BACKGROUND Numerous, sometimes conflicting, changes in brain functional connectivity have been associated with the transition from wakefulness to unresponsiveness at induction of general anesthesia. However, relatively few studies have looked at: the detailed time evolution of the transition; for different EEG frequency bands; and in the clinical scenario of surgical patients undergoing general anesthesia. METHODS We investigated the changes in the frontal and fronto-parietal directed and undirected functional connectivity to multichannel EEG data recorded from 29 adult male surgical patients undergoing propofol-induced loss of consciousness during induction of anesthesia. Directed functional connectivity was estimated using bivariate frequency domain Granger causality, and undirected connectivity was assessed using EEG coherence. RESULTS Around the point of loss of consciousness: local frontal, interhemispheric frontal, and frontoparietal feedback and feedforward Granger causality all decreased between 31% and 51.5% in the delta-band (median [interquartile range] for local frontal: 0.14 [0.08, 0.27] to 0.08 [0.06, 0.12] (p=0.02)). After a lag of a few minutes, Granger Causality markedly increased in the gamma and beta bands for local frontal (0.03 [0.02, 0.07] to 0.09 [0.07, 0.11](p<0.001)) and long-distance cross-hemispheric frontoparietal feedback (0.02 [0.01, 0.04] to 0.07 [0.04, 0.09], p<0.001) and feedforward (0.02 [0.01, 0.04] to 0.03 [0.03, 0.04], p=0.01) coupling; but not for within-hemispheric frontoparietal feedback and feedforward. Frontal interhemispheric EEG coherence significantly decreased in the lower frequencies (f<12Hz) at loss of consciousness, while no significant increase for the beta and gamma bands was observed. CONCLUSIONS Propofol-induced loss of consciousness in surgical patients is associated with a global breakdown in low-frequency directed functional connectivity, coupled with a high-frequency increase between closely located brain regions. At loss of consciousness, Granger causality shows more pronounced changes than coherence.

中文翻译：

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异丙酚引起意识丧失期间脑电图信号中半球内和跨半球定向功能连接的变化。


背景技术大脑功能连接的许多（有时是相互矛盾的）变化与全身麻醉诱导时从清醒到无反应的转变有关。然而，相对较少的研究关注的是： 转变的详细时间演变；针对不同的脑电图频段；以及接受全身麻醉的手术患者的临床情况。方法 我们研究了 29 名成年男性手术患者在麻醉诱导过程中因丙泊酚导致意识丧失而记录的多通道脑电图数据，研究了额叶和额顶叶定向和非定向功能连接的变化。使用双变量频域格兰杰因果关系估计定向功能连接，并使用脑电图相干性评估无向连接。结果在意识丧失点附近：局部额叶、半球间额叶、额顶叶反馈和前馈格兰杰因果关系在 Delta 频带中均下降了 31% 至 51.5%（局部额叶中位[四分位距]：0.14 [0.08, 0.27] ] 到 0.08 [0.06, 0.12] (p=0.02))。延迟几分钟后，局部额叶 (0.03 [0.02, 0.07] 至 0.09 [0.07, 0.11](p<0.001)) 和长距离跨半球的伽马和贝塔波段的格兰杰因果关系显着增加额顶反馈（0.02 [0.01, 0.04] 至 0.07 [0.04, 0.09], p<0.001）和前馈（0.02 [0.01, 0.04] 至 0.03 [0.03, 0.04], p=0.01）耦合；但不适用于半球内额顶叶反馈和前馈。意识丧失时，额叶半球间脑电图一致性在较低频率 (f<12Hz) 中显着降低，而 β 和 γ 波段没有观察到显着增加。 结论 手术患者中异丙酚引起的意识丧失与低频定向功能连接的整体破坏以及邻近大脑区域之间的高频增加有关。当失去意识时，格兰杰因果关系显示出比一致性更明显的变化。