neuro: schizophrenia Flashcards
what is major psychoses?
major psychoses ‘madness-cancer of mental illnesses’
examples: schizoaffective disorder = schizophrenia and bipolar
-delusional disorder
-some depressive and manic illnesses
why is schizophrenia important?
-happens early on- in adolescence
-quite prevalent
- disabling and chronic
schizophrenia is more related to thoughts compared to mood.
It is a mental state that is out of touch with reality
Abnormalities of perception thought and ideas
Profound alterations in behaviour
Prevalence of schizophrenia and some stats?
- 1% of the population
-no significant influence of culture ethnicity background etc
-increased in urban areas
-men show an earlier age onset higher behaviour to negative symptoms, co morbid substance abuse etc impart to women who display a late onset of behaviour with more affective symptoms.
Explain the three classes in which schizophrenia symptoms can be grouped
- positive : hallucinations (visual and auditory)
- delusions
-disorganised thought - movement disorders
negative: social withdrawal
-anhedonia (disninterest or pleasure in life)
- poverty of speech
-emotional flatness
cognitive (happens later on) :
- impaired working memory
-impaired attention *
-impaired comprehension
2 or more of these symptoms must persist for at least6 months to be classed as schizophrenia
what are the four phases of schizophrenia?
1- the pro dome : late teens/early twenties - often mistaken for anxiety or depression
2- the active/acute phase: onset of positive symptoms
differentiation of what is and isn’t real becomes difficult
3- Remission: treatment —-> return to normality
4- relapse
how do we know that genes are involved in one of the causes of schizophrenia?
- twins studies
-homozygous twins have a 50% chance of developing schizophrenia if one twin is already diagnosed
-heterozygous twins have a 14% chance if one twin is already diagnosed
This tells us genes have involvement
what are candidate genes?
-genes that are the “risk” or. “ candidate genes” of schizophrenia: so if you have them it does not mean you will 100% have schizophrenia, but more risk
The genes associated with dopamine metabolism, have been associated with increasing risk of developing schizophrenia.
So scz is not directly inherited, but it can run in families
Candidate risk genes : gene deletion, gene mutation
what research has been shown to cause schizophrenia?
- pregnancy birth complications during the influenza season
- a Finnish study reported a spike in scz for people who were foetuses during the 1957 influenza epidemic
- pregnant women in the uk are advised to be vaccinated against seasonal flu
Low birth weight, premature birth, asphyxia during birth
What are some environmental factors for schizophrenia?
- pregnancy/birth complications
- stress
- drug use
what is the dopamine theory?
mesolimbic pathway: pathway for dopamine
dopamernergic neurones that project from the ventral tegmental area to the amygdala to the hippocampus and the nucleus accumbens where dopamine gets released
The dopamine theory says that hyper stimulation of this mesolimbic pathway, is a cause for the positive symptoms of scz (hallucinations, delusions etc)
However, hypo stimulation of the mesocrotical pathway that projects from the VTA to the frontal cortex, is associated with some of the negative symptoms of scz.
why do we think the dopamine theory of schizophrenia is correct?
- you would expect the plasma and CSF dopamine levels to be higher, however there is no clear change in CSF concentration.
-the reason why we think it’s correct is bc all of the anti psychotics work by blocking the dopamine d2 receptor, you get a decrease in positive symptoms of schizophrenia.
what is the difference in brain structure between someone with scz and someone without?
with scz:
- overall brain size slightly smaller
- reductions in grey matter
- enlarged lateral ventricles, smaller hippocampus
However nit all people with schizophrenia have such profound structural differences.
what is hypofrontality?
-state of decreased cerebral blood flow in the prefrontal cortex of the brain.
-this is seen with schizophrenic patients.
prefrontal cortex associated with decision making, which is why they find it hard to make decisions.
what is the association with glutamate and schizophrenia?
If you block the glutamate receptor (NMDA) with an NMDA antagonist (ex ketamine) , it is said to cause hallucinations ans thought disorders.
-they looked into the brains and found a low level of glutamate, and a low glutamate receptor density in the prefrontal cortex.
- experiment done on a mouse where the NMDA receptor expression was downregulated, they began to show the symptoms associated with schizophrenia.
how is serotonin related to schizophrenia?
- evidence :
LSD (which is a hallucinogen) is a partial 5HT agonist, which causes hallucinations. So blocking the serotonin receptor causes antipsychotic effects.
