What is REM sleep and why is it important?
Short Answer
REM (rapid eye movement) sleep is a stage with active brain activity, vivid dreaming, and temporary muscle paralysis. It’s important for emotion regulation, learning integration, and supporting memory—especially late in the night.
Why This Matters
REM matters because its chemistry and connectivity shift how the brain processes emotion and association, which leads to vivid dreams and memory integration. REM atonia prevents acting out dreams, resulting in safer sleep for most people. When REM is reduced—by alcohol, medications, or short sleep—people often see REM rebound, leading to unusually intense dreaming.
Where This Changes
REM increases toward morning, so early alarms cut it disproportionately. If someone moves violently or injures a partner during dream enactment, that can indicate REM sleep behavior disorder, which is different from normal REM dreaming.