Schizophrenia Flashcards
what is the number one cause of premature death among people with schizphrenia?
suicide
what are some positive symptoms of schizophrenia?
- hallucinations
- thought disorders (incoherent speech, delusions)
- sterotypes behaviours (repeptitive movements)
what are the negative symptoms of schizophrenia?
- poverty of affect (depression, low mood)
- cognitive impairment
- temporal disorientation
- social withdrawal
- inability to feel pleasure or act spontaneously
what is the time course of schizophrenia?
positive -> negative symptoms
onset 15-25 years old
out of first degree relatives who has the highest rates of schizophrenia among relatives
identical twins
children - both parents schizophrenic
what the proposed causes of schizophrenia?
- Genetic
- psychoscial
- structural brain damage
- viral infection
give 4 potential causes of schizophrenia
- Genetic
- Psychosocial
- Structural brain damage
- Viral infection
what evidence from adoptive studies was there for a gentic cause of schizophrenia?
Tienari looked at this, babies adopted away from ‘normal’ or ‘schizophrenic’ mothers:
incidence of schizophrenia among babies from noraml birth mothers was 1%
incidence of schizophrenia among babies from schizophrenic birth mothers was 8%
what is the concordance rate of schizophrenia among monozygotic twins?
48%
what are endophenotypes?
- A trait related to the psychiatric disorders and its genetic basis
- things you can recapitulate in animal models to measure/study psychiatric disorders
give an example of an endophenotype for schizophrenia
- A good example is pre-pulse inhibition
o Essentially this is a measure of an individuals startle response
(eg by an unexpected noise stimulus, then measure ocular motor response. In a normal individual the second response will be lower than the first response, this is called sensory motor gating.
pre pulse inhibition is typically impaired in schizophrenia (some sort of aberration in sensory motor gating)
what evidence is there that there is a psychosocial cause for schizophrenia
- adolescent onset – at a time where there are a lot of changes and stress
- stress can precipitate illness - the first instance of illness and subsequent episodes seem to follow stress in life
- higher rate of relapse in ‘emotionally charged’ home environment
- blunted cortisol response
give evidence that structural brain damage could be a cause of schizophrenia
in schizophrenics there has been observed:
some studies (CAT Scans and MRI) show ventricular enlargement and
decreased volume of temporal lobe (hippocampus)
cytoarchitectural abnoramlities in cortex
cytoarchitectural abnormalisties in the cortex of schizophrenics manifests as:
- decreased numbers of small neurones in superficial layers
- increased numbers of large neurones in deeper layers
- Loss of volume – not neurons
- Reduction in dendritic spine density
o In schizophrenia aberrant spine density has been reported in multiple brain regions – reduction in volume of grey matter in the cortex
what cricumstantial evidence pointed to viral infection as a potential cause of schizophrenia?
higher incidence in patients born in late winter or spring
hypothesis that exposure of mother to virus during second trimester increases risk of schizophrenia to the child
what are the major sites of brain dysfunction in schizophrenia?
- Limbic structures in the temporal lobes (decreased size)
- dysfunction of dominant cerebral hemisphere
- hypofunctionality of dorsal-lateral pre-frontal cortex
- basal ganglia (change in size of nuclei)
give evidence to support limbic structures as the site of brain dysfunction in schizophrenia
Some limbic structure harboured in the temporal lobe
Decreased size of temporal lobe, (due to dendritic pruning not death of neurons)
Increase activity during auditory hallucination
- Temporal lobe involved in language and auditory processing and emotion and memory
in indivudials with epilepsy, if the locus for the seizure is in the temporal lobe then they will experience hallucinations during the seizures.
Those with tumour in the temporal lobe also experience hallucinations that can be psychotic
give evidence to show dysfucntion of dominant cerebral hemisphere in schizophrenics is the site of brain dysfunction
Lateralisation of cerebral function is important for normal cognitive processing
Left hemisphere is specialised for verbal function (in most indixisualts) and the right hemisphere is for special processing)
The corpus callosum that allows the hemispheres to communicate means we don’t notice this
In normal individuals this is shown by increased brain activity to the left side of the brain during a verbal task
This lateralisation appears disrupted in schizophrenia
Don’t show the same lateralisation of function, this might underpin the poor performance in some cognitive tasks
More recent studies focussing on cennectivity - via mapping tracts using diffusion tensor imaging
Anatomical abnormality in the commissural trascks in indivuduals with psychosis – maybe this is the anatomical pehnoemenon that’s resulting in disrupted lateralisation
give evidence that the hypofunctionality of dorsal lateral pre frontal cortex is the site of brain dysfunction in schizophrenics
using the wisconsin card sorting test to assess decision making capability, metabolic activity was measured in the brain of control vs schizophrenic subjects
schizophrenic performed poorly in the task - and the metabolic activity in the dorsal lateral pre frontal cortex was much lower than in the control subjects
studies mapping changes in cortical thickness showed that schizophrenics had thinning of the cortex
give evidence that the basal ganglia is the site of brain dysfunction in schizophrenia
(site of action of antipsychotics)
Involved in sensory motor gating
A number of studies reported changes in sizes of nuclei in the basal ganglia occur in schizophrenia relative to the control – resulting in changes in sensory motor processing
what area of the brain is involved in the postive symptoms of schizophrenia
temporal lobe
what area of the brain is involved with the negative symptoms of schizophrenia?
prefrontal cortex
give 4 pieces of indirect, circumstantial evidence to implicate dopamine in the neurchemical basis of schizophrenia
- Reserpine is an antipsychotic – has sedative, calming properties, obtained from indiand herbal snake root. Acts to deplete levels of dopamine in the brain
- Amphetamine causes toxic psychosis in susceptible individuals – elevates dopaminergic levels in the brain, clinicians say this psychosis is indistinguishable from schizophrenia itself. Responds to antipsychotic drugs, phenotypically similar to schizophrenia
- L-DOPA can trigger psychotic episodes – parkinsons treatment, those receiving it sometimes experience psychotic episodes as a side effect,
- Chlorpromazine – the first antipsychotic, works by increasing dopamine turnover
how were chlorpromazine antipsychotic properties discovered?
Discovered by chance (serendipity)
Discovered in the 1940s by a French military surgeon.
Testing derivates of promethysine (an antihistamine) to find beneficial properties in calming agitated patients.
Chlorpromazine properties helps agitated patients
Calmed them but was not a sedative – first use