In the above notation, θj(F, t) denotes the instantaneous phase signal obtained from, e.g., Hilbert or wavelet transform of the bandpass filtered signal j; F denotes the frequency band of interest; τ denotes a given time delay; and H(Z) : = −∫p(Z) ln (p(Z)) denotes the information entropy of the random variable Z, where p(Z) is the probability density function (see Lobier et al., 2014, and references therein for more details). The direction of the phase coupling can be assessed through the comparison between the pTE from signal i to j and the one from j to i (Hillebrand et al., 2016). pTE has the advantage over the traditional transfer entropy measure of being able to handle the artificial zero-lag correlation effects (Lobier et al., 2014).
