Schizophrenia and related psychoses are chronic brain disorders whose prognosis is often poor and whose pathophysiology remains obscure. Brain imaging technologies such s positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and magnetic resonance imaging (MRI) offer opportunities to study the pathophysiology of psychotic disorders by evaluating brain function. However, the use of anti-psychotic drugs may interfere with the results of such studies. In this study, psychotropic medication will be discontinued in patients for a short period of time to distinguish the effects of the illness on the brain without the interference of the medication's effects on the brain. Given that there is a risk that the patient's symptoms will increase, they are asked to stay on an inpatient unit where the NIMH clinical staff is available to help them 24 hours a day.