In addition to PLI, we also determined phase synchronization or phase coherence (PC) between different electrode locations to examine the pattern of spatial synchronization between distinct brain areas as a function of task condition. Due to the large number of possible electrode pairs and associated multiple testing issues, we performed a data reduction in two ways: first, to assess the time course of the overall strength of spatial synchrony in three cortical regions (frontal, central, and parietal) at different frequencies using TF (time-frequency) decomposition, we averaged PC values of 18 electrode pairs for three midline electrodes (Fz, Cz and Pz, respectively, Fig. 2). Second, we restricted analyses of PC values to a set of 9 selected pairs of electrodes that are most representative of major inter-regional connections (Fig. 3).
