Ideally, any change in the instantaneous component should have little effect on the lagged or on the imaginary connectivity. However, when a lagged connection exists, the imaginary part of connectivity measures such as coherence [27] fails to detect it by tending to zero if the instantaneous component is large. This is not the case for lagged phase synchronization in Eq. 3 which asymptotically tends to a nonzero value, detecting the presence of a physiological lagged connection. Details on eLORETA connectivity algorithm can be found in recent reports by Pascual-Marqui et al. [30], [31].
