Dr. Gina Poe: Use Sleep to Enhance Learning, Memory & Emotional State

ANDREW HUBERMAN: Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. 

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I'm Andrew Huberman, and I'm a professor of nNeurobiology and ophthalmology at Stanford School of Medicine. Today, my guest is Dr. Gina Poe. Dr. Gina Poe is a professor in the Department of Integrative Biology and Physiology at the University of California Los Angeles. Her laboratory and research focuses on the relationship between sleep and learning, in particular how specific patterns of brain activity that are present during specific phases of sleep impact our ability to learn and remember specific types of information. For instance, procedural information-- that is how to perform specific cognitive or physical tasks, as well as encoding of emotional memories and discarding emotional memories. 

Indeed, her research focuses on how specific phases of sleep can act as its own form of trauma therapy, discarding the emotional tones of memories. In addition, her laboratory focuses on how specific phases of sleep impact things like the release of growth hormone. Growth hormone, of course, plays critical roles in metabolism and tissue repair, including brain tissue repair, and therefore has critical roles in vitality and longevity. 

Today you will learn many things about the relationship between sleep, learning, emotionality, and growth hormone. One basic but very important takeaway that you'll learn about today, which was news to me, is that it's not just the duration and depth of your sleep that matter, but actually getting to sleep at relatively the same time each night ensures that you get adequate growth hormone release in the first hours of sleep. In fact, if you require, let's say, eight hours of sleep per night, but you go to sleep two hours later than your typical bedtime on any given night, you actually miss the window for growth hormone release. 

That's right. Getting growth hormone release in sleep, which is absolutely critical to our immediate and long term health, is not a prerequisite of getting sleep, even if we are getting enough sleep. As Dr. Poe explains, there are critical brain circuits and endocrine, that is hormone, circuits that regulate not just the duration and depth and quality and timing of sleep, but when we place our bout of sleep, that is when we go to sleep each night, plus or minus about a half hour or so, strongly dictates whether or not we will experience all the health promoting, including mind promoting, benefits of sleep. 

Today's episode covers that and a lot more in substantial detail. You will learn, for instance, how to use sleep in order to optimize learning, as well as forgetting, for those things that you would like to forget. So during today's episode, Dr. Gina Poe shares critical information about not just neuroscience, but physiology and the hormone systems of the brain and body that strongly inform mental health, physical health, and performance. So by the end of today's episode, you'll be far more informed about sleep and how it works, the different roles it performs, and you'll have several new actionable steps that you can take in order to improve your mental health, physical health, and performance. 

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 LMNT. LMNT is an electrolyte drink that has everything you need and nothing you don't. That means plenty of salt, magnesium, and potassium, the so-called electrolytes, and no sugar. The electrolytes are critical to the function of every cell in your body, in particular, the neurons, the nerve cells. 

So I've talked about before on this podcast, neurons, nerve cells, require adequate sodium and potassium, as well as magnesium, in order to fire action potentials, which are the electrical signals that allow neurons to do everything from generate focus and attention, allow you to learn, and generate neuromuscular connection, and allow you to exercise or train or do any kind of skilled activity with a high degree of output. I take LMNT about two or three times per day, typically once in the morning and again after or during my bout of exercise each day and sometimes an additional one if I've sat in a hot sauna and sweat a lot or if the weather is very hot. If you'd like to try LMNT, you can go to drinklmnt.com/huberman to claim a free LMNT sample pack with your purchase. Again, that's drinklmnt.com/huberman to claim a free sample pack. 

Today's episode is also brought to us by Helix Sleep. Helix Sleep makes mattresses and pillows that are of the absolute highest quality. Now, sleep is the foundation of mental health, physical health, and performance. When we are sleeping well, all of those things excel, and when we are not sleeping well, all of those things suffer. Now, the surface that you sleep on, that is the mattress that you sleep on, is critical, and Helix understands that everybody has slightly different sleep needs. 

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Today's episode is also brought to us by Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. Now, again, sleep is the foundation of mental health, physical health, and performance. But what many people don't realize is that in order to fall and stay asleep, your core body temperature has to drop by about one to three degrees. Conversely, in order to wake up each morning and feel refreshed, your body temperature actually has to increase by one to three degrees. Therefore, controlling the temperature of your sleeping environment is absolutely key. 

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The Huberman Lab podcast is now partnered with Momentous Supplements. To find the supplements we discuss on the Huberman Lab podcast, you can go to livemomentous.com/huberman. And I should just mentioned that the library of those supplements is constantly expanding. Again, that's livemomentous.com/huberman. And now for my discussion with Dr. Gina Poe. Dr. Gina Poe, welcome. 

GINA POE: Thank you. 

ANDREW HUBERMAN: I've really been looking forward to this conversation because I'm familiar with your work, and I know that many people are going to be excited to learn about your work as it relates to sleep, as it relates to problem solving, creativity, addiction and craving, relapse, and a number of other important topics. So to start things off, I would love for you to educate us a bit about this thing that we are all familiar with and yet very few of us understand, which is sleep. 

And if you would, could you describe the various phases of sleep that exist? What distinguish them? And perhaps frame this within the context of what would a perfect night's sleep look like? 

GINA POE: OK. 

ANDREW HUBERMAN: How long would it last, more or less, and what would the biology look like? What is a perfect night's sleep? 

GINA POE: Yeah, that's a great question. All right. So sleep is really different from wakefulness, and in fact can't be replaced by any state of wakefulness that we've been able to come up with so far. Our brain chemistry is completely different. 

And in the different stages of sleep, which there is non-REM and REM are the two major states of sleep, and every animal we've studied so far seems to have both of those states. Anyway, those two states are entirely different from one another, too. And even within non-REM, there are three states. Stage one, which is what you slip into when you first falling asleep-- it's dozing. There's kind of an interesting rhythm that goes on in the brain. It's kind of a fast, gamma rhythm. 

And then there's stage two, which is a really cool state we sort of used to ignore, sleep researchers, because it was a transient state between wakefulness and the deep stage three, slow wave sleep, which is the most impressively different. And between that and REM sleep. So stage two, I'll talk a little bit more about. And then the deep, slow wave sleep state, which is when big, slow waves sweep through our brain. And now we realize that it cleans our brain. 

One of the things that those big, slow waves do is cleans our brain and does other really important things to restore us from a day of wakefulness. And then REM sleep, which is the most popular because that's where we have the most active dreams. And when you wake up someone out of REM sleep, they'll almost always report having dreamed something really bizarre. That's called REM sleep, rapid eye movement sleep. 

So those are the four states of sleep, of human sleep, and we cycle through them every 90 minutes or so. When we go to sleep, say 10:30, 11:00, our first REM sleep period comes about 105 minutes after we fall asleep and lasts about 20 minutes. Actually, it comes about 95 minutes and lasts 10 or 15 minutes. And then we start over again. And we have about five of those per night for a perfect night's sleep-- four or five, something like that. So a perfect night's sleep is seven and a half, eight hours. 

There was a really great study that put people in a semi-darkened room with nothing but the bed for 12 hours every day for a month. And what people did initially, because we're in a sleep deprived nation, is that they slept a lot more than usual, like 10 or 11 hours of the 12. And then they leveled off after a week or two to about eight hours and 15 minutes of sleep. So you actually can't oversleep. I mean, they had nothing else to do but sleep, and they would round off to an average eight hours and 15 minutes a night and then spend the rest of the time twiddling their thumbs, humming tunes-- 

ANDREW HUBERMAN: Interesting. 

GINA POE: --daydreaming. 

ANDREW HUBERMAN: I want to get back to the contour of a perfect night's sleep, but I'm intrigued by this idea that people can't oversleep. I'm often asked whether or not we can get too much sleep and whether or not sleeping too long can make us groggy the next day. Is there anything to that? And how does one determine how long they should sleep on average? 

GINA POE: On average, yeah. Well, that's interesting because different people seem to need different amounts of sleep, but we don't really even know exactly what sleep is for. So what they need is kind of-- it's murky. So we do know a lot of things that sleep does now for us, but we don't know how long those things take. So how long we need to sleep is also just a big question mark. 

But some people don't feel rested until they've slept nine hours. Some people don't feel rested after three or four and a half. But most people, if they consistently deprive themselves of sleep so that they're only sleeping for four and a half hours a night, build up a cognitive deficit that just builds up over time. The more nights you have with sleep deprivation, the more cognitive deficit you have. And so you need sleep, again, to sleep more to recover. Now, the question you had about um-- 

ANDREW HUBERMAN: Can you oversleep-- 

GINA POE: Can you oversleep, right. 

ANDREW HUBERMAN: Can you sleep to the point where it's too much? You know, growing up, when I was in high school, my girlfriend's dad had this belief that no one should sleep in past 6:00 AM. So he would wake all the-- there were two children in the home. He would wake up the kids in that house. He had this thing against oversleeping, regardless of when people went to sleep, and I always thought that was an interesting mentality. 

GINA POE: Yeah. It's not terrible, actually, because what that will do is it will make you sleepier the next night to get to bed on time. So it'll build up your homeostatic need if you wake up too early. But so I don't think you can oversleep. But people who sleep a lot, like people who sleep over nine hours, it's probably indicative of some other problem because in fact, if you have a lot of different conditions, it will cause you to sleep a lot more. Probably because what it does is it interferes with your efficient sleep, the efficiency of your sleep. 

So if you find yourself sleeping consistently nine hours plus every night, then you might want to consult a doctor about maybe what else it might be. It could be cancer. It could be sleep apnea, which affects a lot of people. It could be that your sleep is super inefficient because you're snoring a lot more than you know, or you're waking up a lot more than you know every night. So you might want a sleep study just to see how your sleep is, and then see what else might be causing you to sleep so much. 

ANDREW HUBERMAN: And that wouldn't be if somebody is sleeping nine or 10 hours every once in a while. You mean if they're consistently sleeping for more than nine hours. 

GINA POE: If they feel like they need it in order to function cognitively the next day, it might be that your sleep is just not efficient, and you might want to look into why that's the case. 

ANDREW HUBERMAN: Interesting. Forgive me for the anecdote, but I can't resist. Years ago I went to an acupuncturist, and he gave me these red pills, of which I don't know what they contained. 

GINA POE: Uh-oh. 

ANDREW HUBERMAN: But I took them because he told me they would help with my sleep. 

GINA POE: OK. 

ANDREW HUBERMAN: And I would fall asleep about 30 minutes after taking them, and I would have incredibly vivid dreams. And I'd wake up four or five hours after having gone to sleep feeling completely rested, something that I've never really experienced on a consistent basis. I want to do mass spec on these pills. I still have no idea what was in them, whatsoever. 

GINA POE: I want to do mass spec on those pills, too. 

ANDREW HUBERMAN: Yeah, exactly. Some people thought perhaps they had GHB, gamma hydroxybutyrate, which is, by the way, an illegal drug. It can kill you. It's not something you want to take. 

GINA POE: No, that's not good. 

ANDREW HUBERMAN: But anyway, if ever someone can figure out what the red pills were, I'll be very-- 

GINA POE: That's really great. 

ANDREW HUBERMAN: And this is not a red pill of the other sort red pill. This is just the red sleep pills. 

GINA POE: Interesting. I mean, it could have been even a placebo effect because placebo is extremely strong. 

ANDREW HUBERMAN: Although, I don't know. There was really something to these red pills. So shout out to the acupuncturists in Eastern medicine. But to return this to this idea of the architecture of a perfect night's sleep. 

So you said we fall asleep. The first 90 minutes of sleep. REM sleep, rapid eye movement sleep, will arrive at about 95 minutes in. Does that mean that the rest of that 90 minutes is consumed with slow wave sleep? 

GINA POE: Yeah, non-REM sleep. 

ANDREW HUBERMAN: OK. And what about the sleep where we are lightly asleep, and we might have a dream that has us somehow thinking about movement or that we jolt ourselves awake? That often happens early in the night, right? 

GINA POE: Yeah, that's the first stage-- stage one and stage two of sleep. And stage two sleep is really cool because that has something called sleep spindles and K-complexes. And what sleep spindles are are a little bit of activity that's 10 to 15 hertz in frequency. It's a conversation between the thalamus and the cortex. The thalamus is the gateway to consciousness, and the neocortex processes all our cognition. 

And so it's these spindles. They're called sleep spindles. And if you wake up out of that state, you will often report a dream, like a hallucination style dream. It won't be a long dream report like you have out of REM sleep, but it will be some hallucination state. 

And while we're falling asleep, one of the reasons we call it falling asleep is because in stage one and stage two our muscles are relaxing. And if there's part of our brain that's conscious enough to sort of recognize that relaxation, we'll feel like we're falling, and we'll jerk awake. So often that hallucination-- it's called hypnagogic hallucination-- will feel like-- it'll include some falling aspect that we'll wake up out of. 

ANDREW HUBERMAN: That's really interesting to me. I've long felt that sensation of almost, like, dropping back into my head. So much so that if I elevate my feet just slightly and I tilt my head back just slightly in order to go to sleep, I find that I fall asleep much faster. 

GINA POE: Interesting. 

ANDREW HUBERMAN: But it does feel as if I'm going to fall, like, almost going to do a backward somersault. I actually really like the sensation and usually because it precedes falling deeply asleep. 

GINA POE: Yeah, that's really interesting. Somebody has to do a study of elevated feet and-- 

ANDREW HUBERMAN: Yeah, there's a little bit on body position and sleep in some of the washout that we'll talk about. So early in the night you've got these lighter stages of sleep, less rapid eye movement sleep. What can we say about the dreams that occur during the, say, first and second 90-minute cycles of sleep. Are they quite different than the patterns of sleep and dreaming that occur later in the night or toward morning? 

GINA POE: Well, OK, that's an interesting question, and there's a lot of facets to it. There is some evidence that the first four hours of sleep are very important for memory processing. And in fact, if you've learned something new that day or have experienced a new sensory motor experience, then your early sleep dreams will incorporate that experience much more than the later sleep dreams. Later, as that memory gets consolidated from the early structures, which are the hippocampus deep in the temporal lobe to the cortex in a distributed fashion, that memory seems to move from that hippocampus to the cortex. And also the dreams that incorporate that memory also move later in the night. 

So nobody knows why, but it does. There was a great study by Siddhartha Ribeiro who studied the consolidation of memories from the hippocampus to the cortex in a rat across the period of a full day's sleep because rats sleep in the daytime. And he found that each subsequent REM sleep period moved that memory from the hippocampus to the first area that projects to it, and then the second area, and then the third area. And you can see the memory moving throughout the sleep period. 

ANDREW HUBERMAN: Cool. Very cool. I have to read that study. So there's a number of different hormones associated with the different stages of sleep. We know that melatonin is a hormone-- 

GINA POE: Of nighttime. 

ANDREW HUBERMAN: --of nighttime that makes us sleepy. What about growth hormone release? When does that occur during sleep? 

GINA POE: So growth hormone release happens all day long and all night long, but the deep, slow wave sleep that you get the very first sleep cycle is when you get a big bolus of growth hormone release, in men and women equally. And if you miss that first deep, slow wave sleep period, you also miss that big bolus of growth hormone release. And you might get, ultimately across the day, just as much overall growth hormone release, but endocrinologists will tell you that big boluses do different things than a little bit eked out over time. 

So that is what we know. There's also a big push to synthesize proteins. So that's when the protein synthesis part that builds memories, for example, in our brain happens in that first cycle of sleep. So you don't want to miss that, especially if you've learned something really big and needs more synaptic space to encode it. 

ANDREW HUBERMAN: How would somebody miss that first 90 minutes? 

GINA POE: Sleep depriving themselves. Yeah. 

ANDREW HUBERMAN: So let's say I normally go to sleep at 10:00 PM. And then from 10:00 to 11:30 would be this first phase of sleep, and that's when the big bolus of growth hormone would be released. Does that mean that if I go to sleep instead at 11:30 or midnight that I missed that first phase of sleep? Why is it not the case that I get that first phase of sleep just simply starting later? 

GINA POE: It is a beautiful clock that we have in our body that knows when things should happen. And it's-- every cell in our body has a clock. And all of those clocks are normally synchronized. And those circadian clocks are synchronized. 

And so our cells are ready to respond to that growth hormone release at a particular time. And if we miss it-- and it's a time in relation to melatonin also-- so if you miss it, yeah, you might get some growth hormone release. But it's occurring at a time when your clock has already moved to the next phase. And so it's just a clock thing. 

ANDREW HUBERMAN: Yeah. I don't think we can overstate the importance of what you just described. And to be honest, despite knowing a bit about the sleep research in circadian biology, this is the very first time that I've ever heard this that if you normally go to sleep at a particular time and growth hormone is released in that first phase of sleep, that you can't simply initiate your sleep out later and expect to capture that first phase of sleep. 

GINA POE: Yeah. 

ANDREW HUBERMAN: That's incredible and I think important and as many listeners are probably realizing also highly actionable. So what this means is that we should have fairly consistent bedtimes in addition to fairly consistent wake times. Is that right? 

GINA POE: Exactly. And in fact, one of the best markers of good neurological health when we get older is consistent bedtimes. 

ANDREW HUBERMAN: Wow. OK. I don't want to backtrack. But I did write down something that I think is important for me to resolve or for you to resolve. So I'm going to ask this people that sleep nine hours or more perhaps that reflecting an issue-- some underlying issue, perhaps, is being a teenager or an adolescent and undergoing a stage of development where there's a lot of bodily and brain growth and exception to that, because-- 

GINA POE: Yes. 

ANDREW HUBERMAN: --I don't recall sleeping a ton when I was a teenager. I had a ton of energy. But I know a few teenagers. And they sleep a lot. 

GINA POE: Yeah 

ANDREW HUBERMAN: Like they'll just sleep, and sleep, and sleep, and sleep. Should we let them sleep, and sleep, and sleep? 

GINA POE: Let them sleep. 

ANDREW HUBERMAN: OK. So that's the one exception. What about-- 

GINA POE: Just like babies. 

ANDREW HUBERMAN: OK. 

GINA POE: When you're developing something in your brain or the rest of your body, you really need sleep to help organize that. Sleep is doing really hard work in organizing our brains and making it develop right. And if we deprive ourselves of sleep, we will-- actually, also just like I said, we have a daily clock. We also have a developmental clock. And we can miss a developmental window if we don't let ourselves sleep extra like we need to. 

ANDREW HUBERMAN: What other things inhibit growth hormone release or other components of this first stage of sleep? In other words, if I go to sleep religiously every night at 10:00 PM, are there things that I, perhaps, do in the preceding hours of the preceding day like ingest caffeine or alcohol that can make that first stage of sleep less effective even if I'm going to sleep at the same time? 

GINA POE: Alcohol definitely will do that because alcohol is a REM sleep suppressant. And it even suppresses some of that stage two transition to REM with those sleep spindles. And those sleep spindles, we didn't talk about their function yet, but they're really important for moving memories to our cortex. It's a unique time when our hippocampus, like the RAM of our brains, writes it to a hard disk which is the cortex. And it's a unique time when they're connected. 

So if you don't want to miss that, you don't want to miss REM sleep when it's also a part of the consolidation process and schema changing process, and alcohol in there before we go to sleep will do that. Until we've metabolized alcohol and put it out of our bodies, it will affect our sleep badly. 

ANDREW HUBERMAN: So probably fair to say no ingestion of alcohol within the four to six hours preceding sleep? 

GINA POE: Yeah. 

ANDREW HUBERMAN: Given the half life? 

GINA POE: Given the half-- 

ANDREW HUBERMAN: Or at all-- or at all would be better. But I know some people refuse to go that way. 

GINA POE: And maybe a little bit is OK. I don't know what the dose response is. But there are studies out there you can look at. 

ANDREW HUBERMAN: Great. 

GINA POE: Yeah. 

ANDREW HUBERMAN: So we're still in the first stage of sleep. And I apologize for slowing us down. But it sounds like it's an incredibly important, first phase of sleep. 

What about the second and third 90-minute blocks of sleep? Is there anything that makes those unique? What is their signature besides the fact that they come second and third in the night? 

GINA POE: There's more and more REM sleep the later the night we get. There's also a change in hormones. The growth hormone and melatonin levels are starting to decline. But other hormones are picking up. 

So it is a really different stage that you also don't want to shortchange yourself on. And I think that's the stage many studies are showing that those are the times in sleep when the most creativity can happen. That's when our dreams can incorporate and put together old and new things together into a new way. And our schema are built during that time. So yeah, we can change our minds best during those phases of sleep. 

ANDREW HUBERMAN: Could you elaborate a little bit more on schema? 

GINA POE: Yeah. 

ANDREW HUBERMAN: No one-- I don't think anyone on this podcast has ever discussed schema. I'm a little bit familiar with schema from my courses on psychology. But it's been a while. So maybe you could just refresh mind and everyone-- 

GINA POE: Well, it's still a concept. 

ANDREW HUBERMAN: Sure. 

GINA POE: Schema-- 

ANDREW HUBERMAN: How do you-- how do you define schema? 

GINA POE: Right. I think of schema as-- like we have a schema of Christmas, right? We have all kinds of ideas that were so together and called Christmas, a holiday season. In the northern hemisphere, it's cold. We have Santa Claus, and reindeer, and jingle bells, and even things that are false but we normally associate with Christmas presents, family gathering when it is. All of this stuff is sewn together into one-- there's a thread linking them all. 

And we can just give ourselves a list of words, and none of them contain the word Christmas. And then ask people later, give them another list of words and include the word Christmas. And they'll say, oh, yeah, that word was there, because in their minds they brought up that word, Christmas, because it's part of that whole schema. So that's what-- it's sort of a related-- lot of related concepts, I guess. 

ANDREW HUBERMAN: I think about the desktop of my computer would scare some people. But it's just a ton of folders. 

GINA POE: Yeah. 

ANDREW HUBERMAN: But each of the folder names mean something very clear and specific to me. 

GINA POE: Right. 

ANDREW HUBERMAN: And inside of those folders are collections of things that make sense in terms of how they're batch. Is that one way to think about-- 

GINA POE: No, that's a great way to think of it. And when you're in REM sleep in the later parts of the night and that transition to REM, that's when your computer of your brain is opening folders and comparing documents, seeing if-- is there anything the same? These two documents look very much the same, but there's a little bit of difference. And it can link those conceptually. 

So that's probably one of the origins of creativity is finding things that are related, maybe just linked a little bit. And you can find that link and strengthen it if it makes your schema interesting and different. 

ANDREW HUBERMAN: Yeah, very interesting. Many people, including myself tend to wake up maybe once during the middle of the night to use the restroom. I've tried to drink less fluid before going to sleep. I've heard also that the impulse to urinate, forgive the topic, but a lot of people deal with this, so the impulse to urinate is also dictated by how quickly you drink fluid, not just the total volume. So I've switched to sipping fluids more slowly from my last beverage of the day which seems to help. 

But the point here is that I think a lot of people wake up once in the middle of the night oftentimes to use the restroom but oftentimes just around 3:00 AM and might be up for a few minutes, hopefully not on their phone or viewing any bright light which can cause more wakefulness, but then go back to sleep. Is there any known detriment to this middle of the night waking or should we consider it a normal feature for some people's sleep architecture? 

GINA POE: Yeah. I think we shouldn't worry about it actually. I think sleep is really incredibly well homeostatically regulated. And so really, don't worry about how much you're sleeping, as long as you're not intentionally depriving yourself of sleep by doing something really rewarding and exciting because even that is stressful to your body and deprives you of a lot of things we're talking about. 

So don't worry about it. It's absolutely normal to wake up at least once in the middle of the night to go to the bathroom. And as long as you can get back to sleep in a reasonable amount of time or even if it takes you an hour, don't worry about it, as long as you have a lifestyle that allows you to then make up that sleep either the next morning or the next night or going to bed a little earlier. 

ANDREW HUBERMAN: So if I understand correctly, there's a little bit of asymmetry to sleep that catching that first phase of sleep it's like you either get it or you don't. And you have to get it by going to sleep essentially the same time each night, maybe plus or minus 15 minutes or so. 

GINA POE: Yeah. 

ANDREW HUBERMAN: But then if I wake up in the middle of the night and go back to sleep I cannot catch up, but I can gather all the sleep that I would have gotten had I just slept the whole way through the night. Is that right? 

GINA POE: Yeah, yeah, yeah. And we don't know actually the answer to whether or not the sleep in the middle between that early sleep and the late sleep is, in fact, different for another reason. And whether depriving yourself of sleep from say, 1:00 to 2:30 in the morning is bad in a different way, we don't know. 

ANDREW HUBERMAN: Well, I suppose I am the experiment in that case, because I do tend to wake up once per night. And I've come to recognize it as part of my normal sleep architecture. I don't obsess over it. 

I do notice that when I go back to sleep and especially toward morning that my sleep is incredibly deep. My dreams are incredibly vivid. 

GINA POE: That's great. 

ANDREW HUBERMAN: I don't always remember them. But what is unique, perhaps, about the architecture of dreams and sleep in the, let's say the last third of the night or the second half of the night? 

GINA POE: Right, yeah. In the second half of the night, we have longer REM sleep periods. And those are considered the deepest sleep, even though slow wave sleep, big slow wave is considered deep. It is deep. 

ANDREW HUBERMAN: They call slow wave sleep deep sleep and REM sleep rapid. But now, you're telling me that REM sleep is actually the deeper sleep? OK. There needs to be a new nomenclature of sleep researchers. 

GINA POE: You really shouldn't call it deeper night. 

ANDREW HUBERMAN: No, please. 

GINA POE: The reason why they call slow wave sleep deep sleep is because it's difficult to arouse people out of that state. And when you do arouse them out of that state, they are most often confused and just want to go back into sleep and can go back pretty easily. If you arouse someone out of REM sleep, they're more likely to report something that was really almost like wakefulness. It was so vivid. 

But in fact, if you give someone a non-threatening kind of stimulation like somebody dropping keys, or a ping, or something like that, instead of waking-- that same volume will wake someone up out of non-REM sleep but out of REM sleep and instead lengthen the amount of time or make it even more dense-- your rapid eye movements more dense. And often people will incorporate that sound into their dreams. 

ANDREW HUBERMAN: So the body and brain are somehow conscious of the of the sound. And I've heard also smells can even make it into our dreams in REM sleep. But that it doesn't rouse us-- 

GINA POE: It doesn't arouse us as often, yeah. 

ANDREW HUBERMAN: Interesting. 

GINA POE: And maybe one of the reasons why REM sleep is deeper especially in adults and older people, that deep slow wave sleep goes away. So it's not as deep. It's not as big. The slow waves aren't as large which is probably problematic, but we are not sure. And so then REM sleep becomes the deepest stage. 

Actually in children, it's kind of a toss up, because it's really hard to wake them up out of that deep slow wave sleep. And in fact, fire alarms don't wake them up, even really loud fire alarms out of that state of sleep. So that's why they're trying to change fire alarms so that instead of something that the kids don't associate with anything like the, whatever, they don't associate them, it says their name or something else that may be less loud but more salient to them and will wake them up. 

ANDREW HUBERMAN: I don't know having carried sleeping children in from the car, I don't know that I want children to start waking up from sleep because that's one of the best things when we get home and the kids are asleep in the backseat. You can literally throw them over your shoulder, gently of course, and put them to sleep. They are completely out. 

GINA POE: Yeah, it's wonderful. 

ANDREW HUBERMAN: It is wonderful, one of nature's gifts. I'd like to take a quick break and acknowledge one of our sponsors, Athletic Greens. Athletic Greens, now called AG1, is a vitamin mineral probiotic drink that covers all of your foundational nutritional needs. I've been taking Athletic Greens since 2012. So I'm delighted that they're sponsoring the podcast. 

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So this enhanced volume or proportion of rapid eye movement sleep in the second half of the night relates to more elaborate dreams. We are paralyzed during REM sleep, correct? 

GINA POE: Yes, normally paralyzed. And that's really good, because that's the time when we're actively dreaming storyline dreams. And we could hurt ourselves. We're actually really cut off from the outside world in terms of responding to, say, this table, or window, or a door. 

And so different from sleepwalking which is out of slow wave sleep. And out of slow wave sleep, that sleepwalking is a mixture between sleep and wakefulness. So you actually will respond to the door, or you can cook a full meal, drive your car while you're in deep slow wave sleep. 

It's scary, because you never know what you're going to do. You don't have voluntary, involuntary control over it. You have no conscious control over it. But you can actually safely navigate some situations in sleepwalking and actually have a conversation. Although, it may not make much sense when you're sleep talking. 

In REM sleep, you're not processing the outside world. And instead, when you're acting out your dreams, you could be doing things like walking through a plate glass window or falling off of down the stairs, things like that. So you really want your muscles to be inactivated during REM sleep. Otherwise, you will act out those dreams and really hurt yourself or your bed partner. 

ANDREW HUBERMAN: What about sleep talking or talking in sleep? I don't know how many relationships have been saved by sleep talking. But I'm guessing a few have been destroyed. And I'm guessing that talking in sleep could have meaning or perhaps has no meaning just as dreams could have meaning or no meaning, as we recall them. 

GINA POE: Yeah. Do not take sleep talking seriously no matter what people say. It doesn't necessarily reflect truth. So it's not like you're being more truthful when you're sleep talking. 

ANDREW HUBERMAN: You just saved a number of relationships. 

GINA POE: I hope so. 

ANDREW HUBERMAN: I'm not directing this at anyone in particular. But I guarantee you just did. Noted. 

So as people start to approach morning or the time when they normally would wake up, I've heard that it's important to, if possible, complete one of these 90-minute cycles prior to waking up. That is if you set your alarm for halfway through one of these 90-minute cycles that come late in the night of sleep, that it can lead to rather groggy patterns of waking. So I'll just ask you directly. Do you use an alarm clock? 

GINA POE: I do not. Thankfully, I'm in a line of work that doesn't require me normally to do anything at any particular time. I do it when I do it. Unless I have to catch a plane and then I always set my alarm just in case. 

ANDREW HUBERMAN: Well, as a fellow academic, I can tell you there are plenty of punishing features about being an academic scientist that offset the fact that you don't have to use an alarm clock. But it is nice that you can often set your own schedule. So would you recommend that if possible that people not use an alarm clock? 

GINA POE: Yeah, absolutely. If you can just listen to your body and wake up when you need to wake up, that would be great. But one of the reasons why we have such a grogginess, it's called sleep inertia when we wake up out of the wrong state which is deep slow wave sleep, is because-- I liken it to like a washing machine cycle. 

This 90-minute cycle is like a washing machine cycle. And the first part is to add water, right? And then your clothes are soaking wet. You don't want to open the washing machine and try and function, put them on, and wear them around while they're soaking wet and full of soap. 

So you have to wait until the cycle is through before you can, well, actually, let's put it in the dryer, too, before you want to wear them. So yeah, you can function. It just takes a little while for those clothes, that brain to dry out, so you can actually function well. But it's better to wait through the whole cycle is complete. And so that's why you want to set that 90-minute, alarm clock. 

And again, that's around 90 minutes because the first stage of sleep, the first cycle of sleep is actually a little longer, more like 105, 110, minutes. But then the second ones and third ones, they get shorter and shorter as the night goes on. And in the last few cycles, you're just doing the end to REM sleep cycle which takes less time. And if you wake up out of REM sleep, there's usually no problem cognitively. You're good to go. 

ANDREW HUBERMAN: Are you a fan of sleep trackers? 

GINA POE: Sure, yeah. 

ANDREW HUBERMAN: Do you use one? 

GINA POE: I have one on. I don't take-- I don't live my life by them, because they are-- the best ones right now are about 70% effective at staging your sleep. So 70%, it's OK, it's OK. But take it with a grain of salt is what I'm saying. 

ANDREW HUBERMAN: Yeah. I've tried various ones. And I compare the mattress based one to-- actually wear it on my ankle instead of my wrist. And I do find it informative. 

But a colleague of mine at Stanford, Ali Crum, who works on mindset and belief effects talked to me about a study they did where people often will bias their sense of daytime wakefulness based on their sleep score more than their subjective score. In other words, if they were told they got a poor night's sleep, even if they got a great night's sleep-- and this was of course measured in the sleep lab so they were able to compare-- people report feeling more groggy. And the opposite is also true that if it says 100% or 90% on your sleep score, then people go, oh, I feel great, even though they might not have slept well. So this speaks to the, I don't want to say placebo effect, but the belief effects that are woven in with a score. 

GINA POE: Yeah. That's right. 

ANDREW HUBERMAN: So it seems to me that combining subjective and objective data is probably best. 

GINA POE: And I do believe that you should trust your own physiology and the way that your body is telling you to feel because in fact, it used to be that people with insomnia weren't-- were often not believed because you put them in a sleep lab, and they look like they slept great. And you wake them up in the morning, they say, oh, I didn't sleep very well at all. And that's because probably we just came out with a paper that shows that subcortical structures can be in a completely different sleep state than cortical structures which is what we measure in the sleep lab what the cortex is doing. 

ANDREW HUBERMAN: Interesting. 

GINA POE: So it might be that people who say, I did not sleep all night long even though the cortex is saying, oh, no, you had great sleep, was because they're monitoring their subcortical, hypothalamus, hippocampus, thalamus, other structures that the sleep lab just can't access unless you have depth electrodes which nobody really wants. 

ANDREW HUBERMAN: Right. Because that requires holes in the skull and wires. Wow. So does that mean that the last 50 plus years of sleep science is potentially flawed in some way, because they're only recording from-- I guess this would be the analogy would be-- it's like recording from the surface of the ocean as opposed to the depth of the ocean. 

GINA POE: Right. And trying to ascertain the life moving down deep in the depth-- 

ANDREW HUBERMAN: Brace yourselves colleagues at Stanford sleep lab and elsewhere. But please just tell us because I think scientists want to know the truth. 

GINA POE: Yeah. It's not for nothing that you want to know what the cortex is doing. The cortex is really important for a lot of things. But it doesn't necessarily tell you what a lot of other really important parts of the brain are doing in terms of sleep. 

But there's hope, because in fact, it would be great. I think that's possible, from the paper if you look at it, it's in PNAS this year, that you could detect subtle changes in the cortical EEG that might be able to tell you what the subcortical structures are doing. Things like the absolute power in that sleep spindle band, that sigma band would change if the hippocampus is in REM sleep and the cortex is in that sleep spindle state and vise versa. So there is some hope that we can gain from people with depth electrodes or animals with depth electrodes that we could backwards machine learn what the cortex might be able to tell us about subcortical structures from the cortical EEG, so. 

ANDREW HUBERMAN: Interesting. This is going to be a stimu-- yes, stay tuned. It's going to be a stimulus for development of new technology which is always going to assist in scientific discovery. There is one more thing I wanted to ask about the architecture of the night sleep in terms of early part of the night. 

Earlier, you mentioned the washout of debris and the so-called lymphatic system, I think is what you're referring to. Could you tell us a little bit more about the washout that occurs in the brain during sleep, what that is, and what roles it's thought to serve, and perhaps if there are any ways to ensure that it happens or to ensure that it doesn't happen, and obviously we want this to happen? 

GINA POE: Yeah. All right, great question. We talked about the circadian clock and how certain things happen at certain times. Well, one of the things that happens when we're awake and talking to each other is that there's a lot of plasticity. There's something that I'm learning from you today. And you're learning from me. And that changes our synapses, and it changes the way our proteins are going to be folded and changed during sleep. 

It unfolds. This process actually uses a lot of ATP, the power structure the fuel of the brain. And it unfolds also proteins while we're doing this, while we're using them. 

And so during that first part of the night, when we first fall asleep in the first 20 minutes or so, we're building that adenosine back into ATP. And that's probably why power naps are called power naps, because we're actually rebuilding the power. And then we're also cleaning out through the deep slow waves of slow wave sleep. We're cleaning out all those misfolded proteins, unfolded proteins, and other things that get broken down and need to be rebuilt when we're asleep because of its use during wakefulness. 

So I liken that to having a big party during wakefulness. And you need all those partygoers to leave in order to do the cleanup. And so what I think the mechanism is, and this is still something to be tested, is actually slow waves themselves which is bad news for us as we get older. And those slow waves get smaller. And so your sleep goes away. 

So what happens when a neuron is firing is that it expands, the membrane expands a little bit, becomes more translucent. That's how we know-- one of the ways we know that neurons expand when they fire. And so every action potential, the membrane expands a little bit, as sodium brings water into the cell. And then when they're silent, they contract. 

And so during slow waves, the cool thing is that the reason why you can measure them is that all the neurons at the same time-- not all of them but a good portion of them-- are firing at the same time and silent at the same time. And so you think about that as contracting and expanding all at the same time. It's like a bilge pump of the brain. So that can pump out-- glia are also really important for this in terms of cleaning up debris and transferring it to where it needs to go. So I think of it actually as a bilge pump cleaning out our brain. 

ANDREW HUBERMAN: Interesting. I've heard about the lymphatic system and lymphatic wash out. I've never thought about the mechanical aspects of it before. I always thought that for some reason that now it's obvious to me, there had to be something mechanical but only now that you've educated me about this. 

I thought that for some reason the cerebral spinal fluid just starts washing through. But here, you're talking about literally an expansion and a contraction of the neurons in unison and pushing the fluid through, cleaning out any misfolded proteins or debris that might occur on the basis of these metabolic pathways. And the consequence of that is to, what, to leave the brain in a state of more pristine action for the next day. is? That right? 

GINA POE: Yeah you think of it, again, like a party. And if you don't clean up after that party and you try and hold another one the next day, it's going to get more clogged. People have a harder time moving around and enjoying themselves. And if that builds up day after day, it's going to be cognition. That would be the partygoers moving around becomes hard, yeah. 

ANDREW HUBERMAN: And so this bilge pump that you describe is associated with the big slow waves of deep-- well, of slow wave sleep. So this is going to occur more or less in the first third of the night, is that right? 

GINA POE: That's right. 

ANDREW HUBERMAN: And are there things that inhibit this process and are there things that facilitate this process? 

GINA POE: Yeah. So well, one thing to inhibit is not to get it but-- 

ANDREW HUBERMAN: Right. And here, too-- sorry to interrupt but-- and is this similar to the case with growth hormone where if you go to sleep later than you would normally, you miss the washout? 

GINA POE: Yeah. 

ANDREW HUBERMAN: It's not you don't delay it. You miss-- you missed the washout. 

GINA POE: That's right. That's right. So if you go to sleep at 1:00 or 2:00 in the morning, your sleep is still going to be dominated by N2, NREM sleep not by slow wave sleep. So you need to-- you need to get that first bit of sleep. 

ANDREW HUBERMAN: Would a caveat to that be if somebody normally goes to sleep at 1:00 or 2:00 AM and wakes up at 10:00 AM if that's their normal sleep cycle-- 

GINA POE: Yeah. That should be OK. It should be OK. You would probably want to do-- somebody would want to do a sleep study with people who do that normally and see if also the melatonin release is later and the corticosterone rise that happens normally in the morning also happens later. So if everything shifted, good. 

ANDREW HUBERMAN: OK. Yeah. There are a few studies I've come across that really do argue for the fact that waking up circa sunrise, that doesn't mean at sunrise but within an hour or two, maybe three hours of sunrise and going to sleep within four hours after sunset or so is actually better for the health of all human beings than is being a night owl. And the night owl, there's almost like a night owl posse out there, especially on social media. They get very upset when you say that you should see morning sunlight that after 10:00 AM, you kind of miss the boat. 

They get very upset, because I think there are about 20% or 30% of people perhaps who really feel like they function better staying up late and waking up late. And they function much less well waking up early and going to bed early. But the data on health metrics suggests that, sorry night owls, that they are wrong. 

GINA POE: Yeah, sorry me because I'm a night owl. 

ANDREW HUBERMAN: Oh, boy. OK. Well, then I'm apologizing directly. Here, I'm not a really early morning person. I'm more typical. I wake up naturally around 6:30, somewhere between 6:30 and 7:30 AM, go to sleep somewhere between 10:00 and 11:00 PM. These are averages. 

But I do notice that when I force myself to get up a little earlier and go to sleep a little earlier, that my mood and alertness and just overall productivity is much higher. And there could be other variables to that, too. 

GINA POE: You're absolutely right. I'm a night owl. I love staying up late at night doing you know, writing grants, writing papers, watching movies, whatever it is. I love it. But like you and like every human being on earth would do better if I go to bed earlier and wake up earlier. 

So one good thing for night owls is to have a child, because they will wake you up. Their circadian rhythms are so strong. They will wake up. And even if you deprive them of sleep in the first half of the night they will still wake up like clockwork, because their circadian rhythms are so strong at 6:00 AM. 

And so what you've-- you haven't done anything good for your kid. You haven't moved their cycle to later and be more in line with yours. In fact, you've just sleep deprived them and made them miss a window and made them cranky the next day and made your life more miserable. So go to bed soon after your kids go to bed and wake up with them. That's the way to do it. 

ANDREW HUBERMAN: Great. The child alarm clock, another reason to have children. 

GINA POE: Yes. 

ANDREW HUBERMAN: I got a dog, a puppy, and then that became a dog, specifically, well, for many reasons. But one reason was I wanted to be one of those early morning rides, 5:30 AM every morning. But I ended up getting a bulldog that would literally sleep 16 hours if he could. A nuclear bomb could go off, and he wouldn't wake up. 

But what I started to learn was that Bulldogs actually have sleep apnea. As far as I know, they're the only species that has a genetically-- they're essentially an inbred sleep defect. And so I actually don't encourage people to get bulldogs because it's kind of a cruel breed. They suffer a lot in that body that they're born into. 

Anyway, a dog can accomplish some of this. But get the breed of dog that is going to wake up early. So in other words, don't get a bulldog or a mastiff. 

GINA POE: Well, interestingly, all predatory animals like dogs, and cats, and lions, and us-- well, more dogs, cats, and lions, then us, well, can sleep 16 hours a day. Ferrets are predatory. 

ANDREW HUBERMAN: I had a pet ferret. I used to-- and sadly, I also used to work on ferrets, published a number of papers, delightful animals. 

GINA POE: Yeah. And great because you can study development. It's really cool, because they're born very artricial like we are with brains that are not very well developed. And so you can see what happens through development and how important these different phases of development really are. 

But yes, yeah, maybe we're not as much predators as we think because in fact, our sleep is somewhere between the prey and the predators in terms of the amount of sleep that we usually need a night. But those predators can sleep 16 hours, napping all day long. And they're more crepuscular, perhaps, like their prey are, more-- 

ANDREW HUBERMAN: So dawn and dusk active. 

GINA POE: Yeah, dawn and dusk active. Yeah. But anyway, yes, children and dogs-- actually, there was a poll done by the National Sleep Foundation to see what the number one thing is that wakes people up at night. And number two is going to the bathroom. Number three is children, because-- when your children are young. But that only lasts a few years that they'll wake you up when they're babies. 

But the number one thing is pets. And pets needing to go out or cats wanting to curl up with you or whatever it is, pets' needs will wake you up more in the middle of the night than anything else. 

ANDREW HUBERMAN: Another reason to not get a nocturnal pet. People who get hamsters, pretty quickly realize that they are nocturnal, and they want to run on their wheel around. 

GINA POE: Yeah, you got to put them in the living room away from where you sleep. 

ANDREW HUBERMAN: I vote fish tank, folks, freshwater fish tank. There are all sorts of reasons to not get a salt water fish tank or a child. 

[LAUGHS] 

I appreciate that vote. And I appreciate you mentioning ferrets. And by the way, folks, they are carnivores. They are not rodents. And they are-- they have very elaborate brain structures. 

They're very smart, in the same family as the honey badgers and the other mustelids. Anyway, I shouldn't geek out too much on the mustelids or else I'll take the remainder of all our time. 

I'd love for you to tell us about REM sleep and the sleep later in the night as it relates to dreams and emotionality. And this is probably the appropriate time for you to introduce us to this incredible structure in the brain, which is the locus coeruleus a difficult structure to spell but a beautiful-- a beautifully named structure. I find locus coeruleus to be just fascinating. And I know a small fraction of what it does. And I'm hoping you're going to educate me and our audience more about what it does and hopefully tell us a little bit about its relationship to epinephrine a.k.a. adrenaline. 

GINA POE: Yeah. I am so glad you brought this up, because I can totally geek out on the locus coeruleus. 

ANDREW HUBERMAN: Please do. 

GINA POE: Locus, meaning spot or place and coeruleus, meaning blue so you could just call it the blue spot. That's the easiest. Every animal with a brain has a blue spot and-- yeah, and I mean, every other animal with a brain because of course, there are animals with nervous systems that are not centralized like jellyfish. But anyway, we're digressing there. 

So the local coeruleus is filled with neurons that have in them norepinephrine which is the brain's version of epinephrine or adrenaline, is also called noradrenaline. And what it does is, just like adrenaline and the rest of our bodies, it helps prime us to respond to our environment. So when locus coeruleus neurons fire and fire in a burst, we can switch our attention. And they will fire in a burst if, for example, a loud noise happens in the middle of your concentrating on something. 

So you can-- it helps-- it fires. And it helps you switch your attention to that thing and then learn quickly from it. So it's really important in a stress response. It helps us do quick one trial learning. 

And then tonic activity during the day when you're just doing normal going about your normal concentration activities is really good for sustained attention. It works with the cholinergic system of our basal forebrain which is really important for learning and memory also to help us learn about things and put things together. But just tonic levels are signature of wakefulness and alertness. 

So too much is panic with a locus coeruleus activity. A burst is switching attention. And then tonic levels are sustained constant attention. 

And then when we go to sleep, the locus coeruleus slows and goes from about on average two Hertz to about one Hertz, one cycle per second, tonically. And then when we go into REM sleep, it's the only time when it shuts off completely. 

And it appears that, that complete silence is really, really important for a number of things. And the main thing that I think it's important for is the ability to erase and break down synapses that are no longer working for us. So they encode things that are false now, or they are encoding things that we learned in the novelty, encoding pathway of our brain that have now been consolidated to other pathways. And so we need to now erase them from the novelty encoding pathway. And that is really, really important for being able to continue to learn things all of our lives, so like erasing that REM or that-- what you call those, disks that you stick into computers that-- 

ANDREW HUBERMAN: Hard drive-- no, thumb drives. 

GINA POE: Yeah, erasing your thumb drive. So that thumb drive is what you carry around all day long. And then during sleep, you write that thumb drive to the cortex, to the long term memory structures. And you need to refresh that thumb drive. 

And that's what happens during REM sleep when the locus coeruleus is off, because whenever it's on and noradrenaline is there, it helps us to put things together. It helps us to learn and strengthen synapses. But it does not allow us to actually weaken synapses that are also a really important part for life-- important part of lifelong learning. Yeah, so much more I could say about that. 

ANDREW HUBERMAN: Yeah, locus coeruleus sounds fascinating. So it's connected to the basal forebrain cholinergic system. The neurons in locus coeruleus, if I'm not mistaken, release norepinephrine, perhaps epinephrine as well? 

GINA POE: Well, no, the brain's version of epinephrine is norepinephrine. The other thing it also-- the precursor to norepinephrine is dopamine. And so the source of dopamine in the hippocampus seems to be the locus coeruleus. And it's still a mystery is under what conditions the locus coeruleus also releases dopamine. But it's really important when we're learning something new to also release dopamine or to at least activate the dopaminergic receptors in our hippocampus. 

So yeah, so dopamine, norepinephrine, and then there's also galanin which is important for releasing when we're stressed. And it helps also without rapid learning. It works in concert with norepinephrine and in doing what it needs to do to strengthen synapses so that we learn really quickly. 

ANDREW HUBERMAN: I love that there are multiple molecules involved, because that signals us to a principle which is that even if people can't remember all the names, that rarely in biology is something handled by just one molecule or pathway. That redundancy is the rule because signaling attention to specific events is so important. So that-- I'm going to use that as just a story. I always say I wasn't consulted at the design phase. But it makes sense to me as to why redundancy would exist in this system. 

GINA POE: Absolutely. And in fact, when we form a hypothesis about the brain, we are always wrong. And the reason why we're always wrong is because it's more complicated than we'd like to think. And because in our brains when we're forming hypotheses, it's we fail to account for all of the factors that are involved, the glia, the neuropeptides, the neurotransmitters, the physical structure of synapses. 

And so when I was going through grad school 35 years ago, we-- the dogma was that every neuron contains one neurotransmitter and releases one neurotransmitter. And you had excitatory neurotransmitters, and inhibitory neurotransmitters, and neuro-- modulatory neurotransmitters. But that's as complicated as it's got. 

And then we started talking about neuropeptides. And people said, oh, no, please don't complicate it. And then we started talking about how neurons contain both neuropeptides and neurotransmitters and maybe more than one neurotransmitter-- 

ANDREW HUBERMAN: Maybe even hormones, too. 

GINA POE: And hormones and-- oh, Lord, it's just so complicated. But I've got to admit that's why it works, right? And every time the brain teaches us something new about itself that we didn't hypothesize, we say, oh, of course, that wouldn't work if the way I hypothesized it-- with it. We actually need redundancy. We need all of these systems to work together. 

ANDREW HUBERMAN: Yeah. It's daunting sometimes, but it also insures many careers in science and neuroscience in particular. So note that aspiring scientists, there's plenty of room for discovery. 

GINA POE: Do you want me to talk about norepinephrine-- 

ANDREW HUBERMAN: Yeah. So what-- 

GINA POE: Emotion and-- 

ANDREW HUBERMAN: Yes. Well, what I'd love-- what I'd love for you to tell us about is what role this lack of norepinephrine release during rapid eye movement sleep is thought to achieve? And maybe you can also review some of your work, describing conditions under which norepinephrine invades-- 

GINA POE: Yeah, invade sleep. 

ANDREW HUBERMAN: Rapid eye movement sleep and other patterns of sleep and how that can be detrimental. 

GINA POE: Yeah. So a lot of this is hypothetical but based on a lot of good evidence that we're sewing together into a schema from which these hypotheses come, so a model schema from which the hypotheses come. But one thing that happens to people with post-traumatic stress disorder is that there is a lot of evidence that the locus coeruleus doesn't stop firing in REM sleep. So-- whereas their levels of norepinephrine might be similar to people without PTSD during the day and even during the first part of the night, during the wee hours of the morning. 

And when you measure norepinephrine levels from metabolites in the blood or the cerebrospinal fluid, you see that people with PTSD, it's during the wee hours of the morning when you have the most REM sleep that they have their norepinephrine levels differentiate most from those that don't have PTSD. And so that's evidence that the locus coeruleus is not shutting down during REM sleep like it should. 

Other evidence is heart rate variability. When our locus coeruleus is firing, our heart rates are generally a little higher. And they don't vary as much as they do when the locus coeruleus is not firing. 

So during slow wave sleep, normally, have this big, juicy variability in heart rate with every breath in and breath out because our noradrenergic levels or norepinephrine levels are lower during REM sleep that goes away entirely. And our heart rate is dominated by parasympathetic rather than sympathetic activity and also what our brain is driving, what our dreaming about. For example, if we're dreaming we're running, our heart rates will go up. 

But norepinephrine levels still should be low or off. So people with PTSD that noradrenergic's we're studying these in rats, too, is it true that our locus coeruleus doesn't shut off when we have post-traumatic stress disorder? And the preliminary evidence is yes, it's true that it doesn't shut off. 

So what that would do is norepinephrine would act at synapses to prevent that weakening that you really need for example of novelty encoding structures. And it keeps memories in that novelty encoding structure even once it's consolidated to the rest of the brain. So in the hippocampus which is important for remembering things throughout our lives and it's that thumb drive, we need it to be erased so that we can learn new things once it's been consolidated to the hard drive of our cortex. And so if we're not able to do that, we fill up that RAM really quickly or that thumb drive really quickly, and we're not able to learn new things. 

So for example, after a trauma, I talked about the locus coeruleus responding in stressful situations. That's great. It's very adaptive. But then you need it to stop. 

Once you've learned what you need to learn from it and you want to go to sleep, you need the locus coeruleus to calm down. And during REM sleep, you want it to stop, because then when you consolidated that traumatic memory to the cortex, you need to erase it from the novelty encoding structures, for example, in the hippocampus so that then when you're in the context of safety, you can learn those new things, those new contexts and stop responding to those same stimuli as though you're in that original situation. 

So if you're not able to erase that thumb drive, you will always feel like that trauma happened that same day, earlier that same day and respond as you would to an early-- a recent trauma which is with beating heart and all of that. So even memories that are years past, if you're never able to downscale that novelty encoding structure and purge it from that traumatic memory, it will stay fresh, and new, and then become maladaptive. 

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What approaches are you aware of that can turn down the output of locus coeruleus during these phases of sleep? And for that matter, what things can cause ramping up of locus coeruleus during this phase of sleep? We've had a couple of podcast episodes, solo episodes and with guests talking about trauma. We had Dr. Paul Conti who's a Stanford trained, Harvard trained psychiatrist who talked a lot about trauma wrote an excellent book on trauma and certainly sleep was emphasized as a key thing like get enough sleep. 

But here, you're saying even if somebody with trauma gets enough sleep, if locus coeruleus is hyperactive during sleep, those traumas are going to persist. And most of the trauma treatments that I'm aware of are everything ranging from cognitive behavioral therapy, talk therapy, drug therapy, EMDR, hypnosis. Nowadays, there's a lot of interest and attention on clinical studies on exploring psychedelics, high dose psilocybin, and MDMA. So it's a vast landscape, none of which, as far as I know, is really focused on sleep specifically. 

GINA POE: No, they're not. And they should be, because actually, psychedelics is a sleep like state. And it's a REM sleep like state. Although of course, there are some major differences. So yeah, so much to talk about here. 

So antidepressants are often noradrenergic or serotonergic reuptake inhibitors. So they leave norepinephrine actually out there in the synapses. And what that does is it inhibits REM sleep. And if you're able to get REM sleep, it would probably be REM sleep with some noradrenergic activity. 

So actually, I think-- anyway, I'm not a physician-- that antidepressants are counter indicated. You don't want to take them if you've experienced a trauma and you're experiencing PTSD, because if anything, it's going to make it worse or at least prevent the type of adaptive REM sleep that you really need in order to resolve those emotions and move on. 

ANDREW HUBERMAN: Is that statement specific to antidepressants that tickle the noradrenergic pathway? So the one that comes to mind is-- can never pronounce it, buproprion, which is what-- I think brand name is Wellbutrin. It's a dopaminergic and noradrenergic agonist. So that's the net effect as opposed to the Prozac, Zoloft variety which are SSRIs. 

GINA POE: Yes, yes. But SSRIs themselves also are problematic, because-- we didn't talk about it yet, but the dorsal raphe nucleus which produces serotonin which specific serotonin-- specific serotonin reuptake inhibitors block from being reuptake and leaves too much serotonin out there. And what serotonin also is another noradrenergic-- sorry, another neurotransmitter that's downregulated during REM sleep. That's specifically off during REM sleep. 

And what serotonin does is it weights all of our cognition to being able to recognize novelty again. So it weights our brain away from a sense of familiarity and toward novelty. And it might be one reason why it's an effective antidepressant because it makes the world feel fresh and new again, right? 

But you-- when you have too much, you're holding a novel traumatic memory in your novelty encoding structure too strongly already, you don't want to, again, weight things toward novelty. You need that absence of serotonin also to help you get that sense of familiarity and to start erasing the novelty encoding structures. So you need both to be absent. 

ANDREW HUBERMAN: It's really interesting. We hear a lot about serotonin. And it's not often discussed in terms of its features related to novelty enough I think. 

And what you just described cues me to something that Dr. Paul Conti and others have said in terms of trauma. And here, I'm paraphrasing, so my apologies to them for not getting this exactly right, that an effective treatment for trauma does not erase the traumatic memory. But it causes a transition of what once was disturbing, and invasive, and maladaptive to eventually just become a boring old story that has a fuzzy texture to it as opposed to this sharp high friction texture that invades our thinking and obviously, our sleeping states as well. 

So again, and I appreciate the disclaimer, the caveats around not being a clinician, et cetera. But I do think that there's a lot of interest now in whether or not antidepressants are effective for trauma or not. And I think these aspects of neuromodulation as they relate to, let's call it, erasing traumas or changing the emotional load of traumas during sleep is something important to take note. We also have a lot of clinicians that listen to this podcast. So they should also take note, please. 

So if I want to reduce the amount of norepinephrine released from locus coeruleus during rapid eye movement sleep to eliminate the troubling or maybe even traumatic memories and allow late stages of sleep each night to have their maximum positive effect, is there anything that I can do besides avoiding-- avoiding traumas, avoiding serotonergic or noradrenergic compounds? 

GINA POE: Well, I would also avoid anything just prior to going to sleep that might excite those systems, so a lot of novelty, a lot of the exciting stress inducing video games. Try and enter sleep with as much calm as you can, so maybe deep breathing exercises. That's a beautiful way to calm your sympathetic fight or flight system is deep breathing. 

And we haven't been able to test this with rats because we can't ask them to do a deep breathing exercise. There might be a way we can do that. But I haven't found out or figured it out yet. But if there's a way you can make your sympathetic system, nervous system calm down before you go to sleep, might free for you meditation, or deep breathing exercises might be for some, a warm bath, or a comforting book, nothing too exciting but also nothing too boring, perhaps, just something right in the middle which makes you feel happy and calm is what you should do. And if you instead go to sleep while you're anxious or you're hyped up, then your sleep could become maladaptive. 

Another thing that happens in rats that we have yet to know if it happens in women is that female rats have three phases of their estrus cycle that their locus coeruleus doesn't seem to calm down during REM sleep as much. And we don't know why, but during the high estrogen phases of their estrus cycle, the locus coeruleus shuts down just like it does in male rats. But in the other three phases, it doesn't. 

So one thing that might work and in fact, there are a few studies that show it could work really well is giving women after a trauma event, something that contains estrogen, because estrogen somehow is protective against PTSD. And they know that through a retrospective studies, where they gave women in emergency room either a pill with estrogen and/or without. And those that had the pill with estrogen in it were much less likely to get PTSD from that trauma as measured a year later than those that had the pill without. 

So there's really good studies by Bronwyn Graham-- she's out of Australia-- to really hone in on how much estrogen do you need and also testosterone just so you know, gets converted to estrogen in the brain. So testosterone also can be protective, because it gets converted to estrogen. But there's something about estrogen that's really helpful and protective about from the high locus coeruleus firing. 

And this is, again, preliminary data that we don't have full-- we don't have all the answers yet. And we are looking into it actively right now. But it's really important. 

The other thing about women is that we are two to four times more susceptible to anxiety related mental health disorders including post-traumatic stress disorder. So if we could figure out what's happening to locus coeruleus during sleep in women and then figure out a way to normalize that so the locus coeruleus is silent when it needs to be silent, I think we could go a long way in helping women be more resilient to stress related disorders. 

ANDREW HUBERMAN: What are some other sex differences as they relate to sleep? 

GINA POE: Yeah. That's a really good question. There have been very few studies, unfortunately, of women and sleep, women and estrus cycle or menstrual cycle and sleep. But what we have found which actually largely replicated a study in 1960 is that women or females rather at high estrogen, high hormonal phases of their estrus cycle or menstrual cycle sleep a lot less. But that sleep is more efficient. 

So that sleep is more dense in those sleep spindles, which I haven't gone into what they might do except this connection between the hippocampus and cortex. But those sleep spindles are more dense and more coherent across the brain areas. The theta cycle which is 5 to 10 Hertz in the hippocampus important for one-year learning and also important during REM sleep is also bigger and juicier during the high hormonal phases. So even though there's less sleep, it's more efficient and better. 

So all of that efficiency seems to be reduced in those other hormonal phases. So even though you might sleep a little more, you might need more sleep, in fact, in order to accomplish the same thing that you can get with that short very efficient sleep of high hormonal phases. 

ANDREW HUBERMAN: Very interesting. I think there is a growing trend, at least among NIH-funded grants to require that as they refer to it in the grants of biological sex as a variable. And here, we're talking-- nothing here about sex, the verb, although, I'm sure there are studies about that, too. But biological sex is a variable, because there is a dearth of studies exploring sex differences in most everything. There are all sorts of reasons for that. But more importantly that fortunately, the trend is shifting. 

GINA POE: Yeah. And even when you study males versus females, a lot of people just say include females in their studies but then don't track the estrus cycle or menstrual cycle. And hormones have huge effects on our behavior. Just think about-- when you said sex before our hormones come in, we're not interested in it. And suddenly, that's kind of a main driver of behaviors. 

Hormones can definitely change who we are and what we do. So we should be studying hormones not just sex. 

ANDREW HUBERMAN: I always say that puberty is perhaps the most massive transformation and rate of aging that any of us go through in a short amount of time. An individual, their cognition changes. Their worldview changes. And that's largely hormonal-driven. And obviously, neural architectures change, too. 

I'm very happy that you mentioned-- I'm trying to get into calmer states prior to sleep and some ways to do that. I'm a big fan and I've talked a lot before on this podcast about things like yoga nidra which is a non-movement based practice, sometimes called non-sleep depressed where people actually take some time each day to practice how to go into a more parasympathetic a.k.a relaxed state deliberately, because it's a bit of a skill. 

GINA POE: Yeah. 

ANDREW HUBERMAN: It's-- and there there's some good data really, mostly out of a laboratory in Scandinavia showing huge increases in nigrostriatal dopamine when people go-- basically, engage in a practice of deliberate non-movement and that the brain actually enters states of a very shallow sleep. So it's sort of nap-ish. But the idea is to actually stay awake but motionless. 

And it does seem to restore a certain number of features of neurochemistry. But perhaps more importantly, it teaches people to relax which is something that most people are not very good at. But in any event-- and people who listen to this podcast have heard me say this over and over again, so I sound like a broken record, but this practice as a zero cost practice that doesn't require any pharmacology does seem to really enhance people's ability to fall asleep more quickly and to fall back asleep if they wake up in the middle of the night. So in any event, another plug for NSDR, yoga nidra. 

GINA POE: Well, I just also want to add to that, that's one of the reasons why insomnia is so insidious is because when people feel like they haven't gotten enough sleep, and they're not getting enough sleep, and they become anxious about getting enough sleep, and then they're anxious before going to sleep, like I'm not going to fall asleep, it's going to be 45 minutes, and then that's a positive feedback loop. So you need to break that loop, say, OK, my body is going to get as much sleep as it needs, I needn't worry about it, and then practice this relaxation to say, hey it's all OK, it's going to be all right, and then concentrate on things that relax you, whether it's concentrating or not concentrating, whatever it is. 

You mentioned yoga nidra. And that reminded me of transcendental meditation which is something that also hasn't been studied well, largely because we can't ask nonhuman animals to do it. And so we don't know what's happening with our neurochemistry and our brain activity in a deep and meaningful way. 

But one thing that has been shown in those that can do it really well is that, that theta activity that I said happens when you're learning something or when you're in REM sleep, it's well established and increases during the transcendental meditation. So it might be that some states of meditation could in some ways replace or mimic some functions of, for example, REM sleep. But again, we don't know if all the neurochemistry is right to do, for example, the thing that I was talking about, which is erasing the novelty encoding structures of the brain. That needs an absence of norepinephrine and serotonin, which we don't know if that goes away with transcendental meditation. We just don't know the answer to that yet. 

ANDREW HUBERMAN: Yeah. The studies on yoga nidra and sleep replacement are interesting. It does seem to be the case that nothing can really replace sleep except sleep. But that if one is sleep deprived or is having trouble falling back asleep that these things like-- and I hear it's-- I acknowledge this is essentially like yoga nidra, but we now call it non-sleep deep rest or NSDR, because oftentimes, for names like yoga nidra act as a barrier for what would otherwise be people willing to try a practice. It sounds mystical. 

GINA POE: --and yoga. 

ANDREW HUBERMAN: It sounds like flying carpets. And it sounds like you have to go to Esalen. By the way, Esalen is a beautiful place. But it sounds like you have to go there or live in the West Coast to believe in this stuff. 

But it's simply not the case. These are practices that are really just self-directed relaxation as a practice that allows people to get better and better at directing their brain states towards more relaxation. And most people have an asymmetry. Like for instance, most people can force themselves to stay up later. But they have a hard time going to sleep earlier. And that just speaks to the asymmetry that's probably adaptive in survival-based that we can ramp ourselves up far more easily than we can tend to calm ourselves down. 

GINA POE: Yeah. And actually to appeal to other Christians like me, prayer can be a wonderful way to calm yourself down, because through prayer you're giving your carries to God and saying-- and then you are relaxed, more relaxed. And I just want to say that because, the same reason that yoga might put some people off. It might put some people off to talk about prayer, but it's the same process of being able to relax, and yeah. 

ANDREW HUBERMAN: And get outside our own experience a little bit. 

GINA POE: Yeah. Back out get a world view that might actually also help us to relax. 

ANDREW HUBERMAN: Well, you might be surprised at how many clinicians and scientists who've come on this podcast have mentioned things like prayer from various perspectives, Christianity, Judaism, Muslim traditions, and others that-- as a parallel to all of these things. And I think what it speaks to is the fact that, ultimately, the biological architectures that we're all contending with are going to be identical, right? And so different ways to tap into them and ones that are congruent with people's beliefs, I think are great. 

GINA POE: Yeah, because anything, non-congruent with your beliefs is also stressful. 

ANDREW HUBERMAN: And feels forced. And that's why this idea of calling it non-sleep deep rest in addition to yoga nidra was not to detract from the naming or the history around yoga nidra. But I was finding that it was a barrier. Likewise, yoga nidra tends to include things like intentions whereas NSDR scripts. And by the way, we will provide links to some NSDRs and yoga nidra scripts. 

But NSDR has no intentions. It's simply a body scan deep relaxation-based. So it's the scientific version of all of this stuff. And actually, we study it in the laboratory and some of the brain states that people go into. But that's a discussion for another time. 

GINA POE: This is hard not to-- My mother used to tell me when I would complain, I can't go to sleep, she'd say, well, start with your toes and relax. So you would clench your muscles around your toes then relax them and do that all the way from your toes all the way to your head. And I don't know where she got this, it might have been her own common sense or she might have gotten it from this NPR shows called The Mind Can Keep You Well she used to listen to. But that's another intentional relaxation that focuses on the body rather than on your own mental processes, but. 

ANDREW HUBERMAN: I do a little bit of work with the military. And there's a method within certain communities of Special Operations in the US military, where if they can't sleep or they're having challenges sleeping, they will deliberately try and relax their facial muscles in particular like drape the facial muscles and use long or exhale emphasized breathing does seem to increase the probability of transitioning back into sleep. And those are hallmarks of yoga nidra, non-sleep deep rest, body scans. 

And so I think all of these things converge on a common theme. As neurobiologist, we can say, all of the things that we are describing certainly move the needle away from locus coeruleus activation. And we haven't done the experiment to really look at that. But it seems all these things are counter to noradrenaline release. 

GINA POE: Right. Another one is yawning. Yawning in itself is, in fact, kind of tensing of all the muscles in your face and then relaxing them. So it might be why we yawn. We don't know why we yawn yet. But it might also-- it would be really great. 

Actually, animals yawn, too. 

ANDREW HUBERMAN: My bulldog was a-- perpetually. If he wasn't sleeping, he was yawning. 

GINA POE: And it would be interesting to see what yawning does to the locus coeruleus. Does that also calm and switch the locus coeruleus activity, because it's an interesting that facial nerve like trigeminal nerve through the vagus connects indirectly to the locus coeruleus and has a powerful effect on that. 

ANDREW HUBERMAN: Interesting. A common, I think friend of ours and direct colleague of yours, Jack Feldman was a guest on this podcast telling us about all the amazing structures he and others have discovered in respiration and breathing. It sounds like we have a collaboration brewing the three of us should definitely carry out. 

I'd love for you to share with us a little bit more about the spindles that have come up a few times. And I don't know if it's relevant to this. So if it's not, let's separate it out. 

But I'd love for you to tell us a little bit about the role of sleep in problem solving and creativity. And if spindles are involved, then I'll consider myself lucky for batching them in the same question. And if they're not involved, simply feel free to separate them out. 

GINA POE: I think they could be involved. And the reason why I think they could be involved because we now know a lot more about spindles. First of all, the first thing that we knew-- first of all, we ignored them. Then we thought they had something to do with keeping us asleep. And that was their function is when an external stimulus came, they would keep us asleep because they would arise. 

But now, we know that the density of our sleep spindles, the number that we produce per minute is well correlated with our intelligence in the first place and that no matter what your intelligence is and no matter what your sleep spindle density is, if you're learning something during the day and increase your sleep spindle density, it's really almost perfectly correlated with our ability to consolidate that information and incorporate it into the schema that we already have in our brain. 

So if you try and learn something new, even if your sleep spindle density at baseline is great, if you don't increase your sleep spindles that night, you're not going to use sleep to really incorporate. Interestingly, sleep spindles are poor in those with schizophrenia. It's one of the characteristic signatures of sleep is that sleep spindles are very few and far between, which might mean that people with schizophrenia might not be able to incorporate new information into already existing schema. And instead, it flaps in the breeze out there and can be accessed erroneously at times when you don't want it to be involved. 

So I digress, so sleep spindles and creativity. So one of the things we now through some great studies by Julie Seibt and Anita Lüthi is that sleep spindles are accompanied by an incredible plasticity out in the distal dendrites, the listening branches of our neurons that listen to other cortical areas. So there are proximal dendrites in our neurons that listen to the external world and are conducted through the thalamus. 

And then there are distal dendrites which listen to an internal conversation that's happening in our brains. It's kind of our internal state, really. And during sleep spindles, that's when those distal dendrites are able to best learn from other cortical areas and from the hippocampus. It is during sleep spindles that the hippocampus and the cortex are best connected and when that incredible plasticity can happen. 

When I talk about schema, that's a cortical, cortical thing. That's when the image of Santa Claus and presents comes together. It's not through some external thing. Once we learn those things together, it's our cortex that encodes that and brings those images back up together. And that's during sleep spindles when that's happening, when that-- there's big surges of calcium into those distal dendrites, and where plasticity happens in just huge amounts. 

During that sleep spindle stage of sleep which is N2 stage, there's also another excitatory event that comes all the way from the brainstem and projects everywhere in our cortex which is called PGO waves. That's P for pons, G for geniculo nucleus of the thalamus which is where they're first discovered, and O for occipital area which is our visual area which is, again, where they're first discovered. But in fact, it's now been shown that PGO waves, which we should generalize to P waves because they come from the pons and go to the thalamus and then the cortex, happens all over the brains. And that is where glutamate, which is a major excitatory neurotransmitter involved in learning and plasticity is being released in big amounts, also in those distal dendrites. 

So P waves and spindles work together to cause plasticity and sew our schema together which could be the origins for insight and creativity. Now, when PGO waves or P waves were first discovered, it was thought to be random, because this small area that generates P waves all over the brain projects all over the thalamus and causes P waves all over. And you don't measure P waves all over the brain at the same time. In fact, it's just seems sporadic and random. 

So that's probably-- and P waves also happening even more during REM sleep, rapid eye movement sleep. So that's why people think that REM dreams are so random is because these P waves are random. And they could generate dreams because they're an internal source of excitation that replaces the outside world during our dream state. 

And so these P waves, if they are random, could function-- could be the underlying reason why REM sleep dreams are random. And it might also be why creativity can happen there because we're randomly activating-- co-activating different things in our brain that we can then sew together. But it might not be as random as we think. So that's the caveat there. 

ANDREW HUBERMAN: I just learned a lot from you, because I teach brain stem to medical students. And I talk about the pons. And the pons is like this dense collection of all these different nuclei involved in a bunch of different things. And it's close by a bunch of interesting things. And it's still a mysterious brain area. 

But when I learned about PGO waves, I thought pons-geniculo-occipital, because occipital is most commonly associated with visual cortex, I thought it was the origin of the visual component of dreams. 

GINA POE: And probably is. 

ANDREW HUBERMAN: I'm very happy to learn that they should be called P waves, because they include lots of different areas of the brain. And it makes really good sense to me why the pseudo randomness of dreams especially these late night and early morning-- later in sleep I should say and early morning dreams seem to be cobbled together from disparate experiences. You walk through a door and suddenly, it's a completely different context and landscape. 

GINA POE: Yes, beautiful. beautiful. 

ANDREW HUBERMAN: I like this idea a lot. It makes intuitive sense it makes biological sense. It also gives me something to talk about to the medical students next quarter when I talk about pons. 

GINA POE: Right. You want to talk about where in the pons, it's right below the locus coeruleus. It's called the sub coeruleus. They're glutamatergic. It's also called SLD, sub lateral dorsal nucleus, so. 

ANDREW HUBERMAN: So note to any aspiring neurobiologist, there's a vast landscape of yet to be undiscovered structure and functions in the pons. You want to work on something that is sure to reveal something novel, work on the pons because it's in every textbook. It's clinically very important structure. Sadly, gliomas and other cancers of the brain can sometimes-- can often surface in the pons. But we still know very little about it. 

I read a paper this last year or-- and I think it was covered in a bit of popular press, that during rapid eye movement sleep, people can solve problems or respond to external stimuli. For instance, they would give them math problems. They'd whisper in their ear while they were in REM sleep, what's 2 plus 2. And then people would say, even though they were paralyzed, apparently they could still move their mouth, because they'd say four or something like that. Or they'd say, what's your name. And people could respond. And so that in REM sleep, perhaps, people-- some elements of cognition are still active. 

GINA POE: I'm glad you brought that up. 

ANDREW HUBERMAN: What are you thinking-- and I don't know the authors of that study and-- listen, if ever I say something wrong, it's great on this podcast because someone will tell us in the YouTube comments. It's one of the great uses of YouTube comments. But I'd love to know your thoughts on that study. Is that just kind of an odd feature that or does this have meaning. Should we actually care about this result? 

GINA POE: There is no just about it. It's really actually intriguing and interesting and might relate to this paper that I talked about where we said different areas of the brain can be in different states at the same time. So lucid dreaming is another thing we can't ask animals to do or can't ask them if they've done it. But we can certainly ask humans to do it. And some people can do it really well. 

And it would be really interesting to see in those people who could lucid dream really well whether they spend more or less time in this asymmetrical state where one area of the brain is in one state and another area of the brain is in another. And it might be that those people can respond to questions during REM sleep. Best are those that have the most asymmetry or dissimilarity or dissociation between subcortical and cortical structures. Or it might be that they're the ones with the most symmetry, we don't know. 

I do worry a little bit about lucid dreaming, because people are-- it's a fad. People are really excited about it. And to be able to remember one's dreams is fun often unless there are nightmares. But it's really interesting. Or to be able to direct one's dreams if they are a nightmare is really a wonderful power to have, to be able to redirect a nightmare that has been repeated to something else and then kick yourself out of that. 

Repetitive nightmare is really nice. But I worry a little bit about it, because we know so little about what's actually going on in the brain. And if this lucid dreaming state is preventing us from, for example, from the locus coeruleus from calming down or the serotonergic system from silencing like it should, and maybe what we're doing during this state is Yeah we're activating the learning and memory structures but in a way that's maladaptive in terms of the erasure that we need to do. 

So maybe one of the reasons why most people don't remember most of their dreams is for good reason. Your hippocampus is in a state where it's not writing new memories. In fact, it's writing out its-- the memories it learned during the day to the cortex. And it's immune from incoming new information. 

So maybe lucid dreaming is bad, because you're activating the hippocampus in a way that's writing new memories. And it might be really maladaptive for things like PTSD. On the other hand, let me just argue myself right out of this, when I used to have a repeated nightmare when I was a kid, my mother who was so wise would tell me, well, listen, just-- next time you're in that dream, say, hey, I'm in a dream and then change something about it. 

So she and I rehearsed what the horrible dream that it was, big monster running after me. And my legs were like mud, and I couldn't run away. And it was just terrifying. And that was a dream I would have time and time again. 

She said, OK, next time what are you going to do when that monster comes after you? I'm going to run away. No, that's what you do every time. And it's always the same outcome. You can't run. 

So let's do something different. What could you do that's different? So I came up with all-- I could turn around and punch it in the nose. Yeah, that's great. 

And so the next time I had that dream-- I did recognize this is that same old dream which means that there's part of my brain that's conscious enough to know that I'm in a dreaming state. And then I didn't have the courage in my dream because I was still terrified to punch or touch the monster in any way. But I did have the courage to turn around and look it in the eye and say no. That was enough. I said no. 

And that was enough to knock me out of that rut of that dream so that I never had it again. I never had that same dream again. And in fact, it gave me peace about dreaming, because I knew that if ever there was a nightmare that was just too scary, I could probably do something to change it and knock myself out of it. 

So even though, I don't recommend lucid dreaming on a normal day-to-day basis, if it's enough that can knock you out of a rut-- one thing that happens with people with PTSD is they have the same repeated horrible nightmare which is often a reliving of the days trauma that had. So maybe lucid dreaming can be used on occasion to be a powerful tool, because there's so much plasticity that happens during REM sleep to knock you out of that rut of reliving that event and just change it. 

And you could probably practice that during wakefulness, rehearse the event that happened that was so traumatic and then just introduce a new element like, now, I'm safe. Now, the sound that was associated with that really traumatic thing, I should now associate with something else. And the next time I have that dream, I'm going to change it so that sound is now this new thing that it should be associated with safety. 

And that might be enough, maybe, I hope, to knock you out of that repeated nightmare and maybe even start you on the path to recovery, because if you can calm down about those nightmare states of sleep, then maybe your local coeruleus which is involved in stress can also relax. And you can do the erasure parts that need to be done. 

ANDREW HUBERMAN: I love it. I seem to recall a paper-- and I'll have to find the reference and send it to you, we will also put in the show note captions-- that described a protocol essentially matches this idea. And I think what they had people do was either cue themselves to a particular smell or tone in wakefulness then to try and recall a recurring nightmare. Then during the night sleep, they had the tone playing in the background which would then cue them to the wakeful state-- they're still asleep, mind you, but in the pseudo lucid or lucid state, and then try and change some variable as you're describing. Some either look the predator in the eyes or do something different. 

And then in the waking state, take a little bit of time to try and script out a different narrative altogether. And it took several nights, as I recall, or more but that they were able to escape this recurring nightmare. 

GINA POE: It's like a week or something, yeah. 

ANDREW HUBERMAN: So you're familiar with the study? 

GINA POE: That's a beautiful study. I loved it. 

ANDREW HUBERMAN: Yeah, we will put a reference to that. I need to revisit that study. It was pretty recent, but I need to dive into it again, because I think I didn't go as deep into it as I should have. 

GINA POE: No, no but the one thing that you-- you said many right things. But one of the things you said is that they were able to cue the dreamer when they knew-- when they were going to REM sleep. And then they played the sound or had the odor. 

Now, when you're normally asleep alone in your bed, you're not going to be able to cue yourself. But it might be that rehearsal enough before you go to sleep is enough to help cue you to that repeated nightmare, remembering what the nightmare is and then figuring out how to cue yourself to do something different. 

ANDREW HUBERMAN: For years, I had the same recurring nightmare over, and over, and over again. And it was so salient and so clear. And I'm not going to share what it is, because it's not that it's that disturbing. It was just-- I think it was the emotional load of it and just how salient certain features were, like one person who's a real life person had a particular clothing on. And it's like, and that just served as this cue. 

And I don't know if I ever did any direct work to try and deal with it. But now, it almost seems silly to describe it. 

GINA POE: Oh, yeah. Well, dreams are usually silly to describe. 

ANDREW HUBERMAN: It pretty silly. But it was a pretty violent dream. 

GINA POE: Yeah. And your emotional system is so geared up during REM sleep which is another thing we could talk about. 

ANDREW HUBERMAN: Yeah, please. I would love to. Yeah, so locus coeruleus is ideally suppressed. So we can't release norepinephrine. We can't act out our dreams during these very emotionally laden thoughts and storylines during sleep. 

This almost starts to sound like a little bit of a built in while sleeping trauma therapy, because most trauma therapies involved trying to get people into states of counter to what most people think you actually want to get close to the trauma in terms of the narrative or try and suppress the emotional activity of it or-- I guess that's the motivation for ketamine-based therapies for trauma-- or I've also heard, and this is still perplexing to me, that other waking-based trauma therapies involve taking people the other way, making it very cathartic, take them to the peak of the emotional response but then allow that to finally cycle down into a more relaxed response. 

So please, if there's anything about locus coeruleus and dreams and that can help people basically extinguish traumas or traumatic features to real life events, we definitely want to know about them. 

GINA POE: Yeah. Well, I think one of the things that people thought might help after a trauma like a school shooting or whatever, car accident, is to talk about it. But in fact that ended up being counterproductive. And I think one of the reasons why it was counterproductive is because it didn't take them back down. It brought them up and continued to reactivate the emotions of it but then didn't emphasize the safety of the fact that it's over or help them work through how they might avoid it again in the future to calm the sympathetic nervous system down again before they went to sleep. 

And none of these studies has sleep ever been considered. But to me, that's the key part, is bringing down your sympathetic nervous system before you go to sleep so that your sleep can be adaptive, your locus release can shut off like it normally does or should do and then able to erase the novelty of it. The other thing that I just mentioned a minute ago was that the emotional system is highly activated in REM sleep. And that's definitely true. And that might seem counterproductive in terms of the nightmares and how to help REM sleep be a therapeutic thing rather than reinforcing the emotionality of the trauma. 

And I think the key to that again is the absence of norepinephrine. So even though the emotional system is in high gear, without norepinephrine, you can actually divorce those highly activated emotions from the cognitive parts of the memory that you have just written out in that N2 stage of sleep when the sleep spindles are going. So you've just now consolidated the information that you'll need to survive and to make that adaptive. 

And now, you need to divorce from that schema and from that semantic parts of memory, the emotional part, because whenever you remember something, it's fine if you remember the being emotional at the time. But you don't want to bring back and sew into that memory all of the same emotional systems. You don't want to bring back the heart rate changes, and the sweating, and all of that. You want to be able to remember all the parts of it and even remember that you were traumatized and that you did cry and that you did have-- your heart was racing. 

But when you're talking about it years later, you don't want to have to relive all that, otherwise who would ever want to recall a traumatic memory because you're basically putting yourself through the same trauma which is what people with PTSD have. They don't want to recall this traumatic memory, because it's reliving it. Like it's just happening again. 

So that's what we're thinking is that the emotional parts are no longer-- are not able to be divorced because the norepinephrine system is not downscaled during REM sleep. And so that REM sleep serves to instead reinforce and in fact amplify the emotions because your emotional system is up, locus coeruleus is high, re-sewing in every night the emotionality of those memories and with the memory itself. 

ANDREW HUBERMAN: You've told us a lot about locus coeruleus and norepinephrine from locus coeruleus. Is there any role for norepinephrine, epinephrine, and cortisol released from the adrenals? My understanding is that norepinephrine and epinephrine will not cross the blood brain barrier which is probably why we have a brain-based noradrenergic system, locus coeruleus, and other neurons. Actually, that's a question I should ask you. Are there other sites in the brain where norepinephrine is released from or is it just locus coeruleus? 

GINA POE: So there are seven, nine different adrenergic. Yes, there's nine different adrenergic structures. 

ANDREW HUBERMAN: I'm sorry I didn't ask. But it just occurred to me that in some cases like with raphe, there are other sources of serotonergic drive in the brain. But raphe is like the main side. 

GINA POE: Yeah, that's the one that goes to the cortex and the locus coeruleus is also the one that goes to the cortex. But there are other adrenergic sources, some that-- from the brainstem that descend and help us to ignore pain, for example, when we're stressed and needing to run away from the tiger, right? We don't want to be thinking, oh, my ankle hurts. You want to just be able to ignore it and go do what you need to do. 

So yeah, so there are lots of other noradrenergic nuclei. But the locus coeruleus is the main one that projects all over the brain. Actually, the only place that doesn't project is the dorsal striatum. You talked about ventral striatum and addiction. 

The dorsal striatum is the only place the locus coeruleus doesn't project to. And that's involved in procedural learning and motor learning, kinds of learning that take over when your hippocampus, for example, is compromised. Bilateral, if you don't have good hippocampus, you can still do procedural learning and do-- and it's great. It's a redundant system. 

And so if your locus coeruleus is not working, if you don't have it anymore, you can still do a-- if you don't have a good hippocampus, you can still do learning through this dorsal striatum on the structure. So it might be for those kinds of learning functions, sleep deprivation where you never let the locus coeruleus stop firing is OK, because it doesn't have any receptors for norepinephrine anyway. So yeah. 

ANDREW HUBERMAN: And what about bodily like adrenals. I often remind people there's no such thing as adrenal burnout, per se, that adrenals don't actually burn out. But some people have adrenal insufficiency syndrome. Other people have adrenals that are just chronically cranking out epinephrine, norepinephrine, and cortisol at the wrong times in particular. 

GINA POE: Yeah. So that-- those are great questions. And I think the answers to them have yet to be discovered, the connections between our periphery and our central nervous system. But we know that there are beautiful connections. And it's untapped source of being able to manipulate our brains is to work through our bodies. 

And so our adrenals do great things. They constrict our blood vessels, causing higher blood pressure which helps blood rush out to all the extremities that need blood, our muscles for example, for running away from the lion, or the tiger-- 

ANDREW HUBERMAN: Or meeting a grant deadline or catching a train. 

GINA POE: Or catching a train, yeah. The adrenals help our hearts pump faster. Our muscles get perfused with the blood it needs. It diverts blood and everything away from our parasympathetic system which is rest and digest. We don't really need to digest that croissant when we're running for a train. We can do that later. 

So it's doing really important things. What we don't know, because it doesn't cross the blood brain barrier, is how that affects the brain and whether our-- if we can independently activate our adrenals, when a time when our brain thinks that we should be fine and calm and asleep, how our brain detects that. Is it a feedback through heart is racing? And then our brainstem says, what's going on, my heart is racing, and then wakes us up. And then our hearts were racing together with our brain racing. 

We just don't know the answers to these questions yet. There are some good studies, old studies. But we need a lot more. 

ANDREW HUBERMAN: I will-- another nod to the fact that there's lots of great work ongoing and still to do. I'd love for you to tell us about some of the work that you're doing more recently on the relationship between sleep and opiate use, withdrawal relapse, and craving, just addiction, generally. I get a lot of questions about people trying to come off benzodiazepines or people's challenges with benzodiazepine and other types of addiction. What is the role of sleep in addiction and recovery from addiction and opiates in particular? 

GINA POE: Yeah. This is a very young area. And in fact, my laboratory has just started. I have a graduate student who's been in my lab for just one year. She's done amazing work already but completely groundbreaking work. 

And what she has discovered already-- we don't have the paper out yet, but we're working on it-- is that when animals withdraw from opiates-- and this has been replicated in other ways with other types of things-- our sleep is disturbed. Our sleep is terribly disturbed. And the amount of sleep disturbance predicts relapse behaviors. 

And you might think, well, of course, you're going to relapse if you can't sleep because opiates calm you down. Well, then one of the reasons why opiates calm you down is because the locus coeruleus, again, the blue spot, is covered with opiate receptors that are normally really responsive to our endogenous opiates. And so what happens when we are pleased, for example, or laughing or whatever, endogenous dodges opiates activate those receptors in the locus coeruleus and calm it down. It actually suppresses locus coeruleus activity. It makes us happy and relaxed. 

One of the things, reasons why opiates are so addictive is because it also calms us down and makes us relaxed. But the problem with exogenous opiates is that they really strongly bind these receptors on our locus coeruleus. And if you take exogenous opiates again and again like you're recovering from surgery, for example, and take these pain medications is that our locus coeruleus struggles to do what it's supposed to do which is keep us awake, and learning, and concentrating on things. 

So it will down regulate. It will internalize these receptors that are normally only occupied by endogenous opiates. And it will do this-- it will change our genes that are associated with producing these receptors. So you actually have very many fewer receptors. So the locus coeruleus, at least, during wakefulness can fire and to help us to do these things learn about our environment. 

And so if you long term reduce the number of receptors out there, then when you withdraw the exogenous opiate, there is not enough of your endogenous opiates to be able to occupy those few receptors that are there. And our locus has nothing to calm it down anymore, no pacifier. And it just fires, and fires, and fires. And that physic and tonic high activity stresses us out, because it's normally associated with stress. 

And so any exogenous stressor that adds to that and also activates our locus coeruleus, there's nothing to calm it down again. And so it just keeps firing. It disturbs our sleep. And that's why maybe sleep disturbance is an indicator of hyperactive locus coeruleus and such a good predictor of relapse behaviors because nobody likes to live in that high stress state. And they will do anything to get back to normal. 

So the problem with taking these drugs is that it leaves you excited-- I'm sorry, excited, relaxed and happy. But then when you come off of it, you're worse than when you were at baseline. You take it again. It only brings you up this far, because you have fewer receptors. When you come off it, you're down, even more depressed and anxious and-- depressed is a word I use loosely, and that's not what I-- 

ANDREW HUBERMAN: Certainly, central nervous system depression, sleepier, less motivated, lower mood. 

GINA POE: Yeah. Our locus coeruleus is actually-- it's a anxiety kind of depression actually, the anxiety related depression. So yeah. So we don't know yet what-- and there's some good research going on right now-- what could restore our own endogenous receptors so that our endogenous opiates can properly calm our locus coeruleus once that they have been tamped down by exogenous opiates. But that would be really one way that you can access the sleep disturbance. 

So we talked about sleep and the importance of sleep in terms of learning and memory, the importance of the structure of the 90-minute cycle for all of that. So you can imagine if your sleep is disturbed by too much locus coeruleus activity. The structure and the function of those sleep spindles and that theta during REM sleep and the lack of norepinephrine, all of those structures, all those functions for learning something new, like a new behavior that doesn't involve the drugs becomes compromised. 

And so that's something that Tania Lugo, in collaboration with Pamela Kennedy at UCLA, that we're looking at how is learning and memory affected by the sleep disturbance. If there's a way we can-- in animals that are coming off of opiates. Can we restore their sleep to normal so that then they are less likely to do relapse kinds of behaviors. 

ANDREW HUBERMAN: Fascinating. And I will certainly have to have you back on to tell us the results of those studies. Meanwhile, I think for anyone who's trying to come off opiates, exogenous opiates and restore these systems, what I'm hearing is that it's going to take some time but that any and all things that people can do to buffer their healthy normal sleep architecture like morning and daytime sunlight, limiting bright light exposure, lowering the temperature at night, a number of things that we've talked about in this podcast-- 

GINA POE: Breathing exercises, meditation, whatever it is that helps you calm yourself before sleep, yeah. 

ANDREW HUBERMAN: Right. Would facilitate not just sleep but perhaps even accelerate the recovery and shorten this period of withdrawal, which from the questions I get and from what I hear can be absolutely brutal. 

GINA POE: Yeah. Oh, I can imagine. I had to take opiates for-- I only took it for three days after giving birth to my first son, I think, second son, one of them. And just-- I just said after three days, this is enough. I'm just going to try Tylenol. And so I weaned myself-- not weaned, I just did a sudden sharp cut off. 

And even though I felt-- I didn't get the high of opiates when I was taking the Tylenol codeine. When I went off it, boy, it was like PMS times 100. I was so anxious and upset at little things. And thankfully, it only lasted a few hours. But if I had taken it for a week or two weeks, who knows if my endogenous opiate receptors would have been permanently downregulated and I would have been an addict-- or an addict-- I would have been addicted. 

I shouldn't say an addict. There's negative connotations. It's just a very physiological state. So no judgments at all associated with it. So yeah, They're powerful, powerful painkillers but can also alter your entire brain and rewire it. 

ANDREW HUBERMAN: Well, all the more reason why I and many others are grateful that you're doing this work to figure out ways that people can recover more quickly and more thoroughly. I must say you've taught us a tremendous amount in a relatively short amount of time about the architecture of sleep, the different phases, the relationship between sleep and dreaming and this incredible structure, locus coeruleus. And I'm so happy we also got into the pons. That just delights me, because we rarely talk about the pons on this podcast. It's such an interesting structure. 

Sex differences that are important in creativity and problem solving and trauma sleep spindles, just such a wealth of information. And much of it that's actionable for people. So first of all, I want to say thank you for taking the time to sit down and have this conversation that so many people are sure to benefit from. 

I also want to thank you for doing the work you do. Even though I'm a fellow neurobiologist, I think that it's not often that we take a step back and realize that it's really the work of hard-- thinking hard, strongly motivated PIs-- it stands for principal investigator by the way, PIs like yourself, graduate students, and post-docs that really drive the discovery forward and that lead to these new therapeutics. 

Physicians are wonderful. Clinicians are absolutely wonderful. But clinicians don't develop new treatments. They only implement the ones that researchers discover. 

So thank you for being a brain explorer with a focus on growing the good in the world. I know I speak for everybody when I say thank you so much. 

GINA POE: Thank you so much, Andrew. Thank you for being an amazing interviewer. You brought a lot out of me in a coherent fashion that normally I can't do when I'm speaking in public. 

ANDREW HUBERMAN: I don't know about that. I've heard your lectures, and they're superb. We'll direct people to some of the other ones. 

GINA POE: Well, thank you. And I also want to put a plug-in for graduate students in general and the key and amazing role that they play in research. I'm a PI, as you said. I used to be a graduate student and a post-doc trainee myself, doing all of this on the ground hands on experimentation. 

It's so hard to do. It's so hard to do, right? It's so hard to think through all of that. 

Now, I'm a PI, I get to be an idea person and just say, hey, why don't you do this and hey, what do you think about that. And they, of course, intellectually contributes so much to these planned experiments. But they also do the really hard work. 

And so I just want to say thank you graduate students. Thank you to my graduate students and all graduate students out there. Thank you post-docs. 

ANDREW HUBERMAN: --underpaid. And listen, and to the major institutions, Stanford UCLA and all other major institutions, pay them more, please. 

GINA POE: Yes. 

ANDREW HUBERMAN: We need them. And they need to have a standard of living. I'm not afraid to say that despite my primary employer. 

Pay them more. They need it. They deserve it. 

GINA POE: They deserve it, absolutely. 

ANDREW HUBERMAN: Great. Well, we will absolutely have you back again if you'll be willing. And meanwhile, we will direct people to where they can learn more about you and your exciting work. And once again, thanks so much. 

GINA POE: Thank you so much. 

ANDREW HUBERMAN: Thank you for joining me today for my discussion about sleep, mental health, physical health, and performance with Dr. Gina Poe. I hope you found it to be as informative and as actionable as I did. In fact, I'm already implementing the regularity of bedtime plus or minus half an hour in order to get that growth hormone release. And I can already see both my sleep scores improving and my feelings of daytime vigor and focus and other markers of sleep health improving as well. 

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