Ginsberg Alexander G, Cruz Madelyn Esther C, Weber Franz, Booth Victoria, Diniz Behn Cecilia G
Department of Mathematics, University of Utah, Salt Lake City, UT, United States.
Department of Mathematics, University of Michigan, Ann Arbor, MI, United States.
Front Neurosci. 2024 Aug 30;18:1431407. doi: 10.3389/fnins.2024.1431407. eCollection 2024.
During sleep periods, most mammals alternate multiple times between rapid-eye-movement (REM) sleep and non-REM (NREM) sleep. A common theory proposes that these transitions are governed by an "hourglass-like" homeostatic need to enter REM sleep that accumulates during the inter-REM interval and partially discharges during REM sleep. However, markers or mechanisms for REM homeostatic pressure remain undetermined. Recently, an analysis of sleep in mice demonstrated that the cumulative distribution function (CDF) of the amount of NREM sleep between REM bouts correlates with REM bout duration, suggesting that time in NREM sleep influences REM sleep need. Here, we build on those results and construct a predictive measure for the propensity to enter REM sleep as a function of time in NREM sleep since the previous REM episode.
The REM propensity measure is precisely defined as the probability to enter REM sleep before the accumulation of an additional pre-specified amount of NREM sleep.
Analyzing spontaneous sleep in mice, we find that, as NREM sleep accumulates between REM bouts, the REM propensity exhibits a peak value and then decays to zero with further NREM accumulation. We show that the REM propensity at REM onset predicts features of the subsequent REM bout under certain conditions. Specifically, during the light phase and for REM propensities occurring before the peak in propensity, the REM propensity at REM onset is correlated with REM bout duration, and with the probability of the occurrence of a short REM cycle called a sequential REM cycle. Further, we also find that proportionally more REM sleep occurs during sequential REM cycles, supporting a correlation between high values of our REM propensity measure and high REM sleep need.
These results support the theory that a homeostatic need to enter REM sleep accrues during NREM sleep, but only for a limited range of NREM sleep accumulation.
在睡眠期间，大多数哺乳动物在快速眼动（REM）睡眠和非快速眼动（NREM）睡眠之间交替多次。一个常见的理论认为，这些转换受一种“沙漏状”的稳态需求支配，即进入在REM间隔期间积累并在REM睡眠期间部分释放的REM睡眠。然而，REM稳态压力的标志物或机制仍未确定。最近，一项对小鼠睡眠的分析表明，REM发作之间的NREM睡眠量的累积分布函数（CDF）与REM发作持续时间相关，这表明NREM睡眠的时间会影响REM睡眠需求。在此，我们基于这些结果构建了一种预测指标，用于衡量自上次REM发作以来进入REM睡眠的倾向与NREM睡眠时间的函数关系。
REM倾向指标被精确地定义为在额外积累预先指定量的NREM睡眠之前进入REM睡眠的概率。
通过分析小鼠的自发睡眠，我们发现，随着REM发作之间NREM睡眠的积累，REM倾向呈现出一个峰值，然后随着NREM睡眠的进一步积累而衰减至零。我们表明，在某些条件下，REM发作时的REM倾向可预测随后REM发作的特征。具体而言，在光照阶段以及对于在倾向峰值之前出现的REM倾向，REM发作时的REM倾向与REM发作持续时间以及一种称为连续REM周期的短REM周期出现的概率相关。此外，我们还发现，在连续REM周期中发生的REM睡眠比例更高，这支持了我们的REM倾向指标的高值与高REM睡眠需求之间的相关性。
这些结果支持了这样一种理论，即进入REM睡眠存在一种稳态需求，这种需求在NREM睡眠期间积累，但仅在NREM睡眠积累的有限范围内存在。
