Dr. Matt Walker: Using Sleep to Improve Learning, Creativity & Memory | Huberman Lab Guest Series

1. 0:00 – 0:59

   Sleep & Learning

   1. AHAndrew Huberman0:00

      (instrumental music) 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 six-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 when and how long to sleep relative to different bouts of learning, as well as the role of naps in 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.

2. 0:59 – 5:48

   Sponsors: Helix Sleep, Whoop & Waking Up

   1. AHAndrew Huberman0:59

      Before we begin, 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 goes so much better, and when we are not getting enough quality sleep, everything in life is that much more challenging. And one of the key things to getting a great night's sleep is to have the appropriate mattress. Everyone, however, has slightly different needs in terms of what would be the optimal mattress for them. Helix understands that people have unique sleep needs, and they've designed a brief two-minute quiz that asks you questions like, do you sleep on your back, your side, or your stomach? Do you tend to run hot or cold during the night? Or maybe you don't know the answers to those questions. If you go to the Helix site and take that brief quiz, they'll match you to a mattress that's optimal for you. For me, it turned out to be the Dusk, D-U-S-K, mattress. It's not too hard, not too soft, and I sleep so much better on my Helix mattress than on any other type of mattress I've used before. So if you're interested in upgrading your mattress, go to helixsleep.com/huberman, take their brief two-minute sleep quiz, and they'll match you to a customized mattress for you, and you'll get up to $350 off any mattress order and two free pillows. Again, that's helixsleep.com/huberman to save up to $350 off and two free pillows. Today's episode is also brought to us by Whoop. Whoop is a fitness wearable device that tracks your daily activity and sleep, but also goes beyond that by providing real-time feedback on how to adjust your training and sleep schedule to perform better. I've been working with Whoop on their scientific advisory council to try and help advance Whoop's mission of unlocking human performance. As a Whoop user, I've experienced the health benefits of their technology firsthand for sleep tracking, for monitoring other features of my physiology, and for giving me a lot of feedback about metrics within my brain and body that tell me how hard I should train or not train, and basically point to the things that I'm doing correctly and incorrectly in my daily life that I can adjust using protocols, some of which are actually within the Whoop app. 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, 5, and even 1-minute meditations that are known to be effective. So 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 makes sure that your meditations are kept fresh and interesting. You never get bored of them. 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. And 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, and 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. So NSDR and yoga nidra are terrific 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. And now for my conversation with Dr. Matthew Walker.

3. 5:48 – 9:32

   Learning, Memory & Sleep

   1. AHAndrew Huberman5:48

      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.... 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-

   2. MWMatthew Walker6:19

      (laughs) Yeah.

   3. AHAndrew Huberman6:19

      ... or protocols as we call them. And 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. And today, we're going to talk about sleep, learning and memory, and a topic that I know everybody is very interested in, creativity.

   4. MWMatthew Walker6:44

      Indeed. Resplendent pleasure to be back on the show. Thank you for having me.

   5. AHAndrew Huberman6:49

      Yeah, absolutely. So, 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. You know, I- I think most people are familiar with being exposed to some new material, cognitive material, physical, uh, skill material, and not being able to learn it right away, but then having a few days in between-

   6. MWMatthew Walker7:18

      (laughs)

   7. AHAndrew Huberman7:18

      ... and then all of a sudden, voila.

   8. MWMatthew Walker7:20

      Yeah.

   9. AHAndrew Huberman7:21

      There's, uh, 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. So, how do you think about sleep as it relates to learning and memory?

   10. MWMatthew Walker7:38

       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 sort of 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, and 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. And why is that beneficial? Because it provides you with creative insights. And so we will perhaps just double-click on each of those three and I can, 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? And 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, and I would love to dive into detail.

4. 9:32 – 13:46

   Memory & Sleep, “All-Nighters”, Hippocampus

   1. MWMatthew Walker9:32

   2. AHAndrew Huberman9:32

      Yeah, so let's do that. Let's talk about this business of sleeping before learning. You know, essentially establishing a milieu within the brain that is-

   3. MWMatthew Walker9:42

      Mm-hmm.

   4. AHAndrew Huberman9:42

      ... optimal for learning. What, what is that about, uh, neurochemically at the level of circuits and, um, 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-

   5. MWMatthew Walker9:57

      Yeah.

   6. AHAndrew Huberman9:57

      ... can be beneficial?

   7. MWMatthew Walker9:59

      Yeah, I love that word, that optimal milieu, and it beautifully describes what we found. We started off asking a very simple question, uh, at my sleep center. Is pulling the all-nighter a wise idea? (laughs) So 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. And both of those groups went through those two different protocols, and 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, and then we tested them to see how effective that learning had been. When we looked at the group that had had a full night of sleep, they had incredibly efficient learning capacity. So 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. And 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? And the structure that we focused on is one you've spoken about before called the hippocampus...And 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 s- right side of your brain. And 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. And 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 up 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. So 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. And then subsequent studies that were not done by us, but, uh, looking at animal models, they were looking at how able the synapses are in that memory structure of the hippocampus, how capable those synapses are for building new connections. And 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. And what they found was that when they, uh, restricted the sleep of these rats or the mice, that part of the brain became very stubborn, it just wouldn't form those new synaptic connections. That's something that we call synaptic plasticity. So we started to understand this was the bad that happened when you take sleep away,

5. 13:46 – 16:59

   Naps & Learning Capacity

   1. MWMatthew Walker13:46

      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? So 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. And 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. And then we brought them back six hours later at 6:00 PM and now we had them learn a whole new set of information. And 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 about 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 sort of average cycle to get some non-REM and to get some REM. And what was interesting is that when we tested the group that remained awake later that following day, their 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 and the difference between those two was about 20%, which is quite a nice benefit.

   2. AHAndrew Huberman15:20

      Yeah, not trivial.

   3. MWMatthew Walker15:21

      Not trivial at- at- at all. And then we said, "Okay, well if sleep is doing something, what is it about that sleep?" So we unpacked the physiology of sleep and the different stages of sleep that we discussed in the first episode, and what we found was that it was the non-rapid eye movement sleep or the non-REM sleep, and particularly those sleep spindles, those short bursts of electrical activity that we have discussed before, that seemed 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, and 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.

   4. AHAndrew Huberman16:10

      Mm-hmm.

   5. MWMatthew Walker16:11

      It's very good during the day at going around and grabbing new files, but it has a limited storage capacity, and 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, a much 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.

6. 16:59 – 26:38

   Early School Start Times, Performance & Accidents

   1. MWMatthew Walker16:59

      We then wanted to say, well, can we translate this out into the real world? And I think there are two regions that we've moved this work out into. One is education, one is, 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.

   2. AHAndrew Huberman17:24

      Sounds about right.

   3. MWMatthew Walker17:25

      And if you think about that for 7:30 school start times, school buses will begin leaving around 5:30, 5:45 in the morning.

   4. AHAndrew Huberman17:35

      Mm-hmm.

   5. MWMatthew Walker17:36

      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. And there's a great study in Edina, I hope I'm pronouncing that correct, Edina, which is a small suburb or it sits in a small suburb outside of Minneapolis in Minnesota. And they shifted their school start times from 7:25 to 8:30 in the morning.And then they wanted to ask, what is the consequence of that on the academic performance of their students? And 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. And 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. So 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-

   6. AHAndrew Huberman19:16

      Amazing.

   7. MWMatthew Walker19:16

      ... as a consequence. Now some people have argued that data, you know, i- in terms of its source and its reliability may not have necessarily been accurate, but now we've got very consistent data. When you s- 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. And you think, "Well, hang on a second, how do you determine that?" The number one cause of death in teenagers 16 to 18 is actually not suicide, turns out to be second, it's road traffic accidents. And 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. And 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. (laughs)

   8. AHAndrew Huberman20:34

      What time are they getting out of school?

   9. MWMatthew Walker20:36

      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 'cause you've got to change the school bus system." And they've argued, pushed back against that. And I would say probably two things. First, I know it's difficult and I'm not saying it's an easy problem to do, it's a complex problem, and I'm sympathetic to that, but I- I think we've put people on the moon, and so I suspect that we can also solve the problem of (laughs) early school start times. The- 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. And if you look at the data, it's very clear, when sleep is abundant, minds flourish, and when it's not, they don't. And so 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, and we got this bill passed firstly in California, and we got it on the governor's desk at the time, it was Governor, uh, 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 the- on his desk and he did sign it. And then, uh, 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. So there's gradual movement happening, but it's hard fought and it's- it's problematic. I still think that it's- it's impossible n- to deny that data. I mean, it was an interesting thing. (laughs) I remember when I was a professor back at Harvard, we were doing this work on sleep and- and learning and they said... And it was sort of published in these sort of, um, kindly, I don't know how we did it, but in nice journals, and they said, "Okay, based on the media attraction, would you write an editorial for the Harvard newspaper?" Which was called the Harvard Crimson. And I said, "I'd love to." So 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 (laughs) to cram information. So...

   10. AHAndrew Huberman23:39

       Well, 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.

   11. MWMatthew Walker23:46

       No.

   12. AHAndrew Huberman23:47

       Ev- 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.

   13. MWMatthew Walker23:55

       Right. Next item, next item, and then-

   14. AHAndrew Huberman23:57

       Right.

   15. MWMatthew Walker23:57

       ... 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-

   16. AHAndrew Huberman24:05

       Right.

   17. MWMatthew Walker24:05

       ... in this sleepless two-week period. So rather than saying, "Look, the students need to change their behavior, they need to understand this is 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."

   18. AHAndrew Huberman24:30

       Mm-hmm.

   19. MWMatthew Walker24:31

       So I put this, uh, editorial out. It received a, um, a rather Baltic, if not Arctic, response and, um, that was the last editorial I was ever invited to- (laughs)

   20. AHAndrew Huberman24:45

       (laughs)

   21. MWMatthew Walker24:45

       ... to write for the newspaper. But, you know, you've got to say your piece.

   22. AHAndrew Huberman24:51

       Well, so but, w- I'm curious why there's resistance to shifting to later school times and to improving the conditions for learning if the goal is to learn. I mean, tradition dies hard.

   23. MWMatthew Walker25:03

       Mm-hmm.

   24. AHAndrew Huberman25:03

       Um, maybe that's why? Um, I think there's also the idea, certainly in the medical profession, that, you know, well, when I was doing my training, we would pull all-nighters all the time, um, and so 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, is that why, do you think motivates the, the resistance to change?

   25. MWMatthew Walker25:27

       I think so. I think you've hit all the points. I think, you know, 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 s- 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? And let's say it's around 4:30. One of the interesting analyses that was published, and we latched onto this, that is this strange bewitching hour when kids get out of school, but often their parents are not home to work, and 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 it's filled. But by pushing school start times later, they get out later, they go home, and if you were to even half that debt that those crimes cause, you would easily pay for the education system.

7. 26:38 – 29:35

   Medical Residency & Sleep Deprivation

   1. MWMatthew Walker26:38

      So 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, and this is another good example. We, and mostly, um, colleagues of mine such as Charles Czeisler at Harvard, have really done a great job at cataloguing 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. And 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 the previous 24, they are almost 70% more likely to cause a surgical error which could result in n- non-trivial consequences. And 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 (laughs) as a patient rather than a physician. And you think, "What are we doing?" Like, Charles Czeisler I think has described, they provided this evidence to the council and at first they just, I think the idea was, "Look, our minds are made up. Don't confuse me with the data." (laughs) And when you appeal on the empathetic basis, but it wasn't well received. So 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 then y- you get the administrators into the room, all of a sudden the schedules change. So 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 residents and not the remaining years, and the question was, "Well, why?" And they said, "Well, the data that you showed us, you only collected in first year residents," 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. (laughs) So-

   2. AHAndrew Huberman29:09

      Well, if anything it would compound and get worse, so- so it seems to me that, um, there's- there's like zero question that getting adequate sleep is good for learning, but- and when the stakes, when it's high risk/high consequences scenarios, or even high consequences scenarios like a medical situation, um,-

   3. MWMatthew Walker29:31

      Mm-hmm.

   4. AHAndrew Huberman29:31

      ... it just seems like, uh, it should almost come down to legal liability.

8. 29:35 – 30:49

   Sponsor: AG1

   1. AHAndrew Huberman29:35

   2. MWMatthew Walker29:35

      Yeah.

   3. AHAndrew Huberman29:36

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9. 30:49 – 35:09

   Tool: Sleep Before Learning; Cramming Effect

   1. AHAndrew Huberman30:49

      So are the errors of sleep deprivation in these scenarios, both in students and in medical professionals, are they due to errors in memory per se? I mean, the, the... So, I mean, 'cause you can imagine all sorts of errors. So with a surgeon, they, like, cut the wrong thing-

   2. MWMatthew Walker31:06

      Right.

   3. AHAndrew Huberman31:06

      ... or they cut too far, the margin on the surgical site is too big, et cetera. But since we're talking about learning and memory, um, and its relationship to sleep, uh, is it that people are forgetting what they did? Are they forgetting what they didn't do? I mean, um, or is it a deficit in motor skills or all of the above?

   4. MWMatthew Walker31:25

      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.

   5. AHAndrew Huberman31:40

      Got it.

   6. MWMatthew Walker31:40

      But it's also decision-making too, that what we know is that your frontal lobe is especially sensitive to a lack of sleep, and 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.

   7. AHAndrew Huberman32:01

      So how should I establish the proper neural milieu for learning by sleeping prior? Should I make sure that I... I mean, in an ideal world, I get an excellent night's sleep for the, you know, every day of my life leading up to a bout of learning, being expo- And here, I'm referring to a bout of learning as being exposed to new material. But life happens. Um...

   8. MWMatthew Walker32:24

      Yeah. Mm-hmm.

   9. AHAndrew Huberman32:25

      So if I know that tomorrow I'm going to take a class in something or I'm going to need to perform a skill that it's pretty nascent skill for me, I only learned it recently, what should I do the night before?

   10. MWMatthew Walker32:39

       I would say think about what you can get in terms of your sleep under current conditions and understand that that is s- staying awake and foregoing sleep is not the right equation that you may think. In other words, think of sleep at 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, you know, say, 'I, I should just focus and stay awake,' 'cause at least then I can just go over the material time and time and time again. Doesn't that offset the, 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. And 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 brought them back, and we haven't published this, this data or I should do. We brought them back a month later, and then we tested them again. And 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.

   11. AHAndrew Huberman34:33

       Got it. So this is the cramming effect.

   12. MWMatthew Walker34:36

       That's right.

   13. AHAndrew Huberman34:36

       Right. And then, uh, and one who knows this from teaching university courses, um, 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.

   14. MWMatthew Walker34:47

       (laughs) Yeah.

   15. AHAndrew Huberman34:48

       So, so it's almost like a... It just never passes from short-term to long-term memory, essentially.

   16. MWMatthew Walker34:53

       That's correct.

   17. AHAndrew Huberman34:54

       Okay.

   18. MWMatthew Walker34:54

       And that seems to be in some ways, that's a, 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.

   19. AHAndrew Huberman35:08

       So

10. 35:09 – 44:25

    Tools: Caffeine; Timing Peak Learning; “Second Wind”

    1. AHAndrew Huberman35:10

       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. And people should refer to that, um-

    2. MWMatthew Walker35:34

       Nothing wrong with your memory, by the way.

    3. AHAndrew Huberman35:36

       Uh, well, I don't know about that.

    4. MWMatthew Walker35:37

       (laughs)

    5. AHAndrew Huberman35:37

       But, uh, (laughs) the, um, the QQRT formula was, was described in the first episode. Um, let, let's come up with a, what I think is a fairly common scenario. So 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 kind of always intuited it, but I, um, it clearly is what works best. If I go to bed at 10:00, I probably want to wake up sometime around, I don't know, 6:00 AM or, or 6:30. And, um, 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 s- get sufficient hours of sleep. So 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 s- stick to that schedule, wake up the next day and...... go do my learning or my performance of something that I had learned. Someone else might have their chronotype where 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. So is there anything that we can do heading into a bout of learning, meaning the night preceding that bout of learning, that can kind of, um, provide a buffer or, or set us up for the best possible learning scenario if we're not able to stick to our perfect schedule?

    6. MWMatthew Walker37:22

       I think there may be two things. There's been a little bit of work that's been done, um, to suggest that caffeine may actually 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 deprive 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? W- 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. And 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. And 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 10:00, 11:00 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 kind of an 11:00 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. So if you've got the choice and you are under slept, 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?

    7. AHAndrew Huberman39:58

       Yes. That, that makes good sense. So 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, right, um, that causes fairly dramatic shifts in wakefulness and sleepiness independent of the adenosine signal.

    8. MWMatthew Walker40:31

       Mm-hmm.

    9. AHAndrew Huberman40:31

       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, and 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, um, 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, you know-

    10. MWMatthew Walker41:09

        Mm-hmm.

    11. AHAndrew Huberman41:09

        ... A+ performance, if one knows that, okay, typically around, you know, between 10:00 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 sort of thing. And then perhaps in the afternoon there's another opportunity bef- uh, after the postprandial dip-

    12. MWMatthew Walker41:29

        That's right.

    13. AHAndrew Huberman41:30

        ... but before the e- uh, postprandial dip co- sometime between 1:00 and 4:00 PM usually lasting about an hour to 90 minutes. This is a dip, natural dip in energy, but then after that is another opportunity to learn. Um, sure, there'll be a lot of adenosine in one's system 'cause you've been up long time, um, but the circadian system is on its sort of, uh, upswing again-

    14. MWMatthew Walker41:52

        It's coming back, yeah.

    15. AHAndrew Huberman41:52

        ... before the downswing that occurs in the evening. Is that right?

    16. MWMatthew Walker41:55

        Th- that's right.

    17. AHAndrew Huberman41:56

        So, so, so you can cu-

    18. MWMatthew Walker41:57

        So you've got two opportunities.

    19. AHAndrew Huberman41:58

        Yeah.

    20. MWMatthew Walker41:58

        Um, and by the way, it's strange you were to ask. If you look at the c- circadian rhythm, right before sort of bedtime, there is this sort of strange little blip, this peak-

    21. AHAndrew Huberman42:08

        Mm-hmm.

    22. MWMatthew Walker42:08

        ... um, that folks at, um, back at Harvard hav- have t- 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?"

    23. AHAndrew Huberman42:30

        Right.

    24. MWMatthew Walker42:31

        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. (laughs)

    25. AHAndrew Huberman42:46

        Yeah, to batten down the hatches.

    26. MWMatthew Walker42:48

        Exactly.

    27. AHAndrew Huberman42:49

        Yeah.

    28. MWMatthew Walker42:49

        So 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 potential threat to you. I'm gonna just boost your alertness very quickly so you travel home safely. Good to go? Great." And now I start my downswing.

    29. AHAndrew Huberman43:09

        I think this is a really important thing for people to know about. Um, I'm familiar with the data, uh, 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 are, for them based on their chronotype, around 9:00 PM they're like wide awake.

    30. MWMatthew Walker43:33

        Second wind.
11. 44:25 – 55:07

    Memory Consolidation in Sleep

    1. MWMatthew Walker44:25

    2. AHAndrew Huberman44:25

       Well, speaking of sleep post-learning, um-

    3. MWMatthew Walker44:28

       (laughs)

    4. AHAndrew Huberman44:28

       ... what is the role of sleep that follows a bout of learning? And here again, we wanna define learning as the exposure to novel information that one is trying to encode, either cognitive i- information, motor information, or c- or a combination of the two. Um, e- and I say that because learning, AKA neuroplasticity, has many different stages.

    5. MWMatthew Walker44:48

       Mm-hmm.

    6. AHAndrew Huberman44:48

       It's a process, not an event. But, um, so l- let's say that, uh, earlier in the day, I took a dance class, Lord knows I need one, or, um-

    7. MWMatthew Walker44:57

       (laughs) You, you and I both.

    8. AHAndrew Huberman44:57

       ... or a musical lesson or was exposed to some interesting information, who knows, maybe on a podcast, and I was, you know, trying to engage in that information and, and pay attention, and then that night I, I planned to sleep, um, or perhaps wanted to take a nap after this bout of learning. How close to the learning episode, bout, as I'm calling it, does the sleep have to arrive in order for sleep-

    9. MWMatthew Walker45:23

       Mm.

    10. AHAndrew Huberman45:23

        ... to maximize the amount of learning that occurs?

    11. MWMatthew Walker45:26

        It's a very good question, which is, what would happen if I were to be learning information and I'm listening to this o- odd British gentleman, should I then immediately dive into bed so that I maximize the retention of that information? And the answer is no, don't worry. I'll come back to why not to worry. Um, 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 of, 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. It a- essentially it's almost like sleep will hit the save button on those new memories so that you don't forget. So in other words, sleep is future-proofing that information within your brain so that you don't forget, and 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, um, gig, (laughs) it goes back as best we can tell to 1929, although I- I- I'll argue with that in a second. But two researchers, Jenkins and Dallenbach, 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. And 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, and then again when they woke up in the morning, eight hours later. And what they found is that in those people who stayed awake after learning, there was essentially just catastrophic forgetting. (laughs) The amount of information two hours, four hours, six hours, eight hours later just declined dramatically. But when they repeated that in the same individuals after learning things to the same degree, two hours, four hours later, memory was starting to decline, but after about two and a half, three hours of being asleep, all of a sudden sleep had fixated those memories almost like, um, like an animal that's been trapped in amber and set in amber like a fossil, and 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 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, the sum total...... two participants. (laughs) But what's stunning is that that finding has gone and been replicated time and time again. So that demonstrated to us that there's something special about sleep that is concretizing, almost literally, like, taking things and setting it in concrete. And then the question became, again, mechanistically, how? How is it... And it's important to understand mechanism because it has ramifications for diseases and medicine. How is sleep doing this fantastic saving of memories? And we now have at least two non-mutually-exclusive mechanisms. So 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, uh, done a fantastic, uh, previous episode on working memory and described all of these different types of memory. So one storyline has been sleep after learning for fact-based memory, but the other, which is equally 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. And here what we found is that it's deep non-REM sleep for fact-based memories, and it's those big, slow, powerful brain waves that we spoke about in the first episode, combined with those sleep spindles that ride on top of them almost like a surfer on a huge amplitude wave. And it's the combination of those two brain waves that acts like a file transfer mechanism, and 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. So that's one mechanism is the, the shifting of memories around the brain through different storage sites from short-term to long-term. The second, I think is perhaps even more fascinating. It's called memory replay. And this was discovered back in the probably 1990s. Bruce McNaughton, um, at the University of Arizona working with a young Matt Wilson, who we know, uh, 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, and they had these electrodes in these hippocampal brain regions. Um, these memory-related regions that we've been discussing, and they were listening to the individual firing patterns of those memory cells in the hippocampus as they were running around the maze. And 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, and as the rat is running round the maze, you can hear the signature of learning. Ba-ba-ba-bum, ba-ba-ba-bum, ba-ba-ba-bum, ba-ba-ba-bum. And it just went 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 replayed. However (laughs) , it wasn't replayed at the same speed. It was replayed somewhere between 10 to 20 times faster. So now all of a sudden instead of hearing ba-ba-ba-bum, ba-ba-ba-bum, you heard barum-barum-barum-barum-barum-barum-barum. Just 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 their version essentially of, that spatial navigation is their version of fact-based memory, and I won't go into detail, but...

    12. AHAndrew Huberman52:56

        Yeah, 'cause 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.

    13. MWMatthew Walker53:05

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

    14. AHAndrew Huberman53:09

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

    15. MWMatthew Walker53:40

        No, you still actually, there's still a... Now you can drive, you know, these rideshare 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. And if you, if you are visiting London, you will see these strange guys who are going around on mopeds and they just have this huge kind of map in front of them, and they are doing The Knowledge, which is that they are learning exquisitely the entire roadmap of London. And 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, were 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, (laughs) 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 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.So coming back to the, the, the rats and 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.

12. 55:07 – 1:00:16

    Sleepwalking & Talking; REM-Sleep Behavioral Disorder

    1. MWMatthew Walker55:07

       What was also fascinating, however, I w- I'm telling you that it's during non-REM sleep that you do all of this memory replay, and 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, sort of 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 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, I don't know, 10 minutes, 15 minutes. But it's been five minutes in the real world, but time has slowed down. Time is dilated. It's almost like a concertina that's stretched out. And 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%. So I always wonder whether or not there is neuronal evidence that helps us explain why dreams seem to pack more time, uh, despite being in real world time a shorter amount. Absolutely fascinating.

    2. AHAndrew Huberman56:52

       Yeah, I have to imagine that, um, rats dream, and dogs dream, and other animals dream. I mean, why wouldn't they? Um, you know, if, uh, all the components of REM sleep that are expressed in humans, uh, appear in these animals and vice versa, you imagine it almost has to be the case.

    3. MWMatthew Walker57:12

       It does, and 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, and 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 sleepwalking 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, sort of the, back to that analogy of going from the basement to the, to the penthouse. And instead, you just get locked into this mixed state of consciousness, sort of, 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, there's harm, they, and ask them, "What was going through your mind just a few minutes ago?" They will say, "Nothing." And the reason is because it wasn't coming from dream sleep. It was from deep non-REM sleep.

    4. AHAndrew Huberman59:02

       I see.

    5. MWMatthew Walker59:03

       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-

    6. AHAndrew Huberman59:17

       That's worse.

    7. MWMatthew Walker59:17

       ... 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, and when you see it and you can understand, I mean, 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, and at that point, you look at that and you say, "Okay, I'm, I'm sorry, but that looks very much like dreaming." Now, we can't, of course, ask dogs question, you know, "What was going through your mind?"

    8. AHAndrew Huberman59:59

       You can ask them.

    9. MWMatthew Walker1:00:01

       But-

    10. AHAndrew Huberman1:00:01

        But they're not going to answer.

    11. MWMatthew Walker1:00:01

        But yeah, but yeah, you can ask them, but it turns out that their responses-

    12. AHAndrew Huberman1:00:05

        I'm just, I'm just... For- for giving.

    13. MWMatthew Walker1:00:05

        ... is less than, it's just a look to say, "Give me a treat." But, you know, in science sometimes, if it looks like a duck, talks like a duck, walks like a duck, maybe it's a duck. (laughs)

    14. AHAndrew Huberman1:00:15

        Mm-hmm. What,

13. 1:00:16 – 1:07:41

    REM Sleep Paralysis, Alcohol, Stress

    1. AHAndrew Huberman1:00:16

       what about, um, 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, and um-

    2. MWMatthew Walker1:00:33

       Mm-hmm.

    3. AHAndrew Huberman1:00:33

       This was a long time ago, uh, probably the 10th grade, which for me, I was, what, 15 years old? I'm 48 now, and um, was at a party that I, I fell asleep on the couch, and I... Goodness, I, I don't believe in underage drinking, but there's a, there's a possibility that I might have been inebriated. I, I was, uh-

    4. MWMatthew Walker1:00:52

       Just a possibility.

    5. AHAndrew Huberman1:00:53

       Kids, parents to, you know, I, I dis- I actively dissuade.... young people from drinking, and many, uh, older people from drinking, but, uh, yeah, I, I started drinking far too young. Um, and I ... But I remember I drank the night before, I got drunk the night before. Again, something I'm, I'm not, um, suggesting or proud of. I woke up and I was wide awake. Gosh, I remember this so well. And I was paralyzed. I could not move. And it was terrifying.

    6. MWMatthew Walker1:01:19

       Isn't it?

    7. AHAndrew Huberman1:01:20

       And then all of a sudden, boom, I could jolt myself awake and I was like, "Oh my goodness." And, um, it must have been an invasion of that atonia, that sleep-induced paralysis into the waking state.

    8. MWMatthew Walker1:01:31

       So, I can explain this and you have the ... 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. And 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 know, you've got a 50/50% chance perhaps 'cause the other state that you're in is stage two 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 don't even think about it. I just wake up and I lean over, I turn off, you know, the alarm, and I get out of bed. Everything's fine. Every now and again, however, the waking up and consciousness reengaging 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 skeletal 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. So, you can't lift up your eyelids, and 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 sort of in bed by yourself at home. Now, your context was a little different. And 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 Jimmy in Wisconsin in the middle of the day was abducted by aliens and everyone saw it." You know, you're at the meeting table and whoosh, what happened? "That was Jimmy. He just got whisked off by an 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. And for me it was happening when I was, um, a, a young, uh, PhD student and I was studying sleep and then I would be awake all night 'cause I'd been monitoring the patients and looking at their sleep.

    9. AHAndrew Huberman1:05:05

       Mm-hmm. The irony of sleep studies.

    10. MWMatthew Walker1:05:07

        Exactly, that you have to deprive yourself of the very thing that you are trying to study. (laughs) Which, which by the way gives you some amazing insights for experiments-

    11. AHAndrew Huberman1:05:15

        Sure.

    12. MWMatthew Walker1:05:15

        ... that I've had as a consequence, not that I would advise that as the way f- ... And we'll come on to why that's i- i- ... Not wise when we speak about creativity. But we were, um, 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 'cause 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 gonna happen? I'm just gonna be awake all the next night and I'm gonna 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 phase, you are in a very r- 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'd 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.

    13. AHAndrew Huberman1:07:17

        Right.Love it. I mean, hate it.

    14. MWMatthew Walker1:07:19

        Yes. (laughs)

    15. AHAndrew Huberman1:07:19

        I do not enjoy it, but I love your description s- ... 'cause it makes so very clear what happened. And f- for those that have had the experience, it can be mildly stressful to terrifying. So, thank you for, um, providing the therapy that is knowledge and, uh, t- so that people don't stress it too much. But we still dissuade people from consuming alcohol prior to sleep.

    16. MWMatthew Walker1:07:40

        Correct.

14. 1:07:41 – 1:08:46

    Sponsor: InsideTracker

    1. MWMatthew Walker1:07:41

    2. AHAndrew Huberman1:07:41

       I wanna take a brief break and acknowledge our sponsor, InsideTracker. InsideTracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and help you reach your health goals. Now, I've long been a believer in getting regular blood work done for the simple reason that many of the factors that impact your immediate and long-term health can only be analyzed from a quality blood test. The problem with a lot of blood tests out there, however, is that you get information back about metabolic factors, hormones, et cetera, but you don't know what to do with that information. With InsideTracker, they make it very easy to understand your results, and they also point you to specific directives that you can follow in the realm of nutrition, exercise, supplementation, even prescription drugs that can help bring the levels back into the ranges that are optimal for you. InsideTracker also offers InsideTracker Pro, which enables coaches and health professionals to provide premium and personalized services by leveraging InsideTracker's analysis and recommendations with their clients. If you'd like to try InsideTracker, you can go to insidetracker.com/huberman to get 20% off any of InsideTracker's plans. Again, that's insidetracker.com/huberman.

15. 1:08:46 – 1:17:03

    Skills, Motor Learning & Sleep

    1. AHAndrew Huberman1:08:46

       Okay, so we've been discussing complete paralysis, and of course that's the inability to move.

    2. MWMatthew Walker1:08:53

       Mm-hmm.

    3. AHAndrew Huberman1:08:54

       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 l- increased power output or endurance? Um, and if you would, could you comment on whether or not there are specific phases of sleep that are specifically linked to motor learning?

    4. MWMatthew Walker1:09:18

       Yeah. Great question. So, 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. So if I were to, you know, ask you, "Okay, Andrew, you know, last night for dinner or yesterday for lunch, do you remember what it was that you had to eat?" And my guess is that you could probably tell me. So, c- do you recall what-

    5. AHAndrew Huberman1:09:56

       Sure.

    6. MWMatthew Walker1:09:56

       ... what some of that food was?

    7. AHAndrew Huberman1:09:57

       My diet's pretty boring-

    8. MWMatthew Walker1:09:58

       (laughs)

    9. AHAndrew Huberman1:09:58

       ... um, 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, uh, grass-fed hamburger patties, maybe a little bit of rice, s- sliced cucumber, some tomatoes, and because I'm a drive-by blueberry eater, there were some dr- uh, blueberries out on the counter, and I had several large fistfuls of those. And then I washed it down with some water and a half mug, just like this, of some cold brew sugar-free yerba mate.

    10. MWMatthew Walker1:10:32

        And I can confirm, folks, I was there at the incident, and that's exactly (laughs) 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." And 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 accomplished within milliseconds. It's stunning what we have as this gift of memory. But as I said, there's another type of memory. So 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. So if I were to say, "How..." 'Cause I am a longtime cyclist. "How do I take, uh, a right turn with my bicycle?" The obvious 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 (laughs) gonna 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?" And 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 at the- for the Decade of the Brain, which it was back then. And 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. And this gentleman, beauti- lovely gentleman, old gentleman with a sort of a white beard. I remember his tweed jacket, this green hue. It was beautiful. And he came up to me at the end, and he said, "Look. I'm a musician. I'm a pianist, and..."... "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. And 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?" And of course, at that moment, my mind starts just Rolodexing with i- ideas, and I'm thinking, "Gosh, there's the next 10 years of my work and grants," and so I sort of said, "Look, I- I think it's a fascinating hypothesis. It could also be that you're just maybe a little bit tired in the evening and... But it's- it's entirely possible. I don't know of any evidence yet that supports that."

    11. AHAndrew Huberman1:14:07

        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, I don't know, 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 or the quality of sleep that the learning could occur. I suppose that's o- one idea.

    12. MWMatthew Walker1:14:34

        No. That's in fact precisely the central hypothesis that we then set out to test, which is that your... Maybe it's- 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? So we designed a study 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 four, one, three, two, four, 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, and you do 12 of those trials. And sure enough, practice seemed to get you better and you were learning and your learning curve went up. And 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%.

    13. AHAndrew Huberman1:16:08

        Wow.

    14. MWMatthew Walker1:16:09

        So 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.

16. 1:17:03 – 1:20:00

    Tool: Timing Sleep & Learning, Skill Enhancement

    1. MWMatthew Walker1:17:03

    2. AHAndrew Huberman1:17:04

       So the sleep that can, let's say, enhance, although I think what we're really talking about here that consolidates motor learning-

    3. MWMatthew Walker1:17:14

       Yeah.

    4. AHAndrew Huberman1:17:14

       ... 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, and in both instances that sleep can enhance or let's say consolidate the motor learning that occurred.

    5. MWMatthew Walker1:17:30

       That's right. So it was to your question actually that we discussed earlier, and I recall now I didn't answer it, which is that you... 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, uh, at what point does the brain sort of fail in terms of its ability to place on hold, sort of on the runway ready to take off into the consolidation phase, and it seems to be about 16 hours-

    6. AHAndrew Huberman1:18:10

       Mm-hmm.

    7. MWMatthew Walker1:18:10

       ... 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. So if you learn at 11 o'clock 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 knitted up and enhanced when it comes to procedural memories. And by the way, that's the 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.

    8. AHAndrew Huberman1:18:53

       Ah, key point. It's- it's not enhancement, it's consolidation of, or essentially, um, 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.

    9. MWMatthew Walker1:19:14

       That's right, in-

    10. AHAndrew Huberman1:19:14

        Right? There's no enhancement. Enhancement would be supra-normal levels of memory if you sleep.

    11. MWMatthew Walker1:19:20

        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... (laughs) I don't know why I came up with... That's a terrible analogy but-

    12. AHAndrew Huberman1:19:31

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

    13. MWMatthew Walker1:19:34

        Yes.

    14. AHAndrew Huberman1:19:34

        Okay. All right.

    15. MWMatthew Walker1:19:35

        Um, but 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.

17. 1:20:00 – 1:27:21

    Naps; Specificity & Memory Consolidation, Sleep Spindles

    1. MWMatthew Walker1:20:00

       So 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 sleep? So 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 two non-REM sleep. I told you that textbook memory requires deep non-REM sleep stages three and four, casting back to episode one. Motor memory, more dependent on stage two, and those beautiful spindles that are the hallmark of beginning your stage two. 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 nighttime? Because that's the other hypothesis. It's not really about sleep, it's just something about nighttimeness, because in all of the studies I described so far, they're all happening at night, and at night they were sleeping. So is it really nighttime or is it specifically sleep? So now we did a nap study with motor skill learning. We repeated that, and sure enough, even though that time period was across the day, not during nightness, they showed this beautiful motor skill benefit if they napped versus if they did not. And then in that nap study, I was telling you that they were learning the sequence with the, um, right nondominant hand, and they were all, we selected all right-handers to, to make it equal. And they were typing 41324, 41324, 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 spindles, the more of them that you had in the nap, the better your motor skill learning was, but there seemed to be a lateralized 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 inactivity. 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, sort of starts massaging the cortex so that you get that plasticity. It's almost like a good masseuse. You know, you sort of sit down and they say, "Where are your problem points?" and you say, "It's, 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.

    2. AHAndrew Huberman1:23:12

       Uh, it's a amazing ... And reminds me of some of this work that was done, I think in the late '90s, early 2000s, Richard Morrison, um, colleagues over in, I think he was in Edinburgh, um, talked about synaptic tagging, you know, th- this notion that animals or humans perform or learn some new s- motor skill, maybe navigation of a novel environment, maybe, uh, motor skill of the 41234 that you described, you know, keys on a piano or something like that, and then it was acknowledged that the, the changes and the connections between neurons don't occur immediately, which meant that there had to be some sort of tag or label to the synapses that marked them for consolidation later, for plasticity, longterm potentiation, things of that sort. The names don't really matter. Um, I think later, it became clear based on Marcus Frank's work and others that indeed during-

    3. MWMatthew Walker1:24:08

       Mm-hmm.

    4. AHAndrew Huberman1:24:08

       ... sleep, the hard, uh, 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, or the specific circuits that are modified, which on the face of it one could say, well, of course-

    5. MWMatthew Walker1:24:28

       Mm-hmm.

    6. AHAndrew Huberman1:24:28

       ... but what that means is that during sleep, the brain is, um, somehow able to, uh, the neurons of the brain, that is, are able to n- chemically or electrically or both signal, like, this is where the, there-

    7. MWMatthew Walker1:24:46

       (laughs)

    8. AHAndrew Huberman1:24:46

       ... needs to be some modifications done. And then, then like a night crew-

    9. MWMatthew Walker1:24:50

       (laughs)

    10. AHAndrew Huberman1:24:51

        ... um, the, the brain self-induces its own changes, which is remarkable.

    11. MWMatthew Walker1:24:55

        It really is. It's almost-

    12. AHAndrew Huberman1:24:56

        It's really remarkable.

    13. MWMatthew Walker1:24:56

        ... as though there are red flags that are planted in the territories that have undergone learning-dependent plasticity, and they are calling out almost like, you know, hungry mouths that are in plasticity famine for the feast relief that comes by way of sleep.

    14. AHAndrew Huberman1:25:16

        Do we know what the factors are that are released in sleep that allow that to occur? Or is it... I'm guessing there are many. Uh, people love to talk about brain-derived neurotrophic factor, BDNF, but, uh, which is a very interesting molecule, but, um, it's probably just one of a panoply of, of molecules that are, that are important.

    15. MWMatthew Walker1:25:34

        We, we don't know necessarily the neurochemical processes, although some people have manipulated plasticity and then blocked it with different types of-

    16. AHAndrew Huberman1:25:42

        Mm-hmm.

    17. MWMatthew Walker1:25:42

        ... NMDA, which is a certain type of receptor in the brain for excitatory activity, which is the underlying basis of brain plasticity. So that certainly is dependent, but what's interesting about the sleep spindles, I said in the first episode that they burst somewhere between about 12 to 15 times per second. Brr, brr.... 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 sort of sweet spot tickling of neurons that forces them to say, "Ooh, I think I should strengthen this circuit." So it's almost as though these sleep spindles are ideally designed at the frequency, at the sort of 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.

    18. AHAndrew Huberman1:26:44

        So interesting, um, 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 a given circuit being replayed, not unlike the- the- the work that you talked about earlier, the fast replay of neurons in- in the hippocampus. But here it's not necessarily just in the hippocampus, like it can be in the neocortex or other structures, that then builds up the, uh, the- the vigor with which that circuit can function in the daytime, AKA learning. Um,

18. 1:27:21 – 1:34:10

    Sleep, Motor Learning & Athletes; Automaticity

    1. AHAndrew Huberman1:27:21

       it's- it's super interesting, and you mentioned that this is occurring largely in stage two of sleep-

    2. MWMatthew Walker1:27:26

       Yeah.

    3. AHAndrew Huberman1:27:26

       ... not in rapid eye movement sleep. Is this business of stage two being the- the main period of sleep in which motor learning occurs unique to motor learning? In other words, cognitive information, um, sur- surely can get, um, wired into the brain at night, but is that largely associated just with rapid eye movement sleep? What this would suggest i- 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- and motor learning from the previous one or two days.

Episode duration: 2:28:27