Which stage of sleep is characterized by rapid eye movement (REM)?

The stage of sleep characterized by rapid eye movement is REM sleep. During this phase, the brain is highly active, resembling the wakefulness state, which is why it is often referred to as "paradoxical sleep." Most vivid dreaming occurs during REM sleep, and during this time, the body experiences muscle atonia, which prevents the person from physically acting out their dreams. REM sleep plays a crucial role in cognitive functions such as memory consolidation and emotional processing.

In contrast, the other sleep stages do not exhibit rapid eye movement. Stage 1 sleep is a light sleep phase where a person transitions from wakefulness to sleep. Stage 2 sleep includes sleep spindles and K-complexes, which help in memory processing, but lacks the distinct characteristics of REM. Stage 3 sleep, also known as slow-wave sleep or deep sleep, is associated with restorative functions and the highest form of sleep depth, yet it also does not feature rapid eye movements. Understanding these distinctions is important for recognizing the unique phases of the sleep cycle and their contributions to overall health and well-being.