Gerber Edden M, Sadeh Boaz, Ward Andrew, Knight Robert T, Deouell Leon Y
Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
Helen Wills Neuroscience Institute, University of California, Berkeley, California.
PLoS One. 2016 Dec 12;11(12):e0167351. doi: 10.1371/journal.pone.0167351. eCollection 2016.
The analysis of cross-frequency coupling (CFC) has become popular in studies involving intracranial and scalp EEG recordings in humans. It has been argued that some cases where CFC is mathematically present may not reflect an interaction of two distinct yet functionally coupled neural sources with different frequencies. Here we provide two empirical examples from intracranial recordings where CFC can be shown to be driven by the shape of a periodic waveform rather than by a functional interaction between distinct sources. Using simulations, we also present a generalized and realistic scenario where such coupling may arise. This scenario, which we term waveform-dependent CFC, arises when sharp waveforms (e.g., cortical potentials) occur throughout parts of the data, in particular if they occur rhythmically. Since the waveforms contain both low- and high-frequency components, these components can be inherently phase-aligned as long as the waveforms are spaced with appropriate intervals. We submit that such behavior of the data, which seems to be present in various cortical signals, cannot be interpreted as reflecting functional modulation between distinct neural sources without additional evidence. In addition, we show that even low amplitude periodic potentials that cannot be readily observed or controlled for, are sufficient for significant CFC to occur.
交叉频率耦合（CFC）分析在涉及人类颅内和头皮脑电图记录的研究中已变得很流行。有人认为，在某些数学上存在CFC的情况下，可能并不反映两个具有不同频率的不同但功能耦合的神经源之间的相互作用。在此，我们提供两个来自颅内记录的实证例子，其中可以证明CFC是由周期性波形的形状驱动的，而不是由不同源之间的功能相互作用驱动的。通过模拟，我们还展示了这种耦合可能出现的一个广义且现实的场景。我们将这种场景称为波形依赖型CFC，当尖锐波形（如皮层电位）在数据的某些部分出现时就会出现，特别是如果它们有节奏地出现。由于波形包含低频和高频成分，只要波形以适当的间隔出现，这些成分就可以内在地相位对齐。我们认为，这种似乎存在于各种皮层信号中的数据行为，如果没有额外的证据，不能被解释为反映不同神经源之间的功能调制。此外，我们表明，即使是难以轻易观察或控制的低振幅周期性电位，也足以导致显著的CFC发生。
