Abstract
Objective To better understand the neural mechanisms behind the effect of intermittent theta-burst stimulation (iTBS), we investigated how the prefrontal blood oxygenation response measured by changes in oxygenated haemoglobin (oxy-Hb) was modulated during a sham-controlled iTBS treatment course, and whether this was related to depressive symptom change. Methods In this randomised, double-blind study, patients with ongoing treatment-resistant depression received either active (n = 18) or sham (n = 21) iTBS over the dorsomedial prefrontal cortex for ten to fifteen days with two sessions daily. Event-related functional near-infrared spectroscopy (fNIRS) was measured during each iTBS train, and resting-state oxy-Hb was compared before and after each iTBS session at the first, fifth, and last treatment day. Results Patients receiving active iTBS had an increase of the event-related oxy-Hb response compared to the sham group on the fifth (bilateral prefrontal cortices p < .001) and last (left prefrontal p = .007, right prefrontal p = .025) treatment day. Resting-state analysis showed suppressed oxy-Hb change in active iTBS compared to sham iTBS on the last treatment day (p = .024). Oxy-Hb change was unrelated to depressive symptom change (p = .474). Conclusions This study describes a modulation of the blood oxygenation response over the prefrontal cortex that was built up during the course of active iTBS treatment in depression.
Highlights
Repetitive transcranial magnetic stimulation is an emerging alternative for treatment-resistant depression
Eighteen patients were randomised to active intermittent theta burst stimulation (iTBS), and 21 to sham iTBS
To the best of our knowledge, this study is the first to describe how prefrontal brain activity is modulated over the course of dorsomedial iTBS treatment as captured with functional near-infrared spectroscopy (fNIRS)
Summary
Repetitive transcranial magnetic stimulation (rTMS) is an emerging alternative for treatment-resistant depression. The dmPFC shows increased functional connectivity to numerous brain regions involved in emotion regulation, including the anterior cingulate cortex (ACC) (Sheline et al 2010), while antidepressant medication reduces functional connectivity within the dmPFC in healthy controls (McCabe et al 2011). Together, this suggests that functional modulation of this brain region might have an antidepressive effect. An initial open-label depression study of rTMS over the dmPFC reported this target being safe and tolerable (Bakker et al 2015)
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