Transcranial Magnetic Stimulation Depression Treatment Induces Positive Bias in Task-Related Brain Function: Results From the BRAEN-MAP Trial

Antidepressant treatments are theorised to act by inducing a positive bias in information processing early on during treatment. Here, we tested for the first time whether this theory generalises to transcranial magnetic stimulation (TMS) treatment, an effective therapy for treatment-resistant depression. 49 patients with major depression received 20 sessions of open-label intermittent theta-burst stimulation applied to left dorsolateral prefrontal cortex. At baseline and after eight stimulation sessions, positive bias was assessed using behavioural and functional magnetic resonance imaging tasks presenting emotional faces. Clinical improvement at the end of treatment was related to an early increase in positive bias (1) in misclassification of emotional faces, (2) in the response of the default mode network (DMN) to emotional faces including rostral anterior cingulate cortex (ACC), and (3) in connectivity between rostral ACC and DMN. These neural changes predicted clinical improvement at the end of treatment beyond early symptom reduction. The results suggest that TMS treatment increases positive bias early on during treatment, and that the neural mechanisms might differ from that of antidepressant drugs.