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Study on Pavlovian Fear Conditioning and Fear Reversal in OCD Patients

Study on Pavlovian Fear Conditioning and Fear Reversal in OCD Patients


Pavlovian fear conditioning mechanisms are often used to explain different situations in psychopathology. They are specifically used to explain the etiology and maintenance of fear symptoms which makes them important factors in cognitive behavioral therapy (CBT). Patients are taught that fear is often learned or acquired. The therapy’s goal is to modify the acquired fear response through reversal or extinction. This is a no-brainer in disorders with easily identifiable events of fear acquisition such as PTSD. However, it can also be applied to obsessive-compulsive disorder (OCD) even if the event that caused the disorder cannot be identified in most cases. 

Pavlovian Learning Studies and Anxiety 

Pavlovian learning processes are one of the best ways to produce reliable results that can be used in research for better treatment because learning mechanisms always represent a behavioral approach to psychopathology. When it comes to anxiety disorders, Pavlovian learning studies show heightened fear response to safe stimuli during fear acquisition and exaggerated response to previously threatening but now safe stimuli during extinction in patients. Only a very small number actually studies Pavlovian fear in OCD patients. 

The Study 

Pavlovian learning mechanisms are key subjects in the field of psychiatric disorders and treatment approaches. However, there isn’t enough research about them in patients with cases of obsessive-compulsive disorder (OCD). The study uses a Pavlovian fear conditioning and reversal procedure to evaluate 41 patients with OCD and 32 matched healthy control participants. The study also aimed to investigate fear reversal learning in patients with OCD in the absence of artifacts and possible claustrophobic tendencies that can be induced by simultaneous functional magnetic resonance imaging recordings present in previous studies (Apergis-Schoute et al., 2017; Milad et al., 2013). 

The addition of color to facial stimuli, which likely facilitates stimulus discrimination, was omitted. Three questions were addressed: First, the researchers hypothesized that previously reported fear reversal effects (Schiller et al., 2008) are replicable. Second, we tested the hypothesis that patients with OCD display reduced differential fear learning of threatening versus safe stimuli. We expected such reductions to be most pronounced during late acquisition and reversal phases, as indicated previously (Apergis-Schoute et al., 2017). Finally, we assessed the effect of antidepressant medication by comparing fear acquisition and reversal responses between medicated and unmedicated patients.


The researchers used the experimental setting of the previous fear reversal study by Schiller et al. (2008). The unconditioned stimulus was a mild electrical stimulation. The amperage of shock level was chosen before the stimulation. It was described as “unpleasant but not painful”. A shock was delivered to the patient’s dominant wrist then two mildly angry faces were used as conditioned stimuli were shown for four seconds for each trial with an intertrial interval of twelve seconds.  

The experiment had two stages. The first was the acquisition stage and included 30 trials. The first face (Face A) was presented in 18 trials and was paired with shock in one-third of the trials. The second face (Face B) was presented in 12 trials but never paired with shock. During the reversal stage, 40 trials were reversed without announcement. Face B was presented in 24 trials and is now paired with the shock in one-third of the trials. While Face A had 16 trials but was no longer shocked.

Psychological assessment

Before the experiment, a clinical psychologist conducted the German version of the Yale-Brown Obsessive-Compulsive Scale interview and the Montgomery Åsberg Depression Rating Scale with all OCD patients. After the final experimental procedure, all participants completed several psychological tests and questionnaires. They included the Wortschatztest in order to estimate verbal intelligence, and a socio-economic status scale, the Obsessive-Compulsive Inventory-Revised (OCI-R; Foa et al., 2002) and the State-Trait Anxiety Inventory (STAI-X; Spielberger et al., 1970) were used in order to assess symptom severity of depressive, OCD, and anxiety symptoms, respectively.


A total of 82 subjects participated in the study. Data from two of the subjects were removed due to technical problems. After careful examination, seven more participants did not show an SCR to shocked trials. These subjects were classified as non-responders and weren’t considered in the analysis. The final sample consisted of 41 patients with OCD and 32 matched healthy controls. All of the patients were registered on the waiting list for cognitive behavioral therapy for psychotherapy at Humboldt-Universität zu Berlin.


Both groups show reversal effects and fear acquisition. When compared, patients showed impaired differential learning of threatening and safe stimuli, all similar to previous research. When compared to early research, differential learning impairments were restricted to fear acquisition. They also weren’t present in the reversal stage. Data from previous and present fear reversal experiments in OCD showed differentiation in the use of color-coding to facilitate stimulus discrimination. The current study suggests that differential learning of threatening versus safe stimuli is impaired in OCD but manifests itself depending on the level of difficulty of the association to be learned. 

When supported by the addition of color, OCD patients acquire early association but fail to reverse it according to changed contingencies. When color-coding of stimuli is not present, data shows that OCD patients show differential learning impairments during fear acquisition. Therefore the researchers conclude that impaired differential learning of threatening versus safe stimuli should be further studied in OCD. This will help determine whether impairments in differential learning predict treatment outcomes in OCD patients. It will also help researchers understand whether they are etiologically relevant for OCD. Despite group differences, we can safely say that the results are consistent with existing literature about reversal and fear acquisition.  

In conclusion, the findings all reveal a Pavlovian learning deficit in OCD. This is presented in the characterization by impairments differentiating safe and threatening stimuli during fear acquisition. The results also confirm the core finding of impaired differential learning from a previous fear reversal study in patients with OCD  (Apergis-Schoute et al., 2017). Recommendations for future studies include the inclusion of the observed deficits in predicting CBT treatment response. 


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