Associative and reinforcing properties of a stimulus element after compound conditioning

Abstract

In two experiments, the nature of an elemental conditioned stimulus (CS) previously trained as part of a compound CS was assessed using unconditioned stimulus (US) devaluation and conditioned reinforcement of a new instrumental response. In Experiment 1, mice underwent appetitive conditioning training with an audiovisual compound CS, followed by devaluation of the sucrose solution US. The US devaluation reduced conditioned magazine entry elicited by the original compound, but not by the element, suggesting that the element does not activate the internal representation of the sensory aspect of the US. Incidentally, the devaluation-insensitive magazine response was preferentially supported by the auditory element. Experiment 2 further evaluated the reinforcing property of the elemental cue by introducing an instrumental contingency between a lever press and presentation of a CS. The results showed that both the original compound and its element functioned as a conditioned reinforcer. Notably, the visual, but not auditory, element supported the new instrumental behaviour, collectively indicating an asymmetry in the roles of visual and auditory elements in conditioned response (CR)-eliciting and reinforcing properties after compound conditioning. Overall, an elemental CS may elicit generalised CRs and reinforce new instrumental behaviour without necessarily activating detailed sensory representations of the US.