Understanding Sleep: Phases and the Perfect Night’s Sleep Transcript: Andrew Huberman Is a perfect night’s sleep? Oh, yeah. Gina Poe 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 are, 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’re 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 then 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, 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, 10.30, 11 o’clock, 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 (Time 0:07:47)
Liberación de hormona del crecimiento está fijada circadianamente Transcript: Andrew Huberman Know that melatonin is a hormone 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 and 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 androchronologists will tell you that big boluses do different things than a little bit Eked out over time. So that is, well, 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? Sleep depriving themselves. Gina Poe Yeah. Andrew Huberman So let’s say I normally go to sleep at 10 PM and then from 10 to 1130 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 1130 or midnight that I miss 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 those clocks are normally synchronized and the 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. (Time 0:19:07)
La limpieza cerebral que provee el sueño Transcript: Andrew Huberman There’s one more thing I wanted to ask about the architecture of the night’s sleep in terms of early part of the night. Earlier you mentioned the washout of debris and the so-called glymphatic 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, 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. Cleaning out through the deep slow waves of slow-wave sleep, 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 slow asleep 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 kind of 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. Interesting. (Time 0:43:18)
Los niños tienen un reloj circadiano muy estricto Transcript: Gina Poe Writing grants, writing papers, watching movies, whatever it is. I love it. But I like you and like every human being on earth that 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 a.m. 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 (Time 0:50:25)
Qué son y para qué sirven los husos del sueño Transcript: Gina Poe 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 learn 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, you know, use Sleep to really incorporate it. (Time 1:28:07)
Husos del sueño y plasticidad en las dendritas distales Transcript: Gina Poe Creativity. So one of the things we now know through some great studies by Julie Siep and Anita Luthi 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 kind of conversation that’s happening in our brains. It’s kind of, you know, 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, you know, the image of Santa Claus and presents, you know, 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 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 (Time 1:29:31)
El sueño REM separa la emoción del recuerdo Transcript: Gina Poe I think one of the things that people thought might help after a trauma, like a school shooting or whatever, you know, car accident 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 aureus 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 is that the emotional system is highly activated in REM sleep, and that’s definitely true. And that might seem counterproductive in terms of, you know, 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, you know, 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 being emotional At the time, but you don’t want to bring back and so into that memory, all of the same emotional systems. You don’t want to bring back, you know, 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, you know, 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 not able to be divorced because the norepinephrine system is not downscaled during REM sleep. And so that REM sleep serves to instead reinforce in fact amplify the emotions because your your emotional system is up locus coerulis is high re-sewing in every night the emotionality Of those memories and with the memory itself you’ve um told (Time 1:44:26)