Targeting the prefrontal-supplementary motor network with online and offline tDCS to modulate disgust: A single-blind and sham-controlled study

In certain individuals, disgust experience is abnormally high. This heightened sensitivity serves as a cognitive component that can lead to dysfunction in neural circuits related to emotion processing and psychological disorders such as contamination-based obsessive-compulsive disorder. In this single-blind study, 36 individuals with high disgust sensitivity were randomly assigned to three groups: online, offline, and sham. The online group received intensified and repetitive transcranial direct current stimulation (tDCS) while performing a disgust image watching task, whereas the offline and sham group received the tDC stimulation prior and after the same task, additionally the sham group received placebo tDC stimulation. Anodal and cathodal stimulation was applied to the left dorsolateral prefrontal cortex (l-DLPFC; F3) and pre-supplementary motor area (pre-SMA; FC2), respectively. The intervention consisted of 10 sessions of tDCS (2 sessions per day) over 5 days, with a stimulation intensity of 2 mA for 20 minutes and a 20-minute interval between sessions. The results showed a significant decrease in disgust experience in the online group compared to the offline group, while there was no significant difference between the online and sham groups. Although these findings suggest potential effects of tDCS combined with a task, further studies are necessary to confirm its efficacy.