Achermann P, Borbely AA: Temporal evolution of coherence and power in the human sleep electroencephalogram. J Sleep Res 7(suppl 1):36-41

Institute of Pharmacology, University of Zürich, Zürich, Switzerland
Journal of Sleep Research (Impact Factor: 3.35). 05/1998; 7(S1):36 - 41. DOI: 10.1046/j.1365-2869.7.s1.6.x
Source: PubMed


Coherence analysis of the human sleep electroencephalogram (EEG) was used to investigate relations between brain regions. In all-night EEG recordings from eight young subjects, the temporal evolution of power and coherence spectra within and between cerebral hemispheres was investigated from bipolar derivations along the antero-posterior axis. Distinct peaks in the power and coherence spectra were present in NREM sleep but not in REM sleep. They were situated in the frequency range of sleep spindles (13–14 Hz), alpha band (9–10 Hz) and low delta band (1–2 Hz). Whereas the peaks coincided in the power and coherence spectra, a dissociation of their temporal evolution was observed. In the low delta band, only power but not coherence showed a decline across successive NREM sleep episodes. Moreover, power increased gradually in the first part of a NREM sleep episode, whereas coherence showed a rapid rise. The results indicate that the intrahemispheric and interhemispheric coherence of EEG activity attains readily a high level in NREM sleep and is largely independent of the signal amplitude.

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    • "This finding was observed in all sleep stages including REM sleep. Interestingly, the interhemispheric coherence of slow waves was stable across sleep episodes, whereas SWA showed a marked decrease (Achermann and Borbely, 1998b). The contribution of the corpus callosum for coherent activity is illustrated by the reduced interhemispheric coherence during NREM sleep in congenitally acallosal children (Koeda et al., 1995; Kuks et al., 1987) and adults (Nielsen et al., 1993), as well as in adults with callosotomy (Montplaisir et al., 1990) and mice with total callosal agenesis (Vyazovskiy et al., 2004). "
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    • ") in the specific domain of state-related interhemispheric variations. 3. Finally, the present results extend, in terms of ''directionality ,'' several previous lines of evidence: 1) the reduction of spontaneous neural activity in the splenium of the corpus callosum across sleep stages in animals (Berlucchi 1965); 2) the reduction in transcallosal inhibition especially from right to left motor areas across sleep stages in humans (Bertini et al. 2004); 3) evidence of slow sleep EEG oscillations as traveling waves having intra-and interhemispheric directions of propagation (Massimini et al. 2004); 4) the drop in functional interhemispheric connectivity during early sleep stages (Massimini et al. 2005); 5) the modulation of interhemispheric EEG coherence across wake--sleep stages in normal subjects (Nielsen et al. 1990; Guevara et al. 1995; Achermann and Borbely 1998) and in patients with partial resection or agenesis of the corpus callosum (Montplaisir 1990; Nielsen et al. 1993); and 6) the decrement of regional cerebral blood flow in the left parietal area during slow-wave sleep (Kajimura et al. 1999). "
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