Which type of sleep decreases while REM sleep increases throughout the night?

The correct answer relates to the relationship between deep sleep stages and the duration of rapid eye movement (REM) sleep across the night. During a typical sleep cycle, as the night progresses, the time spent in deep sleep, which encompasses stages 3 and 4 (often referred to collectively as slow-wave sleep), tends to decrease. Conversely, the duration of REM sleep increases, typically becoming longer in each successive cycle.

Stage 4 sleep is particularly significant as it is characterized by the deepest level of sleep, where restorative processes occur. As the night continues, the amount of time spent in this stage diminishes, allowing for longer periods of REM sleep. This pattern is essential for various functions such as memory consolidation and emotional regulation.

Understanding this dynamic is crucial when studying sleep patterns and the importance of both deep sleep and REM sleep for overall health and cognitive functioning.