What characterizes the REM phase of sleep?

The REM phase of sleep is characterized by rapid eye movement, which is a distinctive feature that sets this phase apart from others. During REM sleep, the eyes move rapidly in various directions, even though the eyelids are closed. This phase is typically associated with the most vivid dreaming, as brain activity increases and resembles that of wakefulness.

Additionally, REM sleep plays a critical role in various neurological functions, including memory consolidation and emotional regulation. In contrast, other phases of sleep do not exhibit this eye movement or the associated brain activity patterns seen during REM. The presence of rapid eye movement serves as a clear indicator that a person is in this specific phase of sleep, making it a key characteristic of REM.