It was proposed that psychotic symptoms in schizophrenia are related to dopaminergic hyperactivity in the brain. Investigators have found an increase of radioligang binding to dopamine receptors in basal ganglia tissue among deceased schizophrenics. “The brain is made up of nerve cells, called neurons, and chemicals, called neurotransmitters. Thus, according to the “dopamine theory,” there is an imbalance of the neurotransmitter dopamine, which is thought to cause the symptoms of schizophrenia. This neurotransmitter is the primary brain chemical that appears to be involved in this disorder, and most medications used to treat schizophrenia target this neurotransmitter and its receptors in the brain” (Sedvall & Farde, 1995). Dopamine is one of several brain chemicals that allow nerve cells to send messages to each other and schizophrenics may either be very sensitive to or they may produce too much of this chemical, which causes interference between chemicals. Researchers believe that because of this interruption between neurotransmitters, the brain of a schizophrenic may not be able to process information correctly. For example, “a person without schizophrenia usually filters out unneeded information. However, a person with schizophrenia cannot always filter out this extra information because of interruption between neurotransmitters” (Sedvall, 1999). Other neurotransmitters and their receptors also may be affected in people with schizophrenia. Serotonin for example may also play a role in causing the symptoms of schizophrenia. Cognitive impairments have always been associated with schizophrenia. There is a wide range of impairments, and perhaps not surprising when the wide range of symptoms and signs that can be observed in schizophrenic patients are taken into consideration . Since these impairments are essential features of the disorder, many researchers have tried to find explanations for the dysf...
