What does it all mean? The science behind sleep and dreams.

Written by: Monique Joy Raranga

A few days ago, I woke up from a dream where I attended a gig in Glasgow. It was essentially a scene from pre-lockdown life months ago, featuring uni friends I hadn’t seen in a while and the standard post-gig conversations on the walk home. Later on, I had another dream, this time I was a dungeon raider traversing a tropical island and narrowly dodging suffocation in noxious gas by jumping out the window of the castle’s seventh floor. Both dreams left me squinting at the ceiling from confusion and curiosity as much as post-sleep grogginess.

With lockdown keeping all of us indoors, I think a lot of us are staying in bed and sleeping more than we otherwise would. For many, this means more dreams to try and decode (at least, for the two minutes you can still remember them). But what exactly is the purpose of these dreams and where do the sometimes-bizarre, sometimes-oddly-realistic images come from?

On the surface, it doesn’t look like much is going on when we sleep. We’re largely immobile, lying still with our eyes closed and only our chests moving as we breathe. We’re not making decisions or thinking conscious thoughts, so it’s easy to assume that our brains are inactive, as well. However, the opposite couldn’t be more true – while the rest of the body winds down, our brains are still up and running, firing tiny electrical signals within itself to transmit information.

There are two types of sleep – REM and non-REM – which we alternate between throughout the night. REM stands for “rapid eye movement” and it’s exactly what it says on the tin – while we’re in this stage, our eyes rapidly flicker left and right (thankfully we have our eyes closed or every midday nap would look like the stuff of nightmares). When we first drift off to sleep, we enter the non-REM stages where brain activity drops. After about 90 minutes, we enter REM sleep. Aside from the disconcerting side-to-side eye movement, other changes occur: our heartbeats and breathing rates pick up, while our muscles become paralysed and we become more still. In the brain, activity is boosted and becomes close to what it’s like while we’re awake. REM sleep is when our most vivid dreams are thought to occur – our muscles are paralysed to prevent us from acting out those dreams while lying in bed.

Dreams are thought to be a side effect of memory consolidation during sleep. The brain is thought to spend sleep (REM in particular) “tidying up” the information we’ve taken in during the day. Imagine that, as you go about your day and interact with the world, you pick up all sorts of things and throw them in a bag. Then, at night, you sort them all out – you get rid of things you don’t need and organise everything else, and store them away. This is what we think the brain is doing with every memory you have of the day – it discards unimportant information, like the hair colour of someone you saw in an advert, and consolidates that which matters, like facts you (maybe) took in from a lecture. To store them away, it moves information from where they’re temporarily stored, a region called the hippocampus, to more permanent regions around the brain. This happens by the repetition of the specific electrical signals which trigger that memory, resulting in all this information flashing in our mind as a “dream” which our (usually) rational human brains draw a plot out of. This might be why we have dreams with familiar details, such as my dream in Glasgow with my friends, because the brain is basically reliving past experiences while we sleep.

As we all know, though, dreams don’t always make sense. If it was just us reliving past experiences, how does that explain my strange dungeon-raiding adventure, or even the gig that is definitely not on the quarantine cards? This can be explained by the differences in activity levels across the brain. Different regions are related to different functions, like how the nose is related to smell and eyes to sight. The prefrontal cortex, which is located at your forehead, is largely involved in rational thought. During sleep, this becomes less active – this makes sense since we don’t need to think very much while we’re knocked out. On the other hand, the limbic system, located deeper in the brain, is involved in emotional responses and is much more active during sleep. Combined, this means that the information we process is less likely to have a strong sense of logic and more likely to be fantastical and emotional. This is also why we have nightmares and anxiety dreams so frequently – the limbic system is linked to our fear responses, which is why our daytime worries and deepest fears can continue to nag us at night. In my case, my brain might have drawn from my love for certain video games, or late-night longing for my life in Glasgow.

Still, there’s a lot of questions we can ask about sleep and dreams. The theory of memory consolidation isn’t a fact – what if dreams aren’t just a side effect, but some big psychological evaluation of our deeper psyche? Like with a lot of brain-related phenomena, it’s not fully certain and research is still ongoing. For now, we can wake up from our weird and wonderful dreams with an appreciation for the complexity of the human brain, at least for a minute before lockdown boredom takes over and we go back to sleep.

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