The convergence of findings across modalities is encouraging; however, a critical question is whether knowledge of the spectral properties of these disturbances tells us something new about MDD pathophysiology. We showed that elevations in phase synchronization within and between networks in the MDD group emerged in the beta-band (12.5–21 Hz). The precise processes that beta-band oscillations support remains a topic of debate, however, one view is that beta synchronization promotes the maintenance of a current motor or cognitive state, and is increased in contexts where the brain’s ‘status quo’ is given priority over new signals [52, 53]. Support for this theory comes from studies showing that pathological enhancement of beta-band synchronization can lead to deterioration of flexible motor and cognitive control. For example, elevated cortico-basal ganglia beta-band synchronization has been linked to impairments in initiating voluntary movement in Parkinson’s Disease [54–56] and artificially inducing excessive beta synchronization via intracranial electrical stimulation of the basal ganglia causes the emergence of movement symptoms [57]. In light of its predominance at rest, beta-band synchronization has been suggested to correspond to an ‘idling rhythm’ in the motor system [58].
