From Cortex to Cardiac Response: tDCS of the Prefrontal Cortex Improves Autonomic Markers of Emotion Regulation

<b>Background:</b> Emotion regulation (ER) plays a vital role in mental health, spanning mood, anxiety, and personality disorders. Cognitive reappraisal (CR) is one of the most common ER strategies and depends on prefrontal brain areas, but its success varies, and its neural basis is not fully clear. Interest is growing in using transcranial direct current stimulation (tDCS) to support ER, yet most studies have focused only on the dorsolateral prefrontal cortex (dlPFC) and used simple tasks. <b>Objective:</b> This study explored whether tDCS applied to either the dlPFC or the ventromedial prefrontal cortex (vmPFC) could shape autonomic responses during CR while people watched emotionally engaging film clips. <b>Methods:</b> Participants were randomly assigned to receive either active or sham tDCS over the dlPFC or vmPFC. While stimulated, they used CR strategies (positive reappraisal, fictional reappraisal, or distancing) to manage their reactions to negative film scenes. Heart rate (HR), skin conductance (SC), and respiratory rate (RR) were tracked throughout as physiological indicators. <b>Results:</b> Active dlPFC tDCS combined with CR led to significantly greater reductions in HR toward the end of emotional exposure, compared to sham or non-CR conditions. dlPFC stimulation also lowered HR even without explicit CR, pointing to possible effects on automatic regulation. vmPFC effects were inconsistent, and no reliable effects were observed for SC or RR. <b>Conclusions:</b> These results suggest that tDCS effects on autonomic ER depend on the brain region and timing. dlPFC stimulation may strengthen both intentional and automatic emotion regulation, especially when combined with reappraisal, highlighting the value of realistic emotional tasks in neuromodulation studies.