[Ontogenesis and organization of sleep]
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Sleep patterns dramatically change from birth to adulthood, with REM sleep decreasing. This developmental process in sleep organization is observed across mammals and prompts questions about REM sleep
Area of Science:
- Developmental biology
- Neuroscience
- Sleep science
Context:
- Sleep-wake cycles are fundamental to mammalian development, beginning before birth.
- Infants spend significantly more time asleep than adults, with sleep patterns evolving progressively.
- Sleep organization undergoes distinct developmental stages from infancy through puberty.
Purpose:
- To describe the ontogenetic organization of sleep and wakefulness states.
- To outline the key developmental milestones in sleep architecture.
- To explore the evolutionary significance of REM sleep.
Summary:
- Sleep development is a continuous process from before birth, characterized by rapid changes in infancy and slower changes until puberty.
- Key organizational changes include the establishment of circadian rhythms, development of physiological variables, their synchronization, and a shift from REM to non-REM sleep.
- This developmental trajectory is conserved across mammalian species.
Impact:
- Provides a framework for understanding normative sleep development in mammals.
- Highlights the crucial role of sleep, particularly REM sleep, in organismal and species evolution.
- Raises questions about the adaptive functions of REM sleep and dreaming across evolutionary timescales.
Abstract:
The newborn infant spends three quarters of his time asleep, while at adulthood his sleep will occupy only 8 hours out of 24. The development of sleep and wakefulness is continuous from before to after birth, and follows a progressive pattern: first rapid in the perinatal period and until one year of age, then much slower until puberty. Schematically, the ontogenetic organization of the states of vigilance consists of: 1. the building up of a circadian sleep-wake rhythm and the lengthening of the ultradian Basic Rest-Activity Cycle, 2. the specific development of each physiological variable which is linked to the states, 3. the synchronization of these variables, and 4. the reduction of REM sleep time and the relative increase of non-REM sleep proportion. This ontogenetic scheme applies by in large to all mammals. It raises the fascinating question of the role of REM sleep and of dreaming in the evolution of the organism and of the species.