Schizophrenia is often associated with abnormalities in neurotransmitters. Huge amount of dopamine in the limbic system may be responsible for symptoms such as hallucination, while a low amount in the prefrontal cortex is associated with negative schizophrenic symptoms. Theories such as the Dopamine Hypothesis has also been proposed regarding schizophrenia and dopamine. The relationship between dopamine and serotonin is also being studied and explored.