Extinction, reinstatement and spontaneous recovery of conditioned suppression in rats and the stability of conditioned inhibitor performance.

Acquisition of the suppressive properties of a conditioned stimulus (CS), terminating with shock, and of the attenuating properties of the conditioned inhibitor (CI), signaling that shock will not be given at the end of the CS, proceed at similar rates. The attenuation of suppression exerted by the CI and the decrement of the suppression due to extinction differed in both the time course and the distribution of barpresses within the CS duration. After extinction the CS still retained some suppressing properties, which were limited to the last 20-30 s, whereas the CI attenuated the suppression throughout the duration of the CS. Extinction of the suppressive properties of the CS did not change the attenuating properties of the CI. The recovery of the suppressive properties of the CS after presentations of unsignaled reinstating shocks or after a long pause in experimental sessions was incomplete and shortlasting. Both procedures did not change the properties of the CS presented in compound with the CI.