Biological explanation 1 - Dopamine Hypothesis Flashcards
(18 cards)
What is an Excitatory neurotransmitter?
Make the post synaptic cell more likely to fire
What is an inhibitory neurotransmitter?
Makes the post synaptic cell less likely to fire.
What is the A01 Content?
- Initial dopamine hypothesis (Griffith Et al)
- Dopamine receptor sites
- Revised dopamine hypothesis and the limbic system
What was the intial dopamine hypothesis?
The idea that schizophrenia is caused by too much dopamine within the brain.
What did Griffith et al do?
He induced psychosis in non schizophrenic patients using amphetamine, he found that they experienced a sudden onset of delusions and hallucinations with a ‘cold’ effect.
Why was the dopamine hypothesis disregarded?
It was argued to be too simple, it did not account for negative symptoms.
What did the research into dopamine receptor sited include?
Looked into the way anti-psychotic drugs were inhibiting receptor sites.
What research was found into dopamine receptor sites?
Found that there were specific receptors that were responsible to regulating dopamine levels. Those experiencing schizophrenia had higher numbers of D2 receptors and therefore took up higher levels of dopamine rather than the body producing too much dopamine.
What is the revised dopamine hypothesis research?
It aimed to understand the link between our dopamine receptors and our limbic system. This way we could understand what causes both positive and negative symptoms.
What are the two pathways within our limbic system?
- Mesolimibic
- Mesocortical
Describe the link between the mesolimbic system and schizophrenia.
Too much dopamine is fired within this area and therefore responsible for positive symptoms.
Describe the link between the mesocortiyal system and schizophrenia.
Too little dopamine is found within this area and therefore responsible for negative symptoms.
Evaluation - Dopamine imbalances may be caused by genes.
Suggests that if dopamine imbalances are responsible fro schizophrenia then there may be a genetic predisposition, this is supported by twin and family studies.
Evaluation - What did Gottesman et al find?
He looked at the incidence of schizophrenia in relatives e.g., cousins, siblings and grandchildren etc. He found that as genetic similarity increased so did the incidence of schizophrenia.
Evaluation - Issues with research methods, measuring metabolites.
It is not easy to have a direct measurement of neurotransmitters such as dopamine, much of the research is based on measuring metabolites. Using cerebrospinal fluid measuring HVA. Lumbar puncture is unpleasant for patients. Factors such as diet could skew the results of the metabolite levels. We need to be cautious until methods are refined.
Evaluation - The role of serotonin
Dopamine is not the only neurotransmitter involved in schizophrenia. Serotonin also has an influence. Suggests that the dopamine hypothesis is only a partial explanation due to research in using Atypical anti-psychotics.
Evaluation - Cause and effect
Could be argued that the increased dopamine is due to the schizophrenia rather than a cause of it. It may just be another symptom. Research is not yet advanced enough to determine which came first.
Evaluation - Application
Cole et al found that anti-psychotics reduced positive symptoms in 75% of individuals compared with only 25% of those taking a placebo. This supports the dopamine hypothesis as suggests that it reduced dopamine levels within the pathway
