Cancellation of EEG and MEG Signals Generated by Extended and Distributed Sources
Cancellation of EEG and MEG Signals Generated by Extended and Distributed Sources
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DOI：
10.1002/hbm.20851
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发表时间：
2010-01-01
影响因子：
4.8
通讯作者：
Halgren, Eric
中科院分区：
文献类型：
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作者：
Ahlfors, Seppo P.;Han, Jooman;Halgren, Eric
用脑电和脑磁图(EEG，MEG)测量的头皮电位和磁场的颅外模式在空间上是广泛的，即使大脑中的潜在来源是局灶性的。因此，当多个大脑区域同时活动时，由于抵消而导致的信号幅度损失是可以预料的。我们在脑电和脑磁图中使用了一个正向模型来描述这些抵消效应，这些源被限制在大脑皮质表面的解剖精确重建上。在多个随机分布的源偶极子的情况下，即使同时偶极子的数目很少，EEG和MEG也被显著地消除。当局部延长的模拟活动斑块延伸到相对的脑沟和脑回壁时，也发生了实质性的取消。对于大的斑块，EEG和MEG消除之间的差异被看到，可能是由于选择性地消除了切向与径向定向的源。当电生理数据与血液动力学测量相关时，消除效应可能是重要的。此外，选择性消除可以用来解释EEG和MEG在局灶性和广泛性皮质活动方面的一些观察到的差异。《哼唱大脑地图》31：140-149,2010。(C)2009年Wiley-Liss，Inc.
Extracranial patterns of scalp potentials and magnetic fields, as measured with electro- and magnetoencephalography (EEG, MEG), are spatially widespread even when the underlying source in the brain is focal. Therefore, loss in signal magnitude due to cancellation is expected when multiple brain regions are simultaneously active. We characterized these cancellation effects in EEG and MEG using a forward model with sources constrained on an anatomically accurate reconstruction of the cortical surface. Prominent cancellation was found for both EEG and MEG in the case of multiple randomly distributed source dipoles, even when the number of simultaneous dipoles was small. Substantial cancellation occurred also for locally extended patches of simulated activity, when the patches extended to opposite walls of sulci and gyri. For large patches, a difference between EEG and MEG cancellation was seen, presumably due to selective cancellation of tangentially vs. radially oriented sources. Cancellation effects can be of importance when electrophysiological data are related to hemo-dynamic measures. Furthermore, the selective cancellation may be used to explain some observed differences between EEG and MEG in terms of focal vs. widespread cortical activity. Hum Brain Mapp 31:140-149, 2010. (C) 2009 Wiley-Liss, Inc.