Non-REM and REM/paradoxical sleep dynamics across phylogeny

• Published in: Current opinion in neurobiology Vol. 71; pp. 44 - 51
• Main Authors: Jaggard, James B., Wang, Gordon X., Mourrain, Philippe
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2021
• Subjects: Animals; Electroencephalography; Mammals; Neocortex; Phylogeny; Sleep - physiology; Sleep, REM - physiology; Wakefulness - physiology
• ISSN: 0959-4388; 1873-6882; 1873-6882
• DOI: 10.1016/j.conb.2021.08.004

All animals carefully studied sleep, suggesting that sleep as a behavioral state exists in all animal life. Such evolutionary maintenance of an otherwise vulnerable period of environmental detachment suggests that sleep must be integral in fundamental biological needs. Despite over a century of research, the knowledge of what sleep does at the tissue, cellular or molecular levels remain cursory. Currently, sleep is defined based on behavioral criteria and physiological measures rather than at the cellular or molecular level. Physiologically, sleep has been described as two main states, non-rapid eye moment (NREM) and REM/paradoxical sleep (PS), which are defined in the neocortex by synchronous oscillations and paradoxical wake-like activity, respectively. For decades, these two sleep states were believed to be defining characteristics of only mammalian and avian sleep. Recent work has revealed slow oscillation, silencing, and paradoxical/REM-like activities in reptiles, fish, flies, worms, and cephalopods suggesting that these sleep dynamics and associated physiological states may have emerged early in animal evolution. Here, we discuss these recent developments supporting the conservation of neural dynamics (silencing, oscillation, paradoxical activity) of sleep states across phylogeny. •Quiescence and sensory gating epitomize behavioral sleep in all animals.•Common neural features of sleep exist from mammals to insects, including silencing, oscillations, wake-like activity.•Animals lacking a centralized brain have been shown to sleep, indicating that the need for sleep predates cephalization.