Northwestern University, Evanston, Illinois, USA.
Psychophysiology. 2022 Mar;59(3):e13981. doi: 10.1111/psyp.13981. Epub 2021 Nov 30.
The Reward-Positivity (RewP) is a frontocentral event-related potential elicited following reward and punishment feedback. Reinforcement learning theories propose the RewP reflects a reward prediction error that increases following more favorable (vs. unfavorable) outcomes. An alternative perspective, however, proposes this component indexes a salience-prediction error that increases following more salient outcomes. Evidence from prior studies that included both reward and punishment conditions is mixed, supporting both accounts. However, these studies often varied how feedback stimuli were repeated across reward and punishment conditions. Differences in the frequency of feedback stimuli may drive inconsistencies by introducing salience effects for infrequent stimuli regardless of whether they are associated with rewards or punishments. To test this hypothesis, the current study examined the effect of outcome valence and stimulus frequency on the RewP and neighboring P2 and P3 components in reward, punishment, and neutral contexts across two separate experiments that varied how often feedback stimuli were repeated between conditions. Experiment 1 revealed infrequent feedback stimuli generated overlapping positivity across all three components. However, controlling for stimulus frequency, experiment 2 revealed favorable outcomes that increased RewP and P3 positivity. Together, these results suggest the RewP reflects some combination of reward- and salience-prediction error encoding. Results also indicate infrequent feedback stimuli elicited strong salience effects across all three components that may inflate, eliminate, or reverse outcome valence effects for the RewP and P3. These results resolve several inconsistencies in the literature and have important implications for electrocortical investigations of reward and punishment feedback processing.
奖励正波（RewP）是一种在奖励和惩罚反馈后产生的额前正中事件相关电位。强化学习理论提出，RewP 反映了一种奖励预测错误，即在出现更有利（与不利相比）的结果时会增加。然而，另一种观点认为，该成分指数了一种突显预测错误，即在出现更显著的结果时会增加。先前的研究包含奖励和惩罚条件，这些研究的证据相互矛盾，支持了这两种观点。然而，这些研究经常改变奖励和惩罚条件下反馈刺激的重复方式。反馈刺激频率的差异可能会引入对不频繁刺激的突显效应，而不管它们是否与奖励或惩罚有关，从而导致不一致。为了检验这一假设，本研究在两个独立的实验中考察了结果效价和刺激频率对奖励、惩罚和中性条件下 RewP 以及相邻 P2 和 P3 成分的影响，这两个实验在条件之间重复反馈刺激的频率不同。实验 1 表明，不频繁的反馈刺激在所有三个成分中产生了重叠的正性。然而，通过控制刺激频率，实验 2 表明有利的结果增加了 RewP 和 P3 的正性。总之，这些结果表明 RewP 反映了奖励和突显预测错误编码的某种组合。结果还表明，不频繁的反馈刺激在所有三个成分中都引起了强烈的突显效应，这可能会放大、消除或反转 RewP 和 P3 的结果效价效应。这些结果解决了文献中的几个不一致之处，并对奖励和惩罚反馈处理的电皮质研究具有重要意义。
