Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
Non-REM sleep refers to the stage of sleep characterized by a lack of rapid eye movement and typically deeper, more restorative sleep. It is divided into four stages, with each stage representing different levels of brain activity.
Related terms
Slow-wave sleep: This term refers to the deepest stage of non-REM sleep, where brain waves become slower and more synchronized.
Sleep spindles: These are brief bursts of rapid brain activity that occur during stage 2 of non-REM sleep.
REM (Rapid Eye Movement) sleep: This term refers to the stage of sleep characterized by rapid eye movements, vivid dreaming, and heightened brain activity.