Transcranial Direct Current Stimulation (tDCS) is a non-invasive, technique for brain stimulation. Anodal stimulation causes neuronal depolarisation and long-term potentiation, while cathodal stimulation causes hyperpolarisation and long-term depression. Stressors are associated with an increase in sympathetic cardiac control, a decrease in parasympathetic control, or both. Associated with these reactions is a frequently reported increase in Low Frequency (LF) Heart Rate Variability (HRV), a decrease in High Frequency (HF) power, and/or an increase in the LF/HF ratio.

The present work aims to explore the tDCS potential in the modulation of the Autonomic Nervous System (ANS), through indirect stimulation of Anterior Cingulate Cortex (ACC).

Two subjects, a 39 year old female and a 49 year old male, gave informed consent. Saline soaked synthetic sponges involving two, thick, metalic (stainless steel) rectangles, with an area of 25 cm2 each have been used as electrodes, connected to Iomed Phoresor II Auto device. It has been delivered a 2 mA current, for 20 minutes, over the left Dorsolateral Prefrontal Cortex (DLPFC) (Anode). Spectrum analysis (cStress software) of HRV has been performed before and after tDCS administration.

The female/male suject results of LF power, HF power and LF/HF ratio, before tDCS administration, were, respectively: 50,1 nu/60 nu, 46,1 nu/21,7 nu and 1,087/2,771; and, after tDCS administration, respectively: 33,5 nu/52,7 nu, 47,6 nu/22,8 nu and 0,704/2,312.

tDCS over the left DLPFC (left ACC) increased parasympathetic activity and decreased sympatethic activity, sugesting the importance of tDCS in the management of stress-related disorders.