Anodal transcranial direct current stimulation over the ventromedial prefrontal cortex enhances fear extinction in healthy humans: A single blind sham-controlled study

Anxiety disorders are among the most common mental disorders [1,2]. Fear extinction is considered essential to promote successful treatment of several anxiety disorders. Neuroscience research has provided evidence for the contribution of the ventromedial prefrontal cortex (vmPFC) in extinction learning and recall [3,4]. Its role in fear extinction has been investigated via transcranial direct current stimulation (tDCS) in a recent sham-controlled study involving healthy participants. In that study [5], 5 minutes of 2 mA anodal stimulation over the left vmPFC during fear extinction reduced the physiological expression of fear (reduction of Skin conductance response - SCR) induced via Pavlovian conditioning. However, no effects were reported for the recall session. We extended this study by applying tDCS for 10 minutes over the vmPFC during fear extinction, and hypothesized that this intensified stimulation enhances tDCS efficacy. Thirty-two participants with an age mean of 24.15 years were recruited. They were randomly assigned to one of two sub-groups: anodal (n = 16, 5 males) or sham (n = 16, 5 males) stimulation. Overall, tDCS over the left vmPFC appears to reduce the sympathetic component of fear reactions in extinction in participants that acquired fear responses during fear acquisition. Therefore, tDCS had a facilitatory effect on consolidation of extinction, as compared to initial extinction learning. In conclusion, our results corroborate and also extend those provided by van ‘t Wout et al. [5], as we showed that prolonged tDCS, as compared to the former protocol, facilitates fear extinction consolidation.