Neural Explanation of Schizophrenia (Biological explanations for Schizophrenia)

Define what is meant by a Neural Correlate

Measurements of the structure or function of the brain that correlate with the symptoms of schizophrenia

Define what is meant by a Hyperdopaminergia

Overactivity of dopamine in the subcortex (central areas of the brain) is linked to symptoms of schizophrenia

Give an example of hyperdopaminergia in the brain and the symptoms it is linked to

High levels of dopamine activity in Broca’s area are linked to auditory hallucinations/hearing voices

Define what is meant by a Hypodopaminergia

Underactivity of dopamine in the cortex is linked to symptoms of schizophrenia

Give an example of hypodopaminergia in the brain and the symptoms it is linked to

Low levels of dopamine activity in prefrontal cortex are linked to avolition (Lack of motivation/failure to engage in goal directed activity)

How does the success of antipsychotic medication support the dopamine hypothesis? (hyperdopaminergia)

• Drugs that reduce dopamine activity reduce positive symptoms of schizophrenia

• This shows that decrease in dopamine is involved in decreasing schizophrenia symptoms

How does the effects of amphetamines support the dopamine hypothesis?

• Recreational drugs that increase dopamine activity can cause hallucinations and delusions

• This shows that increase in dopamine is involved in positive symptoms

How does post mortem evidence support the dopamine hypothesis?

• Brains of schizophrenia patients often show an increased number of D2 receptors in some brain regions

• This shows that an increase in D2 receptors is involved in schizophrenia symptoms

Which other neurotransmitters are involved in Schizophrenia?

• Serotonin

• Glutamate (regulates dopamine → dopamine alone doesn’t determine schizophrenia)

Why is causation an issue for the dopamine hypothesis?

• Correlation does not equal causation

• Could be a 3rd factor variable

What is the problem with post-mortem evidence?

Don’t know if issues found are the cause or effect of schizophrenia

What evidence supports the enlarged ventricle explanation for schizophrenia and what symptoms does it correlate with?

Johnstone et al (1976)

• Procedure: Compared sizes of ventricles in the brain of people with schizophrenia and those without

• Findings: People with schizophrenia had enlarged ventricle suggesting schizophrenia is linked to reduction in temporal and frontal lobe

• Enlarged ventricles linked to negative symptoms of schizophrenia

• This suggests enlarged ventricles are associated with schizophrenia

Why can’t we say neural changes in the brain are the underlying cause of schizophrenia?

Aetiology fallacy → Cannot assume we have found the cause of schizophrenia is “overactivity of dopamine” because drug is effective

What correlation was found between dopamine activities and increase in negative symptoms. Where was the dopamine activity?

• Negative correlation → As dopamine activity lowered, negative symptoms increased

• Ventral striatum