Schizophrenia is a disease caused by fundamental organizational differences in the brain. It is first noticeable in a person's late teens through twenties, in males earlier than females. It is the alteration of pathways and deviation of neurotransmitters from the norm that is believed to be the main influence behind the disorder. In afflicted persons, neurotransmitters "misfire", altering the chemical balance of the brain, resulting in behavioral problems that we see as symptoms. There are deficits in cortical and subcortical cognitive processes as well as enlarged ventricles in the brain causing further impairment of ability. Specifically, a common finding in the brains of people with schizophrenia is larger than normal lateral ventricles. The lateral ventricles are part of the ventricular system that contains cerebrospinal fluid.
Afflicted people do not know that they have the disorder, and therefore resist taking medication for it. It is by this action that scientists draw the conclusion that homeostasis is sufficiently affected as certain signals are not being transmitted to the brain, preventing logical responses.
Abnormalities in the brains of affected persons have been proven by studies that found less gray matter in the temporal and frontal lobes of sufferers, the area that contains the somas and dendrites of the neurons. By reducing gray matter, there is a decrease in the possible action by the nervous system.
Schizophrenia further impairs behavior by preventing the brain from developing particular schemata. Schemata are patterns within the brain that control different functions through homeostasis. Social and cognitive areas also particularly suffer loss by schizophrenia, thus afflicted people often respond innapropriately to social situations. There is an increase in the number of stimuli, creating a delayed reaction time. Afflicted persons also have a reduced hippocampus as well as increased size of the basal ganglia and other abnormalities in the prefrontal cortex, causing them to perform poorly in verbal and visual memory exams, among other things. Schizophrenics also experience behavioral memory problems, the idea that prior habits or attitudes do not influence them.
1.Central Nervous System
a. neurotransmitters
b. pathways
c. cortical and subcortical cognitive processes
d. ventricles
e. gray matter- temporal and frontal lobes
f. somas
g. dendrites
h. schemata
i. stimuli
j. hippocampus
k. basal ganglia
l. prefrontal cortex
Evidence to Support the Dopamine Theory of Schizophrenia:
1. Drugs that block dopamine reduce schizophrenic symptoms
2. Drugs that block dopamine have side effects similar to Parkinson's disease (disease caused by lack of dopamine in parts of the brain called the basal ganglia)
3. The best drugs to treat schizophrenia resemble dopamine and completely block dopamine receptors.
4. High doses of amphetamines cause schizophrenic-like symptoms in a disorder called "amphetamine psychosis". Amphetamine psychosis is a model for schizophrenia because drugs that block amphetamine psychosis also reduce schizophrenic symptoms. Amphetamines also make the symptoms of schizophrenia worse.
5. Children at risk for schizophrenia may have brain wave patterns similar to adults with schizophrenia. These abnormal brain wave patterns can be reduced by drugs that block dopamine receptors.
Evidence Against the Dopamine Theory of Schizophrenia:
1. Amphetamines do more than increase dopamine levels. They also alter other neurotransmitter levels.
2. Drugs that block dopamine receptors act on receptors quickly. However, these drugs sometimes take many days to change the behavior of people with schizophrenia.
3. The effects of dopamine blockers may be indirect. These drugs may influence other systems that have more impact on the schizophrenic symptoms.
4. New drugs for schizophrenia, for example, clozapine, block receptors for both serotonin and dopamine.