Processing of Continuously Provided Punishment and Reward in Children with ADHD and the Modulating Effects of Stimulant Medication: An ERP Study

ObjectivesCurrent models of ADHD suggest abnormal reward and punishment sensitivity, but the exact mechanisms are unclear. This study aims to investigate effects of continuous reward and punishment on the processing of performance feedback in children with ADHD and the modulating effects of stimulant medication. Methods15 Methylphenidate (Mph)-treated and 15 Mph-free children of the ADHD-combined type and 17 control children performed a selective attention task with three feedback conditions: no-feedback, gain and loss. Event Related Potentials (ERPs) time-locked to feedback and errors were computed. ResultsAll groups performed more accurately with gain and loss than without feedback. Feedback-related ERPs demonstrated no group differences in the feedback P2, but an enhanced late positive potential (LPP) to feedback stimuli (both gains and losses) for Mph-free children with ADHD compared to controls. Feedback-related ERPs in Mph-treated children with ADHD were similar to controls. Correlational analyses in the ADHD groups revealed that the severity of inattention problems correlated negatively with the feedback P2 amplitude and positively with the LPP to losses and omitted gains. ConclusionsThe early selective attention for rewarding and punishing feedback was relatively intact in children with ADHD, but the late feedback processing was deviant (increased feedback LPP). This may explain the often observed positive effects of continuous reinforcement on performance and behaviour in children with ADHD. However, these group findings cannot be generalised to all individuals with the ADHD, because the feedback-related ERPs were associated with the severity of the inattention problems. Children with ADHD-combined type with more inattention problems showed both deviant early attentional selection of feedback stimuli, and deviant late processing of non-reward and punishment.研究目的：当前针对注意缺陷多动障碍（ADHD，Attention Deficit Hyperactivity Disorder）的主流模型认为，患者存在奖赏与惩罚敏感性异常，但具体的神经机制尚未阐明。本研究旨在探究持续性奖赏与惩罚刺激对注意缺陷多动障碍儿童绩效反馈加工过程的影响，以及中枢兴奋剂类药物的调节效应。 研究方法：本研究共招募15名接受哌甲酯（Methylphenidate, Mph）治疗、15名未接受哌甲酯治疗的注意缺陷多动障碍混合型儿童，以及17名正常对照儿童。所有被试完成一项包含三种反馈条件的选择性注意任务：无反馈、奖赏增益与惩罚损失。同时，提取与反馈事件及错误事件时间锁定的事件相关电位（ERPs，Event Related Potentials）进行计算分析。 研究结果：相较于无反馈条件，所有组别在奖赏增益与惩罚损失条件下的作业正确率均显著提升。与反馈相关的事件相关电位分析显示，三组被试在反馈相关P2成分上未表现出显著组间差异；但未接受哌甲酯治疗的ADHD儿童，其对各类反馈刺激（包括奖赏增益与惩罚损失）的晚正电位（LPP，Late Positive Potential）幅值显著高于正常对照组。而接受哌甲酯治疗的ADHD儿童的反馈相关ERPs模式与正常对照组无明显差异。针对ADHD组的相关性分析结果显示：注意缺陷症状的严重程度与反馈相关P2幅值呈负相关，与惩罚损失及错失奖赏条件下的LPP幅值呈正相关。 研究结论：注意缺陷多动障碍儿童对奖赏与惩罚性反馈的早期选择性注意功能相对完好，但晚期反馈加工过程存在异常（反馈相关LPP幅值升高）。这一发现或可解释既往研究中观察到的持续性强化对ADHD儿童作业表现与行为的积极改善作用。不过，本研究的组间结果无法推广至所有ADHD患者，因为反馈相关ERPs的变化与注意缺陷症状的严重程度显著相关：伴随更严重注意缺陷症状的混合型ADHD儿童，既存在反馈刺激早期注意选择的异常，也存在非奖赏与惩罚性反馈的晚期加工异常。