Anodal transcranial direct-current stimulation over the left dorsolateral prefrontal cortex and perception of emotional faces

Abstract

The prefrontal cortices have been shown to be engaged in the perception of emotional faces, and imaging studies correlate activation of the left dorsolateral prefrontal cortex (l-DLPFC) with correct identification of emotional expressions. Transcranial direct current stimulation (tDCS)has been shown to modulate cortical function and might influence the perception of emotional faces. Our aim was to evaluate the possible effects of tDCS on a task that required correct identification of emotions represented by human faces presented on a screen. Ten volunteers (ages 18-30; mean = 23.2; SD = 4.3) were evaluated. The experiments were carried out in two 20 minutes stimulation sessions (real and sham tDCS) 4 days apart, at least, to avoid carryover effects, and session orders were randomized. The anode was placed over the l-DLPFC (F3 of the international 10-20 EEG electrode positioning system) and the cathode over the contralateral supraorbital region. Emotional stimuli were 120 consecutive human faces to be verbally classified as "happy", "surprised", "neutral", "angry" or "sad". Real anodal tDCS over the l-DLPFC resulted in significantly longer response times with a trend towards increased error rates, compared to the sham condition.