Dopamine reward prediction error signal

For more on dopamine neurons, see drop down menu 'Subjective value: dopamine neurons'.

According to the frequentist approach, probability reflects the frequency of past events (top left). Reinforcement learning can implement that approach (top right). Monkeys learn to estimate probabilities in choice between a fixed known reward probability and different probabilities indicated by new stimuli (bottom left). Dopamine responses to the new stimuli show an indiscriminate novelty response that declines with stimulus experience and is followed shortly later by a differential value response that develops with experience (bottom right). View the report here Lak et al. 2016).

Dopamine optogenetics

Medium efficacy but high specificity (left). Optogenetic stimulation adds to the dopamine response to juice reward (top center), which enhances the dopamine response to a reward predicting stimulus, compared to juice alone (centre bottom) and enhances the choice probability for that stimulus (right). View the report here (Stauffer et al. 2016).