Final answer:
The duration of REM sleep stages increases as the night progresses, with REM sleep resembling wakeful brain activity and being associated with dreaming and memory consolidation.
Step-by-step explanation:
Changes in REM Sleep Through the Night
As the night progresses, the stages of REM (Rapid Eye Movement) sleep undergo various changes. Initially, sleep begins with non-REM (NREM) stages, which are characterized by a decrease in brain wave frequency and increase in amplitude. The transition from wakefulness to sleep starts with alpha waves, shifting to theta waves, and then, with progression, to deep sleep characterized by delta waves. This deep, slow-wave sleep, known as stage 3 NREM, is marked by the lowest frequency and highest amplitude brain waves.
As sleep cycles continue throughout the night, the duration of REM sleep increases, typically occupying a greater proportion of the sleep cycle in the second half of the night. During REM sleep, brain wave patterns are very similar to those during wakefulness, and this stage is heavily associated with dreaming and memory consolidation. There is muscle paralysis during REM sleep, with the exception of essential functions like respiration and circulation, hence why REM is sometimes referred to as paradoxical sleep. Furthermore, REM sleep importance for learning and memory has been implicated in various studies.