Greicius and colleagues speculated that the increased functional connectivity in mood regulating networks might be associated with impaired cognitive processing in MDD [18]. This speculation is consistent with the established role of oscillatory activity in regulating cognitive networks [32], [75]. The ability to modulate alpha rhythmicity and coherence has been linked to the ability to shift and focus attention, and meet working memory and executive demands [51], [53]–[54], [76]. Successful modulation of beta activity has been related to response preparation and cognitive control [77]–[78]; “pathological” increases in beta activity are associated with deterioration in cognitive flexibility and control [78]. Several neurophysiologic measures of synchronization, including coherence, phase synchronization, and synchronization likelihood, have been related to deficits on measures of attention and working memory, as well as processing of auditory, visual, linguistic, and social cognition information in psychiatric and neurologic illnesses [75]. This wide range of cognitive activities overlaps with the cognitive domains and functions that have been reported to be deficient in some subjects with MDD [3], [79]. Theta oscillations play a significant role in memory function, with modulated coupling
