Elsevier

Neuroscience

Volume 101, Issue 3, 15 November 2000, Pages 523-529
Neuroscience

Dual electroencephalogram markers of human sleep homeostasis: correlation between theta activity in waking and slow-wave activity in sleep

https://doi.org/10.1016/S0306-4522(00)00409-7Get rights and content

Abstract

To investigate the relationship between markers of sleep homeostasis during waking and sleep, the electroencephalogram of eight young males was recorded intermittently during a 40-h waking episode, as well as during baseline and recovery sleep. In the course of extended waking, spectral power of the electroencephalogram in the 5–8 Hz band (theta activity) increased. In non-rapid eye movement sleep, power in the 0.75–4.5 Hz band (slow-wave activity) was enhanced in the recovery night relative to baseline. Comparison of individual records revealed a positive correlation between the rise rate of theta activity during waking and the increase in slow-wave activity in the first non-rapid eye movement sleep episode. A topographic analysis based on 27 derivations showed that both effects were largest in frontal areas.

From these results, we suggest that theta activity in waking and slow-wave activity in sleep are markers of a common homeostatic sleep process.

Section snippets

Subjects and study design

Eight healthy males (mean±S.E.M. age 23±0.46 years, range 21–25 years) recruited among university students participated in the study. They were right-handed, non-smokers, and reported a moderate consumption of alcohol and caffeine-containing beverages, and no drug use. They reported to adhere to regular bedtimes (sleep usually from 23.00 to 07.00) and not to suffer from sleep disturbances. Prior to being selected for the study, they underwent a screening night in the sleep laboratory. Exclusion

Electroencephalogram power spectra during waking

During prolonged wakefulness, power of the waking EEG increased in certain frequency bands. The mean changes after 36 h of waking relative to the mean level of the first 24 h are shown in Fig. 1 (left panel). Although the peak was located at 6.5 Hz, a significant increase was present over a large frequency range (0.75–9.0 Hz) and also included higher frequencies (11.0–16.5 Hz) (see F-values in bottom panel). The rise rate of power over the 40-h waking episode was determined for each 0.25-Hz

Discussion

The main result of this study is that EEG markers of sleep homeostasis in waking and sleep are closely related. This is illustrated in Fig. 6 by the data of the two subjects who showed the maximum and minimum SWA response to prolonged waking in conjunction with maximal and minimal rise rates of theta power (subject 10 was not considered). The line representing the increase of theta power in waking connects the two exponential functions that represent the decline of SWA during sleep. This

Acknowledgements

We thank Dr Roberto D. Pascual-Marqui for providing the software to display the maps, and Drs Thomas Graf and Irene Tobler for comments on the manuscript. This study was supported by Swiss National Science Foundation grant 3100-053005.97 and Human Frontiers Science Program grant RG-81/96.

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