Sara Morrison, Ph.D.

Environmental stimuli, also called cues, that become linked with rewards – e.g., food or drugs – can exert powerful influence over behavior. For example, exposure to drug paraphernalia, or to people and places associated with prior drug use, can trigger craving and relapse in recovering addicts. In both animals and people, reward-associated cues can take on a value and become attractive in their own right, sometimes resulting in impulsive or risky actions. However, there is a great deal of individual variation in how strongly people and animals respond to reward cues, and we believe that uncovering the sources of this variation can help us to understand addiction. We have a particular interest in how adolescents respond to cues and rewards, as adolescence is a time of unique vulnerability to drug abuse and other forms of reward-motivated risky behavior.

In order to study these processes, we use several techniques to measure and manipulate neuronal activity in adolescent and adult rodents while they perform simple reward learning or reward-based decision-making tasks. Typical tasks include Pavlovian conditioning, instrumental conditioning to study habit formation, or the rodent gambling task (rGT) to study risk-taking. We use in vivo electrophysiological recording to examine the task-related activity of single neurons in the prefrontal cortex, limbic structures (such as the amygdala), and basal ganglia (especially the nucleus accumbens). Both reward-related behavior and decision-making are highly influenced by dopamine; therefore, we also use pharmacological methods, optogenetic, and chemogenetic techniques to study how dopamine release impacts both behavior and neural activity. Finally, we study how substances that influence feelings of hunger and satiation, including GLP-1R agonists (such as Ozempic), affect reward processing.