biological explanations of schizophrenia Flashcards
2 explanations ?
- dopamine hypothesis (sidekick)
- structural abnormalities (superhero)
how was the link between dopamine and SZ established ?
Parkinson’s disease sufferers have low levels of dopamine and take the drug L-dopa to increase these levels reducing Parkinson’s symptoms
- however patients suffered SZ type symptoms as a result
what is dopamine?
a neurotransmitter that causes neurons to fire
what was the original dopamine hypothesis?
states SZ suffered from excessive dopamine that caused neurons to fire too often and transmit too many messages, high dopamine leads to positive symptoms
why is the original hypothesis claimed to be too simple/basic?
as they discovered several subtypes of dopamine receptor sites D1-D5 which were widely distributed in the cerebral cortex in the limbic system
why was the D2 receptor of interest ?
as it showed the impact of antipsychotic drugs and became the main focus of the dopamine hypothesis
function of the limbic system?
emotions and memory
2 main pathways of the limbic system?
- mesolimbic pathway
- mesocortical pathway
evaluation of dopamine hypothesis ?
research evidence - supported by evidence of psychoactive drugs such as cocaine which produce similar to SZ behaviour. Additionally Parkinson’s disease sufferers take L-dape to increase low levels of dopamine which sometimes causes SZ symptoms. all this evidence suggests that dopamine levels are involved in the positive symptoms of schizophrenia
who is Emil kreapelin?
the first psychiatrist to classify schizophrenia, he believed that SZ was an organic brain disease which included structural abnormalities
3 structural abnormalities ?
- enlarged ventricles
- cortical atrophy
- reversed cerebral asymmetry
what are enlarged ventricles ?
ventricles are cavities that produce and transport cerebrospinal fluid which protects and stabilises the brain and spinal cord, theres 4 ventricles. in some individuals with SZ the ventricles seem to be larger than those without SZ
researcher for enlarged ventricles?
Andreasen - studied MRI scans of those with and without SZ, found those with SZ had ventricles 20% to 50% larger than in controls
what is cortical atrophy?
cortical atrophy is the loss of neurons in the cerebral cortex, it can occur all over the brain making it look like it had shrunk. if it happens in a limited area then the atrophy will affect the cognitive functions of that particular area. Atrophy appears to affect 20% to 35% of people with chronic SZ
researcher for cortical atrophy ?
VIta - used CAT cans to assess 124 people with SZ and 45 in controls, they found 33% of the induviduals with SZ shows moderate to severe atrophy
what is reversed cerebral asymmetry ?
in most individuals without SZ the left hemisphere is slightly larger than the right however some with SZ the right hemisphere is notably larger than the left, this is relevant when considering language function which is found in the left hemisphere, this perhaps could explain logia or a poverty of speech often seen in those with SZ
researcher for reversed cerebral asymmetry ?
luchins - used CAT scans and compared 80 right handed people without SZ to 57 right handed people with SZ. he found an increase in the ‘reversals’ in both the frontal and occipital lobes of those with SZ but only in those with no form of atrophy.
what are the 2 evaluation points for structural abnormalities?
- research evidence
- structural abnormalities are not only linked to SZ
structural abnormalities - research evidence ?
cortical atrophy - Vita CAT scans
reversed cerebral asymmetry - luchins CAT scans
enlarged ventricles - andreason MRI scans
abnormalities are not only linked to SZ?
weakness - structural abnormalities are evident in other mental health conditions. Paul Roy et al found those with bipolar to also have enlarged ventricles therefore causing overlapping symptoms resulting in similar structural abnormalities
- issue is diagnosing SZ as it can result in misdiagnosis due to similar abnormalities
