Additional Study Information: We are trying to understand what causes bipolar disorder and how medications treat bipolar depression. If you participate, you will have two different brain scans (MRI and PET scan). You will also have antidepressant treatment for free. We will then be able to see whether information on the brain scans connects with how people do on the medications. The medications are common, and are not experimental. You will be able to discuss the treatment with Dr. Lan before starting the study to make sure that it is the proper treatment for you. The medications include valproate (Depakote) and either fluoxetine (Prozac) or citalopram (Celexa). The study is funded by the National Institute of Health (NIH) to improve the treatment of bipolar disorder. Please contact us if you are interested in participating.