Biological Explanation - Dopamine Hypothesis Flashcards
What does the diathesis stress model argue?
That we inherit a predisposition to Schizophrenia (diathesis)
It will be activated if we experience an emotional trigger (stress)
How was the inital dopamine hypothesis proposed?
Initally it was a basic concept, suggesting that Schizophrenics had too much of the neurotransmitter dopamine as they demonstrated symptoms that would suggest that
Built of research that found psychosis could be induced in non scz voulnteers when they were given the drug dextro amphetamine, which increases the amount of dopamine in the brain
Why was the inital hypothesis critisesed?
As it didnt explain the negative symptoms of Scz
How did the discovery of dopamine receptor sites further the dopamine hypothesis?
The discovery of the D1-D5 receptor sites in the cerbal cortex and also in the limbic system were of particular intests , specifically the D2 receptor sites and the effect of Antipyscotics. As a result the limbic system became the main focus of the dopmamine hypothesis
How did the focus on the Limbic system revise the dopamine hypothesis?
The limbic system consists of a variety of subcortical structures that are engaged in many functions, most most notably emotion, memory formation and arousal. Two main pathways associated with Schizophrenia are the Mesolimbic pathway and mesocortical pathway
Describe the importance of the mesolimbic pathway for providing a biological explanation for Schizophrenia
The mesolimbic pathway is significant as dopamine is a major neurotransmitter. The pathway carries signals from the ventral tegmental area to the necleus accumbens, too much dopamine causes the neurons to fire to often or to quickly
Explains the positive symptoms of Schizophrenia
Describe the importance of the mesocortical pathway for providing a biological explanation for Schizophrenia
Dopamine is also a major neurotransmitter in the mesocortical pathway, this pathway carries signals from the ventral tegmental area to the frontal lobe. This nerve pathway is vital in emotional responses, motivation and cognition. Too little dopamine in the D1 receptors is evident in Scz indivudals with cognayite impairments and negative symptoms of Scz
Which subcortical structure of the limbic system explains the positive symptoms of Schizophrenia?
The Mesolimbic pathway
Which subcortical structure of the limbic system explains the negative symptoms of Schizophrenia?
The Mesocortical pathway
What are the 4 evaluation points for the dopamine hypothesis?
Dopamine imbalances may be genetic
Measuring metabolites instead of dopamine
The role of serotonin
Cause and Effect of Dopmaine
Why is the measurement of metabolites a point of evaulation?
Its not easy to directly measure the amount of neurotransmitters such as dopamine. Instead we measure metabolites (what neurotransmitters are broken into) in cerebrospinal fluid. Dopamine is measured by the levels of HVA in this fluid. But research shows that diet and drug use effects these levels drastically. Meaning we cant reliably use current methods to measure dopamine
Why is the role of serotonin a point of evaluation?
Dopamine isnt the only neurotransmitter associated with Scz. Serotonin is also identified as a potential influence. Conventional anti-pyschs ignore serotonin and not all scz benefit from it. Whilst atypucal drugs blocks D2 receptors and 5-HT2A (serotonin receptors). This shows that dopamine may not be a complete explination.
Why is the debate if dopamine is a cause or an effect of Schizophrenia significant?
It could be logical to suggest that scz causes dopamine imbalances. PET scans have been unable to dectect differences in the dopamine activity of brains of Scz and non Scz individuals so we dont know what dopamines significance is.
Why is the fact that dopamine imbalances may be caused by genes a point of evaluation?
We don’t know exactly what causes dopamine imbalances. Twin and families studies suggest that there is a genetic basis for scz. Research into genomes found 108 genetic loci associated with Scz. This suggests its a far more complex issue than a few abnormal dopamine genes.
