of surface Laplacian analysis (Nunez et al., 1997, 1999) to investigate radially oriented sources of neural activity in our EEG data and to find the superficial radial dipoles near the brain surface. However, this approach, and other source analysis approaches, have not been validated in conjunction with SL measures, and this goal is beyond the scope of the present clinical study. Importantly, virtually all prior studies using EEG in bipolar disorder, or SL measures in humans, have utilized voltage rather than Laplacian transforms (Boersma et al., 2011; Buldu et al., 2011; Schoonheim et al., 2013; Stam et al., 2007a). It should be noted that the neural synchrony measure by SL has a strong regional correspondence with the local network characteristics (Fig. 6), although these findings cannot unambiguously be related to specific brain sources.
