Sz: Biological Explanations Flashcards
What are genetics?
Genes consist of DNA strands and are inherited. DNA produces ‘instructions’ for physical features of an organism (e.g. neurotransmitter levels and size of the brain structures) which may impact upon psychological features
What did Gottesman find about genetics?
- the greater the genetic similarities, the greater the risk
- MZ have the highest risk (48%) and share 100% of genes
- DZ twins have a higher risk (17%) than siblings (9%) despite sharing the same number of genes
—> these stats show that although there is a genetic basis here, there must also be some environmental influence
What did Ripke find?
108 separate genetic variations were associated with increased risk of Sz
What did Tienari find about adopted children?
Looked at 164 adopted children whose biological mothers has Sz, they had a concordance of 6.7%, compared to 2% of adopted children without Sz parents.
- shows there is a genetic aspect as its a higher number, but also an environmental aspect - different to Gottesman (13%)
—> however the affect of the experience of being adopted may impact results (trauma, etc)
What are some problems with the genetic approach to explaining Sz?
- deterministic
- reductionist - doesn’t look into other theories, very specific
What is the dopamine hypothesis?
Dopamine is a chemical substance (neurotransmitter) manufactured in the brain that transmits messages between neurons - one of the chemicals that cause neurons to fire
- the original DH stated that Sz suffered from an excessive amount of Dopamine, causing neurons to fire too often and transmit too many messages
- dopamine appears to work different in different Sz patients
- D is particularly important in the functioning of several brain systems that may cause symptoms of Sz - particularly the cortex and subcortex
What is Hyperdopaminergia in the subcortex?
The original dopamine hypothesis
- Sz is a result of high levels of dopamine activity in the subcortical areas of the brain
—> an excess of dopamine activity or receptors in the subcortex and Broca’s area (responsible for speech production) may be associated with speech poverty and could also be associated with experiences of auditory hallucinations
What is the Hypodopaminergia in the cortex?
- abnormally low dopamine levels
—> Davis added cortical hypodopaminergia to the DH
Goldman-Rakic identified low levels of dopamine in the prefrontal cortex (responsible for thinking and decision making) associated with negative symptoms
What did Wise and Stein find to support the DH?
They reported abnormally low levels of DBH in post-mortem studies of Sz patients. Would suggest abnormally high dopamine activity as DBH needed to break dopamine down
—> however this could happen after death - might not have been the case when alive
Who found that the chemicals needed to produce D are taken up faster in the brains of Sz sufferers than controls, suggesting. They produce more D - supporting the DH?
Lindstroem
What did Tauscher find to support DH?
Anti-psychotic drugs work by reducing D activity. Sz symptoms can be treated with D antagonists (e.g. chlorpromazine) - these are effective in 60% of cases with more impact on positive symptoms.
What’s a study that refutes the DH?
Moghaddam and Javitt - found evidence for the role of a different type of neurotransmitter called glutamate in which it appeared that Sz sufferers have a deficiency in glutamate function.
—> suggests DH is not a complete explanation - not just dopamine, other neurotransmitters may also be responsible
What are neural correlates?
A pattern of structure or activity in the brain that occur in conjunction with an experience, in this case Sz
- e.g. low levels of dopamine in the prefrontal cortex is a neural correlate of the negative symptoms of Sz.
- neural correlates are not limited to dopamine levels, there are others which link to the symptoms of Sz
What is the superior temporal gyrus?
- involved in recognising sounds, contains the primary auditory cortex
-Allen scanned patients with auditory hallucinations, compared to control
—> found lower activation levels were found in the superior temporal gyrus in the hallucinations group. Reduced activity in these parts of the brain is a neural correlate for auditory hallucinations - the superior temporal gyrus contains the primary auditory cortex, which is responsible for processing sounds - less activity here may lead to difficulties in detecting the origins of a voice, explaining why they made more errors
—> this could explain auditory hallucinations as inability to recognise internal monologue as being self-generated
What is the ventral striatum?
- involved in motivation and reward anticipation
- if activity in the VS are low then the anticipation of a reward is not present
—>if no anticipation of a reward, theres no reason to engage in behaviours to bring about the reward. Therefore the VS is a neural correlate of negative symptoms (e.g. why go to work?, why have a friend?) - avolition, which includes motivation, has been associated with one of the main reward centres in the brain. Juckel measured activity levels here and found lower levels of activity in Sz compared to controls.
