Schizophrenia / Magnetic Resonance Imaging / Positron Emission Tomography / Prefrontal Cortex / Dopamine / Humans / Female / Male / Amphetamine / Young Adult / Adult / Functional Neuroimaging / Short Term Memory / Case Control Studies / Humans / Female / Male / Amphetamine / Young Adult / Adult / Functional Neuroimaging / Short Term Memory / Case Control Studies