Individuals with schizoaffective disorder have schizophrenia alongside a mood disorder. It has been suggested that these two similar disorders may have a similar root cause: a chemical imbalance in the brain. Dopamine is an inhibitory neurotransmitter that is involved in the diagnostics of schizophrenia. The dopamine hypothesis states that abnormalities of dopamine in the prefrontal and mesolimbic parts of the brain occur in schizophrenia. Dopamine is created in the ventral tegmental and substantia nigra sections of the brain. Positive symptoms of schizophrenia (such as delusions and hallucinations) are caused by an increased subcortical release of dopamine. Negative schizophrenia symptoms (anhedonia, speech impediments) result from reduced dopamine receptor activation in the prefrontal cortex, as well as decreased activity in the nucleus caudatus.