Daily torpor is an energy-saving process that evolved as an extension of non-rapid eye movement (NREM) sleep mechanisms. In many heterothermic species there is a relation between torpor expression and the repartition of the different behavioral states of sleep. Despite the presence of sleep during this period of hypothermia, torpor induces an accumulation of sleep debt which results in a rebound of sleep in mammals. We aimed to investigate the expression of sleep-wake rhythms and delta waves during daily torpor at various ambient temperatures in a non-human primate model, the gray mouse lemur (Microcebus murinus). Cortical activity was measured with telemetric electroencephalography (EEG) recordings in the prefrontal cortex (PFC) during the torpor episode and the next 24 h following hypothermia. Gray mouse lemurs were divided into two groups: the first group was subjected to normal ambient temperatures (25°C) whereas the second group was placed at lower ambient temperatures (10°C). Contrary to normal ambient temperatures, sleep-wake rhythms were maintained during torpor until body temperature (Tb) of the animals reached 21°C. Below this temperature, NREM and REM sleep strongly decreased or were absent whereas the EEG became isoelectric. The different states of sleep were proportional to Tbmin during prior torpor in contrast to active phases. Delta waves increased after torpor but low Tb did not induce greater delta power compared to higher temperatures. Our results showed that Tb was a determining factor for the quality and quantity of sleep. Low Tb might be inconsistent with the recovery function of sleep. Heterothermy caused a sleep debt thus there was a rebound of sleep at the beginning of euthermia to compensate for the lack of sleep.

中文翻译：

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在非人灵长类动物灰鼠狐猴（Microcebus murinus）中的每日睡眠和睡眠。

日常工作是一个节能过程，它是非快速眼动（NREM）睡眠机制的扩展。在许多异热物种中，玉米粥的表达与睡眠的不同行为状态的重新分配之间存在关系。尽管在体温过低的这段时间内存在睡眠，但是Torpor引起睡眠债务的积累，从而导致哺乳动物的睡眠反弹。我们的目的是在非人类灵长类动物模型灰色鼠狐猴（Microcebus murinus）中，研究在不同环境温度下每天进行玉米粥期间睡眠觉醒节律和三角波的表达。皮层活动是通过遥测脑电图（EEG）记录在额干发作期间和体温过低后的24小时内前额叶皮层（PFC）中进行的。灰鼠狐猴分为两组：第一组置于正常环境温度（25°C），而第二组置于较低的环境温度（10°C）。与正常环境温度相反，在烘烤过程中保持觉醒节奏，直到动物的体温（Tb）达到21°C。低于此温度，NREM和REM睡眠强烈减少或消失，而EEG变为等电。与活跃期相反，在睡眠之前，不同的睡眠状态与Tbmin成正比。高温后，三角波增加，但与较高的温度相比，较低的Tb不会产生较大的三角功率。我们的结果表明，Tb是决定睡眠质量和数量的因素。低Tb可能与睡眠的恢复功能不一致。