In this study Positron Emission Tomography (PET) scanning will be performed with D2/D3 ligand 18F-fallypride (a radioactive, injectable substance) to help the researchers measure the use of these receptors. Researchers hope that quantifying the amount of receptors being occupied by the medication will help them to determine the best dose of study medication in terms of improvement and least side effects related to body size and gender as well as in preventing relapse that may be related to hypersensitivity. Magnetic Resonance Imaging (fMRI) will also be performed. MRI is a scanning method which makes pictures of parts of the brain using a large magnetic field. This study will use a particular kind of MRI called fMRI, or functional MRI. fMRI takes pictures of the brain while the person is thinking or doing a simple task. fMRI will allow the researchers to investigate patients regional brain activation during cognitive (mental) and emotional tasks.