AO1 - Genetic Theory and Neural Correlates

• One biological explanation of schizophrenia is the genetic theory
• Genetic theory:

  • Schizophrenia is hereditary and passed on from one generation to the next through genes
  • A person is born with a genetic predisposition to sz - it is believed that several maladaptive 'candidate' genes such as PCM1 are involved which increases an individual's vulnerability to developing sz
  • Studies have shown that 108 separate genetic variations are associated in the risk of developing sz
  • Gottesman studied 40 twins and found that concordance rates for monozygotic twins was 48% and only 17% for dizygotic twins - closer the genetic link, higher chance of developing sz
• One type of neural correlates as a biological explanation for schizophrenia is brain structure or function
• Neural correlates: Brain structure or function

  • One neural correlate of sz is enlarged ventricles
  • A meta analysis by Raz and Raz found that over half of individuals tested with schizophrenia had enlarged ventricles compared to a control group
  • Enlarged ventricles are associated with damage to central brain areas and the pre-frontal cortex (Broca's area) - this damage is associated with negative symptoms of sz, such as speech poverty
• One type of neural correlates as a biological explanation for schizophrenia is the dopamine hypothesis
• Neural correlates: Dopamine hypothesis

  • The brain's chemical messengers appear to work differently in the brain of a patient with sz - Dopamine (DA) is widely believed to be involved as individuals with sz may either release too much DA or have a large amount of D2 receptors on the post synaptic neuron
  • Hyperdopaminergia in the subcortex - High DA activity in central areas of the brain such as Broca's area may be associated with auditory hallucinations
  • Hypodopaminergia in the cortex - Low DA activity in the prefrontal cortex have been associated with negative symptoms of sz such as avolition
• It has been suggested that cortical hypodopaminergia leads to subcortical hyperdopaminergia - both high and low levels of DA in different brain regions are involved in different symptoms of schizophrenia