Schizophrenia- Biological explanation Flashcards
Is there is a genetic component to schizophrenia which means that some individuals are predisposed to it?
Yes
What do family studies show?
The closer the degree iof genetic relatedness, the greater the risk
What is the concordance rate of sz for identical twins? What is the concordance rate of the rest of the population?
-48%
-1%
Why are adoption studies useful?
They separate the environmental and genetic factors which proves that there is a genetic element
What did Tiehari et al study show/ procedure?
-11/164 adoptees whose biological mothers had been diagnosed with SZ had also been diagnosed
-4/197 who were in the control group (whose biological mothers had not been diagnosed) were diagnosed
-Shows that there is a genetic element
What are candidate genes?
Genes that play a specific role in a disorder making it more likely for you to develop it
What is meant by schizophrenia being polygenic?
-Multiple genes are responsible for it being caused
-As many as 108 genes
-
What is the disadvantge of schizophrenia being polygenic?
There is little predictive power
What are genes associated with SZ usually linked to?
The functioning of neurotransmitters such as dopamine
How is dopamine involved with schizophrenia?
-It is active in the limbic system which governs emotions
-Dopamine helps to regulate attention
-If processes involving dopamine are disturbed it can create problems with attention, perception and thought which are all characteristics of SZ
What is an excess of dopamine associated with?
Positive symptoms
Why do SZ patients have abnormal levels of dopamine?
-Have abnormally high levels of D2 receptors on receiving neurons
-Results in more dopamine binding, so more neurons are firing
How does the use of drugs support the dopamine hypothesis?
Drugs that increase dopamine- people who take recreational drugs such as cocaine and amphetamines, ‘Normal’ individuals who take these develop characteristics symptoms of SZ
Drugs that decrease dopamine- Antipsychotic drugs block the activity of dopamine by reducing normal pathways/eliminating symptoms such as hallucinations + delusions
What does the revised dopamine hypothesis mean?
Davis + Kahn:
- an excess of dopamine in subcortical areas such as the mesolimbic pathway still causes positive symptoms
-negative symptoms arise from a decrease in dopamine in the prefrontal cortex which links to the functioning of the pre-frontal cortex
What are neural correlates?
Measurements of the structure/function of the brain that correlate with an experience
How are neural correlates usually studied?
MRI + PET scans
What have neural correlates shown about the prefrontal cortex in SZ patients? What link does this have to symptoms (Mukai et al)?
-It is impaired (Weinberg + Gallhofer)
-Cognitive symptoms of SZ result from deficits within the PFC + its connections with other areas of the brain, particularly the hippocampus
What is the function of the prefrontal cortex?
Executive functioning (planning, reasoning and judgement)
What do Goto and Grace argue?
-Hippocampal dysfunction might also influence levels of dopamine release in the ganglia- which indirectly affects processing of info in PFC
Describe grey matter in individuals with SZ
-Reduced volume of grey matter especially in temporal and frontal lobes
What is white matter and where is it found?
-Found in the brain and spinal cord
-Made of fibres covered in myelin- helps to conduct info quickly through the CNS enabling different info processing
Describe white matter in individuals with SZ
Reduced
Do people with SZ have enlarged ventricles?
-Yes- within grey matter
-Thought to be as a result of nearby parts of the brain not devolping properly
Canon - Steep 1.____ of 2.____ matter at a great rate
- Loss
- Grey
Which type of symptoms has the ventral striatum (VS), the largest structure in the basal ganglia, been associated with?
Negative
What is the VS part of?
The limbic system
What is VS associated with?
Anticipation of reward
superior temporal gyrus (STG), which is thought to control the processing of speech, has been associated with which type of symptoms?
Positive
Where do SZ patients have reduced grey matter?
In the STG
Give an evaluation point for genetic factors (Twin and adoption studies)
-Evidence to suggest that there is biological influence on the devolpment of SZ but it is not conclusive
-If genes alone caused SZ concordance rates between MZ twins would be 100% not the estimated 48%
-However there is strong evidence for the influence of genetic susceptibility
-Adoption studies show that show SZ have a heightend risk if their parents had SZ even when living in a family without a hirstory of SZ
-Although it is difficult to dispute the influence that genes have on the liklihood of devolping SZ, not a complete explanation and other factors such as enviroment need to be considered
Give an evaluation point for the dopamine hypothesis (Drug treatments)
-Evidence from treatment
-Sucess of drug treatments that attempt to regulate dopamine activity in the brain
-Leuchtet al carried out a metanalsis of 212 studies which concluded that all antipsyhcotics drugs tested in the studies were significantly more effective than placebos in the treatment in both P+N symptoms
-Achieved by reducing the effects of dopamine
-Findings also challenge the classification of antipsychotics into typical and atypical because of differneces in their effectiveness was small
Give an evaluation point for neural correlates (treatment as prevention)
-Practical application
-Implications for treatment
-Important as it means early interventions might prevent devolpment of the later stages of SZ
-Concept of treatment as prevention is seen in North American prodome longitudnal study which usees a number of different assesments including neuroimaging to predict who will devolp disorders such as SZ
-Provides better undertanding of how SZ devolps
-Researchers can detect loss of brain tissue early and treat at risk paiatents before psychosis devolps
Give an evaluation point for the dopamine hypothesis
-Challenges to the dopamine hypothesis
-Nell claims that there is strong evidence against both the original and revised hypotheses
-Antipsychotic drugs do not alleviate hallucinations + delusions in about 1/3 of people who experinece them
-Hallucinations and delusions can be present despite levels of dopamine being normal
-Suggets dopamine is not the sole cause of P symptoms
-Other neurotransmitters that act independently could also produce symptoms
