Welcome to the Huberman Lab Guest Series, where I and an expert guest discuss science and science-based tools for everyday life.

I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today's episode marks the fourth in our sixth episode series, All About Sleep, with expert guest Dr. Matthew Walker. During today's episode, we discuss sleep and learning, as well as the impact of sleep and the specific stages of sleep on creativity and memory. We talk about the when and how long to sleep relative to different bouts of learning, as well as the role of naps and consolidating information that you are trying to learn. We discuss the science and protocols of sleep as it relates to both cognitive learning and motor learning, and the mechanism by which sleep encodes memories. As with the previous episodes in this series, today's episode includes information about the biology of sleep, as well as practical tools, that is, protocols, in which you can use sleep to improve your learning, memory, and creativity. Before we begin, Again, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public.

In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Helix Sleep. Helix Sleep makes mattresses and pillows that are customized to your unique sleep needs. It's abundantly clear that sleep is the foundation of mental health, physical health, and performance. When we're getting enough quality sleep, everything in life It goes so much better.

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Given that many of us have goals such as improving our sleep, building better habits, or just focusing more on our overall health, Whoop is one of the tools that can really help you get personalized data, recommendations, and coaching toward your overall health. In addition to being one of the most accurate sleep trackers in the world, Whoop allows you to recover more quickly and fully from physical exercise and other kinds of stress, and thereby to train more effectively and sleep better. If you're interested in trying Whoop, you can go to join. Whoop. Com/huberman today to get your first month free. Again, that's join. Whoop. Com/huberman. Today's episode is also brought to us by Waking Up. The Waking Up app is a meditation app that offers hundreds of guided meditations, mindfulness trainings, yoga Nidra sessions, and more. I started meditating over 30 years ago. At that time, there wasn't very much science on meditation, but by now, we know that there's a lot of strong science supporting the fact that a daily meditation practice can improve mood, focus, and alertness, and can reduce stress and improve sleep and overall health. One thing that I and many others have noticed is that while meditation is excellent for buffering stress, it's oftentimes during periods of stress that we let our meditation practice go.

The Waking Up app overcomes this by offering meditations of different durations, so they have some longer ones of 30 to 60 minutes, but also some much briefer ones, 10, five and even one minute meditations that are known to be effective. No matter how busy or stressed you get, you always make time for your meditation practice. The fact that they have lots of different types of meditations and yoga Nidra sessions and non-sleep deep rest protocols, also make sure that your meditations are kept fresh and interesting.

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I personally use the Waking Up app to do a 5 to 10 minute meditation or a non-sleep deep rest protocol, which is similar to yoga Nidra each and every day. If I miss a day, I try and double up the amount of time that I do NSDR, yoga Nidra, or meditation the following day. Yoga Nidra and non-sleep deep rest protocols can be done essentially any time of day in order to restore mental and physical vigor. I'll sometimes do one first thing in the morning if I wake up and I feel I didn't get quite enough sleep the previous night. You can also do yoga Nidra or NSDR in the middle of the night. If you wake up and you're having trouble falling back asleep, sometimes they will allow you to fall back asleep. If they don't, you'll still feel more refreshed than you would have had you been tossing and turning and worrying about not getting sleep. Nsdr and yoga Nidra are terrific for for both restoring mental and physical vigor and potentially for restoring sleep that you otherwise would have missed. If you'd like to try the Waking Up app, you can go to wakingup.

Com/huberman to get a free 30-day trial.

Again, that's wakingup.

Com/huberman. Now for my conversation with Dr. Matthew Walker.

Dr. Walker.

Dr. Huberman.

Welcome back. We have covered a lot of material. First episode of this series, you gave us an overview of sleep and some actionable items about sleep sleep. Then in the second episode, you gave us far more actionable items of how to think about one's sleep in a way that leads to very concrete decisions about controlling light, temperature, when to sleep, and then some really in-depth advanced tools or protocols, as we call them. Then in the third episode, we talked about caffeine and napping and some other things that people can do to really supercharge their alertness through sleep augmentation in the daytime. Today, we're going to talk about sleep, learning and memory, and a topic that I know everybody is very interested in, creativity.

Indeed. For a splendent pleasure to be back on the show. Thank you for having me.

Yeah, absolutely. I think nowadays, most people understand that there's some relationship between sleep and learning. But I think It would still be a good idea for us to zoom out a bit and establish what that relationship is. I think most people are familiar with being exposed to some new material, cognitive material, physical skill material, and not being able to learn it right away, but then having a few days in between, and then all of a sudden, voila. The skill has been embedded, it seems. But not obvious in that scenario is that sleep is perhaps the pivotal event that allowed the learning process to take place. How do you think about sleep as it relates to learning and memory?

I think I've conceptualized it in three different stages or three different buckets of a benefit. The first is that we need sleep before learning to prepare your brain to initially imprint and lay those memory traces down. But then you need to sleep after learning to take those freshly minted memories and then save them and cement them into the brain so that you don't lose them. The third domain is that sleep will then take those new memories that you've been learning, and it will start to collide them with all of this back catalog of information that you've already got stored in your brain. It updates the iOS of your informational systems so that then you come back the next day and you have a better-abled ability to understand how the world works. In other words, the difference between knowledge, which is learning the facts, and wisdom, which is knowing what it all means when you put it together, that's the third category. Why is that beneficial? Because it provides you with creative insights. We will Perhaps just double click on each of those three, and I can expand them because the data behind them is utterly fascinating.

As you said, I think many people subjectively have a sense that sleep helps me with my memory in some way. But in what way? For people, I think one of the things that you do here is not just protocols, but you help explain the conceptual understanding or the conceptual mechanisms underlying the reasons for all of these protocols I would love to dive into detail.

Yeah, so let's do that. Let's talk about this business of sleeping before learning, essentially establishing a milieu within the brain that is optimal for learning. What is that about? Neurochemically at the level of circuits, and what is the evidence that providing some, I don't know, additional sleep or just adequate sleep prior to the exposure to the new material can be beneficial?

I love that the word that optimal milieu, and it beautifully describes what we found. We started off asking a very simple question at my sleep center, is pulling the all-nighter a wise idea? We took a group of perfectly healthy, smart individuals, and we assigned them to one of two experimental groups, a sleep group and a sleep deprivation group. Both of those groups went through those two different protocols. Then the next day, after sleep or after no sleep, we put them inside of a brain scanner, and we had them try and learn a whole list of new facts as we were taking snapshots of brain activity. Then we tested them to see how effective that learning had been. When we looked at the group that had a full night of sleep, they had incredibly efficient learning capacity. In other words, they had learned and imprinted that information initially very well. When we looked at the sleep deprivation group, not so much. In fact, there was a 40% deficit in the ability of the brain to make new memories without sleep. We've used lots of different types. We've replicated that now. We've had visual information, we've had textbook-like information, and the range is somewhere between 20 to 40%.

I find that, by the way, striking, and we can come back to this, based on what we are seeing in our educational systems right now, there is this paucity of sleep because of this model of early school start times, and I'll explain exactly what's happened there and what we've been doing to try to change that. But coming back to those two groups, the sleep group and the sleep deprivation group, what was going on, as you said, inside of the brain that would help us understand why they couldn't learn, or at least couldn't learn effectively. The structure that we focused on is one you've spoken about before called the hippocampus. You have one on the left side and the right side of your brain. It looks like a long cigar that runs down the left and right side of your brain. People listening can think of the hippocampus almost like the informational inbox of your brain. It's very good at receiving new memory files and then holding onto them. When we looked at that structure and its activity during learning in the sleep group, they had wonderful, powerful activation of the hippocampus as if it was gobbling all of that new information into the inbox.

When we looked at the sleep deprivation group, however, we couldn't find any significant signal whatsoever. It was almost as though sleep deprivation had shut down the memory inbox and any new incoming files, they were just being bounced. You couldn't effectively commit new experiences to memory. Then subsequent studies that were not done by us, but looking at animal models, they were looking at how able the synapses are in that memory structure, the hippocampus, how capable those synapses are for building new connections. The synapses are just those connections between neurons, and we think that part of the way that we make memories is by strengthening the connection in the memory circuit itself. What they found was that when they restricted the sleep of these rats or the mice, that part of the brain It became very stubborn. It just wouldn't form those new synaptic connections. It's something that we call synaptic plasticity. We started to understand this was the bad that happened when you take sleep away. But let's come back to that control group that I said got a full night of sleep. Exactly what is it about sleep when you do get it that seems to support and promote your learning ability?

We decided to do another different study. Instead of manipulating sleep by dialing it down, we instead tried to dial it up by way of a daytime nap. Again, we took two groups and we had them initially learn, again, a huge amount of factual information They learned it over and over and over again. Then we brought them back 6 hours later at 6:00 PM, and now we had them learn a whole new set of information. After each one of those fresh, novel learning sessions. We tested them to see how effective that learning had been again. One of those groups spent that six hours of time awake doing just relaxing activities. The other group was able to obtain a 90-minute nap, and we used that 90-minute nap to allow them to go through a full average cycle to get some non-REM and to get some rem. What was interesting is that when we tested the group that remained awake later that following day, the learning capacity had declined. But in the nap group, it seemed to restore the brain's capacity to learn, and you didn't get that decline in memory. In fact, if anything, you got a little boost.

The difference between those two was about 20%, so it's quite a nice benefit.

Yeah, not trivial.

Not trivial at all. Then we said, Okay, well, if sleep is doing something, what is it about that sleep? We unpacked the the physiology of sleep and the different stages of sleep that we discussed in the first episode. What we found was that it was the non-rapid eye movement sleep or the non-REM sleep, and particularly those sleep spendles, those short bursts of electrical activity that we have discussed before, that seem to predict how restored and refreshed your learning ability was. And the best way that I've been thinking about this in terms of sleep, restoring or refreshing your encoding ability. It's a crass analogy, and I don't mean to make a direct brain to computer analogy, but think of that hippocampus almost like a USB stick. It's very good during the day, going around and grabbing new files, but it has a limited storage capacity. What sleep was doing seemed to be shifting those memories from the USB stick of your hippocampus over up to the cortex, which you can think of almost like your hard drive, bigger storage capacity. And by way of doing that, when you woke up after the nap or after a full night of sleep, you had this cleared out USB stick.

So what could you do? You could go around and start acquiring all these new files again. So that started to teach us a little bit about why sleep before learning is critical, but also mechanistically how sleep is doing this remarkable work of memory restoration. We then wanted to say, Well, can we translate this out into the real world? I think there are two regions that we've moved this work out into. One is education, one is medicine and Alzheimer's disease. But the education piece was very interesting. In the United States, I think the last time I checked, the average school start time is somewhere around 7:30, 7:45.

Sounds about right.

If you think about that for a 7:30 school start times, school busses will begin leaving around 5:30, 5:45 in the morning. That means that some kids are having to wake up at 5:00 AM, maybe even earlier. This is lunacy when you think about it. There's a great study in Edna, I hope I'm pronouncing that correct, Edna, which is a small suburb, or it sits in a small suburb outside of Minneapolis in Minnesota. They shifted their school start times from 7:25 to 8:30 in the morning. Then they wanted to ask, what is the consequence of that on the academic performance of their students? The metric that they used in these teenagers that they were focusing on was something called the SAT score, which is a score I had to learn when I first came to the United States is a critical assessment test that will largely determine which university you go to. They did an analysis which was clever. They focused on the top 10% performing students, which you could argue those are the ones that are closest to the ceiling performance and the hardest to expect any benefit from sleep. In the year before they made the time change, the average score of those top 10% performing students was 1,288, which turns out to be a pretty good SAT score.

The following year, after they made the time change, the average score for that top 10% was 1,500. That difference is non-trivial, and it will change exactly where those individuals will go to university in terms of the tier of the university and likely change the trajectory of their lives as a consequence. Now, some people have argued that data in terms of its source and its reliability may not have necessarily been accurate, but now we've got very consistent data. When you start school times later, academic grades improve, psychological and psychiatric problems decrease, truancy rates decrease. But something else happened in that story of later school start times that we didn't expect, which was that the life expectancy of students increased. You think, Well, hang on a second. How do you determine that? The number one cause of death in teenagers 16 to 18 It's actually not suicide. It turns out to be second. It's road traffic accidents. Here, sleep matters enormously. There was another great example from Teton County in Wyoming, and they shifted their school start times from, I think it was 7:35 in the morning to 8:55. The only thing more remarkable than the extra one hour of sleep those kids reported getting was the drop in car accidents.

That following year, there was a 70% reduction in car crashes in that age range of 16 to 18.

What time are they getting out of school?

Well, they will probably be ejected out of school. That's another interesting part, by the way. Maybe around 4:30. And people have said, Well, look, all of this idea of later school start times, it means that it's going to cost us more because you've got to change the school bus system. And they've argued pushback against that. And I would say probably two I know it's difficult, and I'm not saying it's an easy problem to do. It's a complex problem. I'm sympathetic to that. But I think we've put people on the moon, and so I suspect that we can also solve the problem of Early school start times. The other component of that is, what are we doing as educators? If our goal as educators is truly to educate and not risk lives in the process, then we are failing our children in a most spectacular manner with this incessant model of early school start times. If you look at the data, it's very clear. When sleep is abundant, minds flourish, and when it's not, they don't. That's the reason why myself and a whole group of sleep scientists, we started to try to create a movement for later school start times.

We got this bill passed, firstly in California, and we got it on the governor's desk at the time. It was Governor Brown. Unfortunately, he didn't sign it into law. Then when the organization changed and Governor Newsom came in as governor of California, we got the bill back on his desk, and he did sign it. Then the next state to go was New York. They started to put in legislation for recommendations for later school start times. I think Florida is about to fall as well in that regard. There's gradual movement happening, but it's hard fought and it's problematic. I still think that it's impossible to deny that data. I mean, it was an interesting thing. I remember when I was a professor back at Harvard, we were doing this work on sleep and learning, and it was published in these, I don't how we did it, but in nice journals. They said, Okay, based on the media traction, would you write an editorial for the Harvard newspaper, which was called the Harvard Crimson? I said, I'd love to. At first I thought, I'm just going to write a straight piece about sleep and memory and why it's important.

Then I realized, no, there's a better opportunity because teaching there, and you know this as well as I do, there is this bizarre system where we teach for an entire semester and then we end load the semester full of exams in this stressful two-week period. And what do you think is going to happen? They're not going to sleep, especially at a time when they're trying to cram information.

Especially in college, where you don't actually have the material four weeks before. So there's not really the option to learn it in advance. No. Everything's about university to me was about getting a bunch of information and needing to incorporate it very quickly and then move to the next item.

Right. Next item, next item. And then all of a sudden, there's this cataclysmic moment at the end of the semester, and you are supposed to regurgitate this by cramming everything into your brain in this soupless two-week period. Rather than saying, Look, the students need to change their behavior. They need to understand this is a problem, it's not their fault. I said, It's us as educators and administrators, we have created a system that forces them to undergo deliberate sleep deprivation, and we are educating them amnesic, quite literally. So I put this editorial out. It received a rather Baltic, if not Arctic, response, and that was the last editorial I was ever invited to write for the newspaper. But you've got to say your piece.

But I'm curious why there's resistance to shifting to later school times and to improving the conditions for learning if the The goal is to learn. I mean, tradition dies hard. Maybe that's why. I think there's also the idea, certainly in the medical profession, that, well, when I was doing my training, we would pull all-nighters all the time. And so the idea The idea then is that it's just part of the self-directed hazing process that is getting a degree, that you're going to be doing a lot of all-nighters and cramming and things of that sort. Is that what you think motivates the resistance to change?

I think so. I think you've hit all the points. I think The zeitgeists die one generation at a time, and we see that resistance certainly there, too. I also think that when you come back to later school start times, they have suggested that there is this cost when they tally it up. But you made a point which is, when do they get out of school? Let's say it's around 4:30. One of the interesting analysis that was published, and we latched onto this, that is this It's this strange, bewitching hour when kids get out of school, but often their parents are not home to work. If you look at the teenage crime rate and you look at when those crimes are committed, it's usually in that bewitching hour after they get out of school, but they don't have a home or parents yet to go to that's filled. But by pushing school start times later, they get out later, they go home. If you were to even Half that debt that those crimes cause, you would easily pay for the education system. It's very interesting. I think that also notion of, Well, we went through it, and here I am, so you can go through it, too, is very prevalent in medicine.

This is another good example. We and mostly colleagues of mine, such as Charles Siseler at Harvard, have really done a great job at cataloging exactly why we need to abandon this resident program, which has a fascinating history, by the way, which is young residents should be working 30-hour shifts, often without any sleep whatsoever. When you look at that data, residents who are working a 30-hour shift are going to be almost 460% more likely to make diagnostic errors in the intensive care unit. If you have a surgeon and you're getting elective surgery who's had less than six hours of sleep in In the previous 24, they are almost 70% more likely to cause a surgical error, which could result in non-trivial consequences. Then the irony is that when young residents, after a 30-hour shift, get back into their car at the end of the shift and drive home, there is 168% increased risk that they get into a car accident and then end up back in the ER from where they just came, but now patient rather than a physician. You think, What are we doing? Charles Sey, I think, has described they provided this evidence to the council.

At first, I think the idea was, Look, our minds are made up. Don't confuse me with the data. You appeal on the empathetic basis, but it wasn't well received. Then if you go back and you say, No, I'm going to give you a different argument. If you look at the cost of malpractice caused by insufficient sleep, and if you get the administrators into the room, all of a sudden, the schedules change. Then, based on that data, there was a policy that you couldn't work any longer than, I think it was a 16-hour continuous shift. The problem was that they only said that that was apparent for the first year residence and not the remaining years. And the question was, Well, why? I said, Well, the data that you showed us, you only collected in first year residence. As if something magical was going to happen when you become a second year resident and you don this Teflon coat of immunity against sleep deprivation.

Well, if anything, it would compound and it get worse. So it seems to me that There's zero question that getting adequate sleep is good for learning. When it's high risk, high consequences scenarios or even high consequences scenarios like a medical situation, it just seems like it should almost come down a legal liability.

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Com/huberman. Are the errors of sleep deprivation in these scenarios, both in students and medical professionals, are they due to errors in memory per se? Because you can imagine all sorts of errors. With the surgeon, they cut the wrong thing or they cut too far, the margin on the surgical side is too big, et cetera. But since we're talking about learning and memory and its relationship to sleep, is it that people are forgetting what they did? Are they forgetting what they didn't do? Or is it a deficit in motor skills or all of the above?

It's all of the above plus, which is that learning and memory, your recollection of both what you did or what you need to do or what you should do based on your training is going to be compromised because your recall of that information, it turns out, is also compromised. But it's also decision making, too. That what we know is that your frontal lobe is especially sensitive to a lack of sleep. It's that frontal lobe that really takes complex situations, distills them down, and comes up with the correct output scenario of decisions that you need to make. Not so much when you're sleep deprived.

How should I establish the proper neural milieu for learning by sleeping prior? In an ideal world, I get an excellent night's sleep for every day of my life leading up to a bout of learning. Here I'm referring to a bout of learning as being exposed to new material, but life happens. If I know that tomorrow I'm going to take a class in something or I'm I'm going to need to perform a skill that it's a pretty nascent skill for me. I only learned it recently. What should I do the night before?

I would say think about what you can get in terms of your sleep under current conditions and understand that that is staying awake and foregoing sleep is not the right equation that you may think. In other words, think of sleep that night as an investment in tomorrow rather than a cost opportunity of now or today. That would be the message, I think, for learning and memory. Some people will say, logically and rationally, Well, but if I stay awake, I can at least be learning and going over that material for many more hours. So doesn't that compensate for me going to bed? Let's say I haven't learned it well enough. Well, surely I should just say, I should just focus and stay awake because at least then I can just go over the material time and time and time again. Doesn't that offset the deficit? And to a degree, it does. We did that study. But what was really interesting is that the next day, were you able to at least learn and recall some of that information to a degree. Yes, you were. The more that you kept going over it, the better you performed, even when you were not getting sufficient sleep.

But then we did something interesting. We then We brought them back. We haven't published this data, I should do. We brought them back a month later, and then we tested them again. What you find is that the group that slept was far better able to have retained and remember that information. Whereas the group that did not sleep as much, they performed much more similar to the group that got a full night of sleep the next day. But when you test them a month later, almost none of that material is residing in their brain anymore. Got it.

So this is the cramming effect. That's right. Right. And one of them knows this from teaching university courses, or if they've crammed, that you can learn a bunch of material, but then You regurgitate it for the exam, and then it's gone. Yeah. So it's almost like it just never passes from short-term to long-term memory, essentially.

That's correct. Okay. And that seems to be, in some ways, that's a beautiful description of then what happens next in the sleep process. It's not just about sleep before learning. You then have to sleep after learning to do exactly what you just described.

I have a class in the morning or I'm going to learn something new the next day afternoon. My goal, presumably, should be to maximize the amount of sleep I get and to be on the same sleep schedule. So this gets back to QQRT that was presented in the first episode, Quantity, Quality, Regularity, and Timing. People should refer to that.

Nothing wrong with your memory, by the way.

Well, I don't know about that, but the QQRT formula was described in the first episode. Let's come up with what I think is a fairly common scenario. I like to go to bed early between 8:00 and 9:00 PM. I discovered this recently, thanks to conversations with you, this is clearly what works best for me. I always intude it, but it clearly is what works best. If I go to bed at 10:00, I probably want to wake up sometime around 6:00 AM or 6:30. If I go to bed any later than 10:30, I start running into problems. I don't feel good the next day, even if I get sufficient hours of sleep. This is the importance of regularity and timing, keeping things more or less locked to that 8:30 to 9:30 to bedtime for me, 4:30 to 5:30 wake-up time. That's me. Just by way of example, in an ideal world, therefore, I would stick to that schedule, wake up the next day, and go do my learning or my performance of something that I'd learned. Someone else might have the chronotype, We're going to bed at 11:00 PM and waking up at 7:30 AM is their preferred schedule.

However, often because of travel, because of courses, because of life circumstances, the night before something critical that we need to learn or to perform some critical task, physical or cognitive, the sleep the night before is disrupted in some way, either by virtue of timing or quantity, and then, of course, by extension, regularity. Is there anything that we can do heading into a bout of learning, meaning the night preceding the bout of learning, that can provide a buffer or set us up for the best possible learning scenario if we're not able to stick to our perfect schedule?

I think there may be two things. There's been a little bit of work that's been done to suggest that caffeine may actually enhance enhance the hippocampus, this memory encoding structure, and boost its ability to encode. Now, what they haven't yet done is the study where you sleep-deprived someone, then you give them caffeine the next day, and then you have them try to learn and ask, can caffeine, by way of its effect on the hippocampus, rescue and restore what would otherwise be an encoding deficit? Now, that is entirely possible, and I think it's a fascinating question. By how much? We don't know. But if it doesn't, it's equally likely that the hippocampus, by way of being sleep-deprived, is not receptive to the benefit of caffeine under conditions of sleep deprivation. I told you in the rat studies, when those rats were deprived, the hippocampus once again became stubborn in its ability to form new synapses. It may be that it's equally stubborn to receive the normal benefit of caffeine when you are sleep-rested. But I would love to do that study. The second is to then say, Well, if I have the choice of when I'm going to be learning during the day, let's say that you've had a bad night of sleep or you just had a short night of sleep, non-negotiable, couldn't do anything about it.

And the next day, I've got to cram in some information. I would say, Think about your chronotype and think about when you are at your best operating temperature. So your scenario, let's say, going to bed at 9:00, waking up at 4:30, 5:00, your peak is probably going to be maybe 10, 11 o'clock in the morning, where your biology and your circadian rhythm is on its almost crescendo peak. At that point, we know for circadian influences on learning, and this is independent of sleep influences on learning, that's where things are better. Now, for me, you actually described me, which is I'm a an 11 to 7:30 type person. For me, it's probably going to be much closer to about midday or 1:00 PM, where I feel at my operating peak, both for physical performance and also mental performance. If you've got the choice and you are underslept, there's nothing you can do about the sleep that you've lost the night before, but at least recognize that your circadian rhythm is going to come to your rescue and help offset that as long as you time your learning to that known peak of your circadian rhythm. Does that help a little bit?

Yes, that makes good sense. The idea gets us back to something you described in previous episodes, which is that you have this sleep pressure due to the buildup of the molecule adenosine, which the longer we are awake, the more adenosine in our nervous system, which makes us sleepy. But Separate from that, there's this circadian, circadia, about 24-hour rhythm, that causes fairly dramatic shifts in wakefulness and sleepiness independent the adenosine signal. Now, sometimes the two signals overlap, so that late in the evening, for instance, we have a lot of adenosine, we've been up all day, and our circadian rhythm is such that our alertness is starting to diminish, so they're aligned. In the early part of the day, assuming everything is normal, the adenosine levels are low because we slept well the night before and our circadian rhythm is on the upswing, so to speak, and we are alert. So if I understand correctly, the goal is to, of course, maximize the quality, quantity, regularity, and timing of sleep QQRT, but that in the absence of the ability to really anchor any one of those things to 10 out of 10, A plus performance, if one knows that, okay, typically between 10 AM and noon is when I'm at my sharpest, that would be the time to be exposed to new material or ideally take an exam if one can control that thing.

Then perhaps in the afternoon, there's another opportunity after the postprandial dip. That's That's right. But before the postprandial dip, sometime between 1:00 and 4:00 PM, usually lasting about an hour to 90 minutes. This is a natural dip in energy. But then after that is another opportunity to learn. Sure, there'll be a lot of adenosine in one system because you've been up long time, but the circadian system is on its upswing again before the downswing that occurs in the evening. Is that right? That's right.

You've got two opportunities. By the way, it's strange you were to I ask, if you look at the circadian rhythm right before bedtime, there is this strange little blip, this peak that folks back at Harvard have discovered. And you think, well, why would my circadian system, which needs to really ratchet down for us to get to sleep well, why would it have this little jag upwards in the evening hours right before we need to sleep and it then drops precipitously? It makes no sense until you think about evolution, because after foraging for food during the day, what you need is this final spurt to get you home safely to your nest or to your home.

To batten down the hatches.

Exactly. There is this beautiful little built-in circadian upswing to say, Okay, I know you're returning to home. This is probably a time when there's some maybe potentially potential threat to you. I'm going to just boost your alertness very quickly. So you travel home safely. Good to go? Great. And now I start my downswing.

I think this is a really important thing for people to know about. I'm familiar with the data, although just in top contour. But the idea here, as I understand it, is that many people will feel like, okay, around 6:00 PM, 6:30, they're getting sleepy, 7:30, 8:00 PM, and then they want to get to bed at 10:30. And suddenly for them, based on their chronotype, around 9:00 PM, they're wide awake. Second wind. Right. The second wind. And they're like, oh, no, I need to sleep tonight. Now, maybe it's the case that they would be better off going to bed far earlier and waking up earlier the next morning But in many cases, it's just that transient 45 to 70 minute window of increased alertness. That's right. It's uptick in the circadian alertness system.

This two shall pass. And then also just set yourself up for success. And we discuss a little bit about the methods of really ratcheting things down, dimming down the lights, having a to bed alarm. These types of things will just gradually back you off. And after that second wind comes, give you the greatest ability to decline physiologically, which then permits this beautiful thing called sleep to come in its place.

Well, speaking of sleep post-learning, what is the role of sleep that follows about learning? Here, again, we want to define learning as the exposure to novel information that one is trying to encode, either cognitive information, motor information, or a combination of the two. I say that because learning, a. K. Neuroplasticity, has many different stages. It's the process, not an event. Let's say that earlier in the day, I took a dance class, Lord knows I need one, or a musical lesson, or was exposed I was to some interesting information, who knows, maybe on a podcast, and I was trying to engage in that information and pay attention. Then that night, I planned to sleep, or perhaps wanted to take a nap after this bout of learning. How close to the learning episode about, as I'm calling it, does the sleep have to arrive in order for sleep to maximize the amount of learning that occurs?

It's a very good question, which is, What would happen if I were to be learning information and I'm listening to this odd British gentleman, should I then immediately dive into bed so that I maximize the retention of that information? The answer is No, don't worry. I'll come back to why not to worry. But to your point, not only do you need sleep before learning, as we've been discussing, but there is something unique and equally necessary, and causally necessary, I should say, for sleep after learning, but it does something different. Sleep before learning gets your brain ready to lay down those new memory traces. After you've imprinted them into the brain, sleep after learning then takes those freshly minted memories, and then it strengthens them. Essentially, it's almost like sleep will hit the save button on those new memories so that you don't forget. In other words, sleep is future proofing that information within your brain so that you don't forget. Then the question, and we've been able to, and we and many others have replicated this, in fact, it's nothing new. If you look at the literature on this sleep after learning gig, it goes back, as best we can tell, to 1929.

Although I'll argue with that in a second, but two researchers, Jenkins and Dellenback, did a landmark study They had participants learn a whole bunch of nonsense syllables, and they had them learn them over and over and over again, and gradually they got better. Then they started to test them across an eight-hour period. They tested them two hours later, four hours later, six hours later, and eight hours later. The only difference is that in one of those testing sessions, that two hours, four hours, six hours, eight hours was across a waking day. In the other, they had them learn that information to near perfection before sleep, just as they did in the waking group. But now they woke them up after two hours and tested them, after four hours and tested them, after six hours. Then again, when they woke up in the morning, eight hours later. What they found is that in those people who stayed awake after learning, there was essentially just catastrophic forgetting. The amount of information, 2 hours, 4 hours, 6 hours, 8 hours later, just declined dramatically. But when they repeated that in the same individuals after learning things to the same degree, 2 hours, 4 hours later, memory was starting to decline.

But after about two and a half, 3 hours of being asleep, all of a sudden, sleep had fixated those memories almost like an animal that's been trapped in amber and set in amber like a fossil. Then those memories just would not decay any further, and you retained them. What was stunning about that study is it has been replicated time time and time again. That's not the surprising part. The surprising part is that in that study, they tested a vast number of subjects. In fact, a sum total of two participants. But what's stunning is that that finding has gone and been replicated time and time again. That demonstrated to us that there's something special about sleep that is concretizing, almost literally taking things and setting it in concrete Read. Then the question became, again, mechanistically, how? How is it? It's important to understand mechanism because it has ramifications for diseases and medicine. How is sleep doing this fantastic saving of memories? We now have at least two non-mutually exclusive mechanisms. In other words, both seem to occur. The first is what we call memory translocation. Sleep, and particularly what we found for fact-based memories, and I should note, by the way, that this story of sleep after learning is a two-part or it runs in two different narratives.

One is sleep after learning for fact-based memory, what we describe as declarative memory. And you've done a fantastic previous episode on working memory, you describe all of these different types of memory. So one story line has been sleep after learning for fact-based memory, but the other, which is equally The interesting is sleep for non-declarative or procedural skill memory. In other words, what we think of as motor memory. But I'll come back to motor memory in a second. What we then found for this sleep and textbook-like memory is that there are two mechanisms. The first, translocation. Here what we found is that it's deep non-REM sleep for fact-based memories. It's those big, slow, powerful brain waves that we spoke about in the first episode, combined with those sleep spendels that ride on top of them, almost like a surfer on a huge amplitude wave. It's the combination of those two brain waves that acts like a file transfer mechanism. It moves and shifts memories from a short-term vulnerable reservoir, the hippocampus, to the more permanent long-term storage site, the cortex in the brain, and therefore protecting them and making them safe. That's one mechanism is the shifting of memories around the brain and through different storage sites from short term to long term.

The second, I think, is perhaps even more fascinating. It's called memory replay. This was discovered back in the probably 1990s. Bruce Mcnaughton at the University of Arizona working with a young Matt Wilson. I'm Matt Walker. He's Matt Wilson at MIT now. They were looking at rats, and they were looking at how rats learn a maze. They had these electrodes in these hippocampal brain regions, these memory-related regions that we've been discussing. They were listening to the individual firing patterns of those memory cells in the hippocampus as they were running around the maze. Sure enough, as they ran around the maze, statistically, you would build up what looked like the signature pattern of learning. So think about those neurons that they each had a special tone to them. As the rat is running around the maze, you can hear the signature of learning. I just meant it over and over again. But then they did something clever. When the rats went to sleep after learning, they kept listening. What did they hear? They didn't just hear noise. They heard that same memory signature replate. However, it wasn't replate at the same speed. It was replate somewhere between 10 to 20 times faster.

So now, all of a sudden, instead of hearing, you heard, it's going over and over again. And what we've learned is that this replay of memories for that type of information. Now, for rats, that's the version, essentially, of that spatial navigation is their version of fact-based memory. I won't go into detail.

Yeah, because navigating novel environments is especially important for all species, but rodents, to know where they cached food, where escapes are, and things of that sort.

Yeah, perhaps even more so than us humans, that locational memory is necessary.

And nowadays, there's Google Maps and Uber and things of that sort. But in the old days, as it were, I recall the London taxi drivers were considered the world heavyweight champions of memory. And there were some decent brain imaging studies of their hippocampi. And indeed, they You have amazing spatial memory of the city of London. Now, that's probably changed because of Google Maps. There's no need to rely on internal memory stores when you have-No, you still actually...

Now, you can drive these ride share apps, but for London taxi drivers, they still have to go through. In some ways, it's almost like a hazing. It's called the knowledge. If you are visiting London, you will see these strange guys who are going around on mopeds, and they just have this huge map in front of them. They are doing the knowledge, which is that they are learning exquisitely the entire roadmap of London. What they found in those studies was that the size of the hippocampus, this memory structure related to fact-based memories and also spatial memories, was significantly larger in cab drivers than it was in matched controls. Now, you could say, Well, this is a self-selecting process that people who already have large hippocampi, as we would say, they're just going to be the people who can do the knowledge well and pass, as it were. But what they also found was that a correlation, the longer that you've been doing the knowledge and being a taxi driver, the bigger and bigger your hippocampus, so it's time on task. Coming back to the rats in this spatial learning, it's almost as though sleep after learning is taking that memory trace, and it's like etching into a glass surface.

You just go over that memory circuit over and over again, and you're strengthening that memory circuit. What was also fascinating, however, I'm telling you that it's during non-REM sleep that you do all of this memory replay. Certainly what we found is that for textbook memory, it's deep non-REM sleep. That's the important stage of sleep. But Matt Wilson published at MIT an interesting study looking at rem sleep. What happens to the memory trace in rem sleep? And rem sleep, which we know is associated with dreaming, there the memory replay didn't slow back down to normal waking speed. It slowed down even further to 0.5 times relative to waking speed. So the waking speed versus the dreaming speed in dreaming, in rem sleep, I should say, because we don't know if rats dream or not, but in rem sleep, things had slowed down by essentially 50%. And this It comes back to our conversation in a previous episode that we had about time. And you and I were discussing how there's this strange phenomenon where you are woken up by your alarm and you're in a dream and you have a snooze button that lasts five minutes.

You hit the snooze button, you go back to sleep, and you feel as though you've been dreaming for 10 minutes, 15 minutes. But it's been five minutes in the real world, but time has slowed down, time has dilated. It's almost like a concertina that stretched out. All of a sudden, we were finding in, or Matt Wilson, because we don't do animal research, was finding that this replay was slowed down by 50%. I always wonder whether or not there is neuronal evidence that helps us explain why dreams seem to pack more time despite being in real-world time, a shorter amount. Absolutely fascinating.

Yeah, I have to imagine that rats dream and dogs dream another animal's dream. I mean, why Wouldn't they? If all the components of rem sleep that are expressed in humans appear in these animals and vice versa, you imagine it almost has to be the case.

It does. I think there is some interesting supportive evidence that you can argue. There is a sleep disorder that we understood in humans first called rapid eye movement disorder or rem sleep behavioral disorder. In the first episode, we said that one of the fascinating features of rem sleep, which is when we principally dream, is that your brain, and specifically your brain stem, paralyzes your body so that your mind can dream safely. So you're shut down into this motor paralysis incarceration, rightly so. But what also happens is that as we get older, and it seems to be particularly more so in men than in women, but it can be both. Once we get past our 50s, there's a higher likelihood that that mechanism starts to degrade and you can start to act out your dreams. Now, this is not sleep walking or sleep talking. That actually comes from deep non-REM sleep. And there what happens is that there is a trigger, an awakening, either a brain response, almost like a stress response that wakes the brain up, and you're in the deepest stages of sleep, and you are trying to get forced back up to wakefulness.

Back to that analogy of going from the basement to the house. And instead, you just get locked into this mixed state of consciousness. And as a consequence, you start to enact very rote basic behaviors. You'll go over to the refrigerator, open the door, close the door, pick up a glass, put it to your mouth, put it back down. And if you wake someone up, which you shouldn't necessarily do unless there's harm, and ask them, What was going through your mind just a few minutes ago? They'll say nothing. And the reason is because it wasn't coming dream sleep is from deep non-REM sleep. I see. However, there is a very different condition that sometimes people will mix up as the very same thing, which is rem sleep behavioral disorder. And there you're acting out your dreams. It can be quite violent. Some people have enacted violence on their partner and woken up and been absolutely devastated. I bring this up, however, because human beings are not the only species that suffers from rem sleep behavioral disorder. Dogs suffer from this as well. When you see it and you can understand it, it's very clear, you have electrodes on the head, they go into this rem sleep state, and all of a sudden, they come out of the paralysis and they start enacting what very much looks like a behavior of wakefulness.

It's quite complex. At that point, you look at that and you say, Okay, I'm sorry, but that looks very much like dreaming. Now, we can't, of course, ask dogs, question what was going through your mind. You can ask them.

But they're not going to answer.

But yeah, you can ask them. But it turns out that the response is less than... It's just a look to say, give me a treat. But in science, sometimes, if it looks like a duck, talks like a duck, walks like a duck, maybe it's a duck.

What about this phenomenon, which I've experienced before, of being asleep, presumably in rapid eye movement sleep and being completely paralyzed, but then waking up and I'm still in paralysis, but I'm not asleep. This was a long time ago, probably the 10th grade, which for me, I was what, 15 years old? I'm 48 now. Was at a party that I fell asleep on the couch. I don't believe in underage drinking, but there's a possibility that I might have been inebriated. Just a possibility? Kids, parents. I actively dissuade young people from drinking, and many older people from drinking. But yeah, I started drinking far too young. But I remember I drank the night before. I got drunk the night before. Again, something I'm not suggesting or proud of. I woke up and I was wide awake. Gosh, I remember this so well. I was paralyzed. I could not move. And it was terrifying. And then all of a sudden, I could jolt myself awake. I was like, Oh, my goodness. And it must have been an invasion of that atonia, that sleep-induced paralysis into the waking state.

I can explain this, and you have... This is the perfect prototypical situation when we see this. What you're describing to me is something that many people listening will have experienced called rem sleep paralysis. It's not necessarily a problem or a sign of a condition that you need to be worried about, although if it's happening frequently, we can think about that. What normally happens when we wake up out of rem sleep, and rem sleep, as we spoke about in the first episode, dominates the second half of the night and particularly the last quarter of the night. As you're coming out of rem sleep and waking up out of rem sleep, which you've got a 50, 50 % chance, perhaps, because the other state that you're in is stage 2, light non-REM. As you're coming out of rem sleep, you're regaining consciousness to the external world. And then normally in lockstep with that perfect lockstep, if not a little before, your brain is realizing this and it's releasing you from the paralysis. And we all wake up and we I don't even think about it. I just wake up and I lean over, I turn off the alarm and I get out of bed.

Everything's fine. Every now and again, however, the waking up and consciousness re-engaging occurs. However, the brain does not release you from the rem sleep paralysis. So at that point, it's almost like a locked-in body phenomenon. And it's very frightening because you begin to be aware of your surroundings, but you cannot make any voluntary movements. Because I told you that the voluntary scaletal muscle system is impaired by the atonia, the absence of muscle. You're involuntary, you're still breathing and all that. But your eyelids turn out to be part of your voluntary muscle set. You can't lift up your eyelids. Then normally what happens is that it's associated with a strong sense of often an intruder, it seems to be. If you're doing it in bed by yourself at home. Now, your context was a little different. It turns out that if you look at these descriptions of sleep paralysis where you can't wake up, you can't shout out, you can't move, you have this sense of another presence or another being in the room, it adequately explains most, if not all, alien abduction stories. Because when was the last time you saw a news article or on the news that someone said, Okay, today it was very clear that Jim Jimmy in Wisconsin in the middle of the day was abducted by aliens and everyone saw it.

You're at the meeting table and, Whoosh, what happened? That was Jimmy. He just got whisked off by alien. It doesn't happen that way. It's normally that you're in bed at night. It's the early morning hours just before you're waking up. These aliens came into the room. They injected something into you. They paralyzed you. You couldn't shout. You couldn't move. It's simply rem sleep paralysis. Now, when do we see that? There are ways, and not ways, because these are not protocols that we advise, there are circumstances where the probability of that increases, and I've experienced this, too. When you are sleep-deprived or you are highly stressed, the likelihood that you will experience these rem sleep paralysis events upon awakening is increased. For me, it was happening when I was a young PhD student and I was studying sleep. Then I would be awake all night because I'd be monitoring the patients and looking at their sleep.

The irony of sleep studies.

Exactly. That you have to deprive yourself of the very thing that you are trying to study, which, by the way, gives you some amazing insights for experiments that I've had as a consequence. Not that I would advise that as the way. And we'll come on to why that's not wise when we speak about creativity. But we were doing these studies, and then I would go home, and then I would take a short period of sleep maybe just two and a half hours of sleep. And then I would wake up. I didn't want to because I was ready to go deep into sleep, but I would wake up, and then I would force myself to be awake throughout the day and try to get to bed at a reasonable time because if I slept all day, what's going to happen? I'm just going to be awake all the next night, and I'm going to be out of my rhythm. But what's interesting is that when I would wake up then, I would be waking up maybe at 10:00 AM in the morning, 11:00. And at that point, if you're sleeping there with someone like my face, You are in a very rem sleep desiring state that it's in those last morning hours and into the early morning hours when your brain wants to devour off the menu of sleep stages this thing called rem in vast quantities.

So I was sleep-deprived, point number one. Second, I was going into a very rem sleep-rich phase, in other words, higher likelihood of paralysis, and that occurred to me. Your description is also prototypical. You've been drinking the night before went out to the party. We spoke about in one of our previous episodes that one of the problems with alcohol is that it's very good at blocking your rem sleep. So you'd been absent of rem sleep the prior night, you'd built up what we call a rem sleep debt. And when you slept, all of a sudden, what your brain wanted more because it at least got some sleep, and there you're going to get mostly your deep sleep, the debt on the sheets of your balance account for sleep was not so great for deep non-REM, but you were very much in debt with rem. So what happened as soon as you conked out on the couch, whoosh, you were probably straight into rem sleep. And then when you woke up, you had this mismatch in timing between consciousness and the release of paralysis. What did you experience? Rem sleep paralysis.

Love it. I mean, hate it. I did not enjoy it, but I love your description because it makes so very clear what happened. And for those that have had the experience, it can be mildly stressful to terrifying. So Thank you for providing the therapy that is knowledge so that people don't stress it too much. But we still dissuade people from consuming alcohol prior to sleep.

Correct.

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We've been discussing complete paralysis, and of course, that's the inability to move. Let's talk about the ability to move, meaning motor learning. What is the relationship between sleep and learning physical skills, either coordination of motor movement or who knows, maybe increased power output or endurance. If you would, could you comment on whether or not there are specific phases of sleep that are specifically linked to motor learning?

Yeah, great question. What we've spoken about so far is that you need sleep after learning for that textbook-like memory, and that is one category of memory that resides within your brain. There's another type of memory that you've spoken about, which many of us don't realize is memory, and that's what we call non-declarative or procedural skill memory. If I were to ask you, Okay, Andrew, last night for dinner or yesterday for lunch, do you remember what it was that you had to eat? My guess is that you could probably tell me. Do you recall what some of that food was?

My diet is pretty boring in the sense I tend to eat more or less the same thing every day, although I'm open to being flexible. Yesterday for lunch, I had two grass-fed hamburger patties, maybe a little bit of rice, a slice of cucumber, some tomatoes, and Because I'm a drive-by Blueberry Eater, there were some Blueberries out on the counter, and I had several large fistfuls of those. Then I washed it down with some water and a half mug, just like this, of some cold brew, sugar-free Yerba mate.

I can confirm, folks, I was there at the incident, and that's exactly what he had. But did everyone who was watching or listening just realize what happened in this room today? Something that Einstein suggested would never be possible that Andrew just traveled back in time. That using this incredible gift of memory, you folded time almost like a concertina compressing it, and you raced back within milliseconds. You were shaking your head, Yes, I know what I had. You raced back into that catalog of all of your previous lunches. You found the correct Manila folder for that specific lunch, all of the details and out it popped. That is a spectacularly complex computational process that your brain's memory system accomplish within milliseconds. It's stunning what we have as this gift of memory. But as I said, there's another type of memory. If I were to ask you, Okay, how do you ride a bike? It's very difficult. There is no textbook for, Here is how to ride a bike. The way that you do it when you're a child is that you are taught how to learn how to ride a bike by being on it. If I were to say, because I'm a long-time cyclist, how do I take a right turn with my bicycle?

The obvious My suggestion would be, well, you turn the handlebars. If you turn the handlebars at 30 miles an hour trying to go around a right bend, you're going to crash very quickly. What in fact you do is you alter the steering angle just a little, but you lean. And that is what we call non-declarative, meaning you can't declare to me what it is that you know. You just have to show me through action and behavior. This is skill learning, and we use it for things like sports, surgical procedures, flying planes. There are so many musical performance as well, so many aspects. So we wanted to then say, Well, sleep is helpful after learning for fact-based memory, but what about this other type of memory? In truth, I didn't come up with the idea. It was given to me back in the... Gosh, I'm aging myself. In the early 2000s, I was back in the UK, and I gave a lecture for the decade of the brain, which it was back then. At the end of the course, I'd spoken a little bit about sleep and this informational processing, but no evidence for motor skill memory.

This gentleman, lovely gentleman, old gentleman with a a white beard. I remember his tweed jacket, this green hue, it was beautiful. He came up to me at the end and he said, Look, I'm a musician, I'm a pianist. I was fascinated by what you said about sleep. Sometimes I'll sit down and I'm learning a new piece, and I just don't seem to be able to get it, and I practice, practice, and practice into the evening, and then I just stop. Then I come back the next day and I sit down at the piano and I can just play. Do you think that's sleep? Of course, at that moment, my mind starts just Rolodexing with ideas, and I'm thinking, Gosh, there's the next 10 years of my work and grants. I said, Look, I think it's a fascinating hypothesis. It could also be that you're just maybe A little bit tired in the evening, but it's entirely possible. I don't know of any evidence yet that supports that.

I suppose the alternative hypothesis that there's simply a certain amount of time that needs to elapse after experiencing something new that one wants to learn. The trigger for learning is some biochemical/neural signal. That's like a wave front, and it takes a while for that wave to go ashore, which is learning. And that independent of how much sleep one gets the quality of sleep that the learning could occur. I suppose that's one idea.

No, that's in fact precisely the central hypothesis that we then set out to test, which is that maybe it's practice then some time that helps you create that perfect motor routine. That's one hypothesis, but let's split that apart. Maybe it's time, but time spent awake, or is it time, but time spent asleep? We designed a study to to disambiguate between those two. Both groups learned a motor skill task, and it's very much like learning a piano, and you learn a sequence of movements, let's just say 4, 1, 3, 2, 4, and we have you type that out over and over again for periods of 30 seconds, and then you rest for 30 seconds, and then you do it again. You do 12 of those trials. Sure enough, practice seemed to get you better. You were learning and your learning curve went up. Then we brought those participants back 12 hours later, and we retested them on that same motor memory. Half of those participants spent that 12 hours awake. The others had a night of sleep in between an eight-hour night of sleep. When we brought the people who had learned in the morning and tested in the evening without sleep, they had retained that memory.

They were no worse, they were just no better. But in the people who had slept, what was stunning was that they had improved their performance output speed by 20%, and they'd improved their accuracy by almost 37%. In other words, it wasn't time that you needed to produce perfection. It was time with sleep. In other words, you've often heard the statement, Practice makes perfect, but we violated that edict. It wasn't practice that makes perfect. It's practice with a night of sleep that makes or leads to perfection. In other words, after learning, your brain continues to improve in the absence of any further practice. However, that learning occurs exclusively during periods of offline sleep and not across equivalent time periods while you're awake. Now, what was interesting in the group that remained awake across those 12 hours, we then actually brought them back after a further 12 hours, but now after a night of sleep, and they showed that beautiful benefit.

The sleep that can, let's say, enhance, although I think what we're really talking about here that consolidates motor learning, can arrive the night after, meaning one finishes, let's say, learning at, I don't know, 11:00 AM, and then they sleep later that night, or the following night. In both instances, that sleep can enhance or, let's say, consolidate the motor learning That's right.

It was to your question, actually, that we discussed earlier, and I recall now, I didn't answer it, which is that the things that you learn throughout the day, you don't have to worry about learning them really close to bedtime so that they're available and accessible for this sleep-dependent work of sleep after learning. It seems to be that the human brain, and we've plotted this, we've looked at how at what point does the brain fail in terms of its ability to place on hold on the runway, ready to take off into the consolidation phase. It seems to be about 16 hours that you can hold on to those freshly formed memories for about 16 hours, and then you get the chance to sleep and consolidate them. If you learn at 11:00 in the morning, or if you learn at 7:00 PM in the evening, don't worry about that. Those memories are still going to be gathered together in the beautiful receptive arms of sleep and then knit it up and enhanced when it comes to procedural memories. By the way, that's a key difference to those two types of memory. Sleep will take fact-based memories and simply save them so that you don't forget.

It doesn't necessarily boost them anymore. It just simply prevents you from forgetting, which is what would happen otherwise across a waking day.

Key point. It's not enhancement, it's consolidation of, or essentially Basically, the way I might think about it is the new information is put into a potential memory bank, and that information is either flushed or maintained, depending on whether or not you get sleep. That's right. There's no enhancement. Enhancement would be supra normal levels of memory if you sleep.

And that's the case for textbook-like memory. In other words, sleep comes in and it stems the blood flow of forgetting from the memory wound, as it were to get, I don't know why it came up. That's a terrible analogy.

No, I like it. I guess we might say hemorrhage, right? Like it's-Yes. Okay.

So sleep comes in and prevents that from happening. But with motor memories, it is enhancement. It's that when you're awake across the day, You don't get any worse, which is what happens with fact textbook memory. You hold that performance, but then sleep comes in and it boosts you even further. You get a nice benefit without doing anything further. Then the question became, to your point, if sleep is doing that, if it's not practice that makes perfect, but practice with sleep, what is it about the sleep? We looked at their sleep physiology, and what we found were two interesting components First, it seemed to be related to that lighter form of stage 2 non-REM sleep. I told you that textbook memory requires deep non-REM sleep stages 3 and 4, casting back to episode 1. Motor memory, more dependent on stage 2 and those beautiful bindles that are the hallmark of beginning your stage 2. The more of those that you had, the greater the memory benefit the next day. We then wanted to say, Well, is this effect simply something to do with the night time? Because that's the other hypothesis. It's not really about sleep.

It's just something about night time-ness because in all of the studies I've described so far, they're all happening at night, and at night, they were sleeping. So is it Is it really night time or is it specifically sleep? Now we did a nap study with motor skill learning. We repeated that. Sure enough, even though that time period was across the day, not during night-ness, they showed this beautiful motor skill benefit if they napped versus if they did not. Then in that nap study, I was telling you that they were learning the sequence with their right non dominant hand, and they were all selected all right handers to make it equal. They were typing 41324, 1, 3, 2, 4. And that right-hand, as well you know, is controlled by the left motor cortex. So after in the nap study, when we recorded their sleep, we used very high density EEG, so lots and lots of sensors on top of the head. So we could map with high fidelity resolution the surface of the brain or the surface of the scalp and infer what's going on in the brain. And what was interesting is that, yes, those sleep spendles, the more of them that you had in the nap, the better your motor skill learning was But there seemed to be a lateralised effect such that the sleep-spindle activity on the right side of the brain, which controls the left hand, which was not working, that showed no spindle increased in activity.

However, on the right-hand activity that invoked activation in the left motor cortex, that left motor cortex, and specifically the hand region, showed a local increase in spindle activity. And subsequent work and work prior to ours had demonstrated that it's not sleep physiology globally. It's almost as though your sleep physiology responds to the mapping of the memory in the brain. Wherever the memory is, that's where sleep, when you go to sleep, starts massaging the cortex so that you get that plasticity. It's almost like a good masseuse. You sit down and they say, Where are you problem points? And you say, It's here and here. And so they don't give you a general massage. They go to work on the regions that have been working hardest that require greatest attention. Sleep does that.

That's amazing and reminds me of some of this work that was done, I think in the late '90s, early 2000s, Richard Morris and colleagues over in, I think he was in Edinburgh, talked about synaptic tagging. This notion That animals or humans perform or learn some new motor skill, maybe navigation of a novel environment, maybe a motor skill of the 41234 that you described, keys on a piano or something like that. Then it was acknowledged that the changes in the connections between neurons don't occur immediately, which meant that there had to be some tag or label to the synapses that marked them for consolidation later for plasticity, long term potentiation, things of that sort. The names don't really matter. I think later it became clear based on Marcus Frank's work and others that indeed, during sleep, the hard rewiring of the nervous system occurs, plasticity occurs. But what you're saying is that there's a high degree of specificity, meaning the specific circuits that were active and required for the learning are the specific circuits that are modified, which on the face of it, one could say, well, of course. But what that means is that during sleep, the brain is somehow able to...

The neurons of the brain, that is, are able to chemically or electrically or both signal. This is aware that there needs to be some modifications done. And then like a night crew, the brain self induces its own changes, which is remarkable.

It really is. It's almost as though there are red flags that are planted in the territory that have undergone learning dependent plasticity, and they are calling out almost like hungry mouths that are in plasticity famine for the feast relief that comes by way of sleep.

Do we know what the factors are that are released in sleep that allow that to occur? I'm guessing there are many. People love to talk about brain-derived natrophic factor, BD&F, which is a very interesting molecule, but it's probably just of a panoply of of molecules that are important.

We don't know necessarily the neurochemical processes, although some people have manipulated plasticity and then blocked it with different types of NMDA, which is a certain type of receptor in the brain for excitatory activity, which is the underlying basis of brain plasticity. That certainly is dependent. But what's interesting about the sleep spendles, I said in the first episode that they burst somewhere between about 12 to 15 times per second. If you apply that type of stimulation to a particular neuronal circuit within the brain, that seems to be one of the, and it's not the only, but one of the ideal sweet spot tickling of neurons that forces them to say, Oh, I think I should strengthen this circuit. It's almost as though these sleep spendles are ideally designed at the frequency at the tickling level of neurons to stimulate exactly what we think is the underlying basis of strengthening a memory, which is at the level of the neurons, the strengthening of synapses.

So interesting because we hear this fire together, wire together, high frequency transmission between neurons is what creates plasticity. But this is literally a replay of previously, meaning earlier that day or the previous day, as you pointed out, activity in the given circuit being replayed, not unlike the work that you talked about earlier, the fast replay of neurons in the hippocampus. But here it's not necessarily just in the hippocampus. It can be in the neocortex or other structures that then builds up the the the vigor with which that circuit can function in the daytime, a. K. A. Learning. It's super interesting. You mentioned that this is occurring largely in stage 2 of sleep, not in rapid eye movement sleep. Is this business of stage 2 You being the main period of sleep in which motor learning occurs, unique to motor learning. In other words, cognitive information surely can get wired into the brain at night. But is that largely associated just with rapid eye movement sleep? What this would suggest, in other words, is that the earlier stages of sleep one and two and heading into three and four serves a specific purpose, which is consolidation of motor skills and motor learning from the previous one or two days.

It does seem to be that stage two. Stage one is, we now think of more of a transitional stage, but we will speak perhaps when we discuss the idea of creativity, that it also may have a memory function, that Very light first step of sleep. Stage two is certainly related to motor skill. In fact, stage two is fascinating. We used to think of it as just the stage that you had to go into to get to deep sleep and the stage that you had to go back to get up to rem sleep. Never made any sense to me. Why? Because stage two non-REM sleep is about 40 to 50% of your night. Why would you spend 40 to 50% of your time asleep when it's just simply a gate to get to something better? You would spend more time in the something that's better stages. We started to find functions, and stage 2 is distributed throughout the night, but those sleep spendels in stage 2 are not evenly distributed throughout the night. You get some of them in the first quarter, more of them in the second quarter of sleep, certainly more in the third quarter, but you get a lot more of those sleep spendels in the last quarter of the night.

In fact, when we looked at the overnight study where we had people learn in the evening, tested the next day, we recorded their sleep in between. Yes, sleep spendels, and stage 2, predicted how much better they were the next But it was especially stage 2 in the last quarter of the night. Let's say I'm going to bed, I'm just for argument's sake, for ease, midnight, and I'm waking up at 8:00, it's in that 6:00 AM to 8:00 AM range when I, if I was going to sleep at that time, would be getting my stage 2. I find that interesting because it is the time of night that we all feel it's okay to cut short to get a jump start on the day. It's this modern life erosion of our sleep time. What these findings would suggest is that you are short-changing your brain of some significant motor memory performance, especially those classic Olympic coaches that have the athletes training until 8:00 in the evening. Then they're in bed by 10:00 or 11:00, but they have them waking up at 5:00, back on the athletic field at 6:00. But they would gain some additional motor memory benefit if you just let them sleep a little bit longer.

I recall there was a study done at Stanford, relatively small study, but interesting nonetheless, because I think it was the basketball team that was asked to spend, I think, an additional two hours in bed. It's a sleep extension study. They were even told that they could do other things in bed besides sleep. There might have been some specifications of things they should not do in bed during that time. But at least by self-report, some of the students said that they slept a bit more, or they relaxed a bit more in bed. And indeed, when compared to the control group, there was a significant improvement in their, I forget if it was free throw percentage, excuse me, or other metrics of a basketball performance.

Yeah, it was the point scoring performance. It was the speed up and down the court. It was a great study done by Sherry Maher at Stanford University, and she's done epic work with athletes to replicate those findings. And the athlete story is interesting Some people may be saying, Well, didn't you just make a hop, skip, and a jump from 4,1,3,2,4 to inferring complex motor skill? I thought about that. We did a new series of studies where we… This is control. That's the nice thing about the typing on a sequence, you can really measure that performance with high accuracy. But we then switched it to a bimanual task, much more like learning to play a piano. You were learning sequences that were 12, 14 items in length, and you had learn them over and over. We had a hypothesis, would sleep fail at the task when motor skill performance became much more complex, or would it be different? What we found was that the more and more complex the motor skill became, the greater and the greater the benefit of sleep by way of that consolidation effect. Then I started to hear something because I would often be in the room as these participants were learning the sequence and then as they were testing.

My ears started to hear something that I couldn't quite believe to begin with. They would start to learn these motor sequences, but they would seem to have these pauses, and it's what we call chunking in motor skill memory. Instead of 4,1,3,2,4,4,1,3,2,4, they would do 4,1,3,2,4,4,1,3,2,4, and I would have them be using the same keyboard, and I got to know the sound of the keyboard, so I could hear it. 4,1,3,2,4,4,3,2,4. Then when they came back the next day, yes, they were performing faster, but they weren't just doing 4,1,3,2,4,4,1,3,2,4. They were simply doing 4,1,3,2,4,4,1,3,2,4,4. There was no gap at all. So we went into the individual responses, individual motor finger responses. And sure enough, before sleep, there were these very clear problem points, almost these pain points in the motor memory sequence. But then when we came back after a night of sleep looked at their data, it wasn't as though sleep simply grabbed the motor skill memory profile and lifted everything up. Sleep was selectively going after those pain points and improving them. And that, to me, was interesting because that's the goal of a good athlete. It is automaticity. You don't want to be thinking about it.

At some point, you go from a very conscious act of deliberately trying to remember what you should be doing to then not not thinking about it at all. It's only automaticity that gives you that ability not to think, and it operates below the level of consciousness.

Super interesting. Here we're talking about specific changes in the brain in terms of neural activity, et cetera, that occur during sleep when we've been exposed to or engaged in a particular novel for us, motor skill. You see these spendals in stage two, et cetera. But does it work the other way as well? Meaning, does the process of trying to learn a new motor skill enhance certain components of sleep or maybe even one's ability to sleep? Years ago, I heard that practicing unilateral leg movements, this is perhaps a crazy idea, but it makes sense in the context of what we're talking about, practicing unilateral leg movements, things like everyone's familiar with squats and deadlifts and things of that sort. But there are some one-legged movements. Like a pistol squad. A pistol squad, that's pretty hard. If one can do them, I'm always impressed. Bulgarian split squats, foot up on the bench and then squatting down with a dumbbell, things like that. We're just unilateral movements that require a lot of mental attention to the performance of that movement. Could be in the gym, but it could be something else as well. You think about a dancer trying to learn how to organize their steps where they have to pay careful attention to right versus left foot.

They always say people have two right feet. People can't dance, have two right feet or two left feet.

By the way, for those listening, Andrew is looking at me right now when you're saying two right feet. Rightfully so.

No, I have no knowledge of your dancing ability or challenges. Absence thereof. As I recall, there may have been some very preliminary data about changes in the amount of certain sleep stages, according to whether or not someone had tried to learn a skill. In this case, unilateral limb performance the previous day. In other words, if one wants to improve their sleep, would the attempt to learn a new motor skill be one avenue to improve one's sleep?

It's interesting. If you look at some of the data, it's a little bit mixed in terms of motor skill learning. But there are some studies demonstrating that it's true for textbook-like memory. There's a study, Gosh, done many years ago, again by the great German group of Jan Borne. They simply asked the question, if you were to just not be learning very deliberately and intensively through a textbook-like set of information, and then we just measure your sleep to get a baseline. Then we force you to have a very long, very intensive learning session of these facts. Then we measure your sleep again. Is there any difference relative to the non-intensive learning versus the intensive learning day. Indeed, what they found was that there was an increase in their deep non-REM sleep, in their deep slow wave sleep. Again, we think it's almost... We describe it as a homeostatic response, which is just a fancy way of saying that when the brain is driven to undergo a demand, then sleep will respond to try to accommodate that demand. I would say that there are probably many other things, and we discussed this in episode 2 in terms of, A, how to optimize your sleep, that probably carry a bigger bang for your buck in terms of optimizing and enhancing your sleep.

But is there any evidence to suggest that that's the case? The It does seem to be some evidence in the literature.

So interesting. I certainly know the experience of trying to learn a lot of information and then feeling like my sleep is that much deeper. Although I've also experienced the challenges in, quote I'm turning my brain off when I've been trying to learn something and then it's late in the evening. Forget the caffeine component. Just the information is spooling in my head, maybe some pre-test anxiety, that thing. I think that the tools and protocols that you offered so generously in episodes one, two, and three are especially important under those conditions, learning how to really taper off one's level of thinking and planning and arousal in the evening, really bring things down so that one We can access that sleep. One only wishes that the more we did during the day, the easier it would be to sleep. I think to some extent that's true, but there's some conditions in which doing more, thinking about more. I guess that's The irony, right? I interrupted myself, but on purpose, that wouldn't it be wonderful if the amount and ease of sleep was directly proportional to how much we needed to sleep? That's one of the tricks in this whole business.

A fickle system sometimes.

Sometimes when we really need sleep, we're dealing with something psychologically challenging or we need to learn something, we have an exam, that often can be when it's most difficult to sleep.

It gets right in the way of what we need most. Although, coming back to your point, I think Physical activity does seem to be one of those things that is very good. I'm remiss to have not included it in the optimization or the unconventional tips. There is a very good robust literature now demonstrating that if you are physically active during the day, you can boost the quality of your sleep, particularly your deep sleep at night. It seems to be there are some subtle differences in terms of whether you're doing aerobic versus anaerobic so let's say, versus doing a spin bike class for an hour versus lifting resistance or doing resistance training for an hour or strength training. There's subtle differences. But net that overall, the big picture view is that when you perform exercise, you drive a response from enhanced sleep, particularly deep sleep at night. I think many people have had that experience. You've been out on a long hike, maybe a 10, 12-mile hike, or you've just been working in the garden doing really long landscaping work throughout the day, 6 or 7 hours. You just come in and you go to bed that night and you just know that this is going to be the most royal night of sleep that you could have.

You know it ahead of time, earhold to elbow. That evidence is now very clear. The one interesting thing, if you dig into that data, though, you can drive increases in deep sleep by way of exercise. Exercise, it does seem to come at a little bit of cost to rem sleep. Exercise may throttle back some of your rem sleep. Now, don't fear that. It may just simply be that every night, and we know this, my sleep and my stages of sleep are going to be much different to yours in how they are structured and how they play out. But even within me, the same individual, Matt, my sleep stages vary from one night to the next to the next. Some of that is idiosyncratic. Others, or other reasons, depend on what I've been doing during the day. It may be that we don't need to get concerned about that modest reduction in rem due to exercise enhanced non-REM because it's simply that when you've gone through that form of activity as a human being during the day, what you need is that type of sleep more so than perhaps rem sleep. Therefore, the next night, things calibrate back down.

Let's say I wasn't as active, I just went to work during the day, and I'm back to baseline again. I don't get too concerned about that, but I just want to bring it up. It's there in the literature.

I think it's a very interesting point, and one just has to trust that nature knows best in modifying the percentage of different sleep stages according to our daytime activity. Again, highlighting the key relationship, the closely tethered relationship between daytime activity and sleep and vice versa. Correct.

Yeah, and it's It's a reciprocal loop because what we found is that exercise during the day can enhance sleep at night. But also what we found is that sleep at night enhances your athletic performance the following day. I'm not just talking about motor skill, memory upstairs in the brain. I'm talking about physical activity in the body. If you limit sleep to, let's say, less than 6 hours, the data demonstrates that your peak muscle performance is decreased, your peak vertical jump height decreases, your time to And then the exhaustion decreases. In some studies, it was up to 30%. So if you're training for a 10K marathon, but you don't get enough sleep the night before, you're done by seven. We also know that it decreases perhaps more than almost any of those. And it's striking the brain's motivation to exercise at all. So in fact, many people may be able to get close to their peak muscle strength when they are underslept. Chances are they're probably never going to get to the chance to express that because their motivation to exercise just drops off. I think many people will resonate that you had a bad night of sleep.

I just don't want to go to the gym the next day. The final part of that is injury risk. There is a significantly elevated injury risk. If you ask most athletes, Okay, what am I particularly concerned about? Is it my performance or if I had some injury that knocks me out for the rest of the season? I've had the fortunate chance to work with many professional teams. I've different kinds, and gradually, they are realizing what I've long said, and it's a crass statement, but I think sleep is probably the greatest legal performance-enhancing drug that most athletes are not abusing enough.

I could not agree more. I I feel like every time I say sleep is the bedrock of mental health, physical health, and performance, it's sometimes perceived as just like, Oh, yeah, sleep. We need to sleep. But there's no question that the positive effects of getting excellent sleep on a consistent basis far out weigh and perform any supplement or even performance-enhancing drug. In fact, most supplements and performance-enhancing drugs that can indeed improve performance of various kinds seem to only function or function best, certainly on a backdrop of excellent sleep.

I should say that I think you've done a brilliant job of being very explicit about the fact that You need to get all of the basics in place. Then it's great to think about fine tweaking with optimization of things like supplementation and all these other things. I think sometimes that message has been maybe a little bit more mixed in the social media environment that we often don't think about the basics, and we go straight to supplementation where you would say, Gosh, there's actually a log order of magnitude benefit that's on the table. If only you had to do some of the basic things that your grandmother would probably tell you, eat right, get your stress sorted out, do some physical activity, and make sure that you get some sleep. Do those things, and you're very far along. Now there's more opportunity on the table for fine-tuning, as you've elegantly discussed. But I think I just want to acknowledge that I think you've done a really great job of being balanced in that message. I hope people in the general sphere can appreciate how hard that is to do. It's not an easy thing when you are talking about supplementation, because at first it sounds as though, gosh, all of this speaking, you describe great data means that it is the Holy Grail of enhanced human beings.

But you're always careful to say this after the foundation. I can give a very good example with sleep. Let's say that you're trying to manage your weight and lose weight and you're dieting, but you're not getting sufficient sleep. What we've discovered is that, yes, you will lose weight when you're dieting, even though you're not getting enough sleep, the problem is that almost 60% of the weight that you lose will come from lean muscle mass and not fat. In other words, when you are underslaped and dieting, you keep what you're trying to lose, which is the fat, and you lose what you wish to keep, which is the muscle. So your body does something very interesting in its removal of different types of energy stores in your body When you are not slept, it becomes very stingy with fat, and it will not give it up when you are sleep-deprived, which is very interesting. Why would that be, by the way?

Muscle is such a metabolically demanding tissue. By not sleeping well, you're sending signals that there really isn't the capacity to take care of what you already have, much less increase the size of the engine.

That's exactly right. Then think about fat, which is in terms of its energy unit benefit, it has at least perhaps twice the caloric value that protein does. If you are underslept, that is a warning sign to any evolutionary species past that things are dire. So whatever I'm going to do, this is break glass in case of emergency situation. If you're not getting enough calories, I'm going to hold on to the thing that has the highest caloric value right until the end, which is fat. I'm going to give away the stuff that doesn't have as much caloric benefit because I am in a caloric deficit right now. Now, of course, that's strange because the person trying to lose weight, perhaps, is rightfully trying to lose weight based on them being somewhat overweight. But that's the biology that we think explains That's why that's the case. It's not just a strange phenomenon. It's a very logical one.

It is a logical one. And thanks for the support around my constant voicing and revoicing of the pillars of health that you mentioned, exercise, sleep. Well, I put in the order of sleep as the most important pillar. And then one could argue about the order of the others, but in no specific order. Light, which dovetails with sleep, but nutrition, movement, exercise, social connection, stress modulation, these kinds of things.

The fact that the speed with which that comes out of your mouth tells you how many times you've said it, and you've said it over and over. It's wonderful.

Well, thank you. It's interesting because they are the basics, but they are basics that need to be reupped every 24 hours. And so often I feel like we all need to be reminded every 24 hours. One of the most common questions I is, what should I take? People are like, if I had a dollar for every time somebody said, what should I take? I'd keep podcasting, but I'd be a gazillionaire. But my response is always the same, which is, how's your sleep? The first question I say is, how's your sleep? And then they think I'm going to suggest a sleep supplement, but I want to know whether or not people are sleeping well on a consistent basis. That opens up a whole set of discussions. Then inevitably, we forget about what one should take conversation. I think it's the rare individual who's sleeping very well every of their life. There are such individuals. Then the what should I take conversation makes sense in a certain context. There's something I wanted to just return to for a moment before I move on to the next topic, which is you mentioned all the significant deficits that occur in motor performance when one has not slept that well the night before.

Grip, strength, a vertical jump, motivation, et cetera. We're not here to deliver anything except facts to people. We're certainly not here to soften the blow of reality. But there are a good number of people that will have, say, a physical performance, like a race. They're training for a half marathon, or they have a big game the next day, or they have some performance event the next day. And by virtue of butterflies, anxiety, travel, an alarm going off in a hotel in the middle of the night, I've had that experience, et cetera, that they may not get the best night's sleep the night before. Before. Obviously, there are going to be ramifications of that. But I'm reminded of a study that was done by Ali Crum's lab at Stanford, where people wear sleep trackers. They actually knew how much and how well or poorly they slept the night before. I don't know how detailed the analysis was, but it was Stanford Sleep Center, so presumably it was reasonably detailed. Then the next They, with that knowledge in hand, either lied to the people or told them the truth about how well they had slept the night before or poorly.

For instance, if someone had got eight hours of great sleep the night before, they might have told them, Hey, you got eight hours of great sleep the night before, or they might have been in a condition where they said, Hey, you know what? Your sleep last night wasn't that great. Or if somebody got five hours of sleep, they might have said, Hey, you got eight hours of great sleep.

There was a lot of lying involved in this study.

But basically what they observed is that performance, I think it was motor skill performance, but it might have been cognitive, but that's not the issue here. The point is that much of our performance can be dependent on our subjective understanding of how well or poorly we slept the night before. In other words, there can be belief effects. That's right. This is one of the concerns about placing too much emphasis on the one poor night's sleep. Obviously, people should be mindful of injury, as you pointed out. But if someone has a big race or a big event the next day and they just don't sleep well, I think we have to be careful that the mere knowledge that they're not going to perform as well, because that's what the data say, can potentially be offset by the Alley Crum study, which is if they believe like, hey, a lot of it is about what they believe about their own sleep to be, which just tells you that performance and motivation, presumably, can override some of the physiology. Again, you can't rescue what you can't rescue.

No. And I think it's a very good point because it comes back to our discussion about the placebo effect in some ways, which is this is mind over matter and that your biological state. So one of the things I do when I'm working with professional athletes and we're doing sleep tracking, often I'm working with a coach, and I will say during that period where they're on the road and now they've got seven games to play in the playoffs. Let's keep tracking their sleep and let's you and I make sure that we're trying to optimize this athlete because they've given consent. They want to have their sleep as good as possible, and they want us to help them do that. But I say at that point, we will simply look at the data night after night, and then we can describe the data that they've been having at the end of the week after they've finished the series. Because for exactly that reason, if you start giving them feedback, we We don't want to erode confidence. With sleep trackers, there is such a thing called orthosomnia, and it's now a described situation. Orthosomnia, in medicine, words mean something.

So ortho people will be familiar with in medicine, orthopedics, orthodontics. It's about getting things straight. Orthopedics, getting your bone straight. Orthodontics, getting your teeth straight. Orthosomnia is It's about trying to get your sleep straight and being so worried about that, that it compromises your sleep. Now, we don't know exactly what proportion of people, it may be less than 10% who use sleep trackers, but I would say that to anyone listening, if you are Tracking your sleep with a tracker and you're experiencing this sleep-related anxiety, do one of two things. First, take my recommendation, which is that only on, let's say, Sunday afternoon, do you open up the app and check your data. That way, you can still be measuring your sleep, which is very helpful, but you don't have to get the anxiety morning after morning. The other is that if you are truly starting to get a very negative experience, take it off, put it in the drawer, and just get your sleep confidence back using some of the suggestions that we had in the optimization episode, and only then return to using that tracker. What's also interesting, it relates to what you were saying about beliefs and intention.

They did another great study where they looked at this cortisol rise in the morning that you and I have discussed on this series many times, which starts to happen just before you're waking up and really rises into the morning. What they did was they brought participants into the laboratory and They had them go to sleep at around 11:00 at night. Then in one group, they said, We're going to wake you up at 07:00 AM in the morning. The other group, they said, We're going to wake you up at 05:00 AM in the morning. Well, it turns out that both of those groups groups were woken up at 07:00 AM. But what was bizarre is that in the group that was told they were going to wake up at 05:00 AM, their cortisol release started to rise around 05:00 AM. In other words, just the knowledge before sleep that you're going to be woken up at 05:00 AM changed the non-conscious brain's release of a stock standard prototypical hormonal release mechanism. And that comes right back to this idea that we were speaking about with time, that consciously we have lost time perception when we're sleeping.

But non-consciously, it seems as though the brain is still knowing what's going on because For that early morning flight, you wake up two minutes before your alarm. Well, perhaps the reason why is that you've learned that you have to wake up at that time and you've changed your cortisol response, which would normally, because you don't wake up for an early morning flight every day, would normally not come for 2 hours, but it's arriving earlier. It just blew me away. I couldn't believe that the brain non-consciously could change a hormonal profile simply based on me telling you what time you're going to wake up the next morning.

Spectacular. And really, as you pointed out, really speaks to the fact that during sleep, there is a lot of processing going on, your subconscious, unconscious cognitive processing. And we know this in the form of dreams, a It's a topic that we'll talk about in a subsequent episode of this series. But okay, so you've shared with us the clear value of getting the best possible night's sleep before what I call a bout of learning. You also shared with us the clear value of getting sleep after being exposed to some new information, a bout of learning. You've explained to us the key relationship between sleep and motor learning, learning of new motor skills. What are some other aspects of brain and cognition for which sleep exerts a significant positive effect?

Those, for a while, were the first two things that we really thought sleep was doing for learning and memory. Sleep before learning, to make those memories, sleep after learning, to consolidate them and hit the Save button. But then data started to emerge, and we started to look at this, too, that sleep was much It's more intelligent than we ever imagined when it comes to information processing. Sleep doesn't simply just strengthen individual memories like isolated islands unconnected. Sleep after learning is almost a form of informational alchemy. That sleep will take these new memories and it will start to interconnect them and cross-link them with the new information that you've learned, because usually, information that you're learning during the day is interconnected connected, and sleep was building those connections between new memories, but also it was integrating them into the back catalog of all of your past autobiographical memory systems so that you woke up the next day and you had a revised mind-wide web of associations. A good example of this, we did a study, gosh, very early on, where we asked the question, which stage of sleep then is important for this type I almost think of it as a strange analogy, but almost like group therapy for memories.

That at the end of the day, every new memory gets a name badge and sleep gathers in all of these memories into the same room. It forces you, however, to speak to the people, not at the front of the room that you think you've got the most obvious connection with. It forces you to speak to the people all the way at the back of the room that you don't think you've got really any connection with at all. But it turns out that you do Because sleep doesn't simply build associations and connections. It does. It seems to bias the brain towards building the most non-obvious distant associations. It's almost like a Google search gone wrong, that during the waking day, our memories, which our brains are still associative in how they can build links and connections. That's like page one of the Google search. Let's say that I type in Andrew Huberman. The first page I get, the first hit, is the Huberman Lab website. Great. But if I go to page 20, it's about a field hockey game in Utah, and I think, heck in a second, what's Andrew doing? You didn't know? But yeah, I know exactly.

I don't think I've ever played field hockey. I've been to Utah. It's a beautiful state. It's beautiful.

But if I look, I can actually see that there is a very distant, non obvious association. I can understand why it's there. That's what sleep seems to be over indexing for in this associational framework. So then we asked, Well, what is it about sleep? So we had participants perform anagram solving tasks. Anagrams are simply these words that the letters are all jumbled up and you have to stare at them or work through them. And all of a sudden, you start to see which word it really is, because at first it's all jumbled up and it makes no sense. But we didn't teach them it before sleep and after sleep. We did something different. We woke them up out of different stages of sleep. Why? Well, when you come out of different stages of sleep, there is still some degree of the biology of that sleep state that lingers in your brain, almost like vapors coming off the stage of sleep that you've just exited. It only lasts for about two minutes or so. But what was nice is that this anagram test you could do within two minutes. We would wake them up out of different stages of sleep, and then we'd have them quickly We did these anagrams.

I told you that for fact-based memory, that sleep after learning was important to strengthen the individual memories. It was particularly non-rapid eye movement sleep that was doing that strengthening of the individual facts. Now what we found is that the association creativity benefit of sleep was very different. That cross-linking benefit came by way, it seemed, of rem sleep. Because when we woke them up out of rem sleep compared to non-REM sleep, They were 30% more capable of solving these anagrams. When we looked at how they were solving them, it was interesting. Coming out of non-REM sleep, it was very analogical. It was very what we think of as a very convergent, very focused way of trying to logically solve the problem. But with rem sleep, it was much more divergent fluid intelligence. It was almost that they were just standing back and waiting for it, and then it just popped out in front of them. All the letters reorganized and clicked into place. Then there was a subsequent study that did something different. It looked specifically at creative insight. It was a lovely study, and they performed something called the Numeric Number Reduction Test, which is one of those tests that psychologists love to administer and participants hate to perform.

Here's what happens. You're shown a whole string of numbers, and you are given a certain set of rules, and you have to work through those number problems and come out with a final end answer. You're told that you're going to be judged simply on how many correct final end answers that you get. You work through hundreds of these problems. What they don't tell you in the instructions, however, is that there is a hidden rule here embedded in that all of those sequences, all of the sequences are different, they have to solve. But there is one common rule that binds them all together, which is that the second part, the second component of the solution. So you're working through, let's say it's a 10 digit string number, and you have to apply these rules to the first number, then carry it through to the second number, and then to the third number. The second partial number that you produce in this string of calculations to get to the final end answer, it turns out to be always the same end answer. So in other words, if you clue on to this hidden rule, all you have to do is work up to the first, let's say, 10% of every problem.

You can just shortcut the rest of it and you just write down the number because you are told that the only thing we're going to judge you on is the end answer. They train participants on these numeric number reduction trials and then they brought them back after 12 hours of being awake, and no one seemed to have that light bulb moment of the, Okay, I get it. But then they did the same thing. They trained them, but now they train them in the evening. They gave them a full eight hours of sleep. They came back the next morning. There was a three-fold increase in creative insight problem-solving ability. In other words, people were coming back with that aha moment of, The gig is up. I've got it. I know what you guys are trying to do, and I'm going to show you. Then they did something clever. They said, Back to our question of motor skill learning, well, is that really sleep or is it just circadian? That it's just something about going through the night that gives you this doolally creative benefit. So they took another group, they taught them the information in the evening, and they tested them the next morning, just like the sleep group, but they kept them up all night.

So they went through night time, NUS, for that time period, and they showed no benefit in the problem solving.

My experience is that sleep deprivation leads to all sorts of ideas about how one is coming up with novel ideas and solutions, all of which completely suck after two good night's sleep. But most of the time it seems that sleep deprivation, intoxication of any kind, it gives one the impression that you're coming up with novel solutions, but really, they're just novel.

Yeah, that data is very clear that there's this misnomer that if I go through the night and work through into the morning, I'm just much more creative when I'm sleep-deprived. And it's been tested, and it's the opposite, quite the opposite, in fact. What I We also find interesting, though, about this sleep and creativity lark. It was always there in the literature that there are innumerable anecdotes of people having sleep-inspired insight. It's almost as though when you wake up the next morning, having had that revised set of web connections in your brain, you can divine solutions to previously impenetrable problems. There's a great example, I think Dimitri Mendeleev who at the time was trying to answer one of the most epic questions in human history. How do all of the known elements in the universe fit together in some logical order? And he was failing. He just could not. And he was so obsessed with this problem. He created playing cards with all of the different elements of the universe and their atomic weights and their electron. And he would go on these long train rides and he would just shuffle the cards and he would deal All the cards on the table because he was just desperate to try to see what the pattern was.

He was shuffling and shuffling and shuffling. Then the story goes and it's written that one night he fell asleep and he dreamt. He could start to see all of the cards just dancing around in front of his eyes, and then they snapped together in this logical grid based on the atomic weight and the different electron properties. He wrote it down on the back of envelope, which still exists to this date. Really? Yeah. You can see it. That was the initial basis for what we call the periodic table of elements. Amazing. It revolutionized human history. It's not just in science. I mean, there's great scientific people have won Nobel Prizes for understanding your all transmission, Otto Loew.

Well, and maybe it's worth rattling off a few brief examples because they're so spectacular. Einstein was known for taking naps in the middle of the day multiple times throughout the day in order to come up with novel solutions. I think the discovery of some of the organic- The benzine ring? The benzine ring came to... I'm forgetting his name now. August Kekuling. In a dream, thank you. There are numerous examples of fundamental scientific discoveries that is creative insights that were anchored to real-world experiments and theory, pure theory as well, that came to people in their dreams. What's interesting, though, is that there seems to be some hydraulic pressure created by the waking or within wakefulness attempt to figure something out. So all of these people, to be very clear, didn't just sleep to come up with solutions. They put a lot of hydraulic pressure, feeding a lot of information, thinking about a problem in a structured or unstructured way, taking walks, So they were focusing on their other demands of the day. But then when they went to sleep, clearly that information was still being worked with in important ways. Then you were going to mention some examples from the arts, I think.

Yeah, this is great. I was born and raised in Liverpool in England, and of course, famous for the Beatles and for Liverpool Football Club, and Everton as well, but I'm a Liverpool supporter. However, Paul McCartney has gone on record very clearly to say that two songs that that were probably some of the most successful songs, Yesterday and Let It Be, both came to him by way of dream-inspired insight. There's a lovely description, I think, in his biography. He was filming, it was either Help or A Hard Day's Night down in London with the rest of the Beatles. He was staying in a rental in Wimpole Street in London. He was staying on the third floor. In his bedroom, fortunately, there was a piano on the opposite side of the room. He describes how he woke up one morning with this beautiful melody by way of... It was a string quartet that was playing it, and it was the melody for yesterday. He went straight over to the piano and he started playing it. He said it was just so sumptuous, and he couldn't remember where he had heard it. Then after a while, he remembered, I haven't heard it anywhere before.

It came to me by way of sleep. Same thing with Let it be. Obviously, Mother Mary comes to me singing words of wisdom, let it be. There's often been a suggestion that that has religious overtones in terms of Mother Mary It actually is not. It's his mother, Mary McCartney. He was having a hard time struggling with the Fame of the Beatles at that moment. One night, he slept, and his mother, Mary, came to him and just said, Relax, it's going to be okay. Stay true to yourself. Continue doing what you're doing. Just let it be. And he woke up and he wrote the song.

I love that story. And there's some actionable takeaways here that if I may, I just wanted to mention. A previous guest on this episode, in fact, he's been on the podcast twice, is the great Rick Rubin.

Oh, I've listened to those.

One of the most legendary music producers of all time. The second episode that we did with Rick, he gets heavily into some of his protocols, for lack of a better way to describe them. One of the things that Rick does is when he wakes up in the morning, he makes it a point to He takes walks, he gets sunshine, he hydrates, he does all of those things. But to try and make the transition between sleep and wakefulness to be rather gradual, almost to allow some of the components of sleep to It bleed into the morning and then allow wakefulness to come about. In his case, he's able to push some of the more linear processing and procedural things to later in the day. I've spent a lot of time with Rick. I'm fortunate to be close friends with Rick, and I can tell you that he also spends a fair amount of time sitting or lying down, typically very still with his eyes closed, just thinking or allowing thoughts to emerge as part of his creative process. Now, he's certainly not the only one to do this, but he's a notable example. But what's the takeaway here?

Should everyone be lying with their eyes closed when they first wake up? Perhaps, but there's some potential do's. But I think there's a really strong don't. If one describes the idea that during sleep, there is substantial reorganization of neural circuitry, aka learning, but also expansion of creative opportunity, as you've clearly pointed out, and there are data to support that statement, then it stands to reason that upon waking, there's a key opportunity to capture some of that information that is now in your mind that was created the night before. But that if you immediately look at your phone, that you eclipse that process with sensory input from somebody else's ideas and what's going on in the world. It's not to say that looking at your phone first thing in the morning is a cardinal sin or a violation of any neural circuit requirement. But I, in an attempt to try and capture some of the learning and creativity that occurs during sleep, have tried for a while now to not look at my phone for at least the first 30 minutes after waking. It's very challenging to do for most everybody, but rather to let some of the ideas from sleep percolate up, and I will often be making a morning cup of tea or something, and then go running to my office to write something down that suddenly springs to mind.

Then I'll remember that this was something that came to me in a dream the night before. None of which is significant as the benzene ring or the periodic table or the works that Rick has produced. But I think that we need to be cautious about not short-circuiting these creative insights that no doubt can come to us in sleep.

I think it's very well worth just even for your mental health, firstly, not to just wake up and start your reception of the world, but to do some, as we've mentioned, reflection on what you've just experienced by way of sleep It doesn't necessarily have to be that you're trying to recall your dreams. Just sit with whatever your thoughts are. Think about the day ahead, think about the days prior. There is some benefit. The creative benefit there You mentioned Einstein. Another one that is often mentioned to me is Edison, Thomas Edison, the inventor. Edison was claimed to be a short sleeper. People will say, Well, he was a brilliant inventor, but he said that he didn't sleep sleep very much. It turns out that Edison was a habitual napper during the day. I've got lots of pictures of him napping on his workbench in his studio, him napping in the garden. I love it. I took a 45-minute nap today. Yeah.

I'm no Edison, but I subscribe to these protocols.

But he understood the creative brilliance of sleep, to your point, about writing things down, and he used it ruthlessly as a tool. And here's what he would do. It's genius. He would take a pair of steel ball burings in his right-hand. He would sit in his office on a reclining chair with a rest for his arm, and then he would put a pad of paper and a pen next to him. And then he would gradually start to relax off. But what he'd done was he used a metal source pen and turned it upside down and placed it underneath the armrest. And as he was drifting off into that state, into that liminal state, so he did He didn't go too far into sleep. What would happen is that his muscle tone would gradually relax. He would release the steel ball bearings. They would crash on the source pen, wake him up, and then he would start to write down all of the ideas that he was having from that liminal state.

You said saucepan.

Saucepan, sorry.

No, that's okay. But it made a-Crashing sound.

A metal saucepan underneath. Got it. Or a water pail, whatever it was, and it would crash there, wake him up, and then he would write down these ideas. So interesting. And in fact, if you look at his house, which is preserved, historical, you can walk around, and he had nap cots installed in his house, so he could go into different rooms and take naps in these little cots. Listen, I- For his genius, it's brilliant, isn't it?

It is brilliant. Sorry, I didn't mean to interrupt, but it was out of enthusiasm. I don't want to give too much detailed information about Rick's working environment. But let's just say there are a lot of places to lie down down and access these states of mind. It looks like somebody just lying there with their eyes closed, but there's an extremely active mind in there. Obviously, look at the productive output of Rick's career. It's truly something to behold. Behold in capital bold, underlined, highlighted letters. But it's so clear to me, based on all the examples you gave, the ones that we're batting back and forth now. I think there's a book, the title is something like Winston Churchill's Nap or something like that. My dad is always talking. My dad's a theoretical physicist, always talks about napping is so key to one's ability to come up with novel solutions. I guess that napping frequently throughout the day perhaps violates some of the tenets that you described in the episode on napping in caffeine, episode three.

I think you agree because we put in guardrails and we put in the protocols to say, okay, Obviously, naps under certain circumstances are no bad thing at all. If you're going to do it, here are the suggested guidelines as to exactly how you optimize naps with the protocol. But I think it's very worthwhile to just appreciate exactly how complex sleep is in terms of what it's doing for information processing. If you were to ask me, look, what's the take home of this final section? I think no one has ever told you Andrew, you really need to stay awake on a problem. They've told you that you should sleep.

Now, many times. On a problem.

Go to sleep. Yeah, sleep on a problem. What's interesting is that in every language that I've been quiet about today, from English to Swahili, that phrase, sleeping on a problem, or something like it, very much exists. I think the Spanish someone was telling me is, it translated as, you have a conversation with your pillow, which I thought was lovely. What I I also was struck by a fellow who was French said, You in England, you say you sleep on a problem. Well, the French translation is much closer to you sleep with a problem. I thought that's so much about the romantic difference between the beautiful French and the English. You sleep on a problem versus you sleep with a problem.

Yes, I agree. I think not only does it have more romantic notions, but I like it because there's a symbiotic aspect to sleeping with the problem. There's a meshing with the challenge in a way that isn't as combative. This thing that's weighing on you, you go to sleep with it, then you're supposed to wake up and feel like you solved it, like eureka, right?

Push down on it rather than it's a collaboration with sleep rather than a demand from it. But I also think I make that notion about language translation, maybe Maybe a slight joke, but what it also tells me is this, that that phenomenon of sleep dependent creativity transcends cultural boundaries. It is common across the globe. It's a universal phenomenon. Why? Well, because sleep is a universal phenomenon, not just even in humans, but in almost every species that we've studied carefully to date.

As you describe the French of sleeping with a problem, I think what the image that comes to mind is that perhaps the idea is if you're going to sleep with a problem, that you should be the big spoon and they should be the little spoon, as opposed to the problem being the big spoon, and you're wrapped in the problem. Maybe the problem needs to mesh with you, but maybe I'm taking this-No, I love it. This imagery a little too far. Before we close out this discussion about sleep and creativity, I can't help but bring up a set of questions around a different non-sleep protocol that in many ways seems to mimic sleep, and that for some individuals throughout history, in particular, the great physicist Richard fineman, another habitual Neil Napper.

Yeah, an absolute idol of mine.

Wrote about and spoke about his fondness for these flotation tanks that contain a temperature of water that is fairly neutral, so one doesn't recognize the difference between body temperature and the surrounding water. There's a certain amount of salt, salinity in the water that allows one to float at a depth within the water that one loses their sense of proprioceptive awareness, as you described earlier in the series, a key component of falling asleep. He talked about how under those conditions in the flotation tank, there was an untethering of one's notions of space and time that were very sleep-like, and that that was one of his go-tos for creative solutions. People talked about walks as a go-to for creative solutions. In the shower, people seem to come up with creative solutions. States of mind and activities where it's only somewhat goal-directed, but basically the idea is to just lose lack of one's body positioning and let the mind go, so to speak. For that matter, psychedelics have on occasion been attributed as at least one of the sources of creative solutions. I raised these ideas understanding that each one of those could be a podcast into itself.

But it seems to me that sleep, and in particular dream sleep, is nature's way of creating these states of untethering our rigid linear understanding of what relates to what. It provides this near magical mixing of things learned the day before. That's the essence of creativity. Humans have been trying to tap into the creative process through all these other portals for a long time with expensive technologies. But it's becoming very clear to me that the technology already exists and that it costs absolutely nothing, and that it has tremendous health benefits in addition to its benefits for creativity. That technology is this brilliant technology of sleep.

Yeah, and dreaming. It's a stunning state.

Matt, thank you so much for today's discussion about sleep, memory, learning, and creativity. We are now four episodes into this series on sleep. First episode, we discussed, rather, you You taught us about sleep and the biology of sleep, as well as some actionable takeaway. Actually, I would say some important guidelines for getting one sleep correct. Then in this second episode, you went much further into protocols, both basic and advanced, for getting one sleep right, maybe even optimized. In the third episode, you taught us about naps and caffeine. Today, Today, you've taken us on a beautiful exploration of the relationship between sleep and learning. What's more interesting than neuroplasticity and learning? I mean, after all, humans are unique in our ability to learn so many things throughout the lifespan. It's one of the things that distinguishes us from the other species on the planet, the very, very long window, perhaps lifelong window for the opportunity to learn. Of course, creativity and novel solutions to challenging problems in the world, but also great works of art and music, et cetera. I think we can fairly say, based on what you've taught us today, that sleep has been not only the bedrock of mental health, physical health, and performance since the beginning of time, and still now, but also has been one of the fundamental drivers of human evolution because of all the creative insights that have occurred and all the learning that's occurred in sleep that's then been transformed into real-world technologies.

Indeed, it's much of the way that we have the The blessing of being right here right now.

If that's the flag that you're raising, I will salute it. 5 Waste on Tuesday, very much, yes.

Well, I'll salute that flag right with you. Also point to the exciting fact that the next episode, episode 5 in this series, you're going to teach us about the really tight relationship between sleep and emotional processing and emotionality. I can't think of a more interesting topic to get into, especially at this point in the series. I look forward to that discussion with emotional enthusiasm.

I can't wait. If folks are interested in trying to modulate their mental health, I think that next discussion should be very helpful with regard to sleep. I hope so, at least.

Thank you for joining me for today's episode with Dr. Matthew Walker. To learn more about Dr. Walker's research and to learn more about his book and his social media handles, please see the links in our show note captions. If you're learning from and or enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero-cost way to support us. In addition, please subscribe to the podcast on both Spotify and Apple. On both Spotify and Apple, you can leave us up to a five-star review. Please also check out the sponsors at the beginning and throughout today's episode. That's the best way to support this podcast. If you have any questions for me or comments about the podcast or topics or guests that you'd like me to feature on the Huberman Lab podcast, please put those in the comment section on YouTube. I do read all the comments. On many episodes of the Huberman Lab podcast, we discuss supplements. While supplements aren't necessary for everybody, many people derive tremendous benefit from them for things like improving sleep, for hormone support, and for focus. To learn more about the supplements discussed on the Huberman Lab podcast, go to livmomentus, spelled O-U-S.

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Last, but certainly not least, thank you for your interest in science.