Effects of Left Versus Right Dorsolateral Prefrontal Cortex Repetitive Transcranial Magnetic Stimulation on Affective Flexibility in Healthy Women: A Pilot Study

Objective: To determine the antidepressant mechanism of action for repetitive transcranial magnetic stimulation (rTMS) to the left dorsolateral prefrontal cortex (DLPFC) in healthy women. Our primary hypothesis was that a single session of left DLPFC rTMS, compared with a session of right DLPFC rTMS, would result in better (reduced) negative nonaffective switch costs in healthy women. Background: The antidepressant mechanism of action for rTMS is not clear. It is possible that rTMS to the DLPFC improves emotion regulation, which could be a part of its antidepressant mechanism. Methods: Twenty-five healthy women were randomized to receive left high-frequency (HF) rTMS versus right HF rTMS in one session and then contralateral stimulation during a second session. Emotion regulation was assessed via switch costs for reappraisal of negatively valenced information on an affective flexibility task. Results: For negative nonaffective switch costs, the interaction effect in the two-way ANOVA was not significant (F-1,F-19=3.053, P=0.097). Given that left HF rTMS is the approved treatment for depression, post hoc t tests were completed with particular interest in the left-side findings. These tests confirmed that negative nonaffective switch costs significantly improved immediately after left rTMS (t(1,19)=2.664, P=0.015) but not right rTMS. Conclusions: These findings suggest that left DLPFC HF rTMS may lead to antidepressant effects by improving the regulation of emotion.