Learning about the world Flashcards
What is the main neurotransmitter involved in reward learning (reward-motivated behaviour)?
Dopamine
What characterises the dopamine activity in a schizophrenic person?
Aberrant dopamine activity
- higher D2 receptor density -> higher levels of dopamine
- L-Dopa taken up quicker -> higher production of dopamine
What have molecular imaging suites shown on the association between dopamine activity and psychotic symptoms?
Degree of sensitisation of mesostriatal dopamine system is associated to severity of psychotic symptoms
- > amphetamines and cocaine increase dopamine and worsen symptoms in schizophrenic patients
- > D2 receptor antagonists improve psychotic symptoms
To which neurotransmitter pathway are the negative symptoms of psychosis associated?
Mesocortical pathway
To which neurotransmitter pathway are the positive symptoms of psychosis associated?
Mesolimbic
What is the aim of the treatment of negative symptoms in schizophrenia?
Increase dopamine neurotransmission
What is the aim of the treatment of positive symptoms in schizophrenia?
Slow down dopamine neurotransmission
What are prediction errors?
Dopamine-dependent signal that play a role in learning
- mesolimbic dopaminergic regions
What is the dopaminergic response when there is no prediction of a reward and a reward occurs (Schultz, 1971)?
- Surprise = salient event -> increase in firing when reward is given
- Response variation to unpredicted primary rewards
- > the nice the reward, the higher the signal
What is the dopaminergic response when a reward is predicted and a reward occurs (Schultz, 1971)?
- Dopamine increase at presentation of conditioned stimulus
= recognition that reward will come - Dopamine signal shifts in time from reward to predictive stimulus = prediction learning
- When reward given as expected, there’s no increase in dopamine release
- > no prediction error
What is the dopaminergic response when a reward is predicted but no reward is given (Schultz, 1971)?
Dopamine release decreases to below normal levels
What is the reward prediction learning effect in the study of Schultz (1967)?
Dopamine signal shifts in time from reward to prediction stimulus
What is the effect of expectation and learning on dopamine release?
As learning occurs, dopamine firing adjusts
- when subject geins to expect certain outcome from certain scenario, prediction error becomes smaller and smaller
What is the consequence of the aberrant dopamine activity in schizophrenic patients as explained by Kapur (2003, 2004)?
Aberrant salience and positive symptoms
- Dysregulated firing and/or release of dopamine
- Aberrant sense of novelty and abnormal assignment of salience to stimulant internal representations
- > stimulus that may not be meaningful evokes dopamine firing - Delusions as negative cognitive schema the patient develops to explain aberrant salience
- > an inference is required to account for salient/odd experiences that will be interpreted in meaningful way (e.g. sense of persecution)
-> they shape perception and interpretation of new information
When are psychotic patients treated according to Kapur (2003, 2004)?
When the aberrant salience assigned to stimuli and internal representations impacts on behaviour or causes distress