Neural correlates

• What is the neural correlates explanation of schizophrenia?

  • Focuses on the important role of dopamine and on areas of the brain that are influential in the onset and development of schizophrenia
  • Neural correlates are the neural processes and activities associated with conscious experiences, referring to the brain structures, the original dopamine hypothesis, and the updated dopamine hypothesis
• How did researchers discover the dopamine link?

  • Scientists understood how chlorpromazine worked on the central nervous system by reducing dopamine activity - it was originally a calming sedative used for nausea and allergies but was found to effectively reduce symptoms of schizophrenia symptoms after being given to psychiatric patients
  • They noted that people taking this often experienced symptoms similar to patients with Parkinson's, a neurological disorder linked to low levels of dopamine
  • They concluded dopamine must play a role in schizophrenia.
• What is the original dopamine hypothesis? (hyper-dopaminergia)

  • Claims that schizophrenia is the result of high levels of dopamine in the subcortical regions of the brain, associated with positive symptoms of schizophrenia
• What sources of evidence support the original dopamine hypothesis?

  • Amphetamine is a dopamine agonist (increases dopaminergic activity) that when administered, caused individuals to develop characteristics of a schizophrenic episode. These disappeared with abstinence from the drug
  • Antipsychotic drugs are dopamine antagonists (block dopaminergic activity) that when administered, eliminate positive symptoms like hallucinations and delusions
  • These strengthen the case for the important role of dopamine in the disorder
• What is the updated dopamine hypothesis (hypo-dopaminergia?)

  • In 1991, Davis et al. proposed the additional idea that abnormally low levels of dopamine in the cortical regions of the brain can contribute to schizophrenia
  • Since positive symptoms are thought to be caused by an excess of dopamine in subcortical brain areas like the mesolimbic pathway, the negative and cognitive symptoms are thought to arise from a DEFICIT of dopamine in areas of the prefrontal cortex like the mesocortical pathway

  
• What other specific brain areas are involved in schizophrenia?

  • White matter is made up of nerve fibres covered in an insulating myelin sheath which helps to conduct information quickly through the central nervous system, enabling efficient information processing
  • Du et al. (2013) found reduced myelination of white matter pathways in schizophrenic patients between the prefrontal cortex and hippocampus, showing impairments of information processing
• What is one strength of the neural correlates explanation?

  • Research support for original dopamine hypothesis: Leucht et al. (2013) conducted a meta-analysis of 212 studies concluding that antipsychotics (dopamine antagonists) are more effective in schizophrenia symptom reduction than placebos
  • Displays the link between schizophrenia and high dopamine as a drug that blocks DA activity will reduce symptoms, supporting the hypothesis
• What is another strength of the neural correlates explanation?

  • Research support for updated dopamine hypothesis: Patel et al. (2010) analysed PET scans and found lower levels of dopamine in the prefrontal cortexes of schizophrenia patients compared to neurotypical controls
  • Supports the idea of hyperdopaminergia in the sense that a deficit in dopamine can be linked to negative symptoms
• What is one limitation of the neural correlates explanation?

  • Contrasting evidence: Noll (2009) found that antipsychotics don't alleviate symptoms in about 1/3rd of schizophrenia patients
  • Also people with regular dopamine levels are still found to experience positive symptoms like hallucinations and delusions, making the explanation questionable since evidence shows the dopamine-schizophrenia link is not universal in all patients
  • Limits the generalisability of the explanation
• What is another limitation of the neural correlates explanation?

  • Role of glutamate: there is new evidence for other important neurotransmitters in the onset of schizophrenia
  • McCutcheon et al. (2020) reviewed post-mortems and live scanning studies that found raised levels of glutamate in certain brain regions of people with schizophrenia
  • Several candidate genes are believed to be involved in glutamate production
  • This suggests equally strong cases can be made for neurotransmitters that aren't dopamine, questioning the exclusivity of the dopamine-schizophrenia link