Studying Nicotine Addiction With Transcranial Magnetic Stimulation

Background: \- Nicotine addiction often makes it difficult to stop smoking. Researchers want to understand the areas of the brain that are important in nicotine addiction. They will use a type of brain stimulation called repetitive transcranial magnetic stimulation (rTMS) to look at part of the brain that may be involved in nicotine addiction. They will see how these areas affect brain function, thinking, and decision making. For this study, rTMS will first be tested on nonsmokers, then smokers will be recruited at a later time. Objectives: \- To study areas of the brain involved in nicotine addiction. Eligibility: \- Individuals at least 18 years of age who do not smoke. Design: * Participants will be screened with a physical exam and medical history. They will also provide a urine sample. * There will be four study sessions. The first session will involve a magnetic resonance imaging (MRI) scan. The other three visits will involve rTMS and MRI scans. * The first MRI scan will take a baseline picture of the brain. Participants will also practice the tasks for the other three sessions in a mock scanner. * At the next three visits, participants will have rTMS and MRI scans. Two visits will involve rTMS; the other visit will involve mock rTMS with no actual magnetic stimulation. During the MRI scans, participants will perform tasks that involve decision making.