Sleep Research Laboratory, Department of Pathology and Anatomy, Eastern Virginia Medical School, Norfolk, VA.
Sleep. 2019 Oct 9;42(10). doi: 10.1093/sleep/zsz147.
Sleep, in particular rapid eye movement (REM), has been linked to fear learning and extinction; however, their relationship is poorly understood. We determined how different delays of extinction training (ET) impact fear-conditioned behaviors, changes in sleep, and stress responses.
EEG activity, movement, and body temperature in mice were monitored via telemetry. Following contextual fear conditioning (shock training [ST]), separate groups of mice were reexposed to the context at 24-hour post-ST (24h ET-1) and at 48-hour post-ST (48h ET-1). Post-ET sleep amount and sleep-associated EEG (delta and theta) activity were compared to baseline and to post-ST sleep. Freezing, locomotion, grooming, and rearing were monitored to determine effects of ET on fear behaviors. Body temperature immediately after ET was monitored to assess stress-induced hyperthermia (SIH).
24h ET-1 and 48h ET-1 produced similar freezing and REM reductions, but dissimilar rearing activity and SIH. 24h ET-1 was followed by periods of suppressed REM-associated theta (REM-θ) activity, immediately after ET and during the subsequent dark period. Suppressed REM-θ was specific to sleep after 24h ET-1, and did not occur after ST, nor after 48h ET-1.
ET-1 at 24 and 48 hours after ST was associated with similar freezing and REM amounts, but with differences in other overt behaviors, in REM-θ, and in SIH. Freezing was not predictive of changes in other fear-associated responses. This study demonstrated that consideration of time delay from fear acquisition to extinction is important when assessing the relationships between extinction and behavior, sleep, and stress responses.
睡眠，尤其是快速眼动（REM），与恐惧学习和遗忘有关；然而，它们之间的关系尚不清楚。我们确定了不同的遗忘训练（ET）延迟如何影响恐惧条件反射行为、睡眠变化和应激反应。
通过遥测监测小鼠的脑电图活动、运动和体温。在情景恐惧条件反射（电击训练[ST]）后，分别将小鼠在 ST 后 24 小时（24hET-1）和 ST 后 48 小时（48hET-1）重新暴露于环境中。将 ET 后的睡眠量和与睡眠相关的 EEG（δ 和θ）活动与基线和 ST 后的睡眠进行比较。通过监测冻结、运动、梳理和后肢站立来确定 ET 对恐惧行为的影响。ET 后立即监测体温以评估应激诱导性发热（SIH）。
24hET-1 和 48hET-1 产生相似的冻结和 REM 减少，但不同的后肢站立活动和 SIH。24hET-1 后立即出现 REM 相关θ波（REM-θ）活动抑制，持续到 ET 后和随后的黑暗期。抑制 REM-θ 是 24hET-1 后睡眠的特异性，不会在 ST 后或 48hET-1 后发生。
ST 后 24 和 48 小时的 ET-1 与相似的冻结和 REM 量相关，但与其他明显行为、REM-θ 和 SIH 不同。冻结并不能预测其他与恐惧相关的反应的变化。本研究表明，在评估遗忘与行为、睡眠和应激反应之间的关系时，考虑从恐惧获得到遗忘的时间延迟是很重要的。
