While we all enjoy a long sleep after a stressful day, we aren't clued up to the fact that the brain, sort of, paralyses our body to help us sleep better. But why does the brain do it?
If you’re an athlete or a workaholic or even that most enthusiastic person at a party who drains others out by her/his energy, you are bound to love the feeling of coming home to a nice, cosy sleep. You finally reach your bed, move your duvet aside, slide onto the mattress, crash your head on the pillow, reminisce about the day you spent (don’t overthink because it will mar your sleep) and eventually slip away into a deep and sound sleep.
But while you are asleep, sometimes you have the weirdest or the most fantastic or even too terrifying dreams. Seldom these dreams are so vivid, that when you wake up, you wonder, “why did I not fall out of my bed at all, despite that fire dragon chasing me on my pegasus?”
If this was you anytime after you woke up from sleep, then you need to take a moment and thank your brain for it. Your brain was responsible for deliberately paralysing your body when you fell deep into your sleep. But why does the brain enjoy freezing your body as time passes by in the fiery dungeons of your sleep?
Brain's Defence Mechanism for the Body
First, we must know why the brain finds it necessary to paralyse us when we fall asleep. Brain fears that if you’re not paralysed when you’re sleeping, your body can act out your dreams, causing unnecessary voluntary movements. You might end up physically harming yourself in such scenarios.
Suppose in your dream, you are performing an extraordinary backflip from a cliff into the blue oceans of Hawaii waiting to crash into the salty water. In that case, you will 100 per cent end up crashing into your floor, had it not been for your brain to paralyse your body in sleep.
While this may seem like a funny example, many people have died from bed falls in sleep. Around 450 people die annually from falling from their beds. This means that you’re more likely to die from falling from your bed than being chewed alive by sharks! And this is why your brain finds it essential to paralyse your body when you fall asleep.
The Dream Stage- When You Are Paralysed
Sometimes, you must’ve noticed that your body changes positions while falling asleep to get more comfortable. But if your brain is supposed to paralyse you when you sleep, then how can you move?
To understand this, we need to know how our body falls into a deep sleep phase. Our sleep is divided into stages; these stages make up a cycle known as the sleep cycle, and this cycle repeats on an average of 4-6 cycles during an average 8-hour sleep.
Only during one particular stage, does our brain say, “Alright, it’s enough. Let’s paralyse this sleepyhead (sounds ironic) before they bungee jump straight onto the cold, hard ground”.
So, What Are These Stages?
These are the stages that lead to your brain paralysing your body:
Non REM Sleep or NREM 1
When you initially fall asleep, you enter phase 1 of non-REM sleep. In this, your muscle movement reduces, and your eyeballs have calmer and slower movements behind your eyelids. This is known as the “twilight” stage of sleep since you are aware of your surroundings. This is a light stage of sleep, and noises or other disturbances can usually awake you.
Non REM Sleep or NREM 2
This is the stage where you are now completely asleep and unaware of what is going around in your surroundings. This stage observes the slowing down of heartbeats and lowering of body temperature. Your once frantic eye movements now slow down or even stop (happy dream journey!).
Non REM sleep or NREM 3
Brain waves slow down in stage 3, and only a few spurts of activities can be noticed. This is the state where your body’s muscles take a break, relax, and your breathing slows down further. You cannot be easily woken up in this stage, and you will need something rugged, like that irritating alarm clock, to snap you out of this stage.
Non REM sleep or NREM 4
Stage 4 is when your sleep reaches depths more profound than the Mariana trench! Just kidding, this stage observes your body slipping further into slumber, and your brain waves slow down even further. Researchers reckon that this is probably the stage where most tissue repair occurs (explains the infamous muscle soreness you get after sweating it out in the gym).
It’s even harder to wake someone up from this stage, and you’d maybe have to pick them up and shake them violently like a pepper bottle if you want to wake them. Hormones related to growth are also released in this stage. This is your body’s servicing and repairing process.
REM sleep or Rapid Eye Movement
Congratulations! You have now reached the dream stage, where everything comes true for a while. The REM stage is achieved 90 minutes after you’ve fallen asleep. Your eyes now start to hurry, with both breathing and heartbeats picking up pace. During the REM stage, your brain usually paralyses your body to prevent it from acting whatever you see in your dream and hurting yourself or someone next to you.
REM’s primary purpose is believed to help stimulate the regions of your brain that are responsible for memory and learning. This same state, in which your voluntary muscles have been paralysed by your brain when you’re dreaming is known as REM-atonia.
How Does the Brain Paralyse You?
Professor Takeshi Sakurai and his team were curious about how our brain does this, so they conducted a study at the University of Tsukuba to figure out the neurons responsible for paralysing the body during the REM sleep.
While working with mice, they were able to identify a specific set of neurons which were potentially responsible for the paralysis. These neurons were found in a region of the known as the ventral medial medulla. This area was guided and instructed by another part of the brain, known as the Sublaterodorsal Tegmental Nucleus, or SLD.
To further analyse this, researchers blocked the instruction from the SLD to these neurons. They observed that the mice started moving whilst asleep. This closely resembled a person who carries a lot during their sleep as they could potentially be affected by REM sleep behaviour disorder.
Problems Associated with REM Sleep Behaviour Disorder
Although relatively rare among the human population, REM sleep behaviour disorder can manifest itself in the form of acting out during your sleep, screaming, moving your hands around, kicking and sitting up suddenly. Narcolepsy is another disorder in which the person shortfalls asleep irrespective of the place and time.
Cataplexy is a symptom related to Narcolepsy. A person suddenly loses muscle tone and falls asleep, despite them being awake and aware, their muscles behave precisely during the REM stage. Sakurai said, “We found that silencing the SLD-to-ventral medial medulla reduced the number of cataplexic bouts.”
Hence this study could further help in finding out a cure for healing people with certain sleep disorders. Although the words, ‘sleep disorder’ seem trivial, this could lead to potentially dangerous and lethal situations. After all, everyone on this planet deserves a great sleep!