Overview of the experimental design.
(A). Participants were assigned to the counterconditioning (CC) or extinction (Ext) group. On day 1, participants performed two blocks of acquisition of category-conditioned threat responses separated by a 30 second break, followed by CC or extinction. Day 2 consisted of a spontaneous recovery test, a reinstatement procedure and test, an item memory test and a valence-specific response characterization. Valence and arousal ratings for the different categories were taken before or after the tasks as indicated by ‘V+A Rating’. All tasks were performed in an MRI scanner. (B) During acquisition, participants viewed trial-unique exemplars of objects and animals. Exemplars of one category (CS+ animals or objects counterbalanced) were paired with a shock in 50% of trials. CS- trials were not reinforced. (C) Participants in the CC group could earn a monetary reward if they responded quickly enough to exemplars in the CS+ category. (D) Participants in the Ext group underwent extinction. During the extinction task, recovery test and reinstatement test, neither CS+ nor CS- exemplars were paired with a shock. (E) In the valence-specific response characterization task, participants viewed three different coloured squares. One colour was associated with shock (CS+S), one colour with reward (CS+R) and one colour served as CS-. The trial structure was otherwise identical to the acquisition and CC tasks. (F) In all Pavlovian tasks, trial onset was marked by presentation of a unique category exemplar. After a variable interval, a ring appeared, to which participants were instructed to respond as quickly as possible. Upon response, the ring shifted in colour as response confirmation. In the acquisition task, shocks could occur 0.5-1.5-seconds after the response window had elapsed (indicated as ‘pre-shock). The category exemplar and cue remained visible 1 second after potential shock administration (indicated as ‘post-shock’). During CC, participants received visual feedback for 2 seconds (+€0.50 approximately the fastest 70% of trials, +€0.00 on other trials). During the other tasks, participants viewed neutral feedback (three dots). Trials were separated by an 8-10 s intertrial interval, during which a fixation cross is displayed in the centre of the screen.