Does rTMS on brain areas of mirror neurons lead to higher improvements on symptom severity and empathy compared to the rTMS standard procedure? - Results from a double-blind interventional study in individuals with major depressive disorders

Background: A key feature of major depressive disorders is the lack of emotional processing such as empathy. To counter this, we tested, if brain stimulation on areas rich of mirror neurons on the left inferior parietal lobe (lIPL) might improve emotional processing, including empathy, compared to a standard brain stimulation on the left dorsolateral prefrontal cortex (lDLPFC). Methods: Twenty inpatients (mean age: 38.9 years; 55% females) with severe major depressive disorders and stable treatment of sertraline at therapeutic dosages were randomly assigned to either the rTMS condition on areas of mirror neuron stimulation, that is, the left inferior parietal lobe (rTMS-lIPL), or to the left dorsolateral prefrontal cortex (rTMS-lDLPFC; control condition). Interventions lasted for two consecutive weeks (2 x 5 interventions of 30'). At baseline and at the end of the study, patients completed questionnaires on current mood state and emotion regulation. In parallel, experts rated patients' depression severity. Results: Mood improved over time, but more so in the control condition, compared to the rTMS-lIPL condition (medium-large effect sizes). Emotion regulation improved over time; specifically, empathy improved, but only in the rTMS-lIPL condition, compared to the control condition. Symptoms of depression decreased over time, but more so in the rTMS- lIPL condition. Conclusions: The pattern of results suggests that among inpatients with severe major depressive disorders, and compared to a standard procedure of rTMS, rTMS targeting on areas rich of mirror neurons appeared to improve emotion regulation, and specifically empathy, while there was no advantage on acute mood.