Mandelkow H, Halder P, Brandeis D, Soellinger M, de Zanche N, Luechinger R, Boesiger P
Institute for Biomedical Engineering, University and ETH Zurich, Gloriastr. 35, 8092 Zurich, Switzerland.
Neuroimage. 2007 Aug 1;37(1):149-63. doi: 10.1016/j.neuroimage.2007.04.034. Epub 2007 Apr 27.
It has been suggested recently that the influence of the neuro-magnetic field should make electrical brain activity directly detectable by MRI. To test this hypothesis, we performed combined EEG-MRI experiments which aim to localize the neuronal current sources of alpha waves (8-12 Hz), one of the most prominent EEG phenomena in humans. A detailed analysis of cross-spectral coherence between simultaneously recorded EEG and MRI time series revealed no sign of alpha waves. Instead the EEG-MRI approach was found to be hampered by artefacts due to cardiac pulsation, which extend into the frequency band of alpha waves. Separate brain displacement mapping experiments confirmed that not only the EEG but also the MRI signal is confounded by harmonics of the cardiac frequency even at 10 Hz and beyond. This well-known ballistocardiogram artefact cannot be avoided or eliminated entirely by available signal processing techniques. Therefore we must conclude that current EEG-MRI methodology based on correlation analysis lacks not only the sensitivity but also the specificity required for the reliable detection of alpha waves.
最近有人提出，神经磁场的影响应使脑电活动可通过磁共振成像（MRI）直接检测到。为了验证这一假设，我们进行了脑电图-磁共振成像（EEG-MRI）联合实验，旨在定位人类最显著的脑电现象之一——阿尔法波（8-12赫兹）的神经元电流源。对同时记录的脑电图和磁共振成像时间序列之间的交叉谱相干性进行的详细分析未发现阿尔法波的迹象。相反，发现脑电图-磁共振成像方法受到心脏搏动引起的伪影的阻碍，这些伪影延伸到阿尔法波的频带。单独的脑位移映射实验证实，即使在10赫兹及以上，不仅脑电图信号，而且磁共振成像信号也受到心脏频率谐波的干扰。这种众所周知的心冲击图伪影无法通过现有的信号处理技术完全避免或消除。因此，我们必须得出结论，基于相关性分析的当前脑电图-磁共振成像方法不仅缺乏可靠检测阿尔法波所需的灵敏度，而且缺乏特异性。
