Measuring phase synchrony using complex extensions of EMD

A framework for the robust assessment of phase synchrony between multichannel observations is introduced. This is achieved by using empirical mode decomposition (EMD), a data driven technique which decomposes nonlinear and nonstationary data into their oscillatory components (scales). In general, it is rarely possible to jointly process two or more channels due to the non-uniqueness of the decompositions. To guarantee the same decomposition levels for every pair of channels analysed, we consider phase synchrony within the recently introduced framework of complex extensions of EMD. Simulation results on brain signals support the analysis.