Neural Correlates

• What is the dopamine hypothesis?

  Excess levels of dopamine causes schizophrenia
• What happens if dopamine fires too easily (neuron firing)?

  It sends too many messaged leading to positive symptoms
• Who proposed the original dopamine hypothesis?

  Synder (1976)
• Who proposed an updated version of the dopamine hypothesis?

  Davis (1991)
• What is the updated dopamine hypothesis?

  Positive symptoms are cased by an excess of dopamine in subcortical areas of the brain (mesolimbic pathway). Negative symptoms are caused by a deficit of dopamine in the prefrontal cortex (mesocoritcal pathway)
• Who found support for the dopamine hypothesis using PET scans?

  Patel (2010) found lower levels of dopamine in prefrontal cortex
• Strength 1:

  Antipsychotic drugs that decrease dopamine activity decreased symptoms of schizophrenia. Dopamine releasing drug (L-dopa) created symptoms of schizophrenia in normal patients.
• What relationship is not clear in the dopamine hypothesis? (weakness)

  Cause and effect relationship. Is it raised dopamine the cause of schizophrenia or is it the result?
• Who found no difference between sz dopamine and healthy individuals?

  Farde et al. (1990). Suggests that the conclusion is not definite and more research may be required
• Johnstone et al. (1976) found that schizophrenics have enlarged ventricles which is related to a loss of brain tissue. This leads to lower communication networks
• What are ventricles?

  Fluid filled cavities in the brain that supply nutrients and remove waste
• Torres (2002) found that ventricles of sz are 15% larger on average
• Research support for dopamine hypothesis has high reliability. The research is done in highly controlled environments with specialist equipment which take accurate readings of brain regions. Therefore there is high test-retest reliability
• What are neural correlates?

  The variations in neural structure and bio chemistry that are correlated with an increased risk of developing sz
• The dopamine hypothesis suggest that symptoms of schizophrenia are associated with too much or an imbalance of dopamine across the brain
• Excess amounts of dopamine in speech centres like Broca’s area may lead to auditory hallucinations
• Lower levels of dopamine in areas like the frontal cortex are though to lead to negative symptoms avolition or speech poverty
• The dopamine hypothesis came about form observations that dopamine releasing drugs such as L-dopa can produce schizophrenic like symptoms in healthy patients. Anti-psychotic drugs that reduce dopamine levels also reduced SZ symptoms