Gamma power correlates with clinical response to repetitive transcranial magnetic stimulation (rTMS) for depression

Major Depressive Disorder (MDD) is a significant public health issue and a leading cause of mortality. Due to the limited efficacy of current treatment options, neuromodulation therapies such as repetitive transcranial magnetic stimulation (rTMS) have been explored. However, not all patients experience improvements in depressive symptoms from rTMS, and the reasons for this are not clear. The goal of this study is to contrast functional changes in responders versus non-responders over a single course of treatment. rTMS was administered to the left dorsolateral prefrontal cortex (L-DLPFC) during 5 sessions per week for four weeks. Magnetoencephalography (MEG) recordings were acquired before, during and after treatment in order to make longitudinal assessments. Power spectral density (PSD) analysis revealed differences in gamma band activity that were related to the degree of clinical response. These results suggest that cortical activity measured using MEG could act as an objective measure of anti-depressive response.