Which sleep stage is primarily associated with muscle atonia and vivid dreaming?

REM sleep is primarily associated with muscle atonia and vivid dreaming. During this sleep stage, the body experiences temporary paralysis of major muscle groups, which prevents individuals from acting out their dreams. This atonia is a protective mechanism that allows the brain to engage in vivid and often narrative-like dreaming without the risk of physical movement that could result in injury. REM sleep typically occurs multiple times throughout the night and is crucial for cognitive functions such as memory consolidation and emotional regulation.

In contrast, the other stages of sleep have different characteristics and do not typically feature vivid dreaming or significant muscle atonia. For example, stages 1 and 2 of NREM sleep involve light sleep and do not generally include dreaming as vivid or intense as in REM. Stage 3, also part of NREM sleep, is the deepest sleep phase associated with physiological restoration and is not linked to muscle atonia or vivid dreams. Thus, the unique features of REM sleep clearly align with the aspects of muscle atonia and vivid dreaming highlighted in the question.