[Quantitative characteristics of the electrocorticographic sleep stages in bottle-nosed dolphins]

Quantitative analysis of the ECoG stages in four bottle-nosed dolphins has demonstrated that unihemispheric slow-wave sleep is the dominant type of their natural sleep. All the variants of the bilateral and unilateral ECoG synchronization comprise 33.4% of the total recording time, with unilateral slow-wave sleep accounting for 28.8%. A single brain hemisphere is in a state of ECoG synchronization for 19% of the total recording time. The maximal amount of sleep is registered during a night and the second half of the day. Unihemispheric sleep episodes tend to appear alternatively in both hemispheres.