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Understanding REM Sleep and Its Functions

Apr 19, 2025

The Biology of REM Sleep

Abstract

  • Recent advances in understanding REM sleep due to neuroscience tools.
  • REM sleep impacts sensorimotor function.
  • Review covers:
    • Discovery of REM sleep
    • REM sleep diversity across species
    • Functions of REM sleep
    • Neural circuits controlling REM sleep
    • Disorders linked to REM sleep dysfunction.

Introduction

  • REM sleep discovery credited to Eugene Aserinsky, Nathaniel Kleitman, William Dement, and Michel Jouvet.
  • Characterized by:
    • Rapid eye movements
    • Specific brain-wave patterns
    • Muscle atonia
    • Cortical activity similar to wakefulness.
  • REM sleep alternates with non-REM sleep.
  • Important for memory consolidation.

REM Sleep Across Species

  • Found in terrestrial mammals, birds, reptiles, and some aquatic invertebrates.
  • Variations in REM sleep duration and cycle across species.
  • REM sleep critical for brain development in newborn mammals.
  • Expression varies due to environmental and ecological pressures.

REM Sleep Function

  • REM sleep’s role in biology and neuropsychiatry is still unclear.
  • Potential functions:
    • Brain development
    • Sensorimotor learning
    • Memory consolidation and synapse regulation.
  • Studies show REM sleep deprivation impairs memory.
  • REM sleep may aid in creativity and readiness for wakefulness.

Brain Circuitry Controlling REM Sleep

  • REM sleep involves circuits in the brainstem, especially the sublaterodorsal nucleus (SLD).
  • SLD neurons produce motor atonia by activating inhibitory interneurons.
  • Involves REM-on and REM-off neurons creating a flip-flop switch.
  • Orexin and melanin-concentrating hormone (MCH) neurons influence REM sleep.

Pathobiology of REM Sleep

  • Disorders include REM sleep behavior disorder (RBD) and narcolepsy.

REM Sleep Behavior Disorder (RBD)

  • Loss of normal REM sleep paralysis, leading to motor behaviors during sleep.
  • Linked to neurodegenerative diseases like Parkinson's.
  • May result from synucleinopathy-induced degeneration of REM circuits.

Narcolepsy/Cataplexy

  • Linked to loss of hypothalamic orexin cells.
  • Characterized by excessive sleepiness, disrupted REM sleep, and cataplexy.
  • Cataplexy involves intrusion of REM sleep paralysis into wakefulness.
  • Emotional triggers may link cataplexy with REM sleep circuits.

Conclusions and Future Directions

  • Significant progress in understanding REM sleep's mechanisms and functions.
  • Remaining questions:
    • Universal presence of REM sleep in animals
    • REM sleep's role in learning and memory
    • Complete identification of REM sleep circuits.
  • Importance of studying REM sleep in relation to human diseases, particularly neurodegenerative disorders.