Semantic Relevance of a Conditioned Stimulus Does Not Enhance Fear Extinction Beyond Temporal Proximity to the...

Posttraumatic stress disorder (PTSD) memory processes are often investigated using fear conditioning experiments. Based on the premises of Ehlers and Clark's cognitive model of PTSD, we previously found that an additional stimulus (the CSX) that was presented simultaneously with aversive stimulation became a stronger cue for conditioned fear compared to a standardly presented predictive conditioned stimulus (CS+). In the current study, we tested whether an additional CSX with higher semantic similarity to the aversive stimulus resulted in a stronger cue than the semantically dissimilar CSX (the semantically similar CSX was called CSR). Three groups of participants completed a standard fear conditioning experiment, where the presentation of two CSs (CSX and CSR) occurred simultaneously with a mild electric shock. The effect on return of fear of extinction using the CSX (CSX group), CSR (CSR group), or CS+ (CS+ group) was tested. We found that the CSX and CSR groups had significantly reduced physiological return of fear compared to the CS+ group. Additionally, preliminary Bayesian evidence of no difference between CSR and CSX in reducing return of fear was found, though the study was underpowered to formally test CSR-CSX equivalence. These findings provide provisional evidence that presenting cues during exposure therapy that had temporal proximity to traumatic experiences is the most critical factor for reducing fear, which provides empirical support for the Ehlers and Clark cognitive model.