A direct comparison of Positron Emission Tomography (PET) (11C-Raclopride) and Single Photon Emission Computed Tomography (SPECT) (123I-IBZM) D2 RO measurements would allow GSK to gain understanding on the SPECT results obtained with SB773812, and to accurately interpret future D2 RO results from either PET or SPECT studies with new compounds.

Inclusion criteria:

• Not pregnant or becoming pregnant during the study.
• No abnormality in clinical examination, clinical laboratory test or ECG.
• Not taking drugs
• Patients with schizophrenia, schizophreniform disorder or schizoaffective disorders.
• Patients with at least 1 month antipsychotic monotherapy with either risperidone, olanzapine or clozapine.
• Healthy volunteers with no neurological or psychiatric illness.

Exclusion criteria:

• Have received other antipsychotic during the last month or neuroleptics during the last year.
• If you have taken part in investigations you should not receive a radiation dose of more than 10 mSv over any 3 year period.
• History of bleeding disorder or are taking medication that affects blood clotting
• History of substance dependence (except nicotine)
• Claustrophobia
• Gross head deformity.
• Unable to lie still in the PET or SPECT camera for 1 hour and a half.
• The presence of a cardiac pacemaker or other electronic device or ferromagnetic metal foreign bodies.

This is a methodology study.