Throughout the night we go through several sleep cycles, oscillating between **NREM** and **REM** sleep every ~90 minutes or so. This cycle, Walker hypothesizes, optimizes the [[Neural Functions of Sleep Stages]]. However, the cycle is not a sinusoid. It favors NREM in the first part of sleep, and REM in the latter part of sleep, like so: ![[Pasted image 20250412152652.png]] This more or less reflects what my [[Oura Ring]] shows me each morning on average. **** # More ## Source - [[Why We Sleep]]