Noninvasive ventromedial prefrontal cortex stimulation can enhance and impair affective learning from rewarding and threatening stimuli

The ventromedial prefrontal cortex (vmPFC) is known as a central hub involved in affective learning from appetitive/aversive stimuli, as demonstrated in numerous studies examining affective stimuli. We used vmPFC-stimulation to test whether the concept of enhanced affective learning applies to enhanced inhibition of risky decisions and overgeneralized fear. Therefore, we modulated vmPFC-excitability noninvasively via transcranial direct current stimulation (tDCS) using excitatory, inhibitory, and sham stimulation. We re-analysed previously published behavioural and magnetoencephalography data trial-wise to test whether improved learning is the mechanism underlying modulated gambling/fear generalization. Following excitatory vs. sham stimulation, participants gambled more rationally and got better at discriminating safe from threatening stimuli, as indicated by interactions between tDCS and gambling/fear stimuli. Three-way interactions with trial-number suggest that these improvements developed during the experiment. In contrast, in the inhibitory group, these abilities deteriorated over the paradigm. The neural data dovetailed with behavioural effects, in that neural correlates of modulated learning after stimulation also developed over time. Our results indicate an association between vmPFC activity and the ability to learn from appetitive/aversive stimuli. As impaired affective learning is a driving mechanism in mental disorders, these findings identify excitatory vmPFC-tDCS as a potential treatment, especially in combination with psychotherapy.