This is our animal model for addiction. Rats are placed inside operant chambers and given access to drug (e.g. cocaine). They are allowed to regulate their own intake, or self-administer, the drug for several weeks. After they are "hooked" on the drug, access to the drug is taken away, and the rats learn to stop searching for it. This learning process is called extinction and leads to the formation of an extinction memory trace that can be targeted to reduce relapse.
This is our animal model for learned fear disorders (e.g. posttraumatic stress disorder, or PTSD). Rats are placed inside chambers and given a series of mild, brief electric footshocks. Later, when returned to the feared chamber, rats freeze (click image at left). This fear can be "extinguished" by returning the rat to the chamber and not delivering any more shocks. Rats that fail to learn the chamber is now a safe place are thought to represent a PTSD-like phenotype. 
A future direction of the lab is to develop a model that combines both self-administration of drugs and conditioned fear in an effort to study comorbid PTSD and addiction.