Biological explanations for schizophrenia Flashcards
What are candidate genes?
Individual genes that are believed to be associated with a risk of inheritance.
How many seperate genetic variations were associated with increased risk of schizophrenia in Ripke’s study?
108
Which neurotransmitter is usually the most associated with schizophrenia?
Dopamine
What did the original version of the dopamine hypothesis say?
This version focussed on the possible role of high levels of dopamine in the subcortex. E.g an excess in Broca’s area (responsible for speech production) may be associated with speech poverty etc.
What did the newer version of the dopamine hypothesis say?
More recent versions have focused on abnormal dopamine levels in the cortex. Research has identified that low levels of dopamine in the prefrontal cortex (responsible for decision making and thinking) may link to negative symptoms of schizophrenia.
Are both the older and newer versions of the dopamine hypothesis likely to be accurate?
Yes, both high and low levels of dopamine in different areas of the brain are involved with schizophrenia.
What are neural correlates in the context of schizophrenia?
Measurements of the structure or function of the brain that correlate with schizophrenia.
What are the neural correlates of negative symptoms of schizophrenia?
Research has found that activity levels in the ventral striatum in schizophrenia were lower than those observed in controls. They observed a negative correlation between activity levels in the ventral striatum and the severity of negative symptoms. Therefore, activity in theventral striatum is a neural correlate of negative symptoms of schizophrenia.
What are the neural correlates of positive symptoms of schizophrenia?
Research has found that lower activity levels in the superior temporal gyrus and the anterior cingulate gyrus were found in a group of schzophrenic patients experiencing auditory halluinations as oppose to a control group. Therefore reduced activity in these two areas is a neural correlate of the positive symptoms of schizophrenia.
Strength of biological explanations for schizophrenia- adoption studies
There is strong evidence for genetic vulnerability to schizophrenia from a variety of sources. For example, adoption studies clearly show that children of people with schizophrenia are still at heightened risk of schizophrenia if adopted into families with no family history of schizophrenia.Tienari investigated genetic vulnerability and parenting style in adopted children from 19,000 Finnish mothers. When the biological mother was schizophrenic, there was a 10% chance of developing schizophrenia. When the biological mother was not schizophrenic, there was a 1% chance.
Strength of neural correlates- research evidence.
There is research evidence to support neural correlates from autopsies of schizophrenia sufferers. These autopsies have shown that people with schizophrenia have more dopamine receptors which leads to more neural firing and therefore an overproduction of dopamine.However, some of the genes identified in Ripke’s study code for the production of other neurotransmitters so although dopamine is likely to be an important factor, so are other neurotransmitters. Therefore the dopamine hypothesis is too simplistic.
Limitation of biological explanations for schizophrenia. (reductionist)
Biological explinations for schizophrenia over simplify schizophrenia in terms of genes and neurotransmitters and the social context within it develops has not been considered. In order to explain schizophrenia effectively it would be better to take an interactionist approach such as the diathesis-stress model which suggests that biological factors predispose someone to schizophrenia but this has to be triggered by some sort of experience.
Limitation of schizophrenia. (neural correlates)
Unusual activity in the brain may not actually cause a symptom of schizophrenia. For example, there are several neural correlates of schizophrenia symptoms and research into this is useful to flag up particular brain systems which may not be working properly however it is possible that negative symptoms mean that less information passes through these parts of the brain which results in less activity.
What does the biological explanation of schizophrenia suggest?
Schizophrenia runs in families and although this is a weak genetic link as family members tend to share aspects of their environment as well as many of their genes, it has been found that there is a strong relationship between the degree of genetic similarity and the risk of schizophrenia.
Evidence that schizophrenia is polygenic.
Ripke et al. (2014) carried out a huge study combining all previous data from genome-wide studies of schizophrenia. The generic make-up of 37,000 people diagnosed with schizophrenia was compared to 113,000 controls. 108 separate genetic variations were associated with increased risk of schizophrenia. Genes associated with increased risk included those that coded for the functioning of a number of neurotransmitters.
