Various addictive compounds affect activity of the dopamine transmission in the nucleus accumbens (mesolimbic) and frontal cortical (mesocortical) systems. Additionally, these pathways appear to be functionally unbalanced in patients with schizophrenia. It appears that patients with schizophrenia have diminished dopamine effects through mesocortical systems to the prefrontal cortex. This could produce symptoms such as social withdrawal and diminished emotional responsiveness. Concurrently, there is a relative increase in dopamine effects via the mesolimbic system to the ventral striatal system, resulting in positive symptoms of delusions and hallucinations.