Dopamine's Role in Learning Pavlovian Cues Associated with Different Reward Sizes
Our ability to navigate in the world around us involves learning to make associations between different cues and the expected outcomes. Research suggests that midbrain dopamine neurons of the ventral tegmental area (VTA) and substantia nigra are involved in Pavlovian learning. Studies have examined dopamine's role during early learning with a single cue-reward relationship. People have studied dopamine's role in tasks involving cues denoting different reward values in well-trained animals. However, it is unknown how these value related dopamine signals emerge during early learning. My project examines how value coding in the dopamine system arises during early learning of cues paired with rewards of different magnitudes. Pavlovian conditioning provides a useful behavioral task to approach this question. To address this, I performed voltammetry recordings of dopamine signals while rats were trained on a Pavlovian paradigm. During training, an auditory cue was paired with a single pellet reward and a different auditory cue was paired with a three-pellet reward. I focused on dopamine release in the ventral medial striatum (VMS) and the ventral lateral striatum (VLS), two brain regions that are involved in learning. I also explored potential sex differences in reward related behavior and dopamine activity in the VMS and VLS during Pavlovian training.