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Localization of correlated network activity at the cortical level with MEG

NEUROimage 2008年第4期39卷 1706-1720页

作者： Kujala, Jan Gross, Joachim Salmelin, Riitta Aalto Univ Low Temp Lab Brain Res Unit FIN-02015 Espoo Finland Univ Glasgow Dept Psychol Ctr Cognit Neuroimaging Glasgow G12 8QQ Lanark Scotland

In both hemodynamic and neurophysiological imaging methods, analysis of functionally interconnected networks has typically focused on brain areas that show strong activation in specific tasks. Alternatively, connectivity measures may be used directly to localize network nodes, independent of their level of activation. This approach requires initial cortical reference areas which may be identified based on their high level of activation, their coherence with an external reference signal, or their strong connectivity with other brain areas. Irrespective of how the nodes have been localized the mathematical complexity of the analysis methods precludes verification of the accuracy and completeness of the network structure by direct comparison with the measured data. Therefore, it is critical to understand how the choices of parameters and procedures used in the analysis affect the network identification. Here, using simulated and measured magnetoencephalography (MEG) data, and Dynamic Imaging of Coherent Sources (DICS) for connectivity analysis, we quantify the veracity of network detection at the individual and group level as a function of relevant parameter choices. Using simulations, we demonstrate that coupling measures enable accurate identification of the network structure even without external reference signals, and illustrate the applicability of this approach to real data. We show that a valid estimate of interindividual variability is critical for reliable group-level analysis. Although this study focuses on application of DICS to MEG data, many issues considered here, especially those regarding individual vs. group-level analysis, are likely to be relevant for other neuroimaging methods and analysis approaches as well. (C) 2007 Elsevier Inc. All rights reserved.

关键词： Adult Algorithms Brain Mapping/methods Brain Mapping/methods Cerebral Cortex/anatomy & histology Cerebral Cortex/physiology Cerebrovascular Circulation/physiology computer Simulation Electromyography Fingers/innervation Fingers/physiology Humans image processing, computer-assisted Magnetic Resonance Imaging Magnetoencephalography Magnetoencephalography Movement/physiology Nerve Net/anatomy & histology Nerve Net/physiology

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Hippocampal shape differences in dementia with Lewy bodies

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NEUROimage 2008年第3期41卷 699-705页

作者： Sabattoli, F. Boccardi, M. Galluzzi, S. Treves, A. Thompson, P. M. Frisoni, G. B. IRCCS Ctr San Giovanni di Dio FBF Lab Epidemiol Neuroimaging & Telemed LENITEM Psychogeriatr Ward I-25125 Brescia Italy SISSA Int Sch Adv Studies Cognit Neurosci Sector I-34014 Trieste Italy Univ Calif Los Angeles Sch Med Dept Neurol Brain Mapping DivLab Neuro Imaging Los Angeles CA 90024 USA AFaR Assoc Fatebenefratelli Ric Rome Italy

To assess the morphological changes of the hippocampus in Lewy body dementia (LBD) patients we used radial atrophy mapping, a mathematical modeling method sensitive to subtle differences in hippocampal shape. T1-weighted high resolution magnetic resonance (MR) scans were acquired from 14 LBD and 28 controls of similar age and gender, and were compared to those of 28 patients with Alzheimer's disease (AD) described previously. MR images were normalized by linear (12 parameter) transformation to a customized template. The hippocampal formation was isolated by manual tracing. Group differences were assessed with algorithms that average hippocampal shapes across subjects, using three-dimensional parametric surface mesh models. In LBD patients, significant tissue loss amounting to 10-20% was found in the hippocampal subregions corresponding to the anterior portion of the CA1 field on both sides, along the longitudinal midline in the dorsal aspect within the CA2-3 field, and in the subiculum and presubiculum. The direct comparisons between LBD and AD patients showed that this pattern of local atrophy is different from that characteristic of AD. LBD pattern of hippocampal atrophy might be related to the peculiar neuropathology of the disease. (C) 2008 Elsevier Inc. All rights reserved.

关键词： Aged Algorithms Alzheimer Disease/pathology Female Hippocampus/pathology Humans image processing, computer-assisted Imaging, Three-Dimensional/methods Lewy Body Disease/pathology Magnetic Resonance Imaging Male Models, Theoretical

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White matter tracts in first-episode psychosis: A DTI tractography study of the uncinate fasciculus

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NEUROimage 2008年第3期39卷 949-955页

作者： Price, Gary Cercignani, Mara Parker, Geoffrey J. M. Altmann, Daniel R. Barnes, Thomas R. E. Barker, Gareth J. Joyce, Eileen M. Ron, Maria A. UCL Inst Neurol London England Univ Manchester Manchester M13 9PL Lancs England London Sch Hyg & Trop Med Med Stat Unit London WC1 England Univ London Imperial Coll Sci Technol & Med Fac Med London England Kings Coll London Inst Psychiat Dept Clin Neurosci Ctr Neuroimaging Sci London England

A model of disconnectivity involving abnormalities in the cortex and connecting white matter pathways may explain the symptoms and cognitive abnormalities of schizophrenia. Recently, diffusion imaging tractography has made it possible to study white matter pathways in detail, and we present here a study of patients with first-episode psychosis using this technique. We studied the uncinate fasciculus (UF), the largest white matter tract that connects the frontal and temporal lobes, two brain regions significantly implicated in schizophrenia. Nineteen patients with first-episode schizophrenia and 23 controls were studied using a probabilistic tractography algorithm (PICo). Fractional anisotropy (FA) and probability of connection were obtained for every voxel in the tract, and the group means and distributions of these variables were compared. The spread of the FA distribution in the upper tail, as measured by the squared coefficient of variance (SCV), was reduced in the left UF in the patient group, indicating that the number of voxels with high FA values was reduced in the core of the tract and suggesting the presence of changes in fibre alignment and tract coherence in the patient group. The SCV of FA was lower in females across both groups and there was no correlation between the SCV of FA and clinical ratings. (c) 2007 Elsevier Inc. All rights reserved.

关键词： Adolescent Adult Aging/physiology Algorithms Cerebral Cortex/pathology Diffusion Magnetic Resonance Imaging Female Humans image processing, computer-assisted Longitudinal Studies Male Neural Pathways/pathology Psychiatric Status Rating Scales Psychotic Disorders/pathology Regression Analysis

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Regions of interest analysis in pharmacological fMRI: How do the definition criteria influence the inferred result?

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NEUROimage 2008年第1期40卷 121-132页

作者： Mitsis, Georgios D. Iannetti, Gian Domenico Smart, Trevor S. Tracey, Irene Wise, Richard G. Univ Oxford Ctr Funct Magnet Resonance Imaging Brain Dept Clin Neurol Oxford England Univ Oxford Dept Physiol Anat & Genet Oxford England Pfizer Ltd Sandwich CT13 9NJ Kent England Cardiff Univ Sch Psychol Brain Res Imaging Ctr Cardiff Wales

Prior hypotheses in functional brain imaging are often formulated by constraining the data analysis to regions of interest (ROIs). In this context, this approach yields higher sensitivity than whole brain analyses, which could be particularly important in drug development studies and clinical decision making. Here we systematically examine the effects of different ROI definition criteria on the results inferred from a hypothesis-driven pharmacological fMRI experiment, with the aim of maximising sensitivity and providing a recommended procedure for similar studies. In order to achieve this, we compared different criteria for selecting both anatomical and functional ROIs. Anatomical ROIs were defined (i) specifically for each subject, (ii) at group level, and (iii) using a Talairach-like atlas, in order to assess the effects of inter-subject anatomical variability. Functional ROIs (fROIs) were defined, both for each subject and at group level, by (i) selecting the voxels with the highest Z-score from each study session, and (ii) selecting an inclusive union of significantly active voxels across all sessions. A single value was used to summarise the response within each ROI For anatomical ROIs we used the mean of the parameter estimates (0 values) of either all voxels or the top 20% active voxels. For fROIs we used the mean beta value of all voxels constituting the ROI The results were assessed in terms of the achieved sensitivity in detecting the experimental effect. The use of single-subject anatomical ROIs combined with a summary value calculated from the top 20% fraction of active voxels was the most reliable and sensitive approach for detecting the experimental effect. The use of fROIs from individual sessions introduced unacceptable biases in the results, while the use of union fROIs yielded a lower sensitivity than anatomical ROIs. For these reasons, fROIs should be employed with caution when it is not possible to make clear anatomical prior hypotheses. (c) 2007

关键词： Adult Amines/pharmacology Analgesics/pharmacology Brain/drug effects Brain/physiopathology Capsaicin Capsaicin Cyclohexanecarboxylic Acids/pharmacology Echo-Planar Imaging gamma-Aminobutyric Acid/pharmacology gamma-Aminobutyric Acid/pharmacology Humans image processing, computer-assisted Magnetic Resonance Imaging/methods Male Models, Statistical Oxygen/blood Pain/chemically induced Pain/physiopathology

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Studying the human brain anatomical network via diffusion-weighted MRI and Graph Theory

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NEUROimage 2008年第3期40卷 1064-1076页

作者： Iturria-Medina, Yasser Sotero, Roberto C. Canales-Rodriguez, Erick J. Aleman-Gomez, Yasser Melie-Garcia, Lester Cuban Neurosci Ctr Neuroimaging Dept Havana Cuba Cuban Neurosci Ctr Brain Dynam Dept Havana Cuba

Our goal is to study the human brain anatomical network. For this, the anatomical connection probabilities (ACP) between 90 cortical and subcortical brain gray matter areas are estimated from diffusion-weighted Magnetic Resonance Imaging (DW-MRI) techniques. The ACP between any two areas gives the probability that those areas are connected at least by a single nervous fiber. Then, the brain is modeled as a non-directed weighted graph with continuous arc weights given by the ACP matrix. Based on this approach, complex networks properties such as small-world attributes, efficiency, degree distribution, vulnerability, betweenness centrality and motifs composition are studied. The analysis was carried out for 20 right-handed healthy subjects (mean age: 31.10, S. D.: 7.43). According to the results, all networks have small-world and broad-scale characteristics. Additionally, human brain anatomical networks present bigger local efficiency and smaller global efficiency than the corresponding random networks. In a vulnerability and betweenness centrality analysis, the most indispensable and critical anatomical areas were identified: putamens, precuneus, insulas, superior parietals and superior frontals. Interestingly, some areas have a negative vulnerability (e. g. superior temporal poles, pallidums, supramarginals and hechls), which suggest that even at the cost of losing in global anatomical efficiency, these structures were maintained through the evolutionary processes due to their important functions. Finally, symmetrical characteristic building blocks (motifs) of size 3 and 4 were calculated, obtaining that motifs of size 4 are the expanded version of motif of size 3. These results are in agreement with previous anatomical studies in the cat and macaque cerebral cortex. (C) 2008 Published by Elsevier Inc.

关键词： Adult Algorithms Brain/anatomy & histology Diffusion Magnetic Resonance Imaging Humans image processing, computer-assisted Male Nerve Fibers/physiology Nerve Net/anatomy & histology Neural Pathways/anatomy & histology Neural Pathways/physiology

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The corpus callosum in schizophrenia-volume and connectivity changes affect specific regions

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NEUROimage 2008年第4期39卷 1522-1532页

作者： Rotarska-Jagiela, Anna Schoenmeyer, Ralf Oertel, Viola Haenschel, Corinna Vogeley, Kai Linden, David E. J. Univ Cologne Dept Psychiat & Psychotherapy D-50924 Cologne Germany Univ Frankfurt Dept Psychiat Neurophysiol & Neuroimaging Lab D-60538 Frankfurt Germany Univ Frankfurt Brain Imaging Ctr D-60528 Frankfurt Germany Max Planck Inst Brain Res D-60538 Frankfurt Germany Bangor Univ Sch Psychol Bangor LL57 2AS Gwynedd Wales Bangor Univ N Wales Clin Sch Bangor LL57 2AS Gwynedd Wales

The corpus callosum (CC) is of great interest for pathophysiological models of schizophrenia. Volume and structural integrity of the CC have been examined by volumetric and diffusion tensor imaging (DTI) studies, but results were n ot consistent across methods or studies. A possible explanation may be varying methodologies and accuracy of measurements based on a single slice or small regions of interest. In addition, none of the studies examined volume and diffusion values in the same group of patients, and thus the relationship between these anatomical measures is not clear. We used an automatic algorithm to segment seven midline slices of the CC from DTI images. We compared volume and the DTI measures fractional anisotropy (FA) and mean diffusivity (MD) in the CC and its subdivisions in the schizophrenia patients and matched controls. Patients had decreased volume, decreased FA and increased MD of the whole CC. The important novel finding is, however, that not all regions were equally affected by anatomical changes. The results emphasize the importance of using different methods in evaluation of white matter (WM) in schizophrenia to avoid false negative findings. In addition, the measures were highly correlated with each other, implying a common pathological process influencing FA, MD and volume of the CC. Although we cannot rule out other mechanisms affecting volume, FA and MD, converging evidence from cytoarchitectonic and genetic studies suggests that WM changes observed in schizophrenia may involve disintegration of healthy, functional axons and strengthening of aberrant connections resulting in increased severity of clinical symptoms. (C) 2007 Elsevier Inc. All rights reserved.

关键词： Adult Aging/psychology Algorithms Antipsychotic Agents/therapeutic use Chronic Disease Corpus Callosum/pathology Corpus Callosum/physiopathology Data Interpretation, Statistical Diffusion Magnetic Resonance Imaging Female Humans image processing, computer-assisted Male Middle Aged Nerve Fibers/pathology Neural Pathways/pathology Neural Pathways/physiopathology Psychiatric Status Rating Scales Schizophrenia/drug therapy Schizophrenia/pathology Schizophrenia/physiopathology

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fMRI of the temporal lobe of the awake monkey at 7 T

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NEUROimage 2008年第3期39卷 1081-1093页

作者： Goense, Jozien B. M. Ku, Shih-Pi Merkle, Hellmut Tolias, Andreas S. Logothetis, Nikos K. Max Planck Inst Biol Cybernet Dept Physiol Cognit Proc D-72076 Tubingen Germany NINDS Lab Funct & Mol Imaging NIH Bethesda MD 20892 USA Univ Manchester Manchester Lancs England

Increasingly 7 T scanners are used for fMRI of humans and non-human primates, promising improvements in signal-to-noise, spatial resolution and specificity. A disadvantage of fMRI at 7 T, but already at 3 T, is that susceptibility artifacts from air-filled cavities like the ear canal and nasal cavity cause signal loss and distortion. This limits the applicability of fMRI in these areas, thereby limiting study of these areas, but it also limits study of processes that span large-scale cortical networks or the entire brain. Our goal is to study the inferior temporal (IT) lobe in awake monkeys because of its importance in object perception and recognition, but the functional signal is degraded by strong susceptibility gradients. To allow fMRI of this region, we used an optimized SE-EPI, which recovers signal lost with GE-EPI and we corrected for susceptibility-induced image distortion. SE-EPI has the added advantage that, in contrast to GE-EPI, where the functional signal derives to a large extent from veins, the SE-EPI signal arises from the microvasculature, and hence it better represents the neural activation. We show fMRI at 7 T of the entire visual pathway in the awake primate with robust and widespread activation in all ventral areas of the brain, including areas adjacent to the ear canal. This allows fMRI of areas that normally suffer from artifact and thus more reliable whole-brain studies. (c) 2007 Elsevier Inc. All rights reserved.

关键词： Animals Artifacts Data Interpretation, Statistical image processing, computer-assisted Macaca mulatta Magnetic Resonance Imaging Oxygen/blood Temporal Lobe/anatomy & histology Temporal Lobe/physiology Wakefulness/physiology

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Action potential propagation imaged with high temporal resolution near-infrared video microscopy and polarized light

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NEUROimage 2008年第3期40卷 1034-1043页

作者： Schei, Jennifer L. McCluskey, Matthew D. Foust, Amanda J. Yao, Xin-Cheng Rector, David M. Washington State Univ Dept Vet & Comparat Anat Pharmacol & Physiol Pullman WA 99164 USA Washington State Univ Dept Phys & Astron Pullman WA 99164 USA Univ Alabama Dept Biomed Engn Birmingham AL 35294 USA

To identify the neural constituents responsible for generating polarized light changes, we created spatially resolved movies of propagating action potentials from stimulated lobster leg nerves using both reflection and transmission imaging modalities. Changes in light polarization are associated with membrane depolarization and provide sub-millisecond temporal resolution. Typically, signals are detected using light transmitted through tissue;however, because we eventually would like to apply polarization techniques in-vivo, reflected light is required. In transmission mode, the optical signal was largest throughout the center of the nerve, suggesting that most of the optical signal arose from the inner nerve bundle. In reflection mode, polarization changes were largest near the edges, suggesting that most of the optical signal arose from the outer sheath. In support of these observations, an optical model of the tissue showed that the outer sheath is more reflective while the inner nerve bundle is more transmissive. In order to apply these techniques in-vivo, we must consider that brain tissue does not have a regular orientation of processes as in the lobster nerve. We tested the effect of randomizing cell orientation by tying the nerve in an overhand knot prior to imaging, producing polarization changes that can be imaged even without regular cell orientations. (C) 2007 Elsevier Inc. All rights reserved.

关键词： Action Potentials/physiology Algorithms Animals Data Interpretation, Statistical Electrophysiology image processing, computer-assisted Infrared Rays Infrared Rays Microscopy, Polarization Microscopy, Video Nephropidae/physiology

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Spatiotemporal frequency tuning of BOLD and gamma band MEG responses compared in primary visual cortex

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NEUROimage 2008年第4期40卷 1552-1560页

作者： Muthukumaraswamy, Suresh D. Singh, Krish D. Cardiff Univ Sch Psychol CUBRIC Cardiff CF10 3AT S Glam Wales

In this study, the spatial and temporal frequency tuning characteristics of the MEG gamma (40-60 Hz) rhythmand the BOLD response in primary visual cortex were measured and compared. In an identical MEG/fMRI paradigm, 10 participants viewed reversing square wave gratings at 2 spatial frequencies [0.5 and 3 cycles per degree (cpd)] reversing at 5 temporal frequencies ( 0, 1 6, 10, 15 Hz). Three-dimensional images of MEG source power were generated with synthetic aperture magnetometry (SAM) and showed a high degree of spatial correspondence with BOLD responses in primary visual cortex with a mean spatial separation of 6.5 mm, but the two modalities showed different tuning characteristics. The gamma rhythm showed a clear increase in induced power for the high spatial frequency stimulus while BOLD showed no difference in activity for the two spatial frequencies used. Both imaging modalities showed a general increase of activity with temporal frequency, however, BOLD plateaued around 6-10 Hz while the MEG generally increased with a dip exhibited at 6 Hz. These results demonstrate that the two modalities may show activation in similar spatial locations but that the functional pattern of these activations may differ in a complex manner, suggesting that they may be tuned to different aspects of neuronal activity. (c) 2008 Elsevier Inc. All rights reserved.

关键词： Adult Data Interpretation, Statistical Evoked Potentials/physiology Female Humans image processing, computer-assisted Magnetic Resonance Imaging Magnetoencephalography Magnetoencephalography Male Oxygen/blood Visual Cortex/physiology

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Striatal dopamine transmission in healthy humans during a passive monetary reward task

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NEUROimage 2008年第4期39卷 2058-2065页

作者： Hakyemez, Helene S. Dagher, Alain Smith, Stephen D. Zald, David H. McGill Univ Montreal Neurol Inst McConnel Brain Imaging Ctr Montreal PQ H3A 2B4 Canada Vanderbilt Univ Dept Psychol Nashville TN 37212 USA Univ Winnipeg Dept Psychol Winnipeg MB R3B 2E9 Canada

Research on dopamine (DA) transmission has emphasized the importance of increased phasic DA cell firing in the presence of unpredictable rewards. Using [C-11]raclopride PET, we previously reported that DA transmission was both suppressed and enhanced in different regions of the striatum during an unpredictable reward task [Zald, D.H., Boileau, I., El Dearedy, W., Gunn, R., McGlone, F., Dichter, G.S. et al. (2004). Dopamine transmission in the human striatum during monetary reward tasks. J. Neurosci. 24, 4105-4112]. However, it was unclear if reductions in DA release during this task reflected a response to the high proportion of nonrewarding trials, and whether the behavioral demands of the task influenced the observed response. To test these issues, we presented 10 healthy subjects with an automated (passive) roulette wheel game in which the amount of reward and its timing were unpredictable and the rewarding trials greatly outnumbered the nonrewarding ones. As in the previous study, DA transmission in the putamen was significantly suppressed relative to a predictable control condition. A similar suppression occurred when subjects were presented with temporally unpredictable novel pictures and sounds. At present, models of DA functioning during reward do not account for this suppression, but given that it has been observed in two different studies using different reward paradigms, this phenomenon warrants attention. Neither the unpredictable reward nor the novelty conditions produced consistent increases in striatal DA transmission. These data suggest that active behavioral engagement may be necessary to observe robust statewise increases in DA release in the striatum. (C) 2007 Elsevier Inc. All rights reserved.

关键词： Acoustic Stimulation Adult Affect Caudate Nucleus/physiology Caudate Nucleus/radionuclide imaging Dopamine/physiology Dopamine Antagonists/diagnostic use Functional Laterality/physiology Humans image processing, computer-assisted Magnetic Resonance Imaging Male Motivation Neostriatum/physiology Neostriatum/radionuclide imaging Photic Stimulation Positron-Emission Tomography Putamen/physiology Putamen/radionuclide imaging Raclopride/diagnostic use Raclopride/diagnostic use Radiopharmaceuticals/diagnostic use Radiopharmaceuticals/diagnostic use Reward Synaptic Transmission/physiology

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