Sleep: Feeling awake while asleep

What makes a good night's sleep? It is often assumed that sleep is the deepest when brain activity is dominated by hyper-synchronized slow waves. However, sleep appears subjectively the deepest in rapid eye movement (REM) sleep, when slow waves are absent.

Automated summary

This passage discusses the relationship between sleep depth and brain waves, pointing out that both slow wave sleep and rapid eye movement sleep have an impact on sleep depth.