Lecture: 9 Learning and schizophrenia

Describe the study done by Waelti, Dickinson & Schultz 2001?

Initially trained monkeys to associate pictures with juice or absence of juice, and then measured dopamine activation in single cells based on if the association was unexpected, or expected based on pior conditioning.
They found that the dopamine is associated with surprise, or negative or positive prediction error. The monkeys who were presented with juice when it was unexpected had higher dopamine levels, whereas the monkeys who weren’t presented with juice when it was expected had null or zero dopamine levels.

Describe the link between learning and dopamine?

Dopamine plays a key role in learning about reward, anticipation of rewards typically increases the level of dopamine in the brain.
This anticipation can be linked with the attribution of motivational salience, i.e. what we should be paying attention to things that should be learnt.

What is the link between dopamine and psychosis?

There is a strong link between dopamine and psychosis, higher levels of dopamine normally connotes psychotic symptoms, whereas lower levels connotate the absence of psychotic symptoms.
Suggested by the effect of dopamine agonist (which increase dopamine) increase psychotic symptoms, and the effect of dopamine antagonist (which decrease dopamines) decreasing symptoms.
SZ patients typically show very high levels of dopamine, especially if they have positive symptoms.

Describe the aberrant salience hypothesis?

The idea that SZ may suffer from delusions and hallucinations due to an excess amount of dopamine neurons that mediate too much the attribution of motivational salience. This leads to a higher attention being paid to all cues that lead to international representations having too much salience (creating hallucinations), and result in delusions which are simply attempts to make sense of abnormally salient events.

Do schizophrenic patients display latent inhibition? Explain why or why not?

Schizophrenic patients with high psychotic symptoms do not display latent inhibition.
This is suggested by Rascle et al (2001) study in which as well as testing if preexposure of unrelated stimuli would decrease sequential learning of that stimuli for healthy controls, testing the effect of preexposure on Schizophrenic patients with low or high psychotic symptoms. They found that SZ patients had equal levels of learning whether preexposed to inconsequential stimuli or not

Do healthy adults display Latent Inhibition given pro-psychotic and anti-psychotic mediation?

Latent inhibition - is abolished in adults when amphetamine is applied. Latent Inhibition is enchanted by antipsychotics.

What did Morris, Griffiths, Le Pelley & Weikert (2013) find/do?

In stage 1, trained participants with high, low psychotic symptoms and controls, with predictive or non-predictive cues of seeds predicting trees. In stage 2, all cues came to predict trees. At the test, participants were measured on their CR if they expected their cues to be able to predict.
This study found that high psychotic symptom SZ participants learnt everything with high confidence, as compared to control and low psychotic participant whom have confidence cores in agreement with the predictiveness principles, that is, non-predictive cues were learnt with lower confidence as compared to high predictive cues.
Generally, this supports that aberrant salience hypothesis