title: Short light-dark cycles influence sleep stages and EEG power spectra in the rat.
abstract: To investigate the influence of light on sleep and the electroencephalogram (EEG), chronically implanted rats were continuously recorded during a baseline day under 12-h light-12-h dark (LD 12:12) conditions, and an experimental day with short LD (LD 1:1) cycles. The percentage of non-REM sleep (NREMS) was higher and the percentage of REM sleep (REMS) lower in the 1-h light [corrected] intervals than in the 1-h dark intervals. The maximum of NREMS induction by 1-h light occurred in the habitual 12-h dark period (activity period), while the largest enhancement of REMS by 1-h darkness occurred in the second half of the habitual 12-h light period (rest period). The EEG of waking, NREMS and REMS was subjected to spectral analysis to determine the power density of the frequency components in the range of 0.25-25.0 Hz. The overall 24-h time course of the EEG-spectra in NREMS was similar under baseline and experimental conditions. Nevertheless, the spectra were modified by the short LD-cycle. In NREMS, the values in the middle and high frequencies (greater than 6 Hz in the rest period; greater than 11 Hz in the activity period) were lower in the 1-h light intervals than in the 1-h dark intervals. In contrast, activity in some frequency bands during waking and REMS was higher in the light than in the dark intervals. It is concluded that the short LD-cycle modulates the vigilance states and induces state-specific changes in the EEG, whereas circadian aspects of sleep are little affected.
authors.affiliation: Institute of Pharmacology, University of Zürich, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Alföldi
authors.forename: P
authors.initials: P
authors.lastname: Franken
authors.forename: I
authors.initials: I
authors.lastname: Tobler
authors.forename: A A
authors.initials: AA
authors.lastname: Borbély
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography / Q000295:instrumentation*; D005071:Evoked Potentials / Q000502:physiology; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology*