Don’t fear ‘fear conditioning’: Methodological considerations for the design and analysis of studies on human fear acquisition, extinction, and return of fear
AIMS Classical fear conditioning and extinction has been used to understand the neurobiology of fear learning and its inhibition. The recall of an extinction memory involves the ventromedial prefrontal cortex and the amygdala, and patients with posttraumatic stress disorder (PTSD) have been shown to exhibit deficits in this process. Furthermore, extinction forms the basis of exposure therapies commonly used to treat PTSD patients. It is possible that effective pharmacological and/or psychological treatment regimens could influence the activity of these regions, and thereby increase the ability to retain an extinction memory. However, to test this, a fear conditioning and extinction paradigm must demonstrate within-subject reproducibility over time. We, therefore, sought to test the within-subject reliability of a previously used 2-day, classical fear conditioning and extinction paradigm. METHODS Eighteen healthy participants participated in a 2-day paradigm on three occasions, each separated by at least 12 weeks. Conditioning and extinction took place on Day 1, and extinction recall and fear renewal were evaluated on Day 2 on each of the three occasions. The conditioned stimulus was a visual cue and the unconditioned stimulus was a mild electric shock to the fingers. Skin conductance was recorded throughout the experiment to measure conditioned responses. RESULTS We found that conditioning and extinction recall were not significantly different across time and were correlated within subjects. CONCLUSION These data illustrate the reliability of this paradigm and its potential usefulness in evaluating the influence of a given treatment on the fear extinction network in longitudinal within-subject designs.