Research Projects

Habitual and compulsive cocaine seeking

One of the most insidious aspects of drug addiction is that afflicted individuals are plagued by an uncontrollable drive to seek and use drugs, despite harmful consequences or the desire to quit. This type of drug-taking behavior is described as being compulsive, because of its persistent and uncontrollable nature. To study compulsive drug use, the lab uses a self-administration paradigm in which rats receive a negative consequence for taking cocaine. Previous work by other labs established this paradigm, observing that a subset of rats continues to self-administer cocaine despite aversive consequences. One key question that had yet to be fully answered was whether compulsive drug use is related to habitual behavior. A behavior is considered habitual if it is automatic and performed in response to conditioned stimuli. In contrast, a behavior is considered goal-directed if it is flexible and performed in direct pursuit of the desired outcome. The absence of an empirical link between habits and compulsive use is partially due to the lack of a simple method for determining whether an animal’s actions during cocaine self-administration are goal-directed or habitual. Our lab developed a novel method to distinguish between goal-directed and habitual behaviors in rats self-administering intravenous cocaine. We established that, just as with self-administration behavior for food rewards, goal-directed and habitual behaviors for cocaine rely on dissociable systems in the brain. With the development of this novel method to identify habitual behaviors, the lab is currently conducting a variety of experiments focused on investigating the role of habits in compulsive drug use. In particular, we are examining how dorsomedial and dorsolateral striatum are involved in compulsive drug seeking, due to their established involvement in goal-directed and habitual responding. We are also very interested in the roles played by cortical and thalamic afferents to dorsal striatum.

Research Tools

Animal behavior: cocaine and food self-administration, seeking-taking chained schedules of reinforcement, random ratio and random interval schedules, goal-directed vs. habitual responding, outcome devaluation, punishment resistance, reinstatement Brain/neural manipulations:  optogenetics, DREADDs, pharmacology, lesions Anatomical techniques: retrograde tracing, transsynaptic tracing with modified rabies virus, immunohistochemistry, c-Fos expression