schizophrenia: biological explanations ao1 Flashcards
purpose of family studies
find individuals with schizophrenia and determine whether their biological relatives are similarly affected more often than none relatives
who conducted a family study and when
gottesman 1991
gottesman 1991 procedure
meta analysis of 40 studies
what did gottesman 1991 find
children with 2 schiz parents had a concoordance rate of 46% and those with 1 schiz parent had 13% and siblings had 9%
gottesman findings twins
gottesman family study found mz twins have a 48% shared risk of schiz
and DZ have 17% risk
purpose of twin studies
if mz twins are more concoordant than dz twins it suggests similarity due to genes
looks at relative contribution of genes and environment
who and when conducted twin study
joseph 2004
joseph 2004 procedure
meta analysis of twin studies conducted before 2001
joseph 2004 findings
combined concordance rate of 40% for mz
7% for dz
what are adoption studies
studies of genetically related individuals who have been reared seperately
who and when did adoption study
tienari et al 2000
tienari et al - what did he find
found that 164 adoptees w schiz mothers 6.7% also recieved a diagnosis compared to just 2% of the 197 control adoptees
what are neural correlates of schizophrenia
paterns of structure or activity in the brain that occur in conjunction with an expirence and may be implicated in the origins of that expirence
describe the original dopamine hypothesis
an excess of neurotransmitter dopamine in certain reigons of the brain is associated with the positive symptoms of schizophrenia
revised Dopamine hypothesis
Brain of schiz patients produced more dopamine than that of normal
excess of dopamine in the mesolimbic pathway (reward pathway) - can lead to positive symptoms
or
deficit of dopamine in areas of the prefrontal cortex - areas responsible for thinking, decision making etc leading to negative symptoms (cog impairment, avolition)
Evidence for dopamine hypothesis
PET SCANS
studies w drugs
Post mortem evidence
Explain dopamine hypothesis
Dopamine receptors fire too often and or the dopamine fails to bind to the post synaptic membrane causing too much activity in the synaptic cleft
Role of recreational drugs on dopamine
Ampthetamines and cannabis leads to increase in dopamine levels
Large quantities can lead to delusions and hallucinations in non sufferers
If drugs are given to schizophrenic patients their symptoms get worse
Evidence of dopamine from Parkinson’s disease
Ppl w Parkinson’s have low dopamine levels
L DOPA drug raises dopamine activity
Ppl w Parkinson’s dev schiz symptoms if they take too much
Explain phenothiazine role in providing evidence for dopamines role in schiz
A drug which reduce dopamine levels
Provide considerable relief from the positive symptoms of schiz
What did falkai
et all find 1988
Found that people w schiz have a abnormally large amounts of dopamine receptors
Concluded that dopamine production is abnormal in all schizophrenics
PET scan evidence
Gjedde and wong 1987
There are twice as many dopamine receptors in schizophrenics compared to controls
Farde et al 1990
There is no difference in the number of dopamine receptors between schizophrenics and controls
Cause and effect issue in dopamine hypothesis
Faulty chem causing schiz or other way round
Drugs may influence other systems that impact schiz so can’t be 100% sure about their effects
Updated versions of dopamine hypothesis
Kenneth Davi’s 1991
Proposed the addition Abnormally low levels of dopamine in the brains cortex
Abonormally low levels of dopamine in the prefrontal cortex…
Responsible for thinking
Could explain cognitive problems (-ve symtptoms of schiz)
Via updated hypothesis what makes people more sensitive to higher or Loewe levels of dopamine
Both genetic versions and Earky experiences of stress both psychological and physical make people more sensitive to high or now levels of dopamine
Via updated hypothesis what makes people more sensitive to higher or Loewe levels of dopamine
Both genetic versions and Earky experiences of stress both psychological and physical make people more sensitive to high or now levels of dopamine
Brain structure in schiz ev
Brain struc in patient w schiz different to a non sufferer
What is a neural correlate
Measurements of structure or function
Neural correlates of negative symptoms
Avolition - loss of motivation
Ventral striatum is believed to be involved in the anticipation of reward which links to motivation
Abnormalities of the ventral striatum is thought to to be involved in the development of avolition
Who did evidence supporting ventral striatum
Juckel 2006
Measured activity in this part of the brain in shchiz and found lower levels of activist compared to that of the control group
The found a negative correlation between activity levels in ventral sti and severity of overall negative sympt9ms in schiz
Neural correlate of positive symptoms
Allen 2007
Scanned brains of patients w auditory hallucinations and compared them to a control group whilst they identied their own speech from others off of a recording
Found lower levels of activity in the superior temporal gyrus and anterior cingulate gyrus in the hallucinations group and this group also made more errors
There is a neural correlate of auditory hallucinations in these 2 parts of Thor brain
Schiz Brian struc
Patients have less brain tissue
Stdhues have shows enlargement of cerebral ventricles 15% larger in some but not all people w schiz
Post motortem studies have shown changes in the amount and distribution of brain cells in some people with schizophrenia
Ev for schiz brain structure
Wood et al
79 males who were considered high risk schiz compared to 49 healthy males
They looked at the size of the hippocampus it was slightly smaller in schiz patients
