dopamine hypothesis Flashcards
what are the 3 ways the biological explanation can be explained?
1 - biochemical
2 - genetic
3 - brain structure
what is the biochemical explanation?
the rationale behind it is that if SZ is genetic, biochemical abnormalities should be detectable in the brains. research suggests that one of the main causes of SZ is due to chemical imbalances in the brain - the overproduction of dopamine
what did Randrup find about the dopamine hypothesis?
they injected rats with dopamine and observed their behaviour and found that the behaviour became more stereotypes, aggressive and isolated = becoming more psychotic consistent with that shown in SZ patients.
what is the sensitivity theory?
another dopamine hypothesis argues that the dopamine receptors (D2) are hypersensitive which means that the pateients are likely to overreact to the presence of dopamine.
- Lieberman et al state that around 75% of pateitns with SZ show new symptoms or an increase in psychosis after drugs with amphetamine and methylphenidate which mimic dopamine.
what is amphetamine?
a drug that stimulates the central nervous system
- its effects include increased ctivity and energy as well as appetite suppression and difficulty sleeping
what is methlyphenidate?
a psycho-stimulant drug that acts on the central nervousd system
- it is used to treat ADHD
what is the evidence strength of the dopamine hypothesis?
it is supported by evidence
- Owen et al. found that post mortems of people with SZ have a higher density of dopamine receptors in certain parts of the brain.
traditional antipsychotic meds work by blocking the dopamine receptors
what is the competing argument against the medicine argument?
not all patients respond well to these meds
- Alpert and Friedhoff found that some patients did not respond at all to the antagonist drugs.
more modern antipsyhosis drugs block serotonin receptors as well as dopamine receptors and work just as well
- the modern meds have fewer side effects so maybe it is oversimplistic to assume that SZ is the result of hypersensitivity.
what is the weakness that SZ changes brain chemistry?
evidence can only be gathered from the brains of those with SZ after they have developed it so we cannot know what their brains were like before hand.
what is the explanatory strength of the dopamine hypothesis?
it can explain negative symptoms of the illness
- a reduction of dopamine in the mesocortical pathways can lead to flattened affect, a lack of motivation and depression
what is the reductionist weakness of the theory?
the dopamine hypothesis is reductionist as it explains a disorder that has many complex features by the smallest way - by the imbalance of ONE neurotransmitter.
- it ignores the complex relationship between the brains neurotransmitters and social factors.
- Brown et al found that 50% of SZ patients reported a major life event in the 3 weeks prior to relapse.
