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

The stage of sleep characterized by rapid eye movement (REM) is indeed REM sleep. This stage is notable for various physiological changes that occur during the sleep cycle, including increased brain activity, heightened heart rate, and unpredictable breathing patterns. It is during REM sleep that most vivid dreaming occurs, making it a crucial part of the sleep cycle for cognitive functions such as memory consolidation and emotional processing.

In the context of sleep stages, REM sleep typically follows the non-REM stages and cycles through the night. The occurrence of rapid eye movements distinguishes REM sleep visually, as the eyes move rapidly in various directions beneath the eyelids. This is in contrast to non-REM sleep stages, where such eye movements are generally absent and the individual is in a deeper, restorative state. Understanding the unique features of REM sleep provides insight into its vital role in overall sleep quality and health.