The purpose of this research study is to measure how many of the dopamine receptors lurasidone occupies throughout the brain of patients with schizophrenia or schizoaffective disorder and over what time period the occupancy occurs. This is research because lurasidone is an investigational medication that has not yet been approved by the Food and Drug Administration (FDA). Dopamine receptors have key roles in many processes, including the control of motivation, learning, and fine motor movement. The degree of occupancy and the transience of occupancy D2 receptor occupancy for optimal clinical response and to prevent relapses is a controversial area that this study will address.

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.

Inclusion Criteria:

Subjects are eligible to participate in this study if they:

• are 18 to 60 years of age at the day of first dosing.
• are diagnosed with schizophrenia or schizoaffective disorder.
• are female, subject must be using an acceptable method of birth control or be surgically sterile or postmenopausal. Postmenopausal is defined as no period for at least 12 months. Acceptable methods of birth control include oral, injectable or implanted contraceptives, and barrier methods such as condoms, diaphrams, and spermicides.
• are able to provide written informed consent.
• can safety have an MRI (no metal in the body, not claustrophobic).

Exclusion Criteria:

Subjects are not eligible to participate in this study if they:

• are treatment resisitant or intolerant to lurasidone.
• have had extensive radiation exposure (the study doctor will discuss this with the subject).
• if they have tremors or shaking of the limbs.
• are pregnant or trying to become pregnant or breastfeeding.
• are colorblind.
• have a current or past history of a major medical illness or have abnormal lab values which the study doctor feels is significant (any abnormal lab values will be discussed with the subject).
• are taking certain medications. The study doctor will discuss these medicines with the subject.
• have a history of alcohol, cannabis or cocaine abuse within two weeks prior to the study.