I. Introduction
Neuroscientists use electroencephalograms (EEGs) to study the highly complex spatio–temporal dynamics of brain processes. One important feature of underlying neuronal activity is that brain regions do not act in isolation. In fact, epileptiform activity and cognitive processes require synchronous activation of multiple large aggregates of neurons (see, e.g., [15], [11], and [1]). Thus, it is important to establish an easily interpretable measure of synchrony between brain regions and develop a consistent estimation procedure.