Schizophrenia - Biological explanations Flashcards
1 What is L-dopa?
Drug used to increase the amount of dopamine in parkinsons patients - developed paranoid delusions and had a detached emotional response
1 What are the pathways in the limbic system?
Mesolimbic - carries signals from the VTA to nucelus accumbens - too much dopamine causes overstimunlation and positive symptoms
Mesocortical - carries signls from VTA to frontal labe - dopamine abnormalities are linked with negative symptoms
1 What did Davis et al note?
Low levels of dopamine in D1 receptors of frontal lobe in many individuals with negative symptoms
1 Supporting research (family members) for dopamine hypothesis?
Gottesman - as genetic similarity increased, so did the probability of both individuals developing schizophrenia
1 Limitations of Gottesman’s study?
Not what the hypothesis suggests so is only useful as a partial explanation
1 Alternative explanation (genetics) for dopamine hypothesis?
There were 108 loci association with schizophrenia
1 Limitations of alternative explanation?
Schizophrenia is a very complex matter and is more than just a few abnormal dopamine genes
1 Methodological issues for dopamine hypothesis?
Difficult to measure neurotransmitter levels - needs a lumbar puncture to obtain cerebrospinal fluid - can be uncomfortable
Diet and drug use can influence metabolite levels so caution needs to be taken when drawing conclusions
1 Why is the dopamine hypothesis a partial explanation?
Role of serotonin cannot be ignored - not only dopamine is involved
Typical antipsychotics - block D2 receptors but not all schizophrenics benefit
Atypical antipsychotics - bloth dopamine and serotonin receptor sites - more effective
2 What are ventricles?
Cavities filled with cerebrospinal fluid
Larger in those with schizophrenia
2 What did Weinberger et al found?
Ventricular size was greater in people with chronic schizophrenia than in people in control group
40% - outside range of control group - substantially different
2 What did Andreason find?
Schizophrenica had ventricles 20-50% larger than controls
2 What is cortical atrophy?
Loss of neurons in cerebral cortex - can occur all over the brain or focussed in limited areas
2 What does cortical atrophy result in?
Wideniing of grooves (sulci) covering the cerebral cortex
Characterises 20-35% of schizophrenics
2 What did Vita et al find?
33% of shcizophrenics showed moderate to severe atrophy - not related to individual differnces like age but related to sex specifically male
2 What is reversed cerebral asymmetry?
usually temporal, parietal and occipital lobes are larger on the left and the frontal lobe is smaller on the right - opposite for schizophrenics
2 What can asymmetry explain?
Alogia - language function is located on the left hemisphere as it is smaller in those with schizophrenia
2 What did Luchins et al find?
Increased frequency of ‘reversals’ in both frontal and occipital lobes in schizophrenics
2 Methodological issues (evidence) of structural abnormalities?
Use of brain scans - allow us to see the living brain in action so more precise about abnoralities - highly reliable
Risk of psychological harm - can cause distress to those without schizophrenia - may experience delusions and fear brain scanning more than usual
2 Supporting research (ventricles) for structural abnormalities?
McCarley - presence of enlarged ventricles in people with schizophrenia is the most reliable finding in research using brain scans
2 Limitations of abnormalities?
Abnormalities arent always found in schizophrenics - Age and gender can affect pattern of abnormalities
Abnormalities are also present in other illnesses (bipolar)
2 Methodological issues (antipsychotics) for structural abnormalities?
Lyon et al?
Any abnormalities may be a result of medication and not the illness.
Lyon - as doses increased, density of brain tissue decreased
