As shown in Figure 1b, the processed EEG data were filtered at the two frequency ranges of interest. Specifically, we used a range of phase (2–16 Hz) and amplitude–frequency (18–60 Hz) combinations to examine the extent to which specific low‐frequency (delta, theta, and alpha) phase and high‐frequency (beta, gamma) amplitude values were coupled within each electrode. Subsequently, the low‐frequency phase and high‐frequency amplitude were obtained using the Hilbert transform. Finally, the modulation index (MI) was calculated to characterize PAC (Tort et al., 2010), which measures the divergence of the amplitude distribution from a uniform distribution. The more the phase‐amplitude distribution deviates from the uniform distribution, the higher the coupling (i.e., 0 ≤ MI ≤ 1).
