There has been an explosion of recent research suggesting that the pathophysiology underlying a variety of different neuropsychiatric disease states is a network phenomenon. Despite this, the findings of studies of traditional EEG, fMRI and PET functional connectivity networks have had limited application in clinical neuropsychiatry, for reasons that could be substantially addressed by combining them with brain stimulation techniques. The reasons why traditional neuroimaging network techniques have not been clinically useful to date include: (1) The specific alterations in network connectivity that have been identified in different disease states tend to vary considerably across studies and depending on the precise analysis technique utilized, and therefore reliable & consistent EEG/fMRI network biomarkers of disease and recovery are not currently available. (2) The techniques currently used in EEG, fMRI and PET functional connectivity studies are essentially correlational, and the interactions they identify have not been validated in experiments that directly manipulate neural activity. Consequently, while various techniques may identify correlated activity between two different cortical regions, a direct interaction between the two can only be confirmed by direct and focal stimulation
