Can we solve problems in our sleep?

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By Sam Berry

Edited by Becca Loux

Becca is a guest editor for Brain Domain and an avid fan of science, technology, literature, art and sunshine–something she appreciates more than ever now living in Wales. She is studying data journalism and digital visualisation techniques and building a career in unbiased, direct journalism.

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Have you heard the song “Scrambled Eggs”? You know:

“Scrambled eggs. Oh my baby how I love your legs.”

No? Perhaps you would recognize the tune.

A young Paul McCartney woke up one morning with an amazing melody in his head. He sat at the piano by his bed and played it out, and he liked it so much he couldn’t quite believe it had come to him in a dream. The tune was there, but he just couldn’t find the right words to fit. For several months he tried, but he couldn’t get past “Scrambled Eggs” as a working title.

So how did the famous Beatle complete his masterpiece? He did some more sleeping. Another fateful day, he woke up and the song was there, fully formed with lyrics and the now famous title “Yesterday.”

“Yesterday, all my troubles seemed so far away.”

Recognise it now? A critically acclaimed worldwide hit had formed itself in his sleep. Boom. A chart smashing phenomenon.

—— —– —– —– —— ——

It may seem obvious, but not sleeping is extremely bad for you. Symptoms of sleep deprivation include a marked decline in the ability to concentrate, learn, and retain new information. It can affect your emotions, self-control, and cause visual and auditory hallucinations.

Whether not sleeping at all would actually kill you has not yet been established. The record time for someone staying awake is 11 days and 25 minutes during a science experiment in 1965. The subject was kept awake by two ‘friends’ as they observed him become a drooling delusional mess. Yet there are plenty of studies that demonstrate serious detrimental health effects of both short and long-term sleep deprivation.

Being mentally and physically alert will certainly help you to solve problems, but many scientists think something much more interesting is going on during sleep. Your brain is still learning whilst you are snoring.  

You are only coming through in waves…

Okay, so do we know how sleep can help us to learn? We’re getting there. Using brain imaging technology like fMRI scanners (giant magnets that use blood flow changes to see how different parts of the brain react to things) and EEG (funky hats with electrodes that measure how our neurons are firing in real time), we can have a look at what the brain is doing while we’re dozing off.

Our brains remain active while we sleep. Sleep can be split into different stages, and what happens during these stages is important for memory and learning. Broadly speaking, your sleep is split into non-REM (Stage 1, 2, and Slow Wave) and REM (Rapid Eye Movement) stages. These are traditionally separated depending on what the pattern of electrical output from the EEG is showing. I’ll briefly take you through what these different stages are and how our neuron activity changes as we go through them:

Stage One sleep is when we start to doze off and have our eyes closed. Have you ever noticed a grandparent falling asleep in their chair, but when you ask them to stop snoring they wake up insisting they were never asleep in the first place? That’s stage one sleep; you can be in it without even knowing.

Stage Two is still a light sleep, but when brain activity is viewed using EEG you can see an increase in spiking brain activity known as sleep spindles.

Slow Wave Sleep is so called because in this stage neurons across the brain activate together in unison, creating a slow, large coordinated electrical pattern. This makes the EEG output look like a wave. Slow wave sleep also contains some of Stage Two’s sleep spindles, and as well has something called sharp wave ripples. This is where a brain area called the Hippocampus (involved in memory and navigation) sends bursts of information to the Neocortex (involved in our senses, motor movement, language, and planning to name a few).

REM sleep is when our bodies are paralysed but our eyes dart around. Our blood pressure fluctuates and blood flow to the brain increases. While we dream throughout sleep, our dreams during REM become vivid and our brain activity looks similar to when we’re awake.

We cycle through these stages in 90 -120 minute intervals throughout the night, our sleep becoming deeper and more REM-based as the cycle progresses. Disruptions to the sleep cycle are associated with decreases in problem-solving ability as well as psychiatric and neurodegenerative disorders like Alzheimer’s.

Spikey learning

Problem solving requires memory: you need to use information you already have and apply it to the problem at hand. You also need to remember what you tried before so that you don’t keep making the same mistakes (like singing “Scrambled Eggs” over the same tune forever). The stages of sleep most relevant to helping us keep hold of our memories are the non-REM ones, and in particular Slow Wave Sleep.

Recent research reveals that sleep spindles, slow waves, and sharp wave ripples work together so when a slow wave is at its peak the brain cells are all excited, creating the perfect environment for the sleep spindles to activate. When the wave is crashing down, the sharp wave ripples from the Hippocampus are more likely to fire to the Neocortex. Recent research tells us this coupling of spindles and slow waves is associated with how well you retain memories overnight. Interestingly, in older adults spindles can fire prematurely before the wave reaches its peak, suggesting a possible reason why memory gets worse with age.

Researchers say this pattern of brain activity is a sign of the brain consolidating, or crystallising, what was learned or experienced whilst awake. This process strengthens the neural connections of the brain. Studies show that the pattern of neurons that get excited when we learn something are reactivated during sleep. This could mean that during sleep our brains replay experiences and strengthen newly formed connections.

Getting freaky

So what do our dreams mean? We’ve all had bizarre ones—how about that common dream where all your teeth fall out?

During REM sleep, our brain activity looks similar to when we’re awake. Scientist Deirdre Barrett suggested we think of REM sleep like merely a different kind of thinking. This type of thinking uses less input from the outside world or from the frontal parts of our brain in charge of logical thinking. REM is thought to be involved in consolidating our emotional memories, but it is also when we tend to have the vivid visual dreams that may defy logic. This combination enables REM “thinking” to be creative or even weird. REM sleep may allow us to form connections between ideas that are only distantly related.

Recently, a team in Germany suggested that Non-REM sleep helps put together what we know while REM breaks it up and puts it back together in new ways.

Thoughts before bed

So “sleeping on it” really can help solve problems. It strengthens the memories you make during the day and it helps learn and see things more clearly when you wake up. REM sleep may also allow thinking to be unconstrained by logic and divide and reshape ideas during REM. If reading this article made you sleepy, go ahead and take a nap. You might learn something.

References

Barrett, D. (2017). Dreams and creative problem-solving: Dreams and creative problem-solving. Annals of the New York Academy of Sciences, 1406(1), 64–67. https://doi.org/10.1111/nyas.13412

Carskadon, M. A., & Dement, W. C. (2005). Normal human sleep: an overview. Principles and Practice of Sleep Medicine, 4, 13–23.

Chambers, A. M. (2017). The role of sleep in cognitive processing: focusing on memory consolidation: The role of sleep in cognitive processing. Wiley Interdisciplinary Reviews: Cognitive Science, 8(3), e1433. https://doi.org/10.1002/wcs.1433

Haus, E. L., & Smolensky, M. H. (2013). Shift work and cancer risk: Potential mechanistic roles of circadian disruption, light at night, and sleep deprivation. Sleep Medicine Reviews, 17(4), 273–284. https://doi.org/10.1016/j.smrv.2012.08.003

Helfrich, R. F., Mander, B. A., Jagust, W. J., Knight, R. T., & Walker, M. P. (2018). Old Brains Come Uncoupled in Sleep: Slow Wave-Spindle Synchrony, Brain Atrophy, and Forgetting. Neuron, 97(1), 221–230.e4. https://doi.org/10.1016/j.neuron.2017.11.020

Klinzing, J. G., Mölle, M., Weber, F., Supp, G., Hipp, J. F., Engel, A. K., & Born, J. (2016). Spindle activity phase-locked to sleep slow oscillations. NeuroImage, 134, 607–616. https://doi.org/10.1016/j.neuroimage.2016.04.031

Landmann, N., Kuhn, M., Maier, J.-G., Spiegelhalder, K., Baglioni, C., Frase, L., … Nissen, C. (2015). REM sleep and memory reorganization: Potential relevance for psychiatry and psychotherapy. Neurobiology of Learning and Memory, 122, 28–40. https://doi.org/10.1016/j.nlm.2015.01.004

Lewis, P. A., & Durrant, S. J. (2011). Overlapping memory replay during sleep builds cognitive schemata. Trends in Cognitive Sciences, 15(8), 343–351. https://doi.org/10.1016/j.tics.2011.06.004

Ólafsdóttir, H. F., Bush, D., & Barry, C. (2018). The Role of Hippocampal Replay in Memory and Planning. Current Biology, 28(1), R37–R50. https://doi.org/10.1016/j.cub.2017.10.073

Sio, U. N., Monaghan, P., & Ormerod, T. (2013). Sleep on it, but only if it is difficult: Effects of sleep on problem solving. Memory & Cognition, 41(2), 159–166. https://doi.org/10.3758/s13421-012-0256-7

Staresina, B. P., Bergmann, T. O., Bonnefond, M., van der Meij, R., Jensen, O., Deuker, L., … Fell, J. (2015). Hierarchical nesting of slow oscillations, spindles and ripples in the human hippocampus during sleep. Nature Neuroscience, 18(11), 1679–1686. https://doi.org/10.1038/nn.4119

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