Dopamine responses comply with basic assumptions of formal learning theory

According to contemporary learning theories, the discrepancy, or error, bet ween the actual and predicted reward determines whether learning occurs whe n a stimulus is paired with a reward. The role of prediction errors is dire ctly demonstrated by the observation that learning is blocked when the stim ulus is paired with a fully predicted reward. By using this blocking proced ure, we show that the responses of dopamine neurons to conditioned stimuli was governed differentially by the occurrence of reward prediction errors r ather than stimulus-reward associations alone, as was the learning of behav ioural reactions. Both behavioural and neuronal learning occurred predomina ntly when dopamine neurons registered a reward prediction error at the time of the reward. Our data indicate that the use of analytical tests derived from formal behavioural learning theory provides a powerful approach for st udying the role of single neurons in learning.