Dissociating the role of dACC and dlPFC for emotion appraisal and mood regulation using cathodal tDCS.

Several neuroimaging studies have shown that a distributed network of brain regions is involved in our ability to appraise the emotions we experience in daily life. In particular, scholars suggested that the dorsal anterior cingulate cortex (dACC) may play a role in the appraisal of emotional stimuli together with subcortical regions, especially when stimuli are negatively valenced, and the dorsolateral prefrontal cortex (dlPFC) may play a role in regulating emotions. However, proofs of the causal role of these regions are lacking. In the present study, we aim at testing this model by stimulating both the dACC and the left dlPFC via cathodal tDCS. Twenty-four participants were asked to attend and rate the arousal and valence of negative and neutral emotional stimuli (pictures and words) in three different experimental sessions: cathodal stimulation of dACC, left dlPFC, or sham. In addition to the experimental task, the baseline affective state was measured before and after the stimulation to further assess the effect of stimulation over the baseline affective state after the experimental session. Results showed that cathodal stimulation of dACC, but not the left dlPFC, was associated with reduced arousal ratings of emotional stimuli, both compared with the sham condition. Moreover, cathodal stimulation of left dlPFC decreased participant's positive affective state after the session. These findings suggest for the first time, a dissociation between the dACC and dlPFC, with the former more involved in emotion appraisal, and the latter more involved in mood modulation.

The emotional control of action: ERP evidence.

It is known that unpleasant emotions can modulate the speed of involuntary movements, yet the effects of aversive stimulation on voluntary motor acts have not been systematically investigated. The effects of aversive stimulation on subsequent movement-related cortical activity were examined using a task invalving compatible and incompatible movements. Negative shifts in the timing of two motor event-related potentials were found subsequent to aversive stimulation for compatible movements only. With analogy to the Fear-Potentiated Startle Reflex, a reactive mechanism affecting covert action, these Fear-Potentiated Movement-Related Potentials (FPMPs) reflect preparation for overt actions performed to cope with particular types of danger. Further analysis revealed a positive deflection in the left frontal cortex prior the execution of incompatible movements, which may reflect inhibitory suppression of externally-triggered imitative tendencies.