Schizophrenia. Positron emission tomography (PET) scan series of the brain of an hallucinating patient suffering from schizophrenia. The colour- coded scan through different cerebral layers shows brain activity: from low (blue) to high (yellow). PET scanning relies on an injected radioactive tracer to show metabolic activity in the brain. Normal brain metabolic activity produces a roughly symmetrical pattern in the yellow areas of left and right cerebral hemispheres. PET scanning shows abnormalities of function in the brains of schizo- phrenics. Schizophrenia (split personality") is characterised by delusions, hallucination and depression. Drug treatment offers relief."