A01 Biological Explanations For Schizophrenia

• Genetic basis of schizophrenia

  Sschizophrenia runs in families. Weak evidence for genetic link due to families sharing environment but systematic investigations do show greater genetic similarity is associated developing the disease.
• Gottesman


  Found as genetic similarity increase so does probability of sharing schizophrenia. If both parents have the disease for example, then there is a 46% chance for the child to develop it.
• Gottesman and Shields

  Investigated 57 schizophrenic patients. If a monozygotic twin had schizophrenia, there was a 42% chance their twin would also have schizophrenia. If the twin was dizygotic, the concordance rate dropped to 9%.
• Heston et al


  Found through adoption studies that although the biological parent was not in close contact with the child, there was a genetic development of schizophrenia in the child.
• Candidate genes


  Individual genes are believed to be associated with risk of inheritance. Polygenic as it requires a number of combinations and factors to work. Aetiologcially heterogenous as different combination of factors can lead to contracting schizophrenia.
• Ripke et al


  Combined previous data from genome-wide studies and found 108 genetic variations of schizophrenia associated with risk of schizophrenia.
• The dopamine hypothesis


  Neurotransmitters are chemical messengers of the brain that appear to work differently in people with schizophrenia. Dopamine is particularly involved.
• Hyperdopaminergia


  High levels of dopamine in the subcortex. Excess dopamine. E.g: dopamine receptors in Broca's area associated with poverty of speech and auditory hallucinations.
• Hypodopaminergia


  Abnormally low dopamine in brain's cortex. Low levels in prefrontal cortex which causes negative symptoms of schizophrenia.
• Neural correlates


  Patterns of structure or activity in the brain that occur in conjunction with an experience and are associated with specific cognitive functions, emotions, behaviors, or conscious experience.
• Neural correlates of negative symptoms

  Avolition. Ventral striatum believed to be involved in the anticipation of a reward, caused by motivation. Juckel et al measured activity levels in the ventral striatum in schizophrenia patients and found lower levels of activity than in the control.
• Neural correlates of positive symptoms

  Allen et al scanned the brains of patients experiencing auditory hallucinations while they identified either others or their own recorded speech.
• Allen et al findings


  Lower activation levels in the superior temporal gyrus and anterior cingulate gyrus were found in the hallucination group compared to control. Reduced activity in these two areas of the brain is neural correlate of auditory hallucination.