比较功率谱分析的同时脑电图和脑磁图记录在人类表明非电阻性细胞外介质
Comparative power spectral analysis of simultaneous elecroencephalographic and magnetoencephalographic recordings in humans suggests non-resistive extracellular media
摘要：
大脑细胞外空间的电阻或非电阻性质仍然存在争议，并且是正确建模细胞外电位的重要问题。在这里，我们首先从理论上证明，如果介质是电阻性的，那么在低频（<10 Hz）下，脑电图（EEG）和脑磁图（MEG）信号的频率缩放应该是相同的。为了验证这一预测，我们分析了四个人类受试者的EEG和MEG同时测量的频谱。EEG的频率标度显示了整个大脑的相干变化，通常在1/f和1/f^2之间，并且在顶叶/颞叶区域倾向于较小。在一个给定的区域中，虽然MEG的频率标度指数的变异性高于EEG，但两种信号始终以不同的指数标度。在某些情况下，缩放是相似的，但只有当MEG的信噪比低。对环境噪声和仪器噪声的几种噪声校正方法进行了测试，它们都增加了EEG和MEG标度之间的差异。总之，EEG和MEG之间的频率缩放存在显著差异，如果细胞外介质（包括其他层，如硬脑膜和颅骨）是全局非电阻性的，则可以解释这一点。
英文摘要：
The resistive or non-resistive nature of the extracellular space in the brain is still debated, and is an important issue for correctly modeling extracellular potentials. Here, we first show theoretically that if the medium is resistive, the frequency scaling should be the same for electroencephalogram (EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz). To test this prediction, we analyzed the spectrum of simultaneous EEG and MEG measurements in four human subjects. The frequency scaling of EEG displays coherent variations across the brain, in general between 1/f and 1/f^2, and tends to be smaller in parietal/temporal regions. In a given region, although the variability of the frequency scaling exponent was higher for MEG compared to EEG, both signals consistently scale with a different exponent. In some cases, the scaling was similar, but only when the signal-to-noise ratio of the MEG was low. Several methods of noise correction for environmental and instrumental noise were tested, and they all increased the difference between EEG and MEG scaling. In conclusion, there is a significant difference in frequency scaling between EEG and MEG, which can be explained if the extracellular medium (including other layers such as dura matter and skull) is globally non-resistive.
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