Acquisition and extinction in a substance dependent sample: A de novo fear conditioning study

Substance use disorders are characterized by excessive seeking and taking of drugs in the face of adverse consequences. Issues in the learning of contingencies around negative outcomes may influence such drug use patterns. Studies of drug addicted animals have consistently found deficits in extinction but not acquisition of a learned fear response; however, to my knowledge no studies to date have examined conditioning in drug addicted humans. In the current study, de novo fear conditioning was examined in a sample of opiate-dependent outpatients (SUD) relative to two control groups---a healthy control and a mixed-anxiety control---in an attempt to isolate the unique contribution of substance use on conditioning outcomes from the substantial comorbidity that is associated with drug addiction. Additionally, neuropsychological testing in the SUD group was completed to allow for the investigation of the role of neuropsychological functioning on conditioning outcomes. Results showed that individuals in the SUD group failed to condition successfully as compared to both the mixed anxiety and healthy control groups, suggesting a deficit in the ability to learn associations between cues in this group. Deficits in the acquisition of the learned fear response in the SUD group were significantly related to select deficits in attention and memory. There is growing evidence that attention and memory may play an important role in conditioning. This is informed by research suggesting that agents that enhance memory and attention may also enhance conditioning. Consistent with past studies, participants in the healthy control group showed successful conditioning and extinction and the mixed anxiety control group conditioned successfully but did not extinguish the learned response, providing evidence that the distinctive findings for the SUD sample are not simply a reflection of the affective comorbidity that defines this group, but rather are related to the presence of drug use/addiction and/or associated neuropsychological impairment. As such, it is possible that chronic substance use may make associative learning difficult, and may contribute to the persistence of maladaptive behavior (failure to change behavior in response to aversive outcomes) and impair response to treatments relying on exposure to drug-related cues.