Cognitive and Affective Psychophysiology Laboratory, Department of Experimental Clinical & Health Psychology, Ghent University, Henri Dunantlaan 2, 9000, Ghent, Belgium.
Department of Psychiatry and Medical Psychology, Ghent University, Universitair Ziekenhuis, Ghent, Belgium.
Cogn Affect Behav Neurosci. 2019 Jun;19(3):759-777. doi: 10.3758/s13415-019-00693-4.
Major depression is characterized by abnormal reward processing and reinforcement learning (RL). This impairment might stem from deficient motivation processes, in addition to reduced reward sensitivity. In this study, we recorded 64-channel EEG in a large cohort of major depressive disorder (MDD) patients and matched healthy controls (HC) while they performed a standard RL task. Participants were asked to discover, by trial and error, several hidden stimulus-response associations having different reward probabilities, as enforced using evaluative feedback. We extracted induced fronto-midline Theta (FMT) power time-locked to the response and feedback as neurophysiological index of RL. Furthermore, we assessed approach-related motivation by measuring frontal alpha asymmetry concurrently. At the behavioral level, MDD patients and HCs showed comparable RL. At the EEG level, FMT power systematically varied as a function of reward probability, with opposing effects found at the response and feedback levels. Although this global pattern was spared in MDD, at the feedback level these patients showed however a steep FMT power decrease across trials when reward probability was low. Moreover, they showed impaired approach-related motivation during task execution, as reflected by frontal Alpha asymmetry. These results suggest a dissociation between (globally spared) RL and (impaired) approach motivation in MDD.
重度抑郁症的特征是异常的奖励处理和强化学习（RL）。这种损伤可能源于动机过程不足，除了降低奖励敏感性。在这项研究中，我们在一个大型重度抑郁症（MDD）患者队列和匹配的健康对照组（HC）中记录了 64 通道 EEG，而他们正在执行标准的 RL 任务。参与者被要求通过反复试验发现具有不同奖励概率的几种隐藏的刺激-反应关联，使用评估反馈来强制执行。我们提取了与反应和反馈时间锁定的诱导额中线Theta（FMT）功率，作为 RL 的神经生理指标。此外，我们通过同时测量额部 alpha 不对称性来评估与接近相关的动机。在行为水平上，MDD 患者和 HC 表现出可比的 RL。在 EEG 水平上，FMT 功率系统地随奖励概率而变化，在反应和反馈水平上发现了相反的效果。尽管 MDD 患者中保留了这种全局模式，但在反馈水平上，当奖励概率较低时，这些患者在整个试验中显示出 FMT 功率的急剧下降。此外，他们在任务执行过程中表现出受损的接近相关动机，如额部 Alpha 不对称性所反映的那样。这些结果表明，在 MDD 中 RL（总体保留）和（受损）接近动机之间存在分离。
