Transcranial Magnetic Stimulation Depression Treatment Induces Positive Bias in Brain and Behaviour: Results From the BRAEN-MAP Trial

Description: Antidepressant treatments (medications, CBT) are theorised to act by reducing negatively biased information processing. We tested for the first time whether transcranial magnetic stimulation (TMS) works via this neurocognitive mechanism of treatment action. 49 patients with major depression received 20 daily sessions of open-label intermittent theta-burst TMS to left dorsolateral prefrontal cortex. Change in emotional bias was measured using behavioural and neuroimaging tasks of emotional face processing, between baseline and after eight days of treatment. Clinical improvement after four weeks was related to an early increase in positive bias in (1) misclassifications of emotional faces, (2) task-related response of the default mode network (DMN), including rostral anterior cingulate cortex (rACC), and (3) functional connectivity between rACC and DMN. These early neurocognitive changes predicted clinical outcomes, beyond early symptom reduction. Thus, clinically effective TMS increases positive bias in emotional processing early during treatment, a neurocognitive mechanism causally linked to mood outcome.