 The study involves three study visits to San Diego and one study visit done locally. The first visit will last 13 days, the following visits are single day visits at week 4 and week 8, and the local study visit is a brief outpatient visit at week 6. Physical and neurological exams, videotaping of the patients interactions with the study staff, and blood and urine collection for laboratory analyses will be performed at each San Diego visit. A family member or caregiver will be asked to complete a short assessment form and report any illness or medication changes. In addition, the study staff will have weekly telephone contact with the family to discuss any behavioral changes or study drug issues. 