The effects of neuromodulation priming to Intermittent Theta Burst Transcranial Magnetic Stimulation (iTBS): effects on physiological and subjectives measures of stress in healthy individuals

Abstract In this sham-controlled, within-subjects study, we evaluated the additional effect of priming prefrontal intermittent theta-burst stimulation (iTBS) with transcranial direct current stimulation (tDCS). Sixty-eight healthy individuals were submitted to an active priming (active bifrontal tDCS + active iTBS) and sham priming (sham tDCS + active iTBS) protocol targeting the dorsolateral prefrontal cortex (DLPFC). The Maastricht Acute Stress Test (MAST) was used to activate the stress system. Stress reactivity and recovery were assessed using objective physiological measures (heart rate and its variability, blood pressure and skin conductance), and subjective measures of stress (self-report measures). Results demonstrated that the MAST evoked significant psychophysiological changes. However, no evidence was found for any difference between the active priming and sham priming condition in both stress reactivity and recovery. Moreover, Bayesian analyses revealed conclusive evidence for the absence of an additional effect of priming iTBS with tDCS on stress regulation. Importantly, participants reported more pain and feelings of discomfort to the active priming protocol. All in all, in this innovative study there is no evidence for an effect of active priming (combined tDCS-iTBS) of the DLPFC on stress according to the parameters employed in our study. Future research is mandatory to explore other stimulation parameters, other outcome parameters and neuroimaging methods, to understand a potential additive effect of pairing tDCS with iTBS applied to the prefrontal cortex. Keywords: transcranial Direct Current Stimulation (tDCS), intermittent Theta Burst Stimulation (iTBS), Stress, Psychophysiology