Center for Neural Science, New York University, New York, NY 10003.
Department of Psychology, New York University, New York, NY 10003.
Proc Natl Acad Sci U S A. 2017 Oct 17;114(42):11241-11246. doi: 10.1073/pnas.1702565114. Epub 2017 Oct 2.
In a dynamic environment, sources of threat or safety can unexpectedly change, requiring the flexible updating of stimulus-outcome associations that promote adaptive behavior. However, aversive contexts in which we are required to update predictions of threat are often marked by stress. Acute stress is thought to reduce behavioral flexibility, yet its influence on the modulation of aversive value has not been well characterized. Given that stress exposure is a prominent risk factor for anxiety and trauma-related disorders marked by persistent, inflexible responses to threat, here we examined how acute stress affects the flexible updating of threat responses. Participants completed an aversive learning task, in which one stimulus was probabilistically associated with an electric shock, while the other stimulus signaled safety. A day later, participants underwent an acute stress or control manipulation before completing a reversal learning task during which the original stimulus-outcome contingencies switched. Skin conductance and neuroendocrine responses provided indices of sympathetic arousal and stress responses, respectively. Despite equivalent initial learning, stressed participants showed marked impairments in reversal learning relative to controls. Additionally, reversal learning deficits across participants were related to heightened levels of alpha-amylase, a marker of noradrenergic activity. Finally, fitting arousal data to a computational reinforcement learning model revealed that stress-induced reversal learning deficits emerged from stress-specific changes in the weight assigned to prediction error signals, disrupting the adaptive adjustment of learning rates. Our findings provide insight into how stress renders individuals less sensitive to changes in aversive reinforcement and have implications for understanding clinical conditions marked by stress-related psychopathology.
在动态环境中，威胁或安全的来源可能会出人意料地发生变化，这需要灵活地更新促进适应性行为的刺激-结果关联。然而，我们需要更新对威胁的预测的令人厌恶的环境通常以压力为标志。急性应激被认为会降低行为灵活性，但它对厌恶价值的调节影响尚未得到很好的描述。鉴于应激暴露是焦虑和创伤相关障碍的一个突出风险因素，这些障碍的特征是对威胁的持续、不灵活的反应，在这里，我们研究了急性应激如何影响威胁反应的灵活更新。参与者完成了一个厌恶学习任务，其中一个刺激与电击呈概率相关，而另一个刺激则表示安全。一天后，参与者接受急性应激或对照处理，然后在反转学习任务中完成，在该任务中，原始的刺激-结果关联发生了变化。皮肤电导和神经内分泌反应分别提供了交感神经兴奋和应激反应的指标。尽管初始学习相同，但与对照组相比，应激组在反转学习中表现出明显的损伤。此外，参与者之间的反转学习缺陷与α-淀粉酶水平升高有关，α-淀粉酶是去甲肾上腺素活动的标志物。最后，将唤醒数据拟合到计算强化学习模型中表明，应激诱导的反转学习缺陷源于预测误差信号权重的应激特异性变化，破坏了学习率的适应性调整。我们的发现提供了关于应激如何使个体对厌恶强化的变化不敏感的见解，并对理解以应激相关精神病理学为特征的临床状况具有重要意义。
