Asymmetry and basic pathways in sleep-stage transitions

¹ Institute of Systems Neuroscience, National Tsing Hua University - Hsinchu 30013, Taiwan
² Harvard Medical School and Division of Sleep Medicine, Brigham and Women's Hospital - Boston, MA 02115, USA
³ Center for Polymer Studies and Department of Physics Boston University - Boston, MA 02215, USA
⁴ Institute of Solid State Physics, Bulgarian Academy of Sciences - Sofia 1784, Bulgaria, EU

^(a) plamen@buphy.bu.edu

Received: 8 February 2013
Accepted: 20 March 2013

Abstract

We study dynamical aspects of sleep micro-architecture. We find that sleep dynamics exhibits a high degree of asymmetry, and that the entire class of sleep-stage transition pathways underlying the complexity of sleep dynamics throughout the night can be characterized by two independent asymmetric transition paths. These basic pathways remain stable under sleep disorders, even though the degree of asymmetry is significantly reduced. Our findings demonstrate an intriguing temporal organization in sleep micro-architecture at short time scales that is typical for physical systems exhibiting self-organized criticality (SOC), and indicates nonequilibrium critical dynamics in brain activity during sleep.