Normal control subjects will be recruited through the NIH normal volunteer program and through advertisement in the community and primarily through the "Genetic Study" under protocol 95-M-0150. An additional control group of non-schizophrenic siblings of patients with schizophrenia will also be recruited (from the community and protocol 95-M-0150, A Neurobiological Investigation of Patients with Schizophrenia Spectrum Disorders and Their Siblings). Control subjects will be matched to the patient groups by age, sex, and handedness. Control subjects with history of psychiatric or neurologic disorders or medical illnesses or surgeries that might have relevance to the investigation of brain physiology will be excluded. Normal subjects taking medications with relevance to cerebral blood flow and metabolism will be excluded from study.