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Mammalian NREM and REM sleep: Why, when and how
Rubén V Rial1, Mourad Akaârir1, Francesca Canellas2
1Laboratori de Fisiologia del son i els ritmes biologics. Universitat de les Illes Balears, Ctra. Valldemossa Km 7.5, 07122 Palma de Mallorca (España); IDISBA. Institut d'Investigació Sanitaria de les Illes Balears; IUNICS Institut Universitari d'Investigació en Ciències de la Salut.
Neuroscience and Biobehavioral Reviews
|January 16, 2023
Summary
Fish use spinal-rhombencephalic brain regions for wakefulness. Mammals evolved cortical wakefulness, retaining REM sleep (REMS) for maternal care, though REMS is maladaptive for marine mammals.
Area of Science:
- Neuroscience
- Comparative Biology
- Evolutionary Biology
Background:
- Different vertebrate classes exhibit distinct brain structures supporting wakefulness.
- Mammals possess a highly developed telencephalic cortex for advanced wakefulness (cortical wakefulness).
- Rapid Eye Movement Sleep (REMS) in mammals is a remnant of earlier spinal-rhombencephalic wakefulness.
Purpose of the Study:
- To propose an evolutionary framework for the development of wakefulness across vertebrate species.
- To investigate the adaptive significance of REM sleep (REMS) and its variations in different mammalian groups.
- To elucidate the neural mechanisms regulating different states of wakefulness and sleep.
Main Methods:
- Comparative analysis of brain structures across fish, amphibians, reptiles, and mammals.
- Evolutionary developmental biology principles applied to brain evolution.
- Functional interpretation of sleep states (REMS and NREMS) in relation to behavior and ecology.
Main Results:
- Fish utilize spinal-rhombencephalic regions for wakefulness.
- Amphibians and reptiles rely on brainstem-diencephalic regions for wakefulness.
- Mammals evolved cortical wakefulness, with REMS retaining a paralytic spinal-rhombencephalic function, crucial for maternal care but not universally adaptive.
Conclusions:
- Wakefulness evolved progressively with increasing brain complexity across vertebrates.
- Phasic REMS is highly adaptive for mammalian maternal care but can be neutral or maladaptive in other contexts (e.g., marine mammals).
- Non-Rapid Eye Movement Sleep (NREMS) serves to recover from allostatic loads generated during wakeful states.
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