Behavioral, neurophysiological and evolutionary perspectives on unihemispheric sleep

N. C. Rattenborg, C. J. Amlaner, S. L. Lima

Research output: Contribution to journalArticlepeer-review

414 Scopus citations


Several animals mitigate the fundamental conflict between sleep and wakefulness by engaging in unihemispheric sleep, a unique state during which one cerebral hemisphere sleeps while the other remains awake. Among mammals, unihemispheric sleep is restricted to aquatic species (Cetaceans, eared seals and manatees). In contrast to mammals, unihemispheric sleep is widespread in birds, and may even occur in reptiles. Unihemispheric sleep allows surfacing to breathe in aquatic mammals and predator detection in birds. Despite the apparent utility in being able to sleep unihemispherically, very few mammals sleep in this manner. This is particularly interesting since the reptilian ancestors to mammals may have slept unihemispherically. The relative absence of unihemispheric sleep in mammals suggests that a trade off exists between unihemispheric sleep and other adaptive brain functions occurring during sleep or wakefulness. Presumably, the benefits of sleeping unihemispherically only outweigh the costs under extreme circumstances such as sleeping at sea. Ultimately, a greater understanding of the reasons for little unihemispheric sleep in mammals promises to provide insight into the functions of sleep, in general. (C) 2000 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)817-842
Number of pages26
JournalNeuroscience and Biobehavioral Reviews
Issue number8
StatePublished - 2000


  • Aquatic mammals
  • Birds
  • Functional lateralization
  • Predator detection
  • Reptiles
  • Sleep function
  • Sleep mechanisms
  • Sleep regulation
  • Slow-wave sleep
  • Unihemispheric


Dive into the research topics of 'Behavioral, neurophysiological and evolutionary perspectives on unihemispheric sleep'. Together they form a unique fingerprint.

Cite this