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Comparative Perspectives that Challenge Brain Warming as the Primary Function of REM Sleep
Gianina Ungurean1,2, Baptiste Barrillot2, Dolores Martinez-Gonzalez1
1Avian Sleep Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany.
Iscience
|November 16, 2020
Summary
Brain warming during Rapid Eye Movement (REM) sleep is not universal. While REM sleep brain warming occurred in pigeons, it did not in bearded dragons, challenging its proposed function.
Area of Science:
- Comparative physiology
- Sleep science
- Neurobiology
Background:
- Rapid eye movement (REM) sleep, characterized by wake-like brain activity, follows non-REM (NREM) sleep in mammals and birds.
- Mammalian REM sleep involves brain cooling during NREM sleep and subsequent warming during REM sleep, potentially aiding adaptive function upon awakening.
Purpose of the Study:
- To investigate if brain warming is a universal characteristic of REM-like sleep states across different animal groups.
- To test the hypothesis that brain warming is the primary function of REM sleep by examining its occurrence in non-mammalian vertebrates.
Main Methods:
- Cortical temperature was measured in pigeons and bearded dragons during NREM-like and REM-like sleep states.
- Brain activity resembling wakefulness was observed during REM-like sleep in both species.
Main Results:
- Pigeons exhibited a decrease in cortical temperature during NREM sleep and an increase during REM sleep.
- Bearded dragons did not show an increase in brain temperature when transitioning from NREM-like to REM-like sleep.
Conclusions:
- Brain warming is not a consistent feature of sleep states with wake-like activity across all species.
- The hypothesis that REM sleep primarily functions to warm the brain in preparation for wakefulness is challenged by these findings.
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