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
