Effects of Frontal Transcranial Direct Current Stimulation on Emotional State and Processing in Healthy Humans

Abstract

The prefrontal cortex is involved in mood and emotional processing. In patients suffering from depression, the left dorsolateral prefrontal cortex (DLPFC) is hypoactive, while activity of the right DLPFC is enhanced. Counterbalancing these pathological excitability alterations by repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) improves mood in these patients. In healthy subjects, however, rTMS of the same areas has no major effect, and the effects of tDCS are mixed. We aimed to evaluate the effects of prefrontal tDCS on emotion and emotion-related cognitive processing in healthy humans. In a first study, we administered excitability-enhancing anodal, excitability-diminishing cathodal, and placebo tDCS to the left DLPFC, combined with antagonistic stimulation of the right frontopolar cortex, and tested acute emotional changes by an adjective checklist. Subjective emotions were not influenced by tDCS. Emotional face identification, however, which was explored in a second experiment, was subtly improved by a tDCS-driven excitability modulation of the prefrontal cortex, markedly by anodal tDCS of the left DLPFC for positive emotional content. We conclude that tDCS of the prefrontal cortex improves emotion processing in healthy subjects, but does not influence subjective emotional state.

Exploring prefrontal cortex functions in healthy humans by transcranial electrical stimulation

“…tDCS of the left DLPFC and the right frontopolar cortex improves identification of faces displaying nonneutral mimics independent of stimulation polarity, as compared to sham stimulation (Fig. 2) [70] . Moreover, emotionally aversive faces are rated less unpleasant with anodal stimulation of the left DLPFC [72] .…”

Effects of tDCS over the right DLPFC on attentional disengagement from positive and negative faces: An eye-tracking study

“…Disgust instead of angry faces were used because current research points to a greater threat perception for disgust faces (e.g., Amir et al, 2005). Moreover, a previous study testing effects of tDCS over left DLPFC have demonstrated improvements in the attentional detection of both happy and disgust faces (Nitsche et al, 2012). Therefore, this set was considered ideal to test whether tDCS over right DLPFC leads to valence-specific or general attentional disengagement impairments.…”

“…However, recent studies on lateralized effects of neurostimulation over the left DLPFC have shown general effects in implementing attentional control for all emotional information rather than specific effects for negative information. Nitsche et al (2012) found that anodal tDCS compared to sham stimulation over left DLPFC had temporal effects in improving attentional detection of both disgusted and happy faces. These findings speak against the traditional view on valence lateralization.…”

Acute and repetitive fronto-cerebellar tDCS stimulation improves mood in non-depressed participants

“…Nitsche et al 2012;Peña-Gómez et al 2011;Plazier et al 2012;Vanderhasselt et al 2013), although Fregni et al (2008) completed the final evaluation approximately 10 min after stimulation cessation, while Tadini et al (2011) Batsikadze et al 2013). It is possible that the convention timing of re-assessment following tDCS does not allow for a sufficient period to detect tDCS-induced modulations of mood.…”