While literature on resting state frequency specific coupling by MEG is relatively abundant, less has been investigated about cross-frequency coupled networks. To date, few studies have investigated the coupling between the local phase of a low frequency oscillation and the local amplitude of a high frequency oscillation, i.e., Phase-Amplitude Coupling (PAC). In their interesting paper, Roux et al. (2013) showed that in resting-state MEG, local gamma-band activity is coupled with the phase of the alpha band rhythm in the visual cortex. Furthermore, Florin and Baillet (2015) showed that resting-state networks derived from signal model based on the PAC, substantially overlapped with DMN, DAN/SMN, VN, and right FPN, indicating that the PAC is an important component of the network generation in the resting-state. More recently, an effort to disclose n:m-cross-frequency phase coupling RSNs and to disentangle these networks from phase-amplitude coupling networks has been made by Siebenhühner et al. (2019). Nevertheless, the topic still needs further investigation.
