Why We Sleep


What is sleep? Do your children get enough? What about you?

Sleep has always mystified people, but in his bestselling book Why We Sleep, neuroscientist Matthew Walker gives a comprehensive and fascinating view into its purpose and how it fits into the entire life-cycle of the brain.

Put briefly, the brain has three basic phases - awake, deep sleep and REM sleep. The first phase, awake, is when the organism is taking in new stimuli and data. The second phase, deep sleep, is when the brain is sloughing off old info it no longer needs - Walker likens it to housecleaning. The third phase, REM, often associated with dreaming, is when the brain is building novel connections. Input (awake) - Housecleaning (deep sleep) - and New Connections (REM). Rinse and repeat.

Isn't that astounding?!

But here's where it gets even more interesting - the sleep phases of the brain alternate back and forth throughout the night, and shift significantly throughout childhood, so that it's not just 4 hrs of deep sleep then 4 hrs of REM, but a mix of both throughout the night and more REM (or less) depending on one's age.

An adult has roughly 80 percent deep sleep (cleansing) and 20 percent REM (creation). During a typical night's sleep, the bulk of that REM sleep comes at the latter end. That means that if you're cutting an hour or two off the typical 8hr sleep period (and many of us are), you're still getting most of your housecleaning done. You're just missing out on a lot of creativity and new connections.


And what about kids? Kids are even more interesting, because their sleep patterns are entirely different than adults. Infants in utero are asleep almost the entire day, and as we might suspect - REM (construction) sleep dominates their cycle. The result is that we have more synaptic connections in the brain AT BIRTH than we do at any other time in our lives.

Holy shit!

As a child ages, she is constantly cycling between being awake (taking in stimuli), followed by housecleaning and then the creation of novel arrangements. This is what the brain is always doing - intake, cleaning, creation. Sleep is not rest. It is perhaps the most active our brains ever are.

My goodness!

As a child ages further, the amount of deep sleep increases, while REM ramps down, until the late teenage years when a person stabilizes at the relative 80/20 split between deep sleep and REM sleep for the remainder of their life. This is what growing up is. As a child we are constantly building, over-building in fact, until the ratio of deep sleep begins to take over and starts culling out much of the extraneous connections inside the brain, so that an adult has far fewer synaptic connections than an infant. This is what makes a person smart, mature or wise - LESS BRAINS!

Isn't that fabulous? This dude deserves an A.

PS - If you find this subject interesting, you will not be disappointed by Walker's book, which includes much more than what I've glanced at here, including a very thorough treatment of both caffeine and alcohol. Great stuff.