Efficacy of Transcranial Direct Current Stimulation (tDCS) To Decrease Disgust and Moral Rigidity. Implications For the Treatment of Obsessive-Compulsive Disorder (OCD).

EFFICACY OF TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) TO DECREASE DISGUST AND MORAL RIGIDITY. IMPLICATIONS FOR THE TREATMENT OF OBSESSIVE-COMPULSIVE DISORDER (OCD). Introduction: Several studies indicate that the deontological guilt is related to disgust, and it has been suggested to play a pivotal role in the genesis of obsessive-compulsive (OC) symptoms. At a brain level, deontological guilt has been demonstrated to selectively activate the insula, a region responsible for disgust-processing and consistently hyperactivated in persons with OCD. The present study aimed to test the hypothesis that indirect inhibition of the insula via cathodal transcranial direct current stimulation (tDCS) would decrease disgust and moral rigidity. Methods: By a randomized, sham-controlled, within-subject design, thirty-six healthy individuals underwent 15-min anodal, cathodal, and sham tDCS over the temporal lobe (T3). Trait levels of anxiety, depression, disgust sensitivity, OC tendencies, scrupulosity, and altruistic conduct, as well as pre- and post-stimulation momentary emotional states were assessed. Measures of parasympathetic nervous system activity (Heart Rate Variability, HRV) was derived during the entire experimental protocol. After the first 10 min of stimulation, participants were asked to complete a computerized moral task and a word-stem completion task with either disgust-related words or neutral alternatives. Results: Compared to sham condition, anodal and cathodal stimulation of T3 respectively enhanced and decreased self-reported disgust, severity of moral judgements in the deontological domain, and HRV. Significant and positive associations emerged in the anodal condition between self-reported deontological guilt and the Fear-of-Sin (FoS) subscale of the Pennsylvania Inventory of Scrupulosity, and between self-reported deontological guilt and the washing and obsessing subscales of the ObsessiveCompulsive Inventory-Revised (OCI-R); in the cathodal condition, disgust was inversely correlated with the washing, obsessing (OCI-R), and FoS subscales. Discussion: Results suggest a decrease in self-reported and physiological disgust following cathodal tDCS on T3, with stronger effects in individuals with higher levels of OC traits, with potential implications for the treatment of OCD.