Figure 1.

Study design and experimental procedure. Schematic illustration of the experimental procedure (A) and conditions during the dot-probe task (B). (A) Participants initially accomplished a dot-probe task (baseline) during which three different visual cues were used as stimulus material. Participants were instructed to respond by button press to the dot appearing either on the left or right side of the fixation cross. During the subsequent fear-conditioning procedure, one visual cue (CS⁺) was repeatedly paired with a rectal distension (US) while a second visual cue (CS⁻) was presented without US. Only two out of three visual cues were presented during conditioning. Afterwards participants completed a second run of the dot-probe task (test phase) with the same visual stimuli presented during the baseline task. After each phase, visual analog scale (VAS) ratings of CS valence and CS-US contingency (only after fear conditioning) were accomplished. (B) In the dot-probe task, counterbalanced and randomized order of the three different visual cues yielded four conditions. The cues are color-coded for visual purposes only to illustrate the different CS valences acquired after conditioning. For the CS⁺ /CSⁿ and CS⁻ /CSⁿ conditions, trials were considered congruent if the dot-probe appeared at the location previously occupied by the CS⁺ (shown in red) or CS⁻ (shown in green) and incongruent, if the dot appeared at the location previously occupied by the neutral cue (shown in gray). When CS⁺ and CS⁻ where presented together, the dot-probe was considered CS⁺-congruent when it appeared at the location previously occupied by the CS⁺ and CS⁻-congruent when the dot appeared at the location previously occupied by the CS⁻. During the neutral condition, only neutral cues were presented.