Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
Sleep. 2013 Sep 1;36(9):1377-90. doi: 10.5665/sleep.2970.
To examine the statistical characteristics of short-term sleep-wake architecture and to evaluate their dependence on ultradian and circadian phase.
Observational, time series.
Laboratory.
Ten male adult Sprague-Dawley rats.
N/A.
States of wakefulness (WAKE), rapid eye movement sleep (REM) and nonrapid eye movement sleep (NREM) were recorded in 5-sec epochs over 7 consecutive days. State bout durations were analyzed using parametric regression of survival curves, comparing exponential, biexponential, and power law models. WAKE survival curves were best fit by biexponential models, suggesting that there are two statistically distinct stochastic mechanisms generating two types of WAKE--"brief" WAKE and "long" WAKE. Exponential time constants varied as a function of circadian and ultradian phase, with "long" WAKE showing the largest effect. NREM survival curves exhibited biexponential and monoexponential distributions in light and dark, respectively, with weak effects of ultradian phase. REM survival curves approximated a monoexponential distribution that varied with circadian but not ultradian phase. χ(2) analysis was used in a three-state Markov model to evaluate whether conditional state transition probabilities exhibit the property of first-order dependence. This was partially confirmed, but only after accounting for heterogeneity associated with circadian and ultradian phase. However, there was evidence of residual second-order dependence indicating that additional sources of statistical heterogeneity may remain to be identified.
Sleep-wake state is regulated over short timescales by stochastic mechanisms. When the major sources of heterogeneity are taken into account, including two-component WAKE and NREM states, the sleep-wake system of the rat behaves, to a reasonable approximation, as a Markovian system that is modulated over ultradian and circadian timescales.
研究短期睡眠-觉醒结构的统计特征，并评估其对超昼夜和昼夜相位的依赖性。
观察性、时间序列。
实验室。
10 只成年雄性 Sprague-Dawley 大鼠。
无。
在连续 7 天的时间里，每 5 秒记录一次清醒（WAKE）、快速眼动睡眠（REM）和非快速眼动睡眠（NREM）状态。使用生存曲线的参数回归分析状态持续时间，比较指数、双指数和幂律模型。WAKE 生存曲线最好用双指数模型拟合，表明存在两种统计学上不同的随机机制，产生两种类型的 WAKE——“短暂”WAKE 和“长”WAKE。指数时间常数随昼夜和超昼夜相位变化，“长”WAKE 影响最大。NREM 生存曲线在光照和黑暗中分别呈现双指数和单指数分布，超昼夜相位影响较弱。REM 生存曲线近似单指数分布，随昼夜相位变化而变化，但不受超昼夜相位影响。χ(2)分析用于三状态马尔可夫模型，以评估条件状态转移概率是否具有一阶依赖性。这部分得到了证实，但仅在考虑到与昼夜和超昼夜相位相关的异质性之后。然而，有证据表明存在剩余的二阶依赖性，表明可能还有其他来源的统计异质性有待确定。
睡眠-觉醒状态受随机机制调节，时间尺度较短。当考虑到主要的异质性来源时，包括双组分 WAKE 和 NREM 状态，大鼠的睡眠-觉醒系统在合理的近似程度上表现为一个受超昼夜和昼夜时间尺度调制的马尔可夫系统。
