Effects of Transcranial Direct Current Stimulation on the Fight-or-Flight Response: Potential to Improve Functioning by Modifying Prefrontal Cortex Excitability

OBJECTIVES: Recent reports from studies using transcranial direct current stimulation (tDCS) confirm its potential to improve human functioning in healthy populations. The dorsolateral prefrontal cortex (DLPFC) is thought to exert an inhibitory influence on the activity of the neural stress-evoking systems, including autonomic and neuroendocrine responses. This study aimed to investigate the effect of modulating DLPFC excitability with tDCS on the reactivity of the fight-flight-freeze system as one of the basic temperamental traits framed by the revised reinforcement sensitivity theory.

METHODS: Sixty-three participants aged between 18 and 32 years (M = 21.8; SD = 2.1) with no diagnosed neurological or psychiatric disorders participated in the study. Participants were randomly assigned to receive either real (n = 31) or sham (n = 32) tDCS. For real stimulation, a current intensity of 2 mA was applied for 20 minutes. The anode was placed over the F3 area and the cathode over the F4 area according to the International EEG 10-20 system. Subjects received stimulation for five consecutive days. During the neuromodulation sessions, short videos were shown to promote healthy eating, proper sleeping habits, physical activity and other healthy behaviors needed to complete another part of the study. Participants completed the Polish version of the Reinforcement Sensitivity Questionnaire (RSQ-29) one to two days before the first tDCS session and again ten to fourteen days after the last stimulation. In the post-test, participants were asked to rate their experiences over the previous two weeks.

RESULTS: The results of the one-tailed independent samples t-test indicated that subjects who received real stimulation had significantly lower change scores on the fight reactivity scale compared to the sham stimulation group, but not on the flight or freeze scales.

CONCLUSIONS: This suggests that neuromodulation with tDCS may be beneficial in the prevention of chronic stress, anxiety and psychosomatic disorders.