During which sleep stage does dreaming and muscle atonia predominantly occur?

Dreaming and muscle atonia predominantly occur during REM (Rapid Eye Movement) sleep. This stage of sleep is characterized by rapid movements of the eyes, increased brain activity, and vivid dreaming. During REM sleep, the body experiences muscle atonia, which is a temporary paralysis of most voluntary muscles. This phenomenon serves as a protective mechanism, preventing individuals from acting out their dreams and potentially harming themselves. The brain is highly active during this stage, resembling wakefulness, which is why many of our most vivid dreams occur at this time.

In contrast, non-REM sleep is generally marked by deeper sleep stages without the vivid dreaming associated with REM. Deep sleep, a part of non-REM sleep, is characterized by slow brain waves and a lack of eye movement, making it less conducive to dreaming. Stage 1 sleep is the lightest form of non-REM sleep and is often more transitional, with brief periods of awareness and not the deep dreaming associated with REM.