title: Ultradian rhythm of 100 min in the dark phase EEG of the rat.
abstract: Using the "variance in statistics" as an index of electroencephalogram (EEG) parameters, we observed the cortico-hippocampal EEG rhythm under a 12:12-h light-dark condition in the rat with chronically implanted electrodes for EEG recording. The above EEG variance was simply measured in real time and on line through a personal computer. It corresponded to EEG slow wave activity and expressed the process of slow wave sleep as described in the two-process model by Borbély et al. Only in the dark phase, mean power spectral density of the EEG variance had a significant peak at about 1/100 cycles/min. This 100-min rhythmicity similar to the basic rest-activity cycle in human beings was observed in rats, particularly in the dark (active) phase for nocturnal animals. We propose that this ultradian 100-min rhythm is essential for the rat to maintain the waking state dominantly over the 12-h dark period.
authors.affiliation: Department of Physiology, School of Medicine, University of Tokushima, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sei
authors.forename: T
authors.initials: T
authors.lastname: Azekawa
authors.forename: Y
authors.initials: Y
authors.lastname: Morita
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography / Q000295:instrumentation; D005583:Fourier Analysis; D006624:Hippocampus / Q000502:physiology*; D008027:Light; D008297:Male; D051381:Rats; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D012895:Sleep, REM / Q000502:physiology