REM (rapid eye movement) sleep is the dreaming sleep stage with brain activity similar to wakefulness despite muscle paralysis. Rem sleep serves important functions for memory, emotion, and cognition.
Characteristics
- Rapid eye movements (visible behind closed eyelids)
- Vivid dreaming
- Muscle atonia (paralysis except diaphragm and eye muscles)
- Irregular breathing and heart rate
- Brain activity similar to wake
- Genital arousal common
When REM occurs
- About 90 minutes after falling asleep (first REM)
- 4-6 REM periods per night
- Each REM period longer than previous
- Most REM in second half of night
- ~20-25% of total sleep
Functions
- Memory consolidation, especially procedural and emotional
- Emotional processing
- Creativity and problem-solving
- Brain development (especially infants)
- Learning consolidation
What affects REM
Reduced REM:
- Alcohol
- Many antidepressants (especially SSRIs)
- Sleep deprivation
- Cannabis
- Some other medications
REM rebound:
- After REM-suppressing substances stopped
- After sleep deprivation
- Vivid/intense dreaming common
REM disorders
REM sleep behavior disorder (RBD): Loss of muscle paralysis during REM. Patients act out dreams. Risk factor for Parkinson’s and other neurodegenerative diseases.
Narcolepsy: Abnormal REM intrusion into wakefulness.
Sleep paralysis: REM atonia persisting briefly into wakefulness.
Frequently Asked Questions
How much REM should I get?
~20-25% of total sleep. 1.5-2 hours nightly typical.
Can I increase REM?
Adequate total sleep, avoid alcohol. Specific increase not typically necessary.
Are nightmares related to REM?
Yes — most dreaming occurs in REM.
What’s REM rebound?
Increased REM after REM deprivation. Vivid dreams common.
What’s RBD?
REM Behavior Disorder. Acting out dreams. May predict Parkinson’s or related conditions.
The bottom line on REM sleep
Important sleep stage for memory, emotion, cognition. Affected by many medications and substances. Disorders warrant evaluation.