Assessment of Quantitative Magnetoencephalography using Cross-frequency Phase-phase Coupling

Cross-frequency phase-phase coupling (n:m CFC) within a cortical region has been proposed as a potential mechanism to regulate neural communication between different temporal scales. This study investigated n:m CFC values between high and low frequencies in resting-state networks using magnetoencephalographic (MEG) data. Simulation experiments with different frequency pairs were first conducted to evaluate the effect of SNR on the estimation of phase and CFC. The values of n:m CFC between each pair of delta, theta, alpha, beta, and gamma frequencies were estimated from eye-open resting-state MEG data. The topographic maps of CFC values between alpha and other frequencies were illustrated. The results of simulation data showed the increased accuracy of phase and n:m CFC estimation for balanced power of two targeted frequencies. Results of MEG data exhibited that CFC maps of low-alpha activity presented broadly distributed coupling with high frequencies (including beta and gamma) in the frontal regions of salient-ventral attention and frontoparietal control networks, whereas high-alpha activity coupling with the gamma band in the posterior part of frontoparietal control network. Our study demonstrates the versatile of n:m CFC values at rest in human brain. Caution should be considered when n:mCFC values would be used as an index of dysfunction at resting state in diseased brains.