Inter-individual differences in the dynamics of sleep homeostasis.
OBJECTIVE
The two-process model posits that sleep is regulated by 2 independent processes, a circadian Process C and a homeostatic Process S. EEG slow-wave activity (SWA) is a marker of NREM sleep intensity and is used as an indicator of sleep homeostasis. So far, parameters of the two-process model have been derived mainly from average data. Our aim was to quantify inter-individual differences.


METHODS
Polysomnographic recordings (analysis of existing data).


METHODS
Sound attenuated sleep laboratory.


METHODS
Eight healthy young males.


METHODS
40-h sustained wakefulness.


RESULTS
Process S was modeled by a saturating exponential function during wakefulness and an exponential decline during sleep. Empirical mean SWA (derivation C3A2) per NREM sleep episode at episode midpoint were used for parameter estimation. Parameters were estimated simultaneously by minimizing the mean square error between data and simulations of Process S. This approach was satisfactory for average data and most individual data. We further improved our methodological approach by limiting the time constants to a physiologically meaningful range. This allowed a satisfactory fit also for the one individual whose parameters were beyond a physiological range. The time constants of the buildup of Process S ranged from 14.1 h to 26.4 h and those of the decline from 1.2 h to 2.9 h with similar inter-individual variability of the buildup and decline of Process S.


CONCLUSIONS
We established a robust method for parameter estimation of Process S on an individual basis.
Rusterholz
Thomas
T
Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
Dürr
Roland
R
Achermann
Peter
P
D000328:Adult; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D017286:Polysomnography / Q000379:methods / Q000706:statistics & numerical data; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult
Brain Res Bull. 1993;31(1-2):97-113
8453498
Sleep. 2005 Oct;28(10):1253-9
16295210
J Theor Biol. 1990 Jan 23;142(2):149-61
2161971
Neurobiol Aging. 1989 Nov-Dec;10(6):677-82
2628779
Sleep. 2005 Apr;28(4):479-96
16171293
Science. 2009 Apr 24;324(5926):516-9
19390047
Brain Res. 2000 Feb 28;857(1-2):8-19
10700548
J Neurosci. 2001 Apr 15;21(8):2610-21
11306614
Sleep. 2004 Jun 15;27(4):774-83
15283014
Am J Physiol. 1984 Feb;246(2 Pt 2):R161-83
6696142
Sleep. 2005 Feb;28(2):239-47
16171249
Brain Res. 2000 Jun 2;866(1-2):152-67
10825491
Neurosci Lett. 1991 Sep 16;130(2):141-4
1795873
Sleep. 1995 Dec;18(10):890-4
8746397
Curr Pharm Des. 2008;14(32):3396-407
19075716
Hum Neurobiol. 1982;1(3):195-204
7185792
Sleep. 2008 Jun;31(6):859-67
18548831
Am J Physiol. 1990 Mar;258(3 Pt 2):R650-61
2316712
Curr Biol. 2007 Apr 3;17(7):613-8
17346965
Psychophysiology. 1979 May;16(3):283-91
220659
Sleep. 1989 Dec;12(6):500-7
2595173
Aviat Space Environ Med. 2004 Mar;75(3 Suppl):A37-43
15018264
Neuropsychopharmacology. 2001 Nov;25(5 Suppl):S57-62
11682275
J Sleep Res. 2006 Jun;15(2):162-6
16704571
Sleep. 2005 Nov;28(11):1446-54
16335485
Neuroscience. 2001;102(3):493-502
11226688
J Sleep Res. 2009 Mar;18(1):3-10
19021858
Eur J Neurosci. 2006 Jan;23(2):497-504
16420456
J Sleep Res. 2003 Dec;12(4):275-82
14633238
Proc Natl Acad Sci U S A. 2005 Oct 25;102(43):15676-81
16221767
Electroencephalogr Clin Neurophysiol. 1992 Dec;83(6):339-49
1281079
Neuroscience. 2000;101(3):523-9
11113301
Brain Res. 1996 Nov 4;738(2):205-12
8955514
J Biol Rhythms. 1987 Fall;2(3):207-19
2979661
Brain Res Bull. 2007 Sep 14;74(1-3):37-44
17683787
Clin Neurophysiol. 2000 May;111(5):929-39
10802466
Am J Physiol. 1999 Dec;277(6):R1771-9
10600925
Curr Biol. 2008 Aug 5;18(15):1118-23
18656358
Sleep. 2007 Aug;30(8):980-9
17702267
Electroencephalogr Clin Neurophysiol. 1991 Mar;78(3):203-14
1707792
J Sleep Res. 2001 Sep;10(3):165-72
11696069