Kim Sara Y, Kark Sarah M, Daley Ryan T, Alger Sara E, Rebouças Daniella, Kensinger Elizabeth A, Payne Jessica D
Department of Psychology, University of Notre Dame, Notre Dame, Indiana.
Department of Psychology, Boston College, Chestnut Hill, Massachusetts.
Hippocampus. 2020 Aug;30(8):829-841. doi: 10.1002/hipo.23138. Epub 2019 Jul 17.
Sleep and stress independently enhance emotional memory consolidation. In particular, theta oscillations (4-7 Hz) during rapid eye movement (REM) sleep increase coherence in an emotional memory network (i.e., hippocampus, amygdala, and prefrontal cortex) and enhance emotional memory. However, little is known about how stress during learning might interact with subsequent REM theta activity to affect emotional memory. In the current study, we examined whether the relationship between REM theta activity and emotional memory differs as a function of pre-encoding stress exposure and reactivity. Participants underwent a psychosocial stressor (the Trier Social Stress Task; n = 32) or a comparable control task (n = 32) prior to encoding. Task-evoked cortisol reactivity was assessed by salivary cortisol rise from pre- to post-stressor, and participants in the stress condition were additionally categorized as high or low cortisol responders via a median split. During incidental encoding, participants studied 150 line drawings of negative, neutral, and positive images, followed by the complete color photo. All participants then slept overnight in the lab with polysomnographic recording. The next day, they were given a surprise recognition memory task. Results showed that memory was better for emotional relative to neutral information. Critically, these findings were observed only in the stress condition. No emotional memory benefit was observed in the control condition. In stressed participants, REM theta power significantly predicted memory for emotional information, specifically for positive items. This relationship was observed only in high cortisol responders. For low responders and controls, there was no relationship between REM theta and memory of any valence. These findings provide evidence that elevated stress at encoding, and accompanying changes in neuromodulators such as cortisol, may interact with theta activity during REM sleep to promote selective consolidation of emotional information.
睡眠和压力可独立增强情绪记忆巩固。具体而言，快速眼动（REM）睡眠期间的θ振荡（4 - 7赫兹）会增加情绪记忆网络（即海马体、杏仁核和前额叶皮质）中的连贯性，并增强情绪记忆。然而，对于学习期间的压力如何与随后的REM θ活动相互作用以影响情绪记忆，我们知之甚少。在当前的研究中，我们考察了REM θ活动与情绪记忆之间的关系是否会因编码前的压力暴露和反应性而有所不同。参与者在编码前接受了心理社会应激源（特里尔社会应激任务；n = 32）或可比的对照任务（n = 32）。通过应激源前后唾液皮质醇的升高来评估任务诱发的皮质醇反应性，并且通过中位数分割将处于应激状态的参与者进一步分为高皮质醇反应者或低皮质醇反应者。在偶然编码期间，参与者研究了150张负面、中性和正面图像的线条图，随后是完整的彩色照片。然后，所有参与者在实验室中过夜睡眠，并进行多导睡眠图记录。第二天，他们接受了一项惊喜识别记忆任务。结果表明，相对于中性信息，情绪记忆更好。至关重要的是，这些发现仅在应激条件下观察到。在对照条件下未观察到情绪记忆益处。在有压力的参与者中，REM θ功率显著预测了情绪信息的记忆，特别是对于正面项目。这种关系仅在高皮质醇反应者中观察到。对于低反应者和对照组，REM θ与任何效价的记忆之间均无关系。这些发现提供了证据，表明编码时升高的压力以及诸如皮质醇等神经调节剂的伴随变化，可能与REM睡眠期间的θ活动相互作用，以促进情绪信息的选择性巩固。
