This study focused on brain dynamics changes in the meditative state (short-term changes) and their possible development into trait (long-term changes), in an EEG data set recorded from a group of Mindfulness Meditators (MM, n=36) with varying expertise, a group of transcendental meditators (TM, n=12), and suitable controls. We applied two measures: (a) a functional coupling measure of synchronized activity, named mean phase coherence (MPC) (Lachaux, Rodriguez, Martinerie, & Varela, 1999). This method provides a direct measure of phase-locking as it separates the effects of amplitude and phase in the interrelations between signals, and can test more precisely the assumption that phase synchrony is involved in long-distance neuronal integration (Lutz, Dunne, Davidson, & Thompson, 2007); and (b) a complexity measure of global descriptors (GD), comprising a set of three GDs which bare an intuitive physical meaning (Wackermann, 1999). Using this three-dimensional complexity description, the electrical signature of a brain’s macro-state may be represented by a point in a three-dimensional space, hence the result is dimensional simplicity and data reduction. Our results indicate that both measures are suitable to detect significant state and trait changes, as well as differences between the two meditation forms, MM and TM. In addition, the MPC also revealed an expertise effect between the different expertise levels of MM.
