Alkawadri Cigdem Isitan, Yan Qi, Kocuglu Kinal Ayse Gul, Spencer Dennis D, Alkawadri Rafeed
Human Brain Mapping Program, University of Pittsburgh Medical Centre, Pittsburgh, Pennsylvania, U.S.A. ; and.
Yale University, New Haven, Connecticut, U.S.A .
J Clin Neurophysiol. 2024 Dec 30;42(5):391-399. doi: 10.1097/WNP.0000000000001139.
Our study aimed to compare signal characteristics of subdural electrodes (SDE) and depth stereo EEG placed within a 5-mm vicinity in patients with drug-resistant epilepsy. We report how electrode design and placement collectively affect signal content from a shared source between these electrode types.
In subjects undergoing invasive intracranial EEG evaluation at a surgical epilepsy center from 2012 to 2018, stereo EEG and SDE electrode contacts placed within a 5-mm vicinity were identified. Of these, 24 contacts (12 pairs) met our criteria for signal-to-noise ratio and data availability for final analysis. We used Welch method to analyze the correlation of power spectral densities of EEG segments, root mean square of 1-second windows, and fast-Fourier transform to calculate coherence across conventional frequency bands.
We observed a median distance of 3.7 mm between the electrode contact pairs. Time-aware analysis highlighted the coherence's strength primarily in the high-gamma band, where the median ( r ) was 0.889. In addition, the median power ratios between the SDE and stereo EEG signal was 1.99. This ratio decreased from high-gamma to infra-low frequencies, with medians of 2.07 and 0.97, respectively. The power spectral densities for the stereo EEG and SDE electrodes demonstrated a strong correlation, with a median correlation coefficient ( r ) of 0.99 and an interquartile range from 0.915 to 0.996.
Signals captured by standard subdural and depth (intracranial EEG) electrodes within a 5-mm radius exhibit band-specific coherence and are not identical. The association was most pronounced in the high-gamma band, with coherence decreasing with lower frequencies. Our findings underscore the combined effects of electrode size, design, placement, preferred bandwidth, and the nature of the activity source on signal recording. Particularly, SDE employed herein may offer advantages for high-frequency signals, but the impact of electrode size on recordings necessitates careful consideration in context-specific situations.
The findings relate to surgical epilepsy care and may inform the design of brain-computer interface.
我们的研究旨在比较耐药性癫痫患者中，位于5毫米范围内的硬膜下电极（SDE）和深度立体脑电图的信号特征。我们报告了电极设计和放置如何共同影响这些电极类型之间共享源的信号内容。
在2012年至2018年期间，于一家外科癫痫中心接受侵入性颅内脑电图评估的受试者中，识别出位于5毫米范围内的立体脑电图和SDE电极触点。其中，24个触点（12对）符合我们的信噪比和数据可用性标准，用于最终分析。我们使用韦尔奇方法分析脑电图片段功率谱密度的相关性、1秒窗口的均方根，并通过快速傅里叶变换计算传统频段的相干性。
我们观察到电极触点对之间的中位距离为3.7毫米。时间感知分析突出了相干性主要在高伽马频段的强度，其中位值（r）为0.889。此外，SDE和立体脑电图信号之间的中位功率比为1.99。该比值从高伽马频段到超低频段降低，中位数分别为2.07和0.97。立体脑电图和SDE电极的功率谱密度显示出很强的相关性，中位相关系数（r）为0.99，四分位间距为0.915至0.996。
在半径5毫米范围内，标准硬膜下电极和深度（颅内脑电图）电极捕获的信号表现出频段特异性相干性，且并不相同。这种关联在高伽马频段最为明显，相干性随频率降低而减小。我们的研究结果强调了电极尺寸、设计、放置、首选带宽以及活动源性质对信号记录的综合影响。特别是，本文使用的SDE可能对高频信号具有优势，但电极尺寸对记录的影响在特定情况下需要仔细考虑。
这些发现与外科癫痫治疗相关，可能为脑机接口的设计提供参考。
