Signaling the unconditioned stimulus and backward conditioned inhibition: prior conditioning of the signal and context

We used summation tests in conditioneed suppression with rats to evaluate the effects of two preconditioning manipulations on the acquisition of associative strength by a backward conditioned inhibitory stimulus (CS-) that followed an unconditioned stimuls (US). Two backward CS-s were establisheed within subjects; onee backward CS- followed a US that was always signaled by a conditioned excitatory stimulus (CS+), a second backward CS- followed a US that was never signaleed. In Experiment 1, prior conditioning of the forward CS+ before backward conditioning enhanced inhibitory conditioning to the backward CS- that followed the signaled US. An opposite effect was observed on the unsignaled trials; backward inhibitory conditioning was impaired by preconditioning of the forward CS+. In Experiment 2, prior conditioning of the context, which involved embedding many USs within the context before backward conditioning, facilitated later inhibitory conditioning with both signaled and unsignaled USs. This geneeral facilitative effect was specific, in Experiment 3, to the preconditioned context and was not evident in a nonpreconditioned context. We conclude that backward inhibitory conditioning with a signaled US is multiply determined by contextual and forward CS+ based inhibitory processing. These data are consistent with the preconditions of Wagner's standard operating procedure (SOP) model, as well as a modified veersion of Miller and Schachtman's comparator hypothesis of response generation.