The Science of Sleep II

Here comes the second part of the post unveiling the exciting secrets of what happens in your brain when you close your eyes and drift off to the dream land (and what happens if you don't do it properly). Buckle up and enjoy! 

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4. Dreams

Ah, dreams, the most intriguing, mysterious and exciting part of sleep. How much we know about it? You guessed it -- not enough to be sure of anything.

Let’s skip all the Freudian “wishes of the unconscious” (it is a blog about science after all…) and get straight to the facts. Some researchers think that there is a link between newly made memories, their consolidation and the formation of dreams.1 One hypothesis is that when elements from a new memory appear in dreams it gets easier for the brain to save them as they get replayed in their original state (=you “perceive” the memories again). There are studies showing that in the morning, after dreaming about newly learnt stuff, people are better at recalling this stuff than people who did not dream about it.1

Although the exact brain regions responsible for dream generation remain elusive, in a couple of recent studies scientists have made some progress in identifying which brain part makes us dream. It turns out that the parieto-occipital region, working for mental imagery and processing of all your perceptions during the day, is a hot zone for dreaming during the nighttime.2 And if enjoy your nighttime adventures (Jesus, that came out wrong), you should take really good care of this region -- studies show that brain damage affecting it leads to the loss of the dream experiences.3 Moreover, the scientists looked into what brain areas are activated while you dream of certain stuff. For that, they created five rough categories (thinking/perceiving, speech, faces, movement and any kind of a spatial setting) and found that when people dream of a certain category the brain area which is responsible for it in the waking state was also significantly more active than the others. Meaning that the “perception” of specific information activates the same brain parts, no matter, real or dreamt.

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5. What can go wrong?

As with everything in life, sleep can go wrong -- and there are many ways for it to do so: from the once in a while insomnia we are all familiar with to the incurable “fatal family insomnia”, a disease which prevents you from falling asleep at all, resulting in hallucinations, dementia and death. Woah. Intense. But let’s start with something less heavy.

There are insomnias -- when you cannot fall asleep, hypersomnia -- when you sleep too much, parasomnias -- when you display abnormal behavior during sleep and some others (such as sleep apnea when you have troubles breathing during sleep).

Insomnia can be caused by a myriad of factors -- you might just be too nervous before an exam tomorrow, or you keep going through this stupid thing you said five years ago (or it is a side effect of another medical condition you have). However, sometimes your brain just sabotages your sleep -- research suggests that the brain of people with primary insomnia (that is, insomnia not connected to any other condition) might be lacking a certain neurotransmitter, GABA, which acts as a “brake fluid” of the brain. It was shown that adults with chronic insomnia have 30% less GABA than the average population.4 Consequently the brain is unable to shut down the waking signals, leaving the brain hyperactivated. Moreover, it was found that these patients also have some problems with their brain connectivity -- the connections to and from thalamus, the region of the brain that regulates tons of stuff, among others consciousness, sleep and alertness, were weakened.5 It is not clear yet whether the disrupted connections are the cause or the consequence of insomnia but at least it’s shedding some light on this mysterious disease.

 Red: white matter tracts where the integrity was disturbed in patients with primary insomnia. From https://pubs.rsna.org/doi/full/10.1148/radiol.2016152038

Red: white matter tracts where the integrity was disturbed in patients with primary insomnia. From https://pubs.rsna.org/doi/full/10.1148/radiol.2016152038

Hypersomnias, on another hand, make you sleepy all the time. Narcolepsy, a disease when you are excessively sleepy and uncontrollably fall asleep during the day time, is a prime example of a hypersomnia. It was found that people with narcolepsy have too little hypocretins in their brains.6,7 Hypocretins (what a slightly offensive term) are chemicals produced in hypothalamus (remember, we mentioned it in the first part?) which signal to the brainstem, a region which keeps us alert and awake, to.. well, keep us alert and awake. So when these hypocretin cell die off for some reason (mostly autoimmune response) it becomes hard for the affected person to stay awake for the longer period of times as nothing is signaling the brain that it should keep itself awake.

 The number of hypocretin-producing neurons in a healthy person (left) vs. a narcoleptic person (right). From http://healthysleep.med.harvard.edu/narcolepsy/what-is-narcolepsy/science-of-narcolepsy

The number of hypocretin-producing neurons in a healthy person (left) vs. a narcoleptic person (right). From http://healthysleep.med.harvard.edu/narcolepsy/what-is-narcolepsy/science-of-narcolepsy

Now parasomnias include such things as sleep-walking, sleep terror and even sleep sex (although sometimes sleep sex is grouped in the same category as sleep-walking). A 2012 study revealed that 29,2% of Americans have had at least one sleepwalking episode in their lives.8 It typically occurs during the deep sleep of the stage 4 (the one that leaves you groggy should you wake up during it). While most occurrences are harmless, sometimes sleepwalking can really escalate (cue Kenneth Parks who sleep-drove 23 kilometres to his in-laws house and sleep-killed them and then sleep-drove himself to the police station). Studies suggest that such episodes might be due to our more “primitive” brain parts involved in emotional response (limbic system) and complex motor activity staying awake while the higher developed brain areas controlling rationality and memory remain dormant. The brain is stuck in the wake-sleep-limbo and is regulated by an archaic survival system as our normal control mechanisms are still asleep. 9

The man who murdered his in-laws during a sleepwalking episode.

Now lastly let’s look at what happens how not getting enough sleep actually affects your brain. We all know sleep deprivation is a bitch -- you don’t feel well, you start forgetting things, you snap at people and you are just operating on an autopilot. But what exactly does it do to your brain?

 Agent Cooper knows best.

Agent Cooper knows best.

Just recently, scientists found that 24 hours of sleep deprivation can cause symptoms similar to schizophrenia: people developed strong attention and concentration deficits and were not able to filter incoming sensory information which in turn led to a sensory overload.10 They also reported an altered sense of time and smell and some people even said they had an impression that they were able to read thoughts.

Not long ago there was also a study making rounds on all social media titled something like “Brain EATS ITSELF when you don’t sleep enough!!!”. What the study actually found was that the cells responsible for cleaning out trash, destroying and digesting worn-out cells and pruning unnecessary connections between brain cells (synapses) go into overdrive in sleep-deprived mice.11 Astrocytes, cells which take care of redundant synapses, were active in only about 5% of cells in the brains of the well-rested mice; in the sleep deprived mice, however, this number increased to 13%. Not only that, astrocytes in sleep deprived mice began to not only carefully prune the synapses to refresh brain’s wiring, but to actually eating them in a process known as “phagocytosis” (from an Ancient Greek word meaning “to devour”). However, despite how bad it sounds (and how well the sensationalist headers like “the brain eats itself!!!” sound) the scientists said that the synapses which are getting eaten are one of the strongest, oldest and most heavily used. So in a way it is like old pieces of furniture being taken care of with a little bit of tough love. Which the researchers did not deem to be too catastrophic. Another result was a bit more worrisome. Microglia, cells which clear out old and worn-out cells (also using phagocytosis) went into overdrive after chronic sleep deprivation as well. This is not that good because microglial hyperactivation was linked to diverse neurodegenerative diseases such as Alzheimer’s.12,13 It has also been shown that disturbed sleep makes people more vulnerable to dementia14, 15 -- so maybe there is a link there.

Another study has found that sleep deprivation led to a much slower reaction to outside events -- caused by the slower transmission rates between neurons.16 So basically brain cells got tired too and just couldn’t transfer information in a normally fast way leading to cognitive lapses and slowed down reaction times. Instead of a post-8-hour-sleep Bugs Bunny-like race the thoughts were crawling like a turtle. So the moral of the story is: go to bed. No more Netflix and facebook for today.

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6. So how much sleep do we need and how to sleep well?

We all have heard of the magic 8 hours of sleep. Eight hours for the most restful sleep, eight hours to align your chakras, eight hours this eight hours that. But is it actually accurate? It seems that articles challenging the 8 hour notion and offering hot new takes on the optimal sleep duration are popping up more often than I actually manage to get a full-night sleep.17, 18 So what’s the truth?

Well, although there is no ultimate exact-to-the-minute answer there is at least an estimate scientists seem to converge on. Of course, there are people, aptly called “short sleepers”, who, due to a rare genetic mutation, wake up fully rested after a very short amount of sleep (such as 4 or 5 hours) and for whom the normal rules don’t apply.19 However, the majority of the population is less lucky and for us ordinary people seven to eight hours seem to be a pretty good estimate. There are studies investigating the relationship between sleep and things like cardiovascular disease20,21,22, obesity23, depression24, and mortality rate25,26,27 and showing that this relationship looks like a U-shaped curve with the above mentioned things being the lowest at 7 to 8 hours of sleep. Furthermore, the American Academy of Sleep Medicine (AASM)28 and the National Sleep Foundation29 have released the sleep time duration recommendations and they both agree that it should be 7 or 8 hours (the AASM cryptically calls it “7 or more” while stating that more than 9 hours might also have adverse effects). Oversleeping does, indeed, have adverse effects: one study has found that long sleepers might be at a higher risk for dementia30, some studies have shown that over-the-top long sleep duration (as well as too short btw!) lead to decrease in cognitive functioning31 and impaired memory32 and some more studies have found that inflammation levels are much higher in people sleeping more than 8 hours.33,34

 Risk for the overall mortality, cardiovascular disease, coronary heart disease and stroke is at the lowest for 7-8 hours of sleep. From http://jaha.ahajournals.org/content/6/9/e005947

Risk for the overall mortality, cardiovascular disease, coronary heart disease and stroke is at the lowest for 7-8 hours of sleep. From http://jaha.ahajournals.org/content/6/9/e005947

By this criteria it appears that the Western society is constantly toying with sleep deprivation -- some surveys estimate that 35% of the US adults and three quarters of Brits participating in the questionnaire are getting less than 7 hours of sleep.35, 36 This is pretty unfortunate since, as we remember from the previous sections, lack of sleep can take a heavy toll on your health. Moreover, it is estimated that in the US alone the sleep deprivation costs the economy billions of dollars in lost efficiency and performance.37 So, it is important to plan your days the way that you get at least 7 hours of sleep most of the days -- I know, I know, it is annoying considering that an average adult in our society needs like 30 hours every day just to catch up on all the chores and workload and social life and relaxation and and and, but in the long run it is really important to not deprive our body of the precious sleep time and to make time for a full recovery.

You are probably asking: can I catch up on sleep? What if I just sleep 12 hours on the weekend: will it make my body forget the terrible all-nighters I pulled all week? Unfortunately it doesn’t work like this. One study has found that catching up on sleep on a weekend after having a sleep deprived week only decreased the subjective feelings of sleepiness and the level of inflammation.38 The impaired cognitive performance (speak focus and attention) resulting from the sleep deprivation did not improve after the extensive weekend sleep session. Meaning: sleeping a lot in advance (or retroactively) won’t help your impaired concentration and attention levels; you have to sleep an adequate amount every night to keep them high.

 I imagine it affects not only Britons and Americans.

I imagine it affects not only Britons and Americans.

Now how to actually sleep better?

As we learnt in the previous part, blue light is not a friend when it comes to falling asleep. Meaning a power-down routine including putting away your devices around an hour or two before going to bed, not using the said devices in bed in order to not associate rest with work or the overwhelming information flow (she typed on her laptop while laying in bed) or at least downloading an app called f.lux which decreases the brightness of the screen before bedtime and eliminates the blue light from it.

Another method to wind down before bed includes relaxation. A mindfulness meditation (meaning no more and no less than just concentrating on your breathing, bodily experiences, your environment and noticing your thoughts instead of engaging with them) has been shown to help people with insomnia and to improve sleep quality (aside from its other 10000 health benefits).38,39,40,41,42, 43 Something as simple as concentrating on your breath for 10 minute instead of looking at r/funny can go a long way. Your mind calms down and stops racing with the To-Do-List for tomorrow or the embarassing situations list from today. Personally I use the 10% Happier App (Meditation for Fidgety Sceptics) and I couldn’t be happier with it. They also have free meditations! (I was not paid for this ad… Unfortunately).

Another intuitive thing to help you sleep is to avoid caffeine before bed -- and by before bed I mean already after lunch. One study found that consuming caffeine as early as 6 hours before bedtime delays reduced total sleep time by 1 hour.44 So to make sure caffeine does not interfere with your sleeping habits it is probably a good idea to drink it at maximum 7-8 hours before bed. Another study has found that caffeine also can delay the timing of your internal clock and thus reduce your sleeping time by keeping you awake longer45 -- just another small reminder not to drink coffee in the second half of the day. To sum up, the sleep-friendly way to consume your daily drug would be the following: stick to the 2pm cut-off and taper caffeine as the day goes on.

 Oh boy was I excited to use two Agent Cooper gifs in this article.

Oh boy was I excited to use two Agent Cooper gifs in this article.

Finally, it is important to keep it cool in the bedroom (insert an awkward sex joke here) -- it has been suggested that the optimal range for sleeping is between 18 and 21 degree Celsius (65 to 68 degrees Fahrenheit).46,47,48,49 Some hours before falling asleep our body temperature starts to fall -- and the mild drop in the room temperature helps induce sleep. One study has found that just a 0.4C increase in skin temperature (which allows the body to release more heat) led to sounder sleep and fewer wake-ups.50 In fact, some studies show that disturbed thermoregulation (and thus a too high body temperature during the night) is associated with some forms of insomnia.51

So now you have a good idea of how to make the most of your sleep, what are the adverse effects of thinking 3 hours of sleep after an all-nighter are enough and also that some guy killed people during a sleep-walking episode. Good night and stay tuned for a neuroscience news block coming soon!