Effects of combined theta burst stimulation and transcranial direct current stimulation of the dorsolateral prefrontal cortex on stress

Objective: Research suggests that the combination of different non-invasive brain stimulation techniques, such as intermittent theta-burst stimulation (iTBS) and transcranial direct current stimulation (tDCS), could enhance the effects of stimulation. Studies investigating the combination of tDCS and iTBS over the dorsolateral prefrontal cortex (DLPFC) are lacking. In this within-subjects study, we evaluated the additive effects of iTBS with tDCS on psychophysiological measures of stress. Method: Sixty-eight healthy individuals were submitted to a (bifrontal)tDCS + iTBS and (sham)tDCS + iTBS protocol targeting the DLPFC with a one-week interval. The Maastricht Acute Stress Test was used to activate the stress system after stimulation. Stress reactivity and recovery were assessed using physiological and self-report measures. Results: The stressor evoked significant psychophysiological changes in both stimulation conditions. However, no evidence was found for differences between them in stress reactivity and recovery. Participants reported more pain and feelings of discomfort to the (bifrontal)tDCS + iTBS protocol. Conclusion: In this study set-up, iTBS plus tDCS was not superior to iTBS in downregulating stress in healthy subjects. Significance: There is no evidence for an effect of combined tDCS-iTBS of the DLPFC on stress according to the parameters employed in our study. Future studies should explore other stimulation parameters, additive approaches and/or neurobiological markers. (C) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Automated summary

The study found that the combination of iTBS with tDCS on the DLPFC was not superior to iTBS alone in reducing stress in healthy subjects. There were no significant differences in stress reactivity and recovery between the two stimulation conditions. Future research should explore other stimulation parameters, additive approaches, and/or neurobiological markers.