Different stages of sleep refer to the distinct and recurring patterns of brain activity and physiological changes that occur during the sleep cycle. These stages are characterized by varying levels of brain wave activity, eye movement, muscle tone, and vividness of dreams.
Related terms
Rapid Eye Movement (REM) Sleep: REM sleep is a stage during which rapid eye movements occur, and most dreaming takes place.
Non-Rapid Eye Movement (NREM) Sleep: NREM sleep consists of three different stages (N1, N2, N3) that are progressively deeper and associated with slower brain waves.