Technical University of Denmark, Department of Electrical Engineering, Building 349, Oersteds Plads, 2800 Kgs. Lyngby, Denmark.
Clin Neurophysiol. 2013 Aug;124(8):1570-7. doi: 10.1016/j.clinph.2013.02.112. Epub 2013 Apr 8.
To estimate the area of cortex affecting the extracranial EEG signal.
The coherence between intra- and extracranial EEG channels were evaluated on at least 10 min of spontaneous, awake data from seven patients admitted for epilepsy surgery work up.
Cortical electrodes showed significant extracranial coherent signals in an area of approximately 150 cm(2) although the field of vision was probably only 31 cm(2) based on spatial averaging of intracranial channels taking into account the influence of the craniotomy and the silastic membrane of intracranial grids. Selecting the best cortical channels, it was possible to increase the coherence values compared to the single intracranial channel with highest coherence. The coherence seemed to increase linearly with an accumulation area up to 31 cm(2), where 50% of the maximal coherence was obtained accumulating from only 2 cm(2) (corresponding to one channel), and 75% when accumulating from 16 cm(2).
The skull is an all frequency spatial averager but dominantly high frequency signal attenuator.
An empirical assessment of the actual area of cerebral sources generating the extracranial EEG provides better opportunities for clinical electroencephalographers to determine the location of origin of particular patterns in the EEG.
评估影响颅外 EEG 信号的皮层面积。
对 7 例癫痫手术患者至少 10 分钟的自发清醒数据进行了颅内和颅外 EEG 通道之间的相干性评估。
尽管基于考虑颅骨切开术和颅内网格硅酮膜影响的颅内通道的空间平均，视野可能仅为 31cm²，但皮质电极显示出约 150cm²的显著颅外相干信号。选择最佳的皮质通道，与具有最高相干性的单个颅内通道相比，可以提高相干值。相干性似乎随累积面积呈线性增加，累积面积为 31cm²时，可获得最大相干性的 50%（仅累积 2cm²，对应于一个通道），累积 16cm²时，可获得最大相干性的 75%。
颅骨是一种全频带空间平均器，但主要是高频信号衰减器。
对产生颅外 EEG 的脑源的实际区域进行经验评估，为临床脑电图师提供了更好的机会，以确定 EEG 中特定模式的起源位置。
