What are the stages of sleep according to sleep science?

The stages of sleep as understood in sleep science include multiple phases of non-REM sleep along with REM sleep. Non-REM sleep consists of stages 1 through 4, each characterized by different physiological features and brain wave patterns.

Stage 1 is a light sleep, where one can be easily awakened and might experience the sensation of falling. Stage 2 involves a deeper level of sleep, reflected by specific brain wave activity and a decrease in heart rate and body temperature. Stages 3 and 4 represent deep sleep, essential for restorative processes in the body, such as tissue repair and growth.

Following these non-REM stages, the sleep cycle includes REM sleep, where most dreaming occurs, and the brain exhibits activity similar to wakefulness. This cycling through non-REM and REM stages is crucial for various functions, including memory consolidation and emotional regulation.

Thus, the correct answer highlights the holistic understanding of the sleep cycle, which incorporates both non-REM (stages 1-4) and REM sleep, recognizing their unique contributions to overall sleep architecture and health.