Fig. 6: Simulation of feature-dependent Phase Amplitude Coupling (PAC) and estimation thereof.

a Simulated phase-amplitude coupling: The left panel shows a simple phase-amplitude coupling where the slow phase of the signal in red modulates the amplitude of a faster signal in green. b We simulated three scenarios of PAC mechanism: (1) reproduces the global PAC effect of (a) without any time-locking to events, in the other two examples the amplitude is modulated differently depending on the timing (2) and values (3) of an external feature signal. c–e We computed the modulation index for PAC using either equation (5) (mean vector length, black dashed line) or the TRF-based method described in the main text (green and pink lines). The computation is done on each of three PAC simulations from (b). d, e show that we can recover the effect of an individual feature affecting phase-amplitude coupling from the linear forward model. On the other hand, the mean vector length method is unable to disentangle if the PAC is induced by onsets only (green line) or valued features (pink).