Penny Lewis
Here is the full transcript of neuroscientist Penny Lewis’ TEDx Talk Presentation on Sleep-Engineering: Improve Your Life By Manipulating at TEDxGrandRapids conference. Dr. Penny (Penelope) Lewis is a neuroscientist at the University of Manchester and is the author of The Secret World of Sleep.
Listen to the MP3 Audio: Sleep-Engineering- Improve Your Life By Manipulating Your Sleep by Penny Lewis at TEDxGrandRapids
Penny (Penelope) Lewis – Neuroscientist
You know, for a sleep scientist, I actually don’t sleep very well. Any little chink of light in the room and I’m awake all night. And my eye mask is just as important to me as my laptop. But really I take sleep very seriously, and I’m hoping this talk will be a sort of a wake-up call to all of you, to make some of you feel the same about it.
Now, what I’m not going to do is preach to you about how you should get more sleep. We all know that; we all know we live in a sleep-deprived society.
Instead, I’m going to talk about something which I think is much more interesting. This is how we can manipulate the sleep that we do get in order to get the most out of it, in order to improve our quality of life and I call this the New Science of Sleep Engineering.
But let’s start from the beginning. As humans, we spend roughly a third of our lives of sleep, eight hours a day. That’s more time than we spend doing anything else. That’s a huge amount of time. And just the pure fact of that time investment suggests that sleep must be doing something incredibly important.
Sleep is All About The Brain
But what is this? Well, it turns out that sleep is all about the brain. Contrary to popular opinion, the brain doesn’t just switch off when we go to sleep. Instead it goes through a series of highly specific different types of activities. We can measure these by putting electrodes all over the scalp like this. This by the way is a sleep scientist’s idea of a selfie.
With these electrodes, we can measure the electrical activity of the brain, and during wake it looks something like this, just a wiggly line, with time going from left to right. And what that tells us is the brain is active, good — and that the activity is not particularly synchronized. So things aren’t summing up in any particular way.
But as we fall asleep, the pattern changes a little bit. It slows down a little bit and the amplitude of those brain waves gets a little bit higher showing a bit more synchrony. And we also start to see occasional bursts of high-frequency activity that we call Sleep Spindles. These spindles don’t occur across the whole brain; they just occur in localized areas at any one time. And I’m going to come back to them several times during the talk to try and remember what those look like.
Now as we go deeper into sleep, the activity slows down still more. And we start to see these high amplitude slow oscillations that we call Slow Waves. And this shows a high degree of synchrony in the firing across the cortex. Many neurons are all firing together, then pausing, then firing together. It’s very different than the kind of activity that we see during awake.
And if we go still deeper, we go into a sleep stage that I’m sure you’ve all heard about Rapid Eye Movement Sleep. This is famous for the way the eyes dart around under closed lids. And it actually looks very similar to the brain activity that we see during wake, probably because of all the dreaming that’s happening, not much cortical synchrony.
So why do we do this? Why do our brain spend a third of our life going through these highly precise different types of activity in a cycle from one stage to another?
Well, there are two main answers to this. One of them relates to sleep’s role in maintaining a healthy brain; and the other to its role in learning and memory. And I’m going to start by talking about the healthy brain.
Sleep plays sort of a housekeeping role. It cleans our brains. It helps us to remove toxins. And some of the most interesting studies of this have shown that the spaces between brain cells expand during that slow wave sleep I showed you by as much as about 60%. And this allows cerebrospinal spinal fluid (CSF), the fluid in the brain, to flush through and efficiently clear away toxins that have built up during wake.
One of these toxins that’s particularly interesting is something you might have heard about: beta amyloid. This is a protein that can build up not only during wake but actually across a lifetime and build-ups of beta-amyloid are linked to the formation of plaques in the brain that are predictive of cognitive impairment, particularly problems with memory. If it gets bad, it’s also linked to dementia and Alzheimer’s disease.
Beta amyloid is also linked to cell death in the brain and a gradual degeneration of some parts of the cortex that can happen with aging — again in dementia and Alzheimer’s disease. So it’s obvious that it’s important for us to flush this out of the brain if we possibly can.
Now, interestingly, as we age our sleep patterns also change. As sleep becomes more fragmented and those high amplitude slow oscillations that I told you about gradually stretch and flatten out and after the age of 65 or so is quite common not to get any more slow wave sleep at all; problem, right?
Furthermore, this gradual decline in slow wave across the life cycle has been shown to predict the extent to which the cortex actually attributes and shrinks. So some of the prefrontal regions of the cortex and that shrinkage is predicted by the decrease in slow wave sleep.
So wouldn’t it be great if there was a way that we could maintain those slow waves as we got older and not have that decline? And this is where we come to sleep engineering.
Very recent research has suggested a way that we can do this. If we play sounds to people, just click — simple click sounds while they’re in slow wave sleep, and if we place those sounds near the peaks of those high amplitude slow oscillations, it turns out that it can enhance them. Let me show you what this looks like.
So the clicks occurring just near the peak boost the amplitude and they’ve also been shown to improve memory the next day. That works very well in healthy young people. And I’ve got several quite sleep-deprived graduate students who are working hard on taking this to the older population. And right now our results are very promising. So we’re hoping that in not too many years we might be able to offer a sort of a preventative treatment that could help people to maintain their slow wave sleep as they get older, and possibly might slow down some of this decline — cortical and cognitive that happens.
So let me move on now to talk about learning and memory. And in his famous book One Hundred Years of Solitude, Gabriel García Márquez wrote about a plague of insomnia that swept across the land. People just couldn’t sleep and at first they didn’t mind that at all. But eventually negative symptoms started to manifest and these symptoms were the fact that they lost their memories. They couldn’t learn new things and they started to forget what objects were; they had to cover things with note, saying things like ‘This is a cow; it gives milk, pull here.’
Given that this book was published in 1967 when we knew almost nothing about sleep’s role in memory, it’s really quite remarkable that Garcia Marquez had insight into this. But subsequent research has shown that he was absolutely right. Sleep is very important for forming new memories and also integrating those memories with what we know already, also strengthening memories.
Let me give you an example of this. I want you all to hold up your left hand and we’re numbering your fingers from one, pinky to four, index finger and now I want you to press your fingers on your thumb in this pattern: 4, 1, 3, 2, 4. 4, 1, 3, 2, 4. 4, 1, 3, 2, 4. Okay, I think you all got it.
This was the task that was used in the experiment I want to tell you about. People were asked to press 4, 1, 3, 2, 4 sequences like this as quickly as they could for about two hours. They were pretty bored but they also stopped getting faster, and that’s what the experimenters wanted. And when they got to that point, they were given a test. 30 seconds; press as many 4, 1, 3, 2, 4 sequences as you can. And this all happened around about 10am and what people did just find — they pressed about 21 sequences and then they were told to go away, come back 12 hours later and do it again. And their performance didn’t change much.
Now here’s the interesting bit. They went away a second time and they slept overnight and they came back and did this a third time. And now their performance improved dramatically, about 20% improvement. And furthermore, the extent to which they improved was predicted by the sleep spindles –remember those high frequency oscillations I told you about — that occurred over the bit of their brain, the motor cortex, that’s particularly associated with hand movement.
So this is the kind of data that suggested that sleep is doing something really important for memory. It’s helping us to strengthen up memories.
But it turns out it doesn’t just help us to strengthen memory; sleep also helps us to integrate memories and to make connections between things that we might not otherwise have realized were connected. And this is critical for solving some kinds of problems. It’s critical for creativity and forms of innovation. And I bet everyone here if you think about it has experienced this: you’ve woken up in the morning with a solution to something that you hadn’t been able to solve the day before.
So in fact, our history is peppered with examples of this.
[Music]
So this sonata by Tartini is an example. This was inspired by a dream that he had of the devil playing violin on his bed. A more scientific example comes from Friedrich Kekulé who won the Nobel Prize for discovering the chemical structure of benzene: it’s cyclical rather than acyclic or linear. And again, this was inspired by a dream in which he saw a serpent biting its own tail. Interestingly, this type of associative problem-solving is linked to REM sleep rather than spindles, or slow wave sleep.
What’s Going On in Sleep?
So what you might be wondering is well, what’s going on in sleep? How does sleep allow us to do these things? And the answer seems to be linked to the fact that memories are spontaneously replayed during sleep. So the neural activity associated with something that you’ve done replays spontaneously when you’re asleep.
Let me explain to you an experiment which shows this. This is a maze which participants were asked to navigate around in a video game. And while they were doing this, their brain activity was measured and unsurprisingly the hippocampus amongst other areas which is associated with spatial memory and navigation was active while they did this.
Then the same participants stayed in the scanner and they’re asked to sleep. And during slow-wave sleep, those high amplitude slow oscillations I told you about, the same structure was active again. And the extent to which it was active actually predicted how much better they got at navigating around the town and when they were tested again the next day.
Furthermore, the sleep spindles that I told you about are thought to be a marker of this type of reactivation. So not only is this experiment a nice example of how a reactivation happens during sleep and is linked to strengthening memories but also that finger tapping experiment I told you — this explains why the spindles over the motor cortex were greater because actually that people were probably reactivating those memories as well.
So what has this got to do with sleep engineering? Well, what’s exciting about it is now that we know reactivation during sleep is important for strengthening memories, we’ve also learned how to manipulate it. So we don’t have to sit and wait for reactivation to happen spontaneously, but instead we can control it.
And let me show you how this works. If I show you a cat in this part of the screen and a dog in this part of the screen, and then tonight when you’re asleep and you enter slow-wave sleep, I’m watching and I play — then the next day when I test you you’ll be much more likely to remember where the cat was on the screen than the dog. And that’s because that sound cue will have triggered reactivation of the memory and strengthened up that memory.
So this doesn’t end with just simply strengthening memories, it’s been shown that if we trigger some kinds of problems while people are asleep, then they can be better at solving those the next day as well. So reactivation can also help with association and potentially with creativity and innovation as well.
But as we all know we don’t want to remember everything always. So I’m sure some of you have had a traumatic experience at some point in your life. You may have been mugged, you may have been in a car crash. It may have been other things that happened to you that you’d really — you might not mind remembering the details but you really don’t want to be as upset about it every time you remember it as you were right after it happened.
And we’re interested in this and how reactivation during sleep might help with it. And it turns out that if we show people upsetting pictures or videos and then play them the associated sounds when they’re in slow wave sleep — then ask them the next day how upsetting that was, the things that have been replayed to them during slow-wave sleep will be less upsetting. So it looks as though triggering replay of memories can actually help to disassociate the emotional response from them as well.
We live in a time when we’re hyper aware of our bodies. We’re all very aware of how important exercises and how important diet is. We have gadgets to measure every calorie that we take in and every calorie that we expend. We even have gadgets to measure our sleep.
But I’d like to finish here by suggesting that we could be taking this to the next level. Instead of just measuring our sleep, we could be using the information that we now have about sleep to manipulate it in order to enhance things like reducing our aging, improving aspects of our memory, enhancing our creativity and also potentially controlling aspects of our emotional responses.
So as a sleep scientist, my hope is that in not too many years when your boss walks into your office and gives you a very difficult problem to work on it, you’ll feel like the most appropriate response to make to show her you’re taking this seriously is to pull out a pillow and tell her you’ll sleep on it.
Thank you very much.
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