Neuronal reward mechanisms.

We investigate principal neurophysiological reward and risk functions during learning, decision-making under risk and social interaction in a variety of novel experiments using proven methods. 1) We study subjective value and adaptive prediction error signals of dopamine neurons while monkeys learn stochastic rewards, experience reward contrasts and make risky decisions. We hypothesise that dopamine neurons track predicted values of choice options for decision-making under risk. 2) In fron tal cortex, where lesions alter risk behaviour, we study how risk affects value coding, and we track the risk associated with choice objects and actions as important decision variable. 3) In monkeys facing each other in a social setting, we study dopamine neurons and neurons in the striatum with convergent influences from different reward structures. Monkeys observe each other while encountering prediction errors during learning, obtaining reward and give reward to one another (agency). We al so investigate the prosocial capacity of rhesus monkeys for coordination and possibly cooperation, using procedures successful in birds. 4) We translate some of these studies to human imaging using the same behavioural tasks. These studies advance our knowledge on normal reward and risk processes underlying decision-making and extend primate neurophysiology to humans to facilitate translational studies on patients.