where the superscripts ℜ and ℑ denote the real and imaginary part of the complex-valued cross-spectral density matrices, (∙)−1 and Tr(∙) are the inverse and trace operators. MIM is the generalization of ImCoh to multivariate time series analysis and, in the case of two univariate time series, it coincides with the squared ImCoh. Similarly to ImCoh, MIM does not lead to artifactual phase coupling detections due to artificial zero-lag correlations. Furthermore, MIM is invariant under invertible and static linear transformations of xI(t) and xJ(t) (Ewald et al., 2012), such as rotations of the physical coordinate system in which the MEG source space is defined.
