Natural Experiences and Addiction Vulnerability Behavioral disorders are often pathological extensions of normal behavioral processes. Just as depression may be an inappropriate expression of feelings of sadness, drug addiction can be thought of as a pathology of motivation. The goal of this laboratory's research is to use female sexual behavior in rodents as a model system to further our understanding of neural mechanisms of motivations, and by extension compare these mechanisms to those mediating abnormal behaviors, such as addiction. One approach that we take is based on the observation that repeated drug use produces changes in the structure and cellular properties of dopaminergic neurons. We have found that similar neural plasticity in dopamine pathways is seen following repeated sexual experience in female hamsters. By comparing neural changes to drugs versus engaging in natural behaviors, we can separate the neural properties of drug addiction that result from exposure to potent, artificial pharmacological agents from the endogenous neural plasticity that underlies activities in everyday life.