Fig. 2
Topographies of grand average interregional phase locking values (PLV) for 11 reference electrodes. The grand average PLV of the reference electrodes with all the other electrodes were obtained from 11 subjects in 64 and 128 channel resting EEG data. The PLVs were computed using original recorded reference electrode signals (oPLV) and the interpolated signal computed by SSI (iPLV). For illustration purposes, only alpha (8 ~ 13 Hz) band oPLV and iPLV were computed using interpolated signals with SSI parameter m = 4, n = 7, and λ = 10−5 in this figure. The differences between iPLV and oPLV were computed by simple subtraction (dPLV = oPLV - iPLV). As shown in dPLV topographies, there were clear differences not only in neighboring pair-electrodes close to the reference-electrodes but also in distant pair-electrodes across all of the 11 reference-electrodes. dPLVs were averaged across pair-electrodes in near and distant groups for the locations marked with red dots in the topographies