Findings emerging from studies using this method highlight its promise as a tool for probing the spectral properties of rsFC disturbances. Research has revealed rsFC disturbances within discrete frequency bands in Alzheimer’s Disease [18, 19], psychosis [20–22], obsessive-compulsive disorder [23], post-traumatic stress disorder [24] and eating disorders [25]. To date, only one study has used lagged phase synchronization to examine the spectral properties of connectivity disturbances in MDD [26]. This study focused on connectivity between a targeted set of frontal brain regions previously associated with metabolic or anatomical abnormalities in MDD. Individuals with MDD had increased alpha-band lagged phase synchronization between the subgenual anterior cingulate cortex and both the left medial prefrontal cortex and left dorsolateral prefrontal cortex [26]. However, these findings are difficult to interpret in the context of an association between increased alpha-band lagged phase synchronization and greater symptom improvement after antidepressant treatment. Furthermore, it remains unknown to what extent altered high-frequency rsFC might represent a state or trait-like marker of MDD.
