The effect of cathodal tDCS on fear extinction: A cross-measures study

BackgroundExtinction-based procedures are often used to inhibit maladaptive fear responses. However, because extinction procedures show efficacy limitations, transcranial direct current stimulation (tDCS) has been suggested as a promising add-on enhancer.ObjectiveIn this study, we tested how cathodal tDCS over the right dorsolateral prefrontal cortex affects extinction and tried to unveil the processes at play that boost the effectiveness of extinction procedures and its translational potential to the treatment of anxiety disorders.MethodsWe implemented a fear conditioning paradigm whereby 41 healthy women (mean age = 20.51 +/- 5.0) were assigned to either cathodal tDCS (n = 27) or sham tDCS (n = 16). Fear responses were measured with self-reports, autonomic responses, and implicit avoidance tendencies.ResultsCathodal tDCS shows no statistically significant effect in extinction, according to selfreports, and seems to even negatively affect fear conditioned skin conductance responses. However, one to three months after the tDCS session and extinction, we found a group difference in the action tendencies towards the neutral stimuli (F (1, 41) = 12.04, p =.001,.p2 =.227), with the cathodal tDCS group (as opposed to the sham group) showing a safety learning (a positive bias towards the CS-), with a moderate effect size. This suggests that cathodal tDCS may foster stimuli discrimination, leading to a decreased generalization effect.DiscussionCathodal tDCS may have enhanced long-term distinctiveness between threatening cues and perceptively similar neutral cues through a disambiguation process of the value of the neutral stimuli-a therapeutic target in anxiety disorders. Future studies should confirm these results and extend the study of cathodal tDCS effect on short term avoidance tendencies.
AGA is supported by the Foundation for Science and Technology, Portugal and Programa COMPETE [grants numbers SFRH/BD/80945/2011, PTDC/MHC-PAP/5618/2014 (POCI-01-0145FEDER-016836); http://www.poci-compete2020.pt/].JA is supported by the Foundation for Science and Technology, Portugal and Programa COMPETE [grants numbers PTDC/MHC-PAP/5618/2014 (POCI-01-0145-FEDER-016836), PTDC/MHC-PCN/3575/2012, PTDC/MHC-PCN/0522/2014, PTDC/MHC-PCN/6805/2014; https://www.fct.pt/index.phtml.en].The Cognitive and Behavioral Center for Research and Intervention of the Faculty of Psychology and Educational Sciences of the University of Coimbra is supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement [UID/PSI/01662/2013; https://www.portugal2020.pt].The Psychology Research Centre of the University of Minho is supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER007653). The Proaction Laboratory and the PTDC/MHC-PAP/5618/2014 (POCI-01-0145-FEDER016836) directly supported this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.