Whole-brain dynamic processes are underpinned by the formation of cell assemblies, i.e., groups of cells that oscillate in synchrony, or precisely timed succession, for transient periods (Nunez and Srinivasan, 2006). As numerous cell assemblies may be active at any given time, oscillation synchronicity within specific frequency bands is thought to be the mechanism by which the output of single units is identified as being part of a coherent network (Singer et al., 1997). Performing even a simple experimental task will excite a number of different cell assemblies which will be active alongside numerous other task-unrelated assemblies. A difficulty faced by EEG researchers is the fact that electrical activity generated by these separate assemblies becomes mixed, and, via volume conduction, smeared, across the scalp. That is, each EEG electrode records a mixture of signals arising from multiple cognitive processes and from on-going “background” oscillatory activity. Furthermore, scalp electrodes also record activity from non-brain sources including muscle (eye-movements, blinking, heartbeat) and in some cases from non-physiological electrical sources (e.g., line-noise). Filtering and artifact rejection reduces the influence of some of these unwanted
