Quantification of the benefit from integrating MEG and EEG data in minimum l2-norm estimation
Quantification of the benefit from integrating MEG and EEG data in minimum l2-norm estimation
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DOI：
10.1016/j.neuroimage.2008.05.064
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发表时间：
2008-09-01
期刊：
影响因子：
5.7
通讯作者：
Hamalainen, M. S.
中科院分区：
文献类型：
--
作者：
Molins, A.;Stufflebeam, S. M.;Hamalainen, M. S.
从电磁(脑磁图和脑电)信号估计源电流是一个不适定的问题，经常产生模糊或不准确的估计。这两种模式都有不同的限制分辨率的因素，例如，脑磁图不能检测到径向来源，而脑电对头部模型的准确性很敏感。这使得EEG+MEG联合估计技术变得可取，但不同的采集噪声统计、头部模型的复杂性以及缺乏相关度量都使所产生的改善的评估复杂化。我们分析了在计算噪声归一化最小L(2)范数估计时，将脑电记录包括在脑磁图研究中与添加新的脑磁图通道的影响。四个受试者的结构MRI扫描建立了三室边界单元正演模型。对得到的正向模型的奇异值分析预测，脑电+脑磁图的情况以更高的矩阵等级的形式表现得更好。利用数据估计的传感器噪声协方差构造了脑电、脑磁图和脑电+脑磁图的MNE逆算子。根据分辨率矩阵得出的度量标准预测，与MEG相比，EEG+MEG具有更高的空间分辨率，这是由于扩散减小(空间离散程度更低，分辨率指数更高)，而偶极子定位误差没有减少。这种影响在所有震源位置都很明显，深部区域如扣带皮质的震级增加。我们还能够利用正中神经反应来证实躯体感觉皮质的结果。(C)2008 Elsevier Inc.保留所有权利。
Source current estimation from electromagnetic (MEG and EEG) signals is an ill-posed problem that often produces blurry or inaccurately positioned estimates. The two modalities have distinct factors limiting the resolution, e.g., MEG cannot detect radially oriented sources, while EEG is sensitive to accuracy of the head model. This makes combined EEG+MEG estimation techniques desirable, but different acquisition noise statistics, complexity of the head models, and lack of pertinent metrics all Complicate the assessment of the resulting improvements. We investigated analytically the effect of including EEG recordings in MEG studies versus the addition of new MEG channels when computing noise-normalized minimum l(2)-norm estimates. Three-compartment boundary-element forward models were constructed using structural MRI scans for four subjects. Singular value analysis of the resulting forward models predicted better performance of the EEG+MEG case in the form of higher matrix rank. MNE inverse operators for EEG, MEG and EEG + MEG were constructed using the sensor noise covariance estimated from data. Metrics derived from the resolution matrices predicted higher spatial resolution in EEG+ MEG as compared to MEG due to decreased spread (lower spatial dispersion, higher resolution index) with no reduction in dipole localization error. The effect was apparent in all source locations, with increased magnitude for deep areas such as the cingulate cortex. We were also able to corroborate the results for the somatosensory cortex using median nerve responses. (c) 2008 Elsevier Inc. All rights reserved.