Nakao M, Nishiyama H, McGinty D, Szymusiak R, Yamamoto M
Neurophysiology and Bioinformatics Laboratory Graduate School of Information Sciences, Tohoku University, Sendai 980-8579, Japan.
Biol Cybern. 1999 Nov;81(5-6):403-14. doi: 10.1007/s004220050571.
We developed a thermoregulatory model of sleep control based on the hypothesis that non-rapid eye-movement sleep participates in homeostatic thermoregulation. This model successfully reproduced several qualitative features of human sleep/wake cycles during entrained as well as the internally desynchronized states. Among the reproduced features, generation mechanisms of the biphasic sleepiness distribution are studied here in the light of the model structure. Harmonic analysis is employed for this purpose. Through linearizations and confining the harmonics of the masking process to the fundamental component, a simplified representation of sleepiness is obtained. The simplified sleepiness is constructed with the fundamental circadian, the second harmonic components, and the constant (DC). The bimodality of the sleepiness is shown to be made by the second harmonic which is added to the fundamental component. The behavior of their amplitudes and phase positions are investigated under the varied sleep/wake durations and phase differences between the oscillators. Since the sleepiness generated by our model is roughly mimicked by the simplified representation under diverse conditions, this simplification can be regarded as adequate. From the behavior of the constituents of respective harmonic components, the fundamental component is shown to originate from the sleep/wake masking process and the circadian oscillators; the second harmonic from the multiplicative interactions between the circadian oscillators and the sleep/wake masking process. These results indicate that the rhythmic processes are principal constituents of the sleepiness, at least in the steady state.
我们基于非快速眼动睡眠参与稳态体温调节这一假设，开发了一种睡眠控制的体温调节模型。该模型成功再现了人类在同步状态以及内部去同步状态下睡眠/觉醒周期的几个定性特征。在此，根据模型结构研究了双相困倦分布的产生机制。为此采用了谐波分析。通过线性化并将掩蔽过程的谐波限制在基波分量，得到了困倦的简化表示。简化的困倦由基本昼夜节律、二次谐波分量和常数（直流）构成。结果表明，困倦的双峰性是由加到基本分量上的二次谐波造成的。在不同的睡眠/觉醒持续时间和振荡器之间的相位差条件下，研究了它们的振幅和相位位置的行为。由于在各种条件下，我们模型产生的困倦大致可由简化表示模拟，所以这种简化可被认为是合适的。从各个谐波分量成分的行为来看，基本分量显示源自睡眠/觉醒掩蔽过程和昼夜节律振荡器；二次谐波源自昼夜节律振荡器与睡眠/觉醒掩蔽过程之间的乘法相互作用。这些结果表明，节律过程至少在稳态下是困倦的主要组成部分。
