Schizophrenia: Biological Epxlanations Flashcards
(12 cards)
Outline the genetic basis of schizophrenia
- schizophrenia does run in families. But this is quite weak evidence for a genetic link because families share the same environment
-there is a strong relationship between degree Of genetic similarity+ risk of schizophrenia (gottesman) - e.g. identical twins shared 100% of their DNA and have a 48% risk of developing schizophrenia
Outline ‘candidate genes’ as a genetic explanation of OCD
- individual genes are belived to be associated with risk of inheritance
- schizophrenia is thought to be polygenic and aetiologically heterogeneous (different combinations of factors can lead to the condition)
- ripke et al - meta analysis, 108 genetic variations were associated with increased risk of schizophrenia
What is the dopamine hypothesis as an explanation for schizophrenia
- the brains neurotransmitters appear to work differently in the brain of a person with schizophrenia
- dopamine, for example, is important in the functioning of several systems that may be implicated in the symptoms of schizophrenia
What is the original version of the dopamine hypothesis
- focused on the possible role of high levels or activity of dopamine in the sub cortex
- e.g. an excess of dopamine in the Broca’s area (speech production) may be associated with speech poverty
What are the more recent versions of the dopamine hypothesis
- focused on abnormal dopamine systems in the brains Cortex
- researchers have found low levels of dopamine in the prefrontal cortex(decision making + thinking) are associated with the negative symptoms of schizophrenia
What are neural correlates and how are they linked to explaining schizophrenia
- measurements of the structure or function of the brain that correlates with an experience
- both positive and negative symptoms have neural correlates
Outline neural correlates of negative symptoms
- negative symptom (avolition) involves the loss of motivation
- motivation involves anticipation of reward, and certain regions of the brain (e.g. ventral striatum) are believed to be involved in this anticipation
- researchers have found a negative correlation between activity levels in the ventral striatum and severity of overall negative symptoms
Outline neural correlates of positive Symptoms
- Allen et al - scanned brains of people experiencing auditory hallucinations + compared to a control group
- lower activation levels in the superior temporal gurus were found in there hallucination group
- so reduced activity levels in these two areas of the brain is a neural correlate of auditory hallucination
What are the three evaluation points for biological explanations for schizophrenia
- multiple sources of evidence for genetic susceptibility
- mixed evidence for the dopamine hypothesis
- correlation-causation problem
Outline ‘multiple sources of evidence for genetic susceptibility ‘ as an evaluation point for biological explanations for schizophrenia
- very strong evidence for genetic vulnerability to schizophrenia from a variety of sources
- gottesman study - shows how genetic similarity and risk of schizophrenia are closely related
- adoption studies -clearly show children of people with schizophrenia are still at risk of it if adopted into families with no schizophrenia history
Outline ‘mixed evidence for the dopamine hypothesis‘ as an evaluation point for biological explanations for schizophrenia
- There is support from a number of sources for abnormal dopamine functioning in schizophrenia
- dopamine agonists like amphetamines (increase dopamine levels) make schizophrenia worse and produce schizophrenic like symptoms in people not diagnosed
- antipsychotic drugs however, reduce dopamine activity
- both kinds of drug studies suggest an important role for dopamine in schizophrenia
Outline ‘correlation-causation problem’ as an evaluation point for biological explanations for schizophrenia
- there are a number of neural correlates of schizophrenia symptoms,including both positive and negative
- studies in this field are useful in flagging up brain systems that may not be working normally
- however, we cannot be sure the unusual brain activity CAUSES the symptom.
