The PET studies will be performed at the PET Center at the North Shore University Hospital. On the day of the PET scan an intravenous line will be placed in an antecubital vein for radiotracer administration, and to draw a plasma drug level at the time of scanning. The subject will be positioned in the General Electric (GE) Advance scanner. A fifteen-minute transmission scan will be obtained. Then, 15 millicuries (mCi) of [11C]-raclopride will be injected. Scanning will begin immediately after radiotracer injection and will last for 60 minutes.