Pornpattananangkul Narun, Nusslock Robin
Department of Psychology, Northwestern University, Evanston, IL, United States; Department of Psychology, University of Singapore, Singapore.
Department of Psychology, Northwestern University, Evanston, IL, United States.
Neuropsychologia. 2016 Oct;91:141-162. doi: 10.1016/j.neuropsychologia.2016.07.037. Epub 2016 Jul 29.
While almost everyone discounts the value of future rewards over immediate rewards, people differ in their so-called delay-discounting. One of the several factors that may explain individual differences in delay-discounting is reward-processing. To study individual-differences in reward-processing, however, one needs to consider the heterogeneity of neural-activity at each reward-processing stage. Here using EEG, we separated reward-related neural activity into distinct reward-anticipation and reward-outcome stages using time-frequency characteristics. Thirty-seven individuals first completed a behavioral delay-discounting task. Then reward-processing EEG activity was assessed using a separate reward-learning task, called a reward time-estimation task. During this EEG task, participants were instructed to estimate time duration and were provided performance feedback on a trial-by-trial basis. Participants received monetary-reward for accurate-performance on Reward trials, but not on No-Reward trials. Reward trials, relative to No-Reward trials, enhanced EEG activity during both reward-anticipation (including, cued-locked delta power during cue-evaluation and pre-feedback alpha suppression during feedback-anticipation) and reward-outcome (including, feedback-locked delta, theta and beta power) stages. Moreover, all of these EEG indices correlated with behavioral performance in the time-estimation task, suggesting their essential roles in learning and adjusting performance to maximize winnings in a reward-learning situation. Importantly, enhanced EEG power during Reward trials, as reflected by stronger 1) pre-feedback alpha suppression, 2) feedback-locked theta and 3) feedback-locked beta, was associated with a greater preference for larger-but-delayed rewards in a separate, behavioral delay-discounting task. Results highlight the association between a stronger preference toward larger-but-delayed rewards and enhanced reward-processing. Moreover, our reward-processing EEG indices detail the specific stages of reward-processing where these associations occur.
虽然几乎每个人都低估未来奖励相对于即时奖励的价值，但人们在所谓的延迟折扣方面存在差异。可能解释延迟折扣个体差异的几个因素之一是奖励处理。然而，为了研究奖励处理中的个体差异，需要考虑每个奖励处理阶段神经活动的异质性。在这里，我们使用脑电图（EEG），根据时频特征将与奖励相关的神经活动分为不同的奖励预期和奖励结果阶段。37名个体首先完成了一项行为延迟折扣任务。然后，使用一项单独的奖励学习任务（称为奖励时间估计任务）来评估奖励处理的脑电图活动。在这项脑电图任务中，参与者被要求估计时间持续时间，并在每次试验的基础上获得表现反馈。参与者在奖励试验中因准确表现而获得金钱奖励，但在无奖励试验中则没有。与无奖励试验相比，奖励试验在奖励预期（包括线索评估期间的线索锁定δ功率和反馈预期期间的反馈前α抑制）和奖励结果（包括反馈锁定的δ、θ和β功率）阶段都增强了脑电图活动。此外，所有这些脑电图指标都与时间估计任务中的行为表现相关，表明它们在奖励学习情境中学习和调整表现以最大化收益方面的重要作用。重要的是，奖励试验期间脑电图功率增强，表现为更强的1）反馈前α抑制、2）反馈锁定的θ和3）反馈锁定的β，与在单独的行为延迟折扣任务中对更大但延迟的奖励有更大偏好相关。结果突出了对更大但延迟奖励的更强偏好与增强的奖励处理之间的关联。此外，我们的奖励处理脑电图指标详细说明了这些关联发生的奖励处理的具体阶段。
