abstract Joke Baas

Joke Baas (University of Utrecht, The Netherlands)

Who’s afraid of the wolf? Factors that determine the acquisition, extinction and maintenance of fear in human fear conditioning studies

Fear conditioning is a translational laboratory model for the acquisition and extinction of learned fear responses. I will start with an overview of studies (N=150 and N=202) that look at genetic, performance and personality factors that explain individual differences in the acquisition and extinction of conditioned fear. Specifically, as predicted from preclinical studies, genetic variation in polymorphisms in the corticotrophin releasing hormone receptor (CRHR1)  and the serotonin transporter (5HTTLPR) are associated with fear responses during uninstructed acquisition. The CRHR1 effect was replicated in the replication sample. Also predicted from preclinical work, we found that a polymorphism in the cannabinoid receptor (CNR1) is associated with the extinction of conditioned responses. In the replication sample this polymorphism did not show the same main effect, but only affected extinction in those individuals who failed to spontaneously acquire cue conditioned responses during the uninstructed acquisition phase. These results indicate that effects of this genetic variant may only determine fear extinction in individuals who are vulnerable to poor learning of such associations in general. A relatively recent interest in my lab is the effects of behavior on the maintenance of fear responses. Lovibond et al. (2009) have shown that consistent avoidance blocks extinction of fear, but what effect does occasional avoidance have? We show that during extinction, occasional execution of a previously acquired avoidance response increases fear-potentiated startle. This implies return of fear even with infrequent avoidance behavior. Taken together, genetic and behavioral factors determine the extent to which individuals learn from conditioning and extinction experiences.