Showing papers by "Steven H. Strogatz published in 1986"

Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle.

Abstract: Human circadian rhythms were once thought to be insensitive to light, with synchronization to the 24-hour day accomplished either through social contacts or the sleep-wake schedule. Yet the demonstration of an intensity-dependent neuroendocrine response to bright light has led to renewed consideration of light as a possible synchronizer of the human circadian pacemaker. In a laboratory study, the output of the circadian pacemaker of an elderly woman was monitored before and after exposure to 4 hours of bright light for seven consecutive evenings, and before and after a control study in ordinary room light while her sleep-wake schedule and social contacts remained unchanged. The exposure to bright light in the evening induced a 6-hour delay shift of her circadian pacemaker, as indicated by recordings of body temperature and cortisol secretion. The unexpected magnitude, rapidity, and stability of the shift challenge existing concepts regarding circadian phase-resetting capacity in man and suggest that exposure to bright light can indeed reset the human circadian pacemaker, which controls daily variations in physiologic, behavioral, and cognitive function.

Circadian regulation dominates homeostatic control of sleep length and prior wake length in humans.

Abstract: During prolonged temporal isolation in caves or windowless rooms, human subjects often develop complicated sleep-wake patterns. Seeking lawful structure in these patterns, we have reanalyzed the spontaneous timing of 359 sleep-wake cycles recorded from 15 internally desynchronized human subjects. The observed sleep-wake patterns obey a simple rule: The phase of the circadian temperature rhythm at bedtime determines the lengths of both prior wake (alpha) and subsequent sleep (rho). From this rule we derive an average alpha:rho relationship that depends on circadian phase. The relationship reconciles the established negative alpha:rho correlation observed in synchronized subjects with the positive alpha:rho correlation found in desynchronized subjects. Our most surprising result concerns the residual deviations of alpha and rho from their circadian phase-adjusted mean values. We report that there is no significant positive correlation between the residuals of alpha and rho, contrary to the prediction of restorative models of sleep duration. Our findings illuminate the mechanisms underlying sleep regulation and provide much-needed tests of mathematical models of the sleep-wake cycle.

The mathematical structure of the human sleep-wake cycle

Abstract: 1. Introduction.- 1.1 Beyond Time.- 1.2 The Rosetta Stone.- 1.3 Overview.- 2. Experimental Background.- 2.1 Phenomena and Terminology.- 2.2 History of Free-Run Studies.- 3. Data Bank.- 3.1 Subject 1.- 3.2 Subject 2.- 3.3 Subject 3.- 3.4 Subject 4.- 3.5 Subject 5.- 3.6 Subject 6.- 3.7 Subject 7.- 3.8 Subject 8.- 3.9 Subject 9.- 3.10 Subject 10.- 3.11 Subject 11.- 3.12 Subject 12.- 3.13 Subject 13.- 3.14 Subject 14.- 3.15 Subject 15.- 3.16 Subject 16.- 3.17 Subject 17.- 3.18 Subject 18.- 3.19 Subject 19.- 3.20 Subject 20.- 3.21 Subject 21.- 3.22 Subject 22.- 4. Patterns.- 4.1 Durations Vary with Circadian Phase of Sleep Onset.- 4.2 Sleep Length and Prior Wake Length.- 4.3 Timing of Wake-Up.- 4.4 Timing of Sleep Onset.- 4.5 Wake-Maintenance Zones.- 4.6 Estimating Circadian Parameters from Sleep Data Alone.- 4.7 Phase-Trapping.- 4.8 Slow Changes in Sleep-Wake Cycle Length.- 4.9 Miscellany and Missing Patterns.- 4.10 Napping and Split Sleep.- 4.11 Summary: The Basic Patterns of Internal Desynchrony.- 5. Theoretical Background.- 5.1 Conceptual Model of Aschoff and Wever.- 5.2 Wever's Noninteractive Model.- 5.3 Kronauer's XY Model: Coupled Van der Pol Oscillators.- 5.4 Conceptual Model of Borbely.- 5.5 Winfree's Half-Model.- 5.6 Gated Pacemaker of Daan, Beersma, and Borbely.- 5.7 Other Approaches.- 6. Analysis of Models.- 6.1 Introduction.- 6.2 BEATS Model.- 6.3 PHASE Model.- 6.4 XY Model of Kronauer et al..- 6.5 Model of Daan et al..- 7. Simulations.- 7.1 Transition from Synchrony to Desynchrony.- 7.2 Napping and Split Sleep Simulations.- 7.3 A Representative Simulation of Internal Desynchrony.- 7.4 Overall Performance During Desynchrony.- 7.5 Summary and Discussion.- 8. Epilogue.- 8.1 Contributions.- 8.2 Directions for Future Research.- References.- Index of Authors.

Analysis of Models

Abstract: This chapter explores the mathematical structure of models of the sleep-wake cycle. As in other chapters, we focus on the empirical phenomenon of spontaneous internal desynchron-ization between the sleep-wake and temperature cycles during free-run. Other important phenomena such as those occurring during sleep deprivation, continuous bedrest or entrainment to 24h or other schedules, will not be discussed. As we shall see, understanding and accounting for internal desynchronization alone is a difficult task.