Grant: Project Grant

About 2.5% of Canadians are diagnosed with treatment resistant depression (TRD) yearly. Intermittent theta burst stimulation (iTBS) is an efficient form of repetitive transcranial magnetic stimulation that is an effective, evidence based treatment for TRD. However, iTBS, like all brain stimulation, is implemented via trial and error, as, to date, there are no predictive methods to assess the likelihood of patient response to iTBS. Work from our centre focused on TRD has previously established changes in cortical activity indexed via TMS-EEG after brain stimulation, but not with placebo, indicating the promise of TMS-EEG markers of cortical activity as markers of brain stimulation response. In contrast to other forms of rTMS, iTBS is known to result in enhanced plasticity, or cortical excitation. Even with these advances, response rates with iTBS remain at 30-40%. The optimization of electric field (E-field) delivery may improve treatment response by accounting for the individual differences in head structure and brain regional anatomy. We will examine if iTBS combined with E-field modeling (iTBSe) better engages TMS-EEG markers of cortical excitation and improves clinical response when compared to conventional iTBS in patients with TRD.