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. 2016 Mar 1;39(3):625–636. doi: 10.5665/sleep.5540

Figure 1.

Figure 1

Unihemispheric and bilateral slow wave sleep in the fur seal. (A) Sleep postures in the fur seal. When on land, fur seals usually sleep while lying on their sides. When in water, they sleep at the surface on their sides, paddling with one fore flipper, while holding the other three flippers above the water to maintain their postures. (B) Electroencephalogram (EEG) and electromyogram (EMG) features of active wakefulness (AW), bilateral slow wave sleep (BSWS), rapid eye movement (REM) sleep and left and right unihemispheric sleep (L-USWS, R-USWS). Top and bottom rows are bilateral and asymmetrical states, respectively. (C) Behavioral states, slow wave activity (SWA, EEG power in the range of 1.2–4 Hz) in the two brain hemispheres and integrated neck EMG in a fur seal recorded over a 24-h period while on land. Two boxes highlight a daytime period of USWS (one episode of L-USWS and two episodes of R-USWS) and nighttime period of predominantly BSWS. Two-min polygrams displayed in B are episodes marked in C.