Assessment of Changes in Functional Brain Connectivity During Depression Treatment with TMS Using Granger Causality Based Methods

Directed transfer function (DTF) method was used to assess brain connectivity disturbances in depression. The results were depicted as a brain model with the electroencephalographic (EEG) registration points, through which the directions of bioelectric activity transfer are defined. Transcranial magnetic stimulation (TMS) is used as an alternative treatment for drug-resistant depression and is considered to restore impaired connections. The combination of TMS and EEG allows to study changes of functional brain connectivity (FBC) in a non-invasive way. It was found that the FBC of resistant patients differed more from that of healthy subjects than in non-resistant patients. The largest changes in connectivity were identified in theta frequency.