The P300 and Reward Valence, Magnitude, and Expectancy in Outcome Evaluation

The event-related potential (ERP) component P300 has, been implicated in outcome evaluation and reward processing, but it is still controversial to what aspects of reward processing it is sensitive. This study manipulated reward valence, reward magnitude, and magnitude expectancy orthogonally in a monetary gambling. task and observed both the valence and the magnitude effects on P300. Moreover, these effects were modulated by whether the amount of reward was expected or unexpected on the basis of a previous cue. The FRN (feedback-related negativity) was found to be sensitive to reward valence and magnitude expectancy, but the expectancy effect was observed only when the amount of reward involved was small. These findings demonstrate that the P300 is sensitive to both reward magnitude and reward valence, but only when the amount of reward is expected