In the present study, we extend the earlier work of Fingelkurts and colleagues by examining synchrony across brain regions with qEEG coherence using a denser electrode array, a broader range of frequency bands, and a greater number of subjects. We compared the global resting functional connectivity of subjects with MDD and healthy controls utilizing the novel method of weighted network analysis [56], which obviates the need to threshold the observed coherence values. The nodes in the weighted (whole brain) network corresponded to pairs of neighboring qEEG recording electrodes (Figure 1), and the coherence between each pair of nodes was considered as a connection or “edge” of the network. Coherence values representing the strength of the network connections (i.e., value of the edges) were examined in each frequency band to identify any differences in the strength of the resting functional connectivity between groups. To further elucidate patterns of difference in functional connections between MDD and control subjects and characterize brain connectivity in the depressed state, we also examined the mean length of the edges showing significant differences, as well as the locations of the nodes most commonly linked by significant edges.
