Biological Explanation

• Dopamine hypothesis


  Dopamine controls satisfaction, motivation and pleasure therefore symptoms caused by abnormal level
• Original dopamine hypothesis


  Excessive activity (hyperdopaminergic) of dopamine causes schizophrenia because neurons fire too often and transmit too many messages which causes a message overload. As a result, the overload produces schizophrenic symptoms
• Updated dopamine hypothesis

  Low levels of dopamine in brain's cortex; Goldman-Rakic 2004 et al. found low levels (hypodopaminergic) in prefrontal cortex
• Neural correlates

  The measurement of brain structure/functions that correlate with positive and negative symptoms (an experience)
• Juckel 2006 et al. - reduced activity in the ventral striatum is a neural correlate of avolition –involved in motivation which is reduced in avolition therefore abnormality of VS is expected in schizophrenics, negative correlation between levels in VS and severity of overall -ve symptoms
• Allen 2007 et al. - reduced activity in superior temporal gyrus and anterior cingulate gyrus are neural correlates of auditory hallucinations – areas less active when hallucination group had to identify pre-recorded speech as theirs or others, made more errors than control group
• Gottesman 1991 et al. found greater genetic similarity of the concordance rate for schizophrenia = 48% for MZ, 13% for one parent, 9% for siblings, 6% for parents
• Ripke 2014 et al. found 108 separate genetic variations associated with increased risk of schizophrenia; a polygenic condition, differing candidate genes suggests different combos of factors can lead to condition
• Gottesman 1991


  Families tend to share environments so that can account for increased risk/exposure therefore it's a combination of environment and genetics
• Support - evidence from adoption studies

  Tienari 2004 = 6.7% of adoptees with schizophrenic biological mother were diagnosed with schizophrenia – reinforces notion that genes create genetic vulnerability to schizophrenia
• Mørkved 2017

  67% schizophrenics had childhood trauma
• Morgan 2017

  Birth complications and smoking TCH-cannabis – upbringing makes schizophrenics more vulnerable to developing the condition because it affects psychological and biological state therefore interactionist
• Patel 2010 = neural imaging and PET scans found low dopamine levels in dorsolateral prefrontal cortex - PFC is responsible for decision-making and thinking therefore it can account for avolition because it decreases motivation
• superior temporal gyrus


  contributes to speech perception and involved in auditory processing