Short light-dark cycles influence sleep stages and EEG power spectra in the rat

Behav Brain Res. 1991 May 15;43(2):125-31. doi: 10.1016/s0166-4328(05)80062-2.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arousal / physiology
  • Cerebral Cortex / physiology*
  • Circadian Rhythm / physiology*
  • Electroencephalography / instrumentation*
  • Evoked Potentials / physiology
  • Light*
  • Male
  • Motor Activity / physiology
  • Rats
  • Rats, Inbred Strains
  • Signal Processing, Computer-Assisted / instrumentation*
  • Sleep Stages / physiology*
  • Sleep, REM / physiology*