Modulations of local oscillatory activity can be observed as a consequence of task execution or stimulus presentation in a variety of conditions. One of the most prominent examples is provided by motor execution in which the oscillatory beta power in the primary motor cortex is reduced during the movement in comparison to the preceding period (ERD, Event Related Desynchronization) while it is enhanced after the movement (ERS, Event Related Synchronization, i.e., beta rebound), see Pfurtscheller and Lopes da Silva (1999) for details, or section “Magnetoencephalography as a tool for imaging brain activity” in Pizzella et al. (2014) and references therein. A modulation of local oscillatory activity shared by two brain regions is often considered as a marker of functional connectivity. In fact, Amplitude Envelope Correlation approaches have been extensively used to disclose brain functional connectivity during task (Brookes et al., 2011a) as well as at rest (de Pasquale et al., 2010; Brookes et al., 2011b). However, a more physiologically oriented probe on brain functional connectivity can be identified by phase-based metrics under the CTC hypothesis (Fries, 2005), that states that
