biological explanations Flashcards
candidate genes
Individual genes believed to be associated with risk of inheritance-number of gene appear to confer a small increased risk of schizophrenia so it appears that schizophrenia is polygenic-requires a number of factors to work in combination genes associated with increased this can include those cording to the functioning of a number of neurotransmitters eg dopamine
dopamine hypothesis
The brains chemical messengers appear to work differently in the brain of a patient with schizophrenia in particular dopamine is widely believed to be involved dopamine is important in the functioning of several brain systems that may be implicated in the symptoms of schizophrenia
hyperdopaminergia
in the subcortex
-high levels of activity of dopamine in the subcortex, dopamine is important in the functioning of the brain systems that may be implicated in the symptoms of schizophrenia, excess levels of dopamine in broca’s area associated with poverty of speech and/or hallucinations
hypodopaminergia
in the cortex
-Goldman-Identified a role for low-level dopamine in the prefrontal cortex responsible for thinking and decision-making in the negative symptoms of schizophrenia
schizophrenia runs in families
As genetic similarity increases so does the probability of sharing schizophrenia family members tend to share aspects of the environment as well as genetic’s
neural correlates of schizophrenia
Measurement of the structure or function of the brain that correlate with an experience in this case schizophrenia both positive and negative symptoms have neural correlates
neural correlates of negative symptoms
- avolition involves loss of motivation, motivation involves anticipation of reward, ventral striatum involved
- Juckel measured activity levels in the ventral striatum and found lower levels of activity than those observed in controls
- observed a negative correlation
neural correlates of positive symptoms
-Allen- scanned brains of patients experiencing hallucination and compared to control group- found lower activation levels in the superior temporal gyrus in the hallucination group
evidence for genetic vulnerability
adoption studies (Tienari)- children of schizophrenia sufferers still at high risk even if adopted into a family with no history -doesn’t mean it’s entirely genetic
mixed evidence for dopamine hypothesis
evidence from post mortem studies show sufferers have increased levels of dopamine but failed to take into account whether the patient has received treatment-ethical implications can’t study people that aren’t treated
twins separated at birth
Kety- twins separated at birth who went on to experience psychosis were around 21% more likely to have biological relative with schizophrenia than their adopted family
-based on 34 people-small sample so can’t be generalised
evidence for other influences rather than just genetics
if schizophrenia was entirely genetic- concordance rate between MZ twins would be 100% and DZ twins would be 50%- this doesn’t happen suggesting other factors are involved
problems in retrospective and prospective studies
studies that are retrospective or prospective have problems as the diagnostic criteria for schizophrenia has changed over time so aren’t necessarily comparing the same symptoms in parents and offspring- could distort the concordance rate
possibility to develop disorder without family history
schizophrenia can occur without family history-one explanation is mutation in parental DNA eg paternal sperm cells- caused by radiation for example, study showed positive correlation between paternal age and risk of schizophrenia
hard to measure
can’t control where dopamine goes in the brain so could mistreat it
