PHYSICS/BK21 SEMINAR [4.19]

[ Quantitative Study of Human Sleep  ] 

 * Speaker : Dr. Jong Won Kim [School of Physics University of Sydney] 

 * Place : Physics Seminar Room (Science Bldg, 3-201) 

* Date & Time : Apr, 19 (Mon)  4:00 ~ 5:00 pm  

l  Abstract

Sleep is essential to maintain the physical condition of the body and probably to

consolidate memories and learning. Despite its importance, social pressure often

leads to a perception that reducing sleep is advantageous, which causes widespread

sleep disorders posing public health issues. In this seminar, we review current sleep

studies in clinics and discuss potential interdisciplinary collaborations between Physics

 and Sleep Medicine. Examples of these collaborations are given below.

Ex.1) Sleep is a very active and complex process showing many electrophysiological

changes in the brain and other organs (e.g., the heart), which causes frequent sleep

 and (spontaneous) wake transitions during a nocturnal sleep period. To study these

 transitions, we propose a new approach, based on a Markov transition matrix that can

be determined by analyzing clinical sleep data (e.g., hypnograms). Our approach shows

that the statistics of sleep can be constructed via a single Markov process and that

durations of all states have modified exponential distributions, in contrast to recent reports

of a scale-free form for the wake stage and an exponential form for the sleep stage.

Ex. 2) At what point can a subject be said to be really asleep, or what is the moment of the

 sleep onset? These questions are potentially important for the public, especially for the

 road safety. To examine the process of the sleep onset quantitatively and explore

differences between narcoleptics and controls, we apply dynamic detrended fluctuation

 analysis to electroencephalograms recorded during multiple sleep latency tests. We find

 that electrophysiological brain activity is changing rapidly across the onset. The sleep onset

 durations of narcoleptics is significantly larger than that of controls, which suggests that the

wake state of narcolepsy being more susceptible to sleep due to a lower barrier to transitioning

 to sleep. 

 Reference:

 - Kim et al., Phys. Rev. Lett. 102, 178104 (2009).

 - Kim et al., Clin. Neurophysiol. 120, 1245 (2009).           

Contact Person : Prof. Seunghwan Kim(054-279-2085, swan@postech.ac.kr )