In what sleep stage does dreaming primarily occur?

Dreaming primarily occurs during REM (Rapid Eye Movement) sleep, which is characterized by increased brain activity, vivid dreams, and physiological changes such as rapid eye movements and increased heart rate. During this stage, the brain exhibits a pattern of activity similar to that of being awake, making it conducive for intense and imaginative dreaming experiences.

In contrast, NREM sleep encompasses several stages, including light sleep and deep sleep, where dreaming is less common and typically less vivid when it does occur. Stages 1 and 4 of NREM sleep represent lighter and deeper stages of sleep respectively, and while it is possible to have fleeting thoughts or dreams in these stages, they are generally not as memorable or vivid as those occurring in REM sleep. Hence, REM sleep is uniquely linked with the most vivid and structured dreaming experiences.