L-DOPA clinical trials

Pharmacological Modulation of Belief Salience

To provide an initial test of the hypothesis that dopamine mediates the motivational salience of stimuli beyond simple stimulus-reinforcement associations, the researchers propose to undertake a study of the modulation of a) levels of agreement or disagreement with; b) the perceived self- relevance; and c) the perceived interest of propositions expressing beliefs and values in healthy male volunteers using Ii) a dopamine antagonist (the D2-blocker haloperidol), and (ii) a dopamine precursor L-Dopa to increase CNS dopamine transmission. The researchers will also administer the Salience Attribution Task (SAT) which will allow researchers to assess reward-learning processing of simple stimuli using a reaction-time game. This task was utilised by Roiser et al in order to explore whether delusions in medicated patients with schizophrenia were related to impairments in associative learning. The authors hypothesised that associative learning was influenced by D2 receptor blockade. The researchers extend this approach to examine the effect of dopamine modulation on the SAT as a measure of associative learning, a basic neuropsychological process that may be involved in the attribution of salience to beliefs. Finally, the researchers will ask participants to perform a within-subjects dictator game to understand the influence of dopaminergic manipulation of the live attribution of harm intention to partners. The task has been previously validated online. Participants will play against 3 partners in a random order in each drug condition. Each partner will play the participant for 6 trials. One partner will always be fair, one will always be unfair, and one will be 50% unfair. We aim to understand whether potentiating dopamine has an additive effect on the harm intention attributions toward partners, regardless of the behaviour of the partner.