Understanding the functional connectivity of the brain has become a major goal of neuroscience. In many situations the relative phase difference, together with coherence patterns, has been employed to infer the direction of the information flow. However, it has been recently shown in local field potential data from monkeys the existence of a synchronized regime in which unidirectionally coupled areas can present both positive and negative phase differences. During the counterintuitive regime, called anticipated synchronization (AS), the phase difference does not reflect the causality. Here we investigate coherence and causality at the alpha frequency band ($f\sim 10$ Hz) between pairs of electroencephalogram (EEG) electrodes in humans during a GO/NO-GO task. We show that human EEG signals can exhibit anticipated synchronization, which is characterized by a unidirectional influence from an electrode A to an electrode B, but the electrode B leads the electrode A in time. To the best of our knowledge, this is the first verification of AS in EEG signals and in the human brain. The usual delayed synchronization (DS) regime is also present between many pairs. DS is characterized by a unidirectional influence from an electrode A to an electrode B and a positive phase difference between A and B which indicates that the electrode A leads the electrode B in time. Moreover we show that EEG signals exhibit diversity in the phase relations: the pairs of electrodes can present in-phase, antiphase, or out-of-phase synchronization with a similar distribution of positive and negative phase differences.

中文翻译：

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人类脑电数据中的预期同步：具有负相位滞后的单向因果关系

了解大脑的功能连通性已成为神经科学的主要目标。在许多情况下，相对相位差以及相干模式已被用来推断信息流的方向。然而，最近在来自猴子的局部场电势数据中显示出存在同步机制，其中单向耦合区域可以呈现正和负相位差。在被称为预期同步（AS）的反直觉状态下，相位差不会反映因果关系。在这里，我们研究了alpha频段的相干性和因果关系（$F〜10$ 在执行GO / NO-GO任务期间，人类的两对脑电图（EEG）电极之间的频率（Hz）。我们表明，人类脑电信号可以表现出预期的同步性，其特征是从电极A到电极B的单向影响，但是电极B在时间上领先于电极A。据我们所知，这是脑电信号和人脑中AS的首次验证。许多对之间还存在通常的延迟同步（DS）机制。DS的特征在于从电极A到电极B的单向影响以及在A和B之间的正相差，这表明电极A在时间上领先于电极B。此外，我们表明，脑电信号在相位关系中表现出多样性：电极对可以呈现同相，反相，