Activity in the midbrain responds to unexpected changes in outcome identity (i.e. sensory prediction error) but does not scale with perceptual distance between expected and receipt reward.
The anticipation of rewards turns out to have its own hedonic value, on top of that of the reward itself; a wide range of behavioral and neurophysiological data suggest that this anticipation is boosted by prediction errors.
Midbrain dopamine neurons in rats signal discrepancies between predicted and actual rewards, regardless of whether the rewards are predicted on the basis of experience or inference.
The formation and refinement of prediction error circuits relies on an experience-dependent balance of excitation and inhibition in canonical microcircuits.
Multivariate analyses of human electrophysiological recordings revealed that the brain represents unexpected visual stimuli with greater fidelity than expected stimuli which arose independently of simple habituation arising from repetition.