[Sleep and wakefulness in Callorhinus ursinus]

Sleep and wakefulness of northern fur seals were studied on three subadult bulls carrying the implanted electrodes for recording the electrocorticogram of the two hemispheres, the neck electromiogram, the electrooculogram and the electrocardiogram. The active wakefulness accounted for 32.0 +/- 5.3% of total recording time, the relaxed wakefulness -31.7 +/- 3.1%, the slow wave sleep -30.5 +/- 5.1% and the paradoxical sleep -5.8 +/- 0.9%. The sleep cycle averaged 22,6 +/- 1.2 minutes. Interhemispheric asymmetry of the ECoG slow waves was pronounced in all three animals. Different forms of the asymmetry occupied 15.0 +/- 0.7% of total recording time. Such interhemispheric asymmetry was found in pinnipeds for the first time, in this respect the northern fur seals differ from the Caspean seals but resemble the dolphins.