Fig. 1.

Schematic illustration of Experimental Design. Independent groups of rats were used for each experiment. Each numbered box indicates a session of Pavlovian conditioning. Yellow boxes illustrate sessions that experimental compounds were administered prior to session start. Grey boxes illustrate sessions where all subjects were administered vehicle. a) Following 7 sessions of Pavlovian conditioning rats were classified as sign- or goal-trackers. For Experiment 1 all animals underwent treatment according to a within subjects design. Following session 19 rats were split into balanced groups based on their performance in the initial 7 sessions of PCA training and proceeded to undergo a test of conditioned reinforcement. For Experiments 2 and 3 rats were split into balanced treatment and vehicle groups based on their average PCA Index score from sessions 6 and 7 prior to testing with pramipexole and raclopride. b) Following 5 sessions of Pavlovian conditioning rats were classified as sign- or goal-trackers and were split into balanced treatment groups based on their average PCA Index score from sessions 4 and 5. All rats then received vehicle prior to session 6, and then their respective treatment prior to session 7