (dfMRI) with relatively high diffusion-weighting strives to ameliorate this shortcoming as it offers functional contrasts more intimately linked with the underlying activity. Insofar, apart from somewhat smaller activation foci, dfMRI's contrasts have not been convincingly shown to offer significant advantages over BOLD-driven fMRI, and its activation maps relied on significant modelling. Here, we study whether dfMRI could offer a better representation of neural activity in the thalamocortical pathway compared to its (spin-echo (SE)) BOLD counterpart. Using high-end forepaw stimulation experiments in the rat at 9.4 T, and with significant sensitivity enhancements due to the use of cryocoils, we show for the first time that dfMRI signals exhibit layer specificity, and, additionally, display signals in areas devoid of SE-BOLD responses. We find that dfMRI signals in the thalamocortical pathway cohere with each other, namely, dfMRI signals in the ventral posterolateral (VPL) thalamic nucleus cohere specifically with layers IV and V in the somatosensory cortex. These activity patterns are much better correlated (compared with SE-BOLD signals) with literature-based electrophysiological recordings in the cortex as well as thalamus. All these findings suggest that dfMRI signals better represent the underlying neural activity in the pathway. In turn, these advanatages may have significant implications towards a much more specific and accurate mapping of neural activity in the global brain in-vivo.
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Affiliation(s)
- Daniel Nunes
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal
| | - Andrada Ianus
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal; Centre for Medical Image Computing, University College London, London, UK
| | - Noam Shemesh
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal.
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5
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Neuroimaging in animal models of epilepsy. Neuroscience 2017; 358:277-299. [DOI: 10.1016/j.neuroscience.2017.06.062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/27/2017] [Accepted: 06/28/2017] [Indexed: 02/06/2023]
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6
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Sonnay S, Just N, Duarte JMN, Gruetter R. Imaging of prolonged BOLD response in the somatosensory cortex of the rat. NMR IN BIOMEDICINE 2015; 28:414-421. [PMID: 25702944 DOI: 10.1002/nbm.3263] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 11/21/2014] [Accepted: 01/05/2015] [Indexed: 06/04/2023]
Abstract
Blood oxygenation level-dependent (BOLD) functional MRI is a widely employed methodology in experimental and clinical neuroscience, although its nature is not fully understood. To gain insights into BOLD mechanisms and take advantage of the new functional methods, it is of interest to investigate prolonged paradigms of activation suitable for long experimental protocols and to observe any long-term modifications induced by these functional challenges. While different types of sustained stimulation paradigm have been explored in human studies, the BOLD response is typically limited to a few minutes in animal models, due to fatigue, anesthesia effects and physiological instability. In the present study, the rat forepaw was electrically stimulated for 2 h, which resulted in a prolonged and localized cortical BOLD response over that period. The stimulation paradigm, including an inter-stimulus interval (ISI) of 10 s, that is 25% of the total time, was applied at constant or variable frequency over 2 h. The steady-state level of the BOLD response was reached after 15-20 min of stimulation and was maintained until the end of the stimulation. On average, no substantial loss in activated volume was observed at the end of the stimulation, but less variability in the fraction of remaining activated volume and higher steady-state BOLD amplitude were observed when stimulation frequency was varied between 2 and 3 Hz every 5 min. We conclude that the combination of ISI and variable stimulus frequency reproducibly results in robust, prolonged and localized BOLD activation.
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Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
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7
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Richards K, Calamante F, Tournier JD, Kurniawan ND, Sadeghian F, Retchford AR, Jones GD, Reid CA, Reutens DC, Ordidge R, Connelly A, Petrou S. Mapping somatosensory connectivity in adult mice using diffusion MRI tractography and super-resolution track density imaging. Neuroimage 2014; 102 Pt 2:381-92. [DOI: 10.1016/j.neuroimage.2014.07.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Revised: 07/07/2014] [Accepted: 07/22/2014] [Indexed: 12/13/2022] Open
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Deterministic diffusion fiber tracking improved by quantitative anisotropy. PLoS One 2013; 8:e80713. [PMID: 24348913 PMCID: PMC3858183 DOI: 10.1371/journal.pone.0080713] [Citation(s) in RCA: 668] [Impact Index Per Article: 60.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/04/2013] [Indexed: 01/19/2023] Open
Abstract
Diffusion MRI tractography has emerged as a useful and popular tool for mapping connections between brain regions. In this study, we examined the performance of quantitative anisotropy (QA) in facilitating deterministic fiber tracking. Two phantom studies were conducted. The first phantom study examined the susceptibility of fractional anisotropy (FA), generalized factional anisotropy (GFA), and QA to various partial volume effects. The second phantom study examined the spatial resolution of the FA-aided, GFA-aided, and QA-aided tractographies. An in vivo study was conducted to track the arcuate fasciculus, and two neurosurgeons blind to the acquisition and analysis settings were invited to identify false tracks. The performance of QA in assisting fiber tracking was compared with FA, GFA, and anatomical information from T1-weighted images. Our first phantom study showed that QA is less sensitive to the partial volume effects of crossing fibers and free water, suggesting that it is a robust index. The second phantom study showed that the QA-aided tractography has better resolution than the FA-aided and GFA-aided tractography. Our in vivo study further showed that the QA-aided tractography outperforms the FA-aided, GFA-aided, and anatomy-aided tractographies. In the shell scheme (HARDI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 30.7%, 32.6%, and 24.45% of the false tracks, respectively, while the QA-aided tractography has 16.2%. In the grid scheme (DSI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 12.3%, 9.0%, and 10.93% of the false tracks, respectively, while the QA-aided tractography has 4.43%. The QA-aided deterministic fiber tracking may assist fiber tracking studies and facilitate the advancement of human connectomics.
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9
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Sui J, Huster R, Yu Q, Segall JM, Calhoun VD. Function-structure associations of the brain: evidence from multimodal connectivity and covariance studies. Neuroimage 2013; 102 Pt 1:11-23. [PMID: 24084066 DOI: 10.1016/j.neuroimage.2013.09.044] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 09/18/2013] [Accepted: 09/20/2013] [Indexed: 12/13/2022] Open
Abstract
Despite significant advances in multimodal imaging techniques and analysis approaches, unimodal studies are still the predominant way to investigate brain changes or group differences, including structural magnetic resonance imaging (sMRI), functional MRI (fMRI), diffusion tensor imaging (DTI) and electroencephalography (EEG). Multimodal brain studies can be used to understand the complex interplay of anatomical, functional and physiological brain alterations or development, and to better comprehend the biological significance of multiple imaging measures. To examine the function-structure associations of the brain in a more comprehensive and integrated manner, we reviewed a number of multimodal studies that combined two or more functional (fMRI and/or EEG) and structural (sMRI and/or DTI) modalities. In this review paper, we specifically focused on multimodal neuroimaging studies on cognition, aging, disease and behavior. We also compared multiple analysis approaches, including univariate and multivariate methods. The possible strengths and limitations of each method are highlighted, which can guide readers when selecting a method based on a given research question. In particular, we believe that multimodal fusion approaches will shed further light on the neuronal mechanisms underlying the major structural and functional pathophysiological features of both the healthy brain (e.g. development) or the diseased brain (e.g. mental illness) and, in the latter case, may provide a more sensitive measure than unimodal imaging for disease classification, e.g. multimodal biomarkers, which potentially can be used to support clinical diagnosis based on neuroimaging techniques.
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Affiliation(s)
- Jing Sui
- The Mind Research Network, Albuquerque, NM 87106, USA; Brainnetome Center, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China; National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China.
| | - Rene Huster
- Experimental Psychology Lab, Carl von Ossietzky University, Oldenburg, Germany
| | - Qingbao Yu
- The Mind Research Network, Albuquerque, NM 87106, USA
| | | | - Vince D Calhoun
- The Mind Research Network, Albuquerque, NM 87106, USA; Dept. of ECE, University of New Mexico, Albuquerque, NM 87131, USA.
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10
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van Luijtelaar G, Mishra AM, Edelbroek P, Coman D, Frankenmolen N, Schaapsmeerders P, Covolato G, Danielson N, Niermann H, Janeczko K, Kiemeneij A, Burinov J, Bashyal C, Coquillette M, Lüttjohann A, Hyder F, Blumenfeld H, van Rijn CM. Anti-epileptogenesis: Electrophysiology, diffusion tensor imaging and behavior in a genetic absence model. Neurobiol Dis 2013; 60:126-38. [PMID: 23978468 DOI: 10.1016/j.nbd.2013.08.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 08/14/2013] [Indexed: 11/18/2022] Open
Abstract
The beneficial effects of chronic and early pharmacological treatment with ethosuximide on epileptogenesis were studied in a genetic absence epilepsy model comorbid for depression. It was also investigated whether there is a critical treatment period and treatment length. Cortical excitability in the form of electrical evoked potentials, but also to cortico-thalamo-cortical network activity (spike-wave discharges, SWD and afterdischarges), white matter changes representing extra cortico-thalamic functions and depressive-like behavior were investigated. WAG/Rij rats received either ethosuximide for 2 months (post natal months 2-3 or 4-5), or ethosuximide for 4 months (2-5) in their drinking water, while control rats drank plain water. EEG measurements were made during treatment, and 6 days and 2 months post treatment. Behavioral test were also done 6 days post treatment. DTI was performed ex vivo post treatment. SWD were suppressed during treatment, and 6 days and 2 months post treatment in the 4 month treated group, as well as the duration of AD elicited by cortical electrical stimulation 6 days post treatment. Increased fractional anisotropy in corpus callosum and internal capsula on DTI was found, an increased P8 evoked potential amplitude and a decreased immobility in the forced swim test. Shorter treatments with ETX had no large effects on any parameter. Chronic ETX has widespread effects not only within but also outside the circuitry in which SWD are initiated and generated, including preventing epileptogenesis and reducing depressive-like symptoms. The treatment of patients before symptom onset might prevent many of the adverse consequences of chronic epilepsy.
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Affiliation(s)
- Gilles van Luijtelaar
- Donders Centre for Cognition, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
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11
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Harsan LA, Dávid C, Reisert M, Schnell S, Hennig J, von Elverfeldt D, Staiger JF. Mapping remodeling of thalamocortical projections in the living reeler mouse brain by diffusion tractography. Proc Natl Acad Sci U S A 2013; 110:E1797-806. [PMID: 23610438 PMCID: PMC3651497 DOI: 10.1073/pnas.1218330110] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
A major challenge in neuroscience is to accurately decipher in vivo the entire brain circuitry (connectome) at a microscopic level. Currently, the only methodology providing a global noninvasive window into structural brain connectivity is diffusion tractography. The extent to which the reconstructed pathways reflect realistic neuronal networks depends, however, on data acquisition and postprocessing factors. Through a unique combination of approaches, we designed and evaluated herein a framework for reliable fiber tracking and mapping of the living mouse brain connectome. One important wiring scheme, connecting gray matter regions and passing fiber-crossing areas, was closely examined: the lemniscal thalamocortical (TC) pathway. We quantitatively validated the TC projections inferred from in vivo tractography with correlative histological axonal tracing in the same wild-type and reeler mutant mice. We demonstrated noninvasively that changes in patterning of the cortical sheet, such as highly disorganized cortical lamination in reeler, led to spectacular compensatory remodeling of the TC pathway.
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Affiliation(s)
- Laura-Adela Harsan
- Department of Radiology, Medical Physics, University Medical Center and the BrainLinks-BrainTools Excellence Cluster of the University of Freiburg, 79106 - Freiburg, Germany
| | - Csaba Dávid
- Department of Human Morphology and Developmental Biology, Semmelweis University, Budapest, H-1094, Hungary
| | - Marco Reisert
- Department of Radiology, Medical Physics, University Medical Center and the BrainLinks-BrainTools Excellence Cluster of the University of Freiburg, 79106 - Freiburg, Germany
| | - Susanne Schnell
- Department of Radiology, Medical Physics, University Medical Center and the BrainLinks-BrainTools Excellence Cluster of the University of Freiburg, 79106 - Freiburg, Germany
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611-2927; and
| | - Jürgen Hennig
- Department of Radiology, Medical Physics, University Medical Center and the BrainLinks-BrainTools Excellence Cluster of the University of Freiburg, 79106 - Freiburg, Germany
| | - Dominik von Elverfeldt
- Department of Radiology, Medical Physics, University Medical Center and the BrainLinks-BrainTools Excellence Cluster of the University of Freiburg, 79106 - Freiburg, Germany
| | - Jochen F. Staiger
- Department of Neuroanatomy and
- Deutsche Forschungsgemeinschaft Center for Molecular Physiology of the Brain/Excellence Cluster 171, Georg-August University, 37075 Göttingen, Germany
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Po C, Kalthoff D, Kim YB, Nelles M, Hoehn M. White matter reorganization and functional response after focal cerebral ischemia in the rat. PLoS One 2012; 7:e45629. [PMID: 23029148 PMCID: PMC3445514 DOI: 10.1371/journal.pone.0045629] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 08/20/2012] [Indexed: 11/18/2022] Open
Abstract
After stroke, the brain has shown to be able to achieve spontaneous functional recovery despite severe cerebral damage. This phenomenon is poorly understood. To address this issue, focal transient ischemia was induced by 60 min middle cerebral artery occlusion in Wistar rats. The evolution of stroke was followed using two magnetic resonance imaging modalities: diffusion spectrum imaging (acquired before, one and four weeks after stroke) and functional magnetic resonance imaging (acquired before and five weeks after stroke). To confirm the imaging observations, immunohistochemical staining for myelin, astrocytes and macrophages/microglia was added. At four weeks after stroke, a focal alteration of the diffusion anisotropy was observed between the ipsilesional ventricle and the lesion area. Using tractography this perturbation was identified as reorganization of the ipsilesional internal capsule. Functional imaging at five weeks after ischemia demonstrated activation of the primary sensorimotor cortex in both hemispheres in all rats except one animal lacking a functional response in the ipsilesional cortex. Furthermore, fiber tracking showed a transhemispheric fiber connection through the corpus callosum, which-in the rat without functional recovery-was lost. Our study shows the influence of the internal capsule reorganization, combined with inter-hemispheric connections though the corpus callosum, on the functional activation of the brain from stroke. In conclusion, tractography opens a new door to non-invasively investigate the structural correlates of lack of functional recovery after stroke.
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Affiliation(s)
- Chrystelle Po
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany
| | - Daniel Kalthoff
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany
| | - Young Beom Kim
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany
| | - Melanie Nelles
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany
| | - Mathias Hoehn
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany
- * E-mail:
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Hoehn M, Aswendt M. Structure-function relationship of cerebral networks in experimental neuroscience: contribution of magnetic resonance imaging. Exp Neurol 2012; 242:65-73. [PMID: 22572591 DOI: 10.1016/j.expneurol.2012.04.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 03/20/2012] [Accepted: 04/23/2012] [Indexed: 11/25/2022]
Abstract
The analysis of neuronal networks, their interactions in resting condition as well as during brain activation have become of great interest for a better understanding of the signal processing of the brain during sensory stimulus or cognitive tasks. Parallel to the study of the functional networks and their dynamics, the underlying network structure is highly important as it provides the basis of the functional interaction. Moreover, under pathological conditions, some nodes in such a net may be impaired and the function of the whole network affected. Mechanisms such as functional deficit and improvement, and plastic reorganization are increasingly discussed in the context of existing structural and functional networks. While many of these aspects have been followed in human and clinical studies, the experimental range is limited for obvious reasons. Here, animal experimental studies are needed as they permit longer scan times and, moreover, comparison with invasive histology. Experimental non-invasive imaging modalities are now able to perform impressive contributions. In this review we try to highlight most recent new cutting-edge developments and applications in experimental neuroscience of functional and structural networks of the brain, relying on non-invasive imaging. We focus primarily on the potential of experimental Magnetic Resonance Imaging (MRI), but also touch upon micro positron emission tomography (μPET) and optical imaging developments where they are applicable to the topic of the present review.
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Affiliation(s)
- Mathias Hoehn
- In-vivo-NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany.
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