REM Sleep
REM sleep is a recurring stage named for the rapid eye movements that often occur beneath closed eyelids. The brain becomes highly active, vivid dreaming is common, breathing grows less regular, and most voluntary muscles are temporarily prevented from moving.
Why the Body Becomes Temporarily Paralyzed
The brainstem suppresses motor signals to many skeletal muscles during REM. This state, called REM atonia, helps prevent the body from acting out most dream movements. Breathing muscles and eye muscles remain active.
Why the Eyes Move
The exact purpose of rapid eye movements is still being studied. They may relate to shifts in internally generated imagery, but they are not simply the eyes following a dream scene in a straightforward way.
REM and Learning
REM appears to contribute to several forms of learning, emotional memory, and the integration of new experiences with existing knowledge. It works alongside non-REM sleep rather than replacing it. A full night allows both systems to alternate repeatedly.
How REM Changes Through the Night
- The first REM period often arrives after an initial sequence of non-REM stages.
- Early REM periods are usually relatively short.
- Deep sleep decreases as the night progresses.
- REM periods become longer and more frequent near morning.
- Waking from late-night REM makes vivid dream recall more likely.
Normal REM Events and Concerning Symptoms
Usually Normal
Vivid dreams, brief eye movements, changing breathing patterns, and temporary muscle inhibition.
Worth Discussing
Repeatedly punching, kicking, shouting, or injuring yourself or a bed partner while apparently acting out dreams.
REM Sleep Questions
How much REM sleep is normal?
The proportion varies by age and individual night. Adults commonly spend roughly one-fifth to one-quarter of sleep in REM, but consumer devices provide estimates rather than clinical measurements.
Can alcohol reduce REM sleep?
Alcohol can suppress REM earlier in the night and contribute to more fragmented sleep later.
What is REM rebound?
After REM has been reduced, the brain may enter REM sooner or spend more time in it during subsequent sleep.