Can vocal emotion processing be modulated by tDCS?

Inferring and recognising emotions is fundamental for adaptive social functioning. Transcranial direct current stimulation (tDCS) has shown promise in modulating emotional processing, particularly in the visual domain. However, its effects on auditory emotional processing remain underexplored. We aimed to address this gap by investigating tDCS effects over the medial prefrontal cortex (mPFC) and the right superior temporal sulcus (STS), key regions for emotional and social cognition, during emotion discrimination of vocalisations. Participants were divided into two groups (mPFC: n=24; STS: n=25) and underwent sham, anodal, and cathodal stimulation. A 1.5mA current was applied for 5 minutes before and during a task in which participants rated the emotional intensity (on a sad-happy continuum), authenticity, and contagion of spontaneous and volitional cries and laughs. Results for both groups consistently showed that laughs were rated as happier, more authentic, and more contagious than cries, and that spontaneous expressions were perceived as more authentic, positive, and contagious than volitional ones. Stimulation over the mPFC did not modulate these perceptions. In turn, cathodal stimulation over the STS led to an overall sadder perception of all vocalisations compared to sham. These findings highlight the robust capability of humans to recognise emotional vocal expressions and their authenticity, corroborating previous research. The effect of cathodal STS stimulation suggests its potential as a target for modulating auditory emotional processing and underlines the relevance of further examining tDCS effects in vocal emotion perception using alternative protocols, especially in clinical populations with disturbances in this domain.