Effects of anodal tDCS applied to the left DLPCF on stress responses in healthy subjects

Abstract

Extended or repeated activation of the stress response can have detrimental effects on mental and physical well-being. The prefrontal cortex, specifically the dorsolateral prefrontal cortex (DLPFC), is believed to have influence on the neuroendocrine stress response system and consequently on emotional state and subjective experience of stress. To explore this hypothesis, we conducted a study in which we enhanced DLPFC excitability using transcranial direct current stimulation (tDCS) in 36 healthy participants (17M; 19F), which were randomly assigned to receive either excitatory tDCS (anodal stimulation) or a sham stimulation over the left DLPFC just before and during the exposure to a psychosocial stress test. We assessed parameters related to the neuroendocrine system (salivary cortisol levels), emotional affect state (positive and negative affect schedule, PANAS) and self-reported experience of stress (visual analogue scale, VAS). The results revealed that a single session of excitatory tDCS over the left DLPFC had an influence on the self-reported experience of stress but no effects in emotional affect and salivary cortisol concentration. Significant differences were found for all the parameters investigated over time both in the active and sham group, indicating that the stress-producing paradigm used has measurable effects in the chosen markers. This study provides initial evidence that a single session of excitatory tDCS over the left DLPFC can attenuate the subjective experience of psychosocial stress confirming the importance of the left DLPFC, a target for non-invasive brain stimulation in depression treatment, in promoting coping strategies in psychosocial stressful situations.