Dynamics of sleep-wake transitions during sleep

¹ Center for Polymer Studies and Department of Physics, Boston University Boston, MA 02215, USA
² Cardiovascular Division, Beth Israel Deaconess Medical Center Harvard Medical School - Boston, MA 02215, USA
³ Gonda Goldschmid Center and Department of Physics, Bar-Ilan University Ramat Gan, Israel
⁴ Klinik für Innere Medizin, Philipps-Universität Baldingerstrasse 1, Marburg D-35033, Germany

Received: 11 September 2001
Accepted: 29 November 2001

Abstract

We study the dynamics of the awakening during the night for healthy subjects and find that the wake and the sleep periods exhibit completely different behavior: the durations of wake periods are characterized by a scale-free power law distribution, while the durations of sleep periods have an exponential distribution with a characteristic time scale. We find that the characteristic time scale of sleep periods changes throughout the night. In contrast, there is no measurable variation in the power law behavior for the durations of wake periods. We develop a stochastic model which agrees with the data and suggests that the difference in the dynamics of sleep and wake states arises from the constraints on the number of microstates in the sleep-wake system.