Graph theoretical analysis of resting-state MEG data: Identifying interhemispheric connectivity and the default mode.
Graph theoretical analysis of resting-state MEG data: Identifying interhemispheric connectivity and the default mode.
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DOI：
10.1016/j.neuroimage.2014.03.065
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发表时间：
2014-08-01
期刊：
影响因子：
5.7
通讯作者：
Whitlow CT
中科院分区：
文献类型：
--
作者：
Maldjian JA;Davenport EM;Whitlow CT
静息状态脑磁图的半球间连通性一直难以捉摸，而默认模式网络（DMN）的证明更具挑战性。最近基于种子的脑磁图分析显示了使用功率包络相关的半球间连通性。本研究的目的是比较在有和没有信号泄漏校正的情况下使用脑磁图生成的脑连通性图，以评估脑半球间连通性的存在。在irb批准的研究中，22名正常男性受试者（年龄16-18岁）获得了8分钟静息状态睁开眼睛的MEG数据。数据使用内部自动化MEG处理管道进行处理，并使用标量波束形成器以7毫米分辨率投影到标准（MNI）源空间。从源空间时间序列中每2.5秒采样一次平均β带振幅。在进行幅度变换之前，对源空间波束形成信号进行时域泄漏校正。对泄漏校正和未校正的数据进行了图论体素级源空间相关连通性分析。对于连接节点的前20%，在各个学科之间设置了度图阈值，以确定枢纽。另外还生成了感觉、视觉、运动和颞叶区域的度图，利用侧度指数来识别半球间的连通性。未校正的MEG网络的中枢主要是对称的和中线的，与fMRI网络有一些相似之处。其中包括扣带皮层、双侧额叶下、双侧海马结构和双侧小脑半球。然而，使用基于roi的度图，这些未校正的网络几乎没有显示出半球间的连通性。泄漏校正后的MEG数据确定了DMN，其中枢位于后扣带区和双顶区。这些校正后的网络显示了基于roi的度图的强大的半球间连通性。图论分析没有信号泄漏校正的MEG静息状态数据可以显示出与fMRI网络有一定相似之处的对称网络。然而，这些网络是信号泄漏引起的高度局部相关的产物，缺乏半球间的连通性。在信号泄漏校正后，MEG中枢出现在DMN中，具有很强的半球间连通性。
Interhemispheric connectivity with resting state MEG has been elusive, and demonstration of the default mode network (DMN) yet more challenging. Recent seed-based MEG analyses have shown interhemispheric connectivity using power envelope correlations. The purpose of this study is to compare graph theoretic maps of brain connectivity generated using MEG with and without signal leakage correction to evaluate for the presence of interhemispheric connectivity. Eight minutes of resting state eyes-open MEG data were obtained in 22 normal male subjects enrolled in an IRB-approved study (ages 16–18). Data were processed using an in-house automated MEG processing pipeline and projected into standard (MNI) source space at 7 mm resolution using a scalar beamformer. Mean beta-band amplitude was sampled at 2.5 second epochs from the source space time series. Leakage correction was performed in the time domain of the source space beam-formed signal prior to amplitude transformation. Graph theoretic voxel-wise source space correlation connectivity analysis was performed for leakage-corrected and uncorrected data. Degree maps were thresholded across subjects for the top 20% of connected nodes to identify hubs. Additional degree maps for sensory, visual, motor, and temporal regions were generated to identify interhemispheric connectivity using laterality indices. Hubs for the uncorrected MEG networks were predominantly symmetric and midline, bearing some resemblance to fMRI networks. These included the cingulate cortex, bilateral inferior frontal lobes, bilateral hippocampal formations and bilateral cerebellar hemispheres. These uncorrected networks however, demonstrated little to no interhemispheric connectivity using the ROI-based degree maps. Leakage corrected MEG data identified the DMN, with hubs in the posterior cingulate and biparietal areas. These corrected networks demonstrated robust interhemispheric connectivity for the ROI-based degree maps. Graph theoretic analysis of MEG resting state data without signal leakage correction can demonstrate symmetric networks with some resemblance to fMRI networks. These networks however, are an artifact of high local correlation from signal leakage and lack interhemispheric connectivity. Following signal leakage correction, MEG hubs emerge in the DMN, with strong interhemispheric connectivity.
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