Compound stimulus extinction reduces spontaneous recovery in humans

Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design (deepened extinction) shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and non-extinguished CSB. Recovery of conditioned skin conductance responses to CSA was reduced 24 h after compound extinction, as compared with a group who received an equal number of extinction trials to the CSA alone.