Cortical rTMS as a Treatment for Depression

Depression is a leading cause of disability worldwide with a 19% lifetime prevalence in the United States. Dysfunctional reward processing is one of the core features of depression. Common treatments of depression include psychological therapies (e.g., cognitive behavioral therapy), medication (e.g., bupropion, sertraline) and psychological therapies and medication combined, but they may not address the function of the reward circuit in depression. These treatments often o not improve depressive symptoms in patients with depression who are classified as having treatment-resistant depression, and they may be unlikely to respond to further medication trials. Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation that enables us to selectively excite or inhibit neural activity. Multiple TMS pulses given consecutively are known as repetitive TMS (rTMS), and the primary clinical location for applying rTMS is the left dorsolateral prefrontal cortex (DLPFC) for treatment of depressive symptoms. Many of these studies have shown that rTMS to the DLPFC may result in decreased depressive symptoms, but is only partially effective (response and remission rates of 41.2 and 35.3%, respectively). This evidence supports the importance of evaluating the efficacy of rTMS in other brain regions, such as the orbitofrontal cortex (OFC), in the treatment of depressive symptoms rather than in the DLPFC.