An unfortunate contrast
Like a door swinging loosely by only one hinge, his mouth hung open, allowing the saliva to pool unpleasantly on the fabric. Hair straggled limply across his forehead while his cheek was squashed unattractively, the features riding high on that side.
And yet, can you believe it, when my daughters are asleep, hair never straggles. It nestles, or frames, but doesn’t straggle. Mouths never hang open. Cheeks never get sqaushed. And the saliva thing? Don’t even go there. It’s like they don’t have it. In fact, they’re beatific enough that I’m sure they glow faintly and harps play.
It is a mystery to us all, or at least to me, why children manage to look so serene and composed while they sleep, and I manage to look like something Dali painted the day he thought he might paint blindfolded.
With his index finger.
Left index finger.
And yet, there’s no escaping sleep, and so there’s some stuff you need to know. We’ve got a couple of posts on sleep and the brain to cover off and, while we can’t hope to answer every question and tick every box, we will cover the big-ticket items. It’s a big subject so be sure to get each post.
Sleep cycles and stages
The brain goes through a pretty predictable process overnight, but it’s by no means as inactive as you might think. When we sleep, we progress through cycles of sleep; four or five sleep cycles in a normal night. Each sleep cycle lasts, on average, about 90 minutes.
These cycles are separated into two types of sleep, based on the features we see in each type. You’ve probably heard of them before.
REM sleep, which is shorthand for Rapid Eye Movement sleep, is one type.
The other type is NREM Sleep, or Non-Rapid Eye Movement Sleep, which is further split into Stages 1, 2 and 3.
During the night, your sleep will usually follow this pattern
- Stage 1
- Stage 2
- Stage 3
- Stage 2
A bit about REM
REM is characterized primarily by rapidly moving eyes, and it’s fascinating to watch someone in REM sleep. Kids are great for it because they have more REM sleep and you can see the eyes going crazy under the eyelids. The second defining feature is loss of muscle tone. But on a brain scan, REM brain waves are easily mistaken for an awake brain. The combination of the awake looking brain with the complete lack of muscle tone gave rise to the nickname paradoxical sleep.
- About 25% of our sleep is REM sleep
- REM periods are short at first, and increase in length overnight
- One REM period per cycle, means 4-5 REM periods per night
- REM tends to drop with age
- Babies spend 75% or more time in REM
A bit about NREM
We’re drifting off to sleep and we wake up with a start. It’s a myoclonic jerk, or twitch, which is a sudden muscle contraction. If we get woken while we’re drifting, or even during Stage 1 sleep, we’ll usually deny that we’ve been asleep at all. Ask my wife…
Once we’re moving into Stage 2, brain waves are slowing down and body temperature is dropping. About half of our time is in Stage 2. From here we’ll move to deep, slow wave, Stage 3 sleep. If we’re prone to sleeptalking or walking, bed wetting or night terrors, the end of Stage 3 is the most likely time for them to occur.
- We’re really, really hard to wake in Stage 3
- We don’t dream much in NREM sleep
- Probably, memory consolidation occurs in NREM, via the hippocampus
So here’s the take home bit
For a good night’s sleep, and we’ll come back to this again, it’s really important that we get full sleep cycles wherever possible. Working on the average of 90 minutes per cycle, and an average 4 to 5 cycles a night, we’re looking at 6 to 7.5 hours a night, pretty close to the old chestnut of 8 hours a night.
If you’re a napper, try and keep it under 20 minutes, unless you can get a full cycle in. If you can, you then want take the 90 minutes at a time when your body is more naturally inclined to sleep. Aim for after lunch, during the postprandial dip.
Impressive words to drop into the morning coffee chat
What have you noticed?
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