The Stages of Sleep: Non-REM, REM & Quality Rest

The Two Types of Sleep: Non-REM and REM

Walker explains that sleep is broadly separated into two main types in humans and all mammalian species: non-rapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep. Non-REM sleep is further subdivided into four stages, with stages three and four being the deepest.

Throughout the night, non-REM and REM sleep engage in a battle for brain domination, cycling every 90 minutes on average. However, the ratio of non-REM to REM sleep within these cycles changes as the night progresses. In the first half of the night, the cycles are comprised mostly of deep non-REM sleep with little REM sleep, while in the second half, REM sleep dominates with very little deep sleep.

This structure has real-life consequences. For example, if someone normally sleeps from midnight to 8 am but decides to wake up at 6 am instead, they may lose 25% of their total sleep but potentially 60-80% of their REM sleep due to the concentration of REM sleep in the latter part of the night.

The Fascinating Stages of Sleep

Walker describes the process of falling asleep and the different stages of sleep. As we start to drift off, we enter stage two non-REM sleep, characterized by sleep spindles – short, synchronous bursts of electrical activity in the brain.

During this stage, brain waves slow down significantly compared to the fast, chaotic activity seen during wakefulness. Occasionally, these slow brain waves are punctuated by the beautiful, rolling “r” sound of sleep spindles.

Walker expresses his awe at the brain’s activity during sleep, having even conducted a project called the “sonification of sleep” where electrical signals were turned into sound waves, allowing one to hear the slowing down of the brain and the distinct sound of sleep spindles.

The Stages of Sleep: What is Great Sleep vs. Mediocre Sleep?

Walker discusses the different stages of sleep and what constitutes great sleep versus mediocre sleep. He suggests that there may be a category of bad sleep that people are unaware of, where they think they are getting good sleep but it’s actually not as beneficial as they believe.

Huberman acknowledges that while Walker may be the bearer of bad news, he also provides powerful tools to improve one’s sleep and, consequently, their waking state. The conversation aims to shed light on the importance of understanding the various aspects of sleep and how to optimize it for overall well-being.

More From this Episode

Leave a Comment