range between 0 (no shared activity between nodes) and 1 (completely synchronous). This measure thus is well-adapted for assessing functional connectivity in RSNs: it has been successfully used to examine spatial integration both at short- and long-distances in the brain [51], [52], and functional connections among sites overlying disparate cortical areas involved in sensory, motor, and cognitive tasks, both during tasks and at rest [51], [53]–[54]. Coherence was first examined in clinical populations with depression or dementia by O'Connor and colleagues [55], but has not been extensively studied in subjects with MDD compared to healthy controls. The most systematic previous study of connectivity in MDD was conducted by Fingelkurts and colleagues [43], who examined 12 medication-free depressed outpatients and used the index of structural synchrony to analyze nine categories of functional connectivity (e.g., short left/right, short anterior/posterior, long left/right, long anterior/posterior, long interhemispheric) separately for the theta and alpha frequency bands).
