Schizophrenia Flashcards
When is the average onset of SZ?
Teen/YA
Which hallucinations are mostly seen in SZ?
Auditory
What is a delusion?
Fixed, rigid belief that does not waver when pressed
Different from any cultural, religious, social background
What are the negative symptoms of SZ?
Withdrawal Poor attention Anhedonia Lethargy Speech reduction
What is passivity phenomena?
Belief that not in full control of actions
What is the lifetime risk of SZ with 2 SZ parents?
45%
What is the concordance between MZ twins?
45%
What is the concordance between DZ twins?
18%
What is a good prognosis a/w?
Being female Sudden onset Married Good premorbid state FHx of mood disorder No ventricular enlargement
How is white matter affected?
Decrease in size in corona radiata and corpus callosum
Kelly et al 2018
How is grey matter affected?
Affected between illness onset
Neuropil elimination
Progressive over disease
What is a neuropil?
Dense network of nerve fibres
With their branches and synapses
Also glial filaments.
Which structures have significant decrease in size?
Hippocampus Amygdala Thalamus Accumbens Lateral vents Palidum
Ven Erp TG et al 2016
How is imaging used to diagnose SZ?
Its not
One image on its own isn’t enough
How might AI be developed to diagnose SZ?
Uses a digital screening tool to phenotype patients and predict disease
Done by measuring the semantic density in patients own natural language
Explain the corollary discharge hypothesis
When motor command happens it sends an “efference copy” out which is processed as the predicted sensory input
Due to transmission issues, reduced white matter and demyelination, this does not match the actual sensory input in SZ - not then perceived as self-generated
(Stephan et al 2009)
What is the corollary discharge system’s main function?
To differentiate between self-generated and external action
Why may corollary discharge abnormalities cause auditory “hallucinations”?
Due to reduced white matter tracts there is reduced communication between Broca’s and Wernicke’s area.
Speech is then not recognised as self-generated
Evidence is limited for this
Stephean et al 2009
What are the two different components to a sense of agency?
Feeling of agency
Judgement of agency
Why may sense of agency be altered?
Dysfunction of communication between action and perception
Similar to abnormal corollary discharge
What are the negative side effects of d2 blockade?
Parkinsonism
Dyskinesias
Give examples of traditional antipsychotics
Haloperidol
Chlorpromazine
Give examples of atypical antipsychotics
Clozapine, risperidone, quetiapine
What is the major side effect of clozapine?
Agranulocytosis
How do antipsychotics normalise salience?
Dampen salience acquisition (as needs d2) so that there can be re-learning of event value
How does abnormal salience come about?
Dysregulated DA function leads SZ patients to draw the wrong meaning from things
Summarise the Whitford et al Hypothesis of SZ Causation
Some kinda genetic trigger
Cause abnormally structured myelin to abnormally insulate
Leads to corollary discharge issues and abnormal agency
Treatable by DA block
Explain what the genetic trigger does in the Whitford hypothesis
Causes abnormal expression of oligodendrocyte linked gene during pre-pubertal myelination of the association cortex
Explain how an abnormal sense of agency comes about according to the Whitford hypothesis of SZ causation?
Myelin abnormally insultes the axon so signals get to the sensory cortex at different times and cant match up
Own actions not tagged as such and this leads to abnormal agency
What did Roy et al 2007 find in purposely disrupted oligodendrocyte growth in mice?
Hyperdopaminergia
Where are the biggest white matter abnormalities?
Corona radiate and corpus callosum
How did Hauser et al 2011 display the enhanced agency in SZ?
Asked patients to produce a drum beat and then played more drum taps over it
Asked if what they head was self generated or not
SZ patients more likely to attribute the sound played to their own tapping action
Why is there though to be increased salience in SZ?
Too much DA
mesolimbic DA needed to attribute importance to events/items
How do antipsychotics work to combat salience?
Dampen down DA to basically make nothing salient
Then allows normal salience to re-form
Which receptors is punishment avoidance related to?
D2
Which receptors is reward-learning related to?
D1
