A PET study .
Drug addiction is a major public health problem worldwide.
Many pharmacological and animal studies indicated a role of the dopaminergic brain reward system in addiction. Subjects performed a spatial and object delayed response task and received a monetary reward for each correct response compared to a nonsense feedback in the baseline condition. We have found rCBF increases in right frontal cortex, right insula, right putamen, right and left cerebellum and left midbrain in the monetary reward condition in controls, whereas no rCBF increase has been found in drug addicts.