Acquisition of US—no US associations in Pavlovian conditioning

Abstract

Typically, in Pavlovian conditioning, subjects receive conditioned stimulus (CS)—unconditioned stimulus (US) pairings separated by an intertrial interval (ITI). The present experiments investigated if subjects, in addition to learning the focal CS—US association, learn that a US signals a short time period in which no further USs will be delivered (so-called US—no US learning). In Experiment 1, rats received light (CS)—food (US) pairings at a constant ITI. In addition to showing light conditioning, subjects showed a loss in the number of magazine entries in the ITI immediately after US delivery. Further, there was no evidence of any excilatory temporal conditioning as the time of the next CS—US pairing approached. Experiment 2 replicated Experiment 1 and found that when all USs were unsignaled, subjects acquired a US—no US association and evidence excitatory temporal conditioning as the time of the next US approached. Experiment 2 also showed that after subjects had acquired a US—no US association, conditioning to another CS was especially rapid when subjects received a US—CS—US conditioning arrangement. The results complement and extend the accumulating evidence that in Pavlovian conditioning multiple associative relations are learned in addition to the focal CS—US association.