Hardmeier Martin, Hatz Florian, Bousleiman Habib, Schindler Christian, Stam Cornelis Jan, Fuhr Peter
Department of Neurology, Hospital of the University of Basel, Basel, Switzerland.
Department of Neurology, Hospital of the University of Basel, Basel, Switzerland; Swiss Tropical and Public Health Institute, University of Basel, Basel, Switzerland.
PLoS One. 2014 Oct 6;9(10):e108648. doi: 10.1371/journal.pone.0108648. eCollection 2014.
Functional connectivity (FC) and graph measures provide powerful means to analyze complex networks. The current study determines the inter-subject-variability using the coefficient of variation (CoV) and long-term test-retest-reliability (TRT) using the intra-class correlation coefficient (ICC) in 44 healthy subjects with 35 having a follow-up at years 1 and 2. FC was estimated from 256-channel-EEG by the phase-lag-index (PLI) and weighted PLI (wPLI) during an eyes-closed resting state condition. PLI quantifies the asymmetry of the distribution of instantaneous phase differences of two time-series and signifies, whether a consistent non-zero phase lag exists. WPLI extends the PLI by additionally accounting for the magnitude of the phase difference. Signal-space global and regional PLI/wPLI and weighted first-order graph measures, i.e. normalized clustering coefficient (gamma), normalized average path length (lambda), and the small-world-index (SWI) were calculated for theta-, alpha1-, alpha2- and beta-frequency bands. Inter-subject variability of global PLI was low to moderate over frequency bands (0.12<CoV<0.28), higher for wPLI (0.25<CoV<0.55) and very low for gamma, lambda and SWI (CoV<0.048). TRT was good to excellent for global PLI/wPLI (0.68<ICC<0.80), regional PLI/wPLI (0.58<ICC<0.77), and fair to good for graph measures (0.32<ICC<0.73) except wPLI-based lambda in alpha1 (ICC = 0.12). Inter-electrode distance correlated very weakly with inter-electrode PLI (-0.06<rho<0) and weakly with inter-electrode wPLI (-0.22<rho<-0.18). Global PLI/wPLI and topographic connectivity patterns differed between frequency bands, and all individual networks showed a small-world-configuration. PLI/wPLI based network characterization derived from high-resolution EEG has apparently good reliability, which is one important requirement for longitudinal studies exploring the effects of chronic brain diseases over several years.
功能连接性（FC）和图论指标为分析复杂网络提供了强大的方法。本研究在44名健康受试者中，使用变异系数（CoV）确定个体间变异性，并使用组内相关系数（ICC）确定长期重测信度（TRT），其中35名受试者在第1年和第2年进行了随访。在闭眼静息状态下，通过相位滞后指数（PLI）和加权PLI（wPLI）从256通道脑电图估计FC。PLI量化了两个时间序列瞬时相位差分布的不对称性，并表明是否存在一致的非零相位滞后。wPLI通过额外考虑相位差的大小扩展了PLI。计算了θ、α1、α2和β频段的信号空间全局和区域PLI/wPLI以及加权一阶图论指标，即归一化聚类系数（γ）、归一化平均路径长度（λ）和小世界指数（SWI）。全局PLI的个体间变异性在各频段为低到中等（0.12 < CoV < 0.28），wPLI更高（0.25 < CoV < 0.55），γ、λ和SWI非常低（CoV < 0.048）。全局PLI/wPLI的TRT良好到优秀（0.68 < ICC < 0.80），区域PLI/wPLI（0.58 < ICC < 0.77），图论指标的TRT一般到良好（0.32 < ICC < 0.73），除了α1频段基于wPLI的λ（ICC = 0.12）。电极间距离与电极间PLI的相关性非常弱（-0.06 < ρ < 0），与电极间wPLI的相关性较弱（-0.22 < ρ < -0.18）。全局PLI/wPLI和地形连接模式在不同频段之间存在差异，并且所有个体网络都呈现出小世界结构。基于高分辨率脑电图的PLI/wPLI网络特征具有明显良好的可靠性，这是探索慢性脑疾病数年影响的纵向研究的一项重要要求。
