Sleep homeostasis and cortical synchronization: III. A high-density EEG study of sleep slow waves in humans

Department of Psychiatry, University of Wisconsin, Madison, WI 53719, USA.
Sleep (Impact Factor: 4.59). 01/2008; 30(12):1643-57.
Source: PubMed


The mechanisms responsible for the homeostatic decrease of slow-wave activity (SWA, defined in this study as electroencephalogram [EEG] power between 0.5 and 4.0 Hz) during sleep are unknown. In agreement with a recent hypothesis, in the first of 3 companion papers, large-scale computer simulations of the sleeping thalamocortical system showed that a decrease in cortical synaptic strength is sufficient to account for the decline in SWA. In the model, the reduction in SWA was accompanied by decreased incidence of high-amplitude slow waves, decreased wave slopes, and increased number of waves with multiple peaks. In a second companion paper in the rat, local field potential recordings during early and late sleep confirmed the predictions of the model. Here, we investigated the model's predictions in humans by using all-night high-density (hd)-EEG recordings to explore slow-wave parameters over the entire cortical mantle.
256-channel EEG recordings in humans over the course of an entire night's sleep.
Sound-attenuated sleep research room
Seven healthy male subjects
During late sleep (non-rapid eye movement [NREM] episodes 3 and 4, toward morning), when compared with early sleep (NREM sleep episodes 1 and 2, at the beginning of the night), the analysis revealed (1) reduced SWA, (2) fewer large-amplitude slow waves, (3) decreased wave slopes, (4) more frequent multipeak waves. The decrease in slope between early and late sleep was present even when waves were directly matched by wave amplitude and slow-wave power in the background EEG. Finally, hd-EEG showed that multipeak waves have multiple cortical origins.
In the human EEG, the decline of SWA during sleep is accompanied by changes in slow-wave parameters that were predicted by a computer model simulating a homeostatic reduction of cortical synaptic strength.

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    • "The homeostatic changes in spectral EEG power are accompanied by changes in the amplitude and frequency of individual slow-waves and in their spatial dynamics (Nir et al. 2011; Riedner et al. 2007; Vyazovskiy et al. 2011b). However, the relevance of such changes for sleep regulatory mechanisms and sleep function remains poorly understood. "
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    Journal of Neurophysiology 02/2015; 113(7):jn.00575.2014. DOI:10.1152/jn.00575.2014 · 2.89 Impact Factor
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    • "DD may further suggest that sleep - disordered breathing may be playing a role . Previous research in healthy male subjects has found that SWA is highest in the frontal regions compared to temporal and parietal regions , and have their highest amplitude during early sleep , or NREM periods 1 and 2 compared to late sleep , or NREM periods 3 and 4 ( Riedner et al . , 2007 ) . Additionally , Ferrara et al . ( 2002 ) also found that , during a recovery night of sleep following selective slow wave sleep deprivation , the left hemisphere showed greater SWA power than the right hemisphere , which they suggest indicates that the left hemisphere has a greater sleep need following sleep depri - vation . With res"
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    ABSTRACT: Individuals with major depressive disorder typically exhibit sleep electroencephalograpy abnormalities which have been shown to vary by sex. Recent research has shown that depressed males display deficits in slow wave sleep and delta electroencephalograph (EEG) activity that are not apparent in depressed females. This may suggest that males and females with depression vary with respect to their homeostatic regulation of sleep. Utilizing archival data, the present study examined the effects of a 3-h sleep delay, which represents a mild sleep challenge, on slow wave activity in healthy controls and individuals with depression. All participants slept in the laboratory for three sequential nights. On the third night in the laboratory, the participants' bedtime was delayed by 3 h. Slow wave activity was calculated utilizing power spectral analysis and compared across groups. Following the sleep delay, males with depression exhibited the lowest slow wave activity compared to all other groups. These results may suggest that males with depression are at a greater risk for homeostatic dysregulation than females, and may require specialized intervention.
    Journal of Sleep Research 08/2014; 23(6). DOI:10.1111/jsr.12174 · 3.35 Impact Factor
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    • "We can only speculate which aspect of sleep plays a role in maintenance of functional connectivity of the prefrontal cortex since we did not record sleep EEG of the subjects in our experiment. The most likely candidate is NREM sleep since it seems to have a restorative effect on prefrontal areas [27]. For example, cerebral blood flow is particularly low in this area during NREM sleep [28]. "
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