Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
Department of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Milwaukee, WI, USA.
Sci Rep. 2024 Jul 31;14(1):17736. doi: 10.1038/s41598-024-67120-8.
Methods to quantify cortical hyperexcitability are of enormous interest for mapping epileptic networks in patients with focal epilepsy. We hypothesize that, in the resting state, cortical hyperexcitability increases firing-rate correlations between neuronal populations within seizure onset zones (SOZs). This hypothesis predicts that in the gamma frequency band (40-200 Hz), amplitude envelope correlations (AECs), a relatively straightforward measure of functional connectivity, should be elevated within SOZs compared to other areas. To test this prediction, we analyzed archived samples of interictal electrocorticographic (ECoG) signals recorded from patients who became seizure-free after surgery targeting SOZs identified by multiday intracranial recordings. We show that in the gamma band, AECs between nodes within SOZs are markedly elevated relative to those elsewhere. AEC-based node strength, eigencentrality, and clustering coefficient are also robustly increased within the SOZ with maxima in the low-gamma band (permutation test Z-scores > 8) and yield moderate discriminability of the SOZ using ROC analysis (maximal mean AUC ~ 0.73). By contrast to AECs, phase locking values (PLVs), a measure of narrow-band phase coupling across sites, and PLV-based graph metrics discriminate the seizure onset nodes weakly. Our results suggest that gamma band AECs may provide a clinically useful marker of cortical hyperexcitability in focal epilepsy.
用于量化皮质兴奋性的方法对于绘制局灶性癫痫患者的癫痫网络具有重要意义。我们假设，在静息状态下，皮质兴奋性增加了发作起始区（SOZ）内神经元群体之间的放电率相关性。这一假设预测，在伽马频带（40-200 Hz）中，幅度包络相关性（AEC），一种相对简单的功能连接测量方法，应该在 SOZ 内比其他区域更高。为了验证这一预测，我们分析了来自通过多日颅内记录确定的 SOZ 靶向手术治疗后无癫痫发作的患者的间歇期脑电（ECoG）信号的存档样本。我们表明，在伽马波段，SOZ 内节点之间的 AEC 明显高于其他区域。基于 AEC 的节点强度、特征中心度和聚类系数在 SOZ 内也显著增加，在低伽马波段达到最大值（置换检验 Z 分数>8），并使用 ROC 分析实现了 SOZ 的中等可区分性（最大平均 AUC~0.73）。与 AEC 相比，相位锁定值（PLV），一种跨站点的窄带相位耦合测量方法，以及基于 PLV 的图度量对发作起始节点的区分能力较弱。我们的结果表明，伽马频带 AEC 可能为局灶性癫痫中的皮质兴奋性提供一种有用的临床标记物。
