Nunez P L, Silberstein R B, Shi Z, Carpenter M R, Srinivasan R, Tucker D M, Doran S M, Cadusch P J, Wijesinghe R S
Department of Biomedical Engineering, Tulane University, New Orleans, LA, USA.
Clin Neurophysiol. 1999 Mar;110(3):469-86. doi: 10.1016/s1388-2457(98)00043-1.
A concentric spheres model was used in an earlier paper to estimate the effects of volume conduction, reference electrode and spatial filtering on different EEG coherence measures. EEG data are used here to verify theoretical predictions.
Three EEG data sets were: (1) 64 channel, recorded during 7 alternating periods of resting and mental calculation. (2) 128 channel, for comparison of eyes open versus eyes closed coherence. (3) 128 channel, recorded during deep sleep (stages 3 and 4) and REM.
The directions of large scale (lobeal) coherency changes between brain states are relatively independent of coherence measure. However, coherence between specific electrode pairs is sensitive to method and frequency. Average reference and digitally linked mastoids provide reasonable semi-quantitative estimates of large-scale neocortical source coherence. Close bipolar, Laplacian, and dura image methods remove most reference electrode and volume conduction distortion, but may underestimate coherence by spatial filtering.
Each EEG coherence method has its own potential sources of error and provides coherence estimates for different neural population sizes located in different locations. Thus, studies of coherence and brain state should include several different kinds of estimates to take full advantage of information in recorded signals.
在早期一篇论文中使用同心球模型来估计容积传导、参考电极和空间滤波对不同脑电图相干性测量的影响。本文使用脑电图数据来验证理论预测。
三个脑电图数据集分别为：（1）64导，在7个静息与心算交替期记录。（2）128导，用于比较睁眼与闭眼时的相干性。（3）128导，在深度睡眠（3期和4期）和快速眼动睡眠期间记录。
大脑状态之间大规模（叶性）相干性变化的方向相对独立于相干性测量方法。然而，特定电极对之间的相干性对方法和频率敏感。平均参考电极和数字连接乳突能提供合理的大规模新皮质源相干性半定量估计。紧密双极、拉普拉斯和硬脑膜成像方法可消除大部分参考电极和容积传导失真，但可能因空间滤波而低估相干性。
每种脑电图相干性方法都有其潜在误差来源，并为位于不同位置的不同神经群体大小提供相干性估计。因此，关于相干性和大脑状态的研究应包括几种不同类型的估计，以充分利用记录信号中的信息。
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