what are the two diagnostic systems for sz?
ICD10 and DSM V
what are the four first rank symptoms of sz?
- delusion
- hallucinations
- thought disorder: passivity of thought
- passivity experiences: delusion of control
what kind of hallucinations occur commonly in sz?
auditory (visual are rare and typically occur in elderly confusional states)
what are auditory hallucinations?
they are not auditory misperception- it sounds like real speech in external space
what are command hallucinations?
an auditory hallucination- persistently hearing a voice in external space telling the patient what to do
what are delusions?
These are fixed rigidly held beliefs that are not understandable on the basis of a patient’s cultural background.
what are examples of negative symptoms? (7)
These are;
- persistent loss of usual activities and interests
- apathy
- blunted emotional responses
- speech reduction, social withdrawal
- impaired attention
- anhedonia
- lethargy
what is passivity phenomena?
This is the patients belief that they are no longer in control of their actions, feelings or thoughts. They are controlled by an external agent that tells them how to act, feel or think. (relatively rare)
what does the positive and negative syndrome scale detail?
positive symptoms
negative symptoms
general psychopathology
what can symptoms of sz possibly be explained by?
abnormalities in the experience of;
- salience (hallucinations and delusions)
- agency (passivity phenomena)
what does Whitford’s theory state?
SZ arises because of some incompletely understood genetic trigger (e.g. sex hormone linked) during late adolescence/early adulthood. E.g. the trigger causes abnormal expression of oligodendrocyte-linked genes during pre-pubertal myelination of the association cortices.
components of Whitford’s theory of sz include; (6)
- Genetic abnormalities in schizophrenia
- Abnormal brain white matter (e.g. measured by fractional anisotropy DTI)
- Corollary discharge hypothesis and abnormalities
- Abnormal sense of agency and passivity phenomena symptoms
- Hyperdopaminergia, D2 receptor blockers antipsychotics, abnormal salience
- Grey matter abnormalities in schizophrenia.
what is the likelihood of developing sz if both parents have sz?
45%
if a child with a mother with sz is adopted by non-sz parents, what is the likelihood the child develops sz?
13% (same as if it was raisied by sz parents)
what are the problems with genetic sz studies?
- even with many 1000s of patients there are still problems with replication between studies.
- Multiple genes in each have a very small effect and the molecular genetics may explain the very small amount of variance.
genetic abnormalities could give rise to what?
white matter abnormalities (study by Kelly in 2018)
what is corollary discharge?
- a motor command (move arm onto table) goes to the motor cortex and a copy is also made of this called the efference copy
- the efference copy goes to the forward model.
- the forward model is there to use the information about the motor command to predict what the sensory consequence will be (corollary discharge)
- there is an area of the brain that compares what the actual sensory feedback is to the corollary discharge and tries to minimise the difference between the two
why do we have corollary discharge?
to inform the CNS about external movements ie. how you know the difference between the external world movement vs. self-generated eye movement.
e.g. when you’re on the train you can distinguish between your eye movements and the movement of the train
how does corollary discharge relate to sz?
- Broca’s area produces speech and the speech is picked up by auditory system and processed in Wernicke’s area
- there is also an internal corollary discharge loop
- if corollary discharge loop is faulty due to impaired white matter tract integrity, your internal voice may not be recognised by the brain as self-generated (hence auditory hallucinations but not all due to this)
what are the two separate cues to the sense of agency?
- Sensorimotor system (corollary discharge)
2. (meta) cognitive system (interprets cues)
what two ways are action and effect linked? (voss 2010)
- Predictively (action predicted to generate a given effect)- corollary discharge
- Retrospectively (interference action caused effect-cognitive mechanism).
what action awareness do healthy subjects have? (predictive and retrospective component)
strong predictive component (corollary discharge) of intentional binding and minimal retrospective component
what did Moore (2012) find out about sz predictive component?
Rather than being a total absence of prediction, patients were generating imprecise predictions rather than no predictions.
The outcome predictions were equally strong in high and low probability conditions (implying aberrant dopamine signalling).
how does hyperdopaminergia come about?
If the brains response to constantly experiencing internally generated events as unexpected external events is to increase dopamine firing then hyperdopaminergia results.
