Full episode transcript below. Beware of typos!
Nick Jikomes
Professor, Bob Stickgold, how are you?
Robert Stickgold 2:17
I'm good. How are you today?
Nick Jikomes 2:19
I'm good. Where are you calling in from Boston? And can you tell everyone a little bit about your background and what you do?
Robert Stickgold 2:28
Sure. I'm a cognitive neuroscientist. And for the last 25 years, I've been studying the role of sleep and dreaming in motional and memory processing.
Nick Jikomes 2:40
Fascinating. I think one of the things that's so interesting about sleep to everyone pretty much is on the one hand, we're all intimately familiar with it, because it's something that we participate in and experience every single day. And yet, despite that fact, it's still so mysterious exactly how dreams work and why we're sleeping. It's obviously got some sort of recruit recuperative benefit that everyone intuits, but I don't think we've fully worked out exactly what's going on in the brain. And I would love if you could start out by just talking a little bit about what actually happens, what is the brain doing at a high level every night when we go to sleep?
Robert Stickgold 3:19
Well, it's doing an immense amount. And this is stuff that we have becoming then becoming more and more aware of overtime. At the simplest level, what the brain does is it shuts off all of its inputs from the outside world, or the vast majority of them, we still have some some minor awareness, our ability to perceive events in the outside room, but we're not aware of them. In fact, our awareness of who we are and where we are pretty much disappears. And we go into a mental state of isolation where we don't know what day it is, what year it is where we are, we just sort of hang out and and we dream. And at that same time, our brain is doing immense amounts of, of calculating and processing of, of the events of our day. So one way to describe it is that evolution has calculated for every two hours, the brain spends taking in new information from the world around us. It literally has to go offline for an hour to just figure out what all that information means. So we're awake for 16 hours, and we need eight hours to figure out what all that means. And so that's a large part of what the brain is doing.
Nick Jikomes 4:42
And how does that process of figuring out what happened while we were awake? How does that relate to the architecture of sleep and the fact that we're actually oscillating between different types of sleep when we are asleep?
Robert Stickgold 4:56
Yes. So one of the strangest things about Sleep only discovered in the 1950s is that we don't just fall asleep and go into a state of sleep. Sleep consists of a series of oscillating states of brain function. And that's referred to as the REM cycle, because it's it's most evident in in REM or rapid eye movement sleep. And it's a 90 minute cycle that we go through every night, and every 90 minutes, we go into deeper and deeper parts of sleep. And then our sleep lightens up, and we enter REM sleep for a while, we go back down. And we do these oscillations all night long. And it's been something of a mystery as to why the brain would want to do this, what's different about these states? And what I believe at this point is that the main driver for the different states is that well, we're trying to answer very different kinds of questions while we sleep. So I think the best explanation for why we have these different brain states across the night is that the brain is trying to solve different classes have problems. So most of my work has been looking at memory processing. And we know that sleep enhances our memories from the day before, but processes it in other ways too. And you can imagine that one thing that sleep does is I learn to type some piano piece in the evening, my brain will actually rehearse that, and I will be better at it the next morning. The same time, if I've learned this series of French verbs, in the evening, I will be remembering them better than next morning than if I had learned them in the morning and been awake all day after the same amount of time. And as you can imagine, the ideal brain state for processing words, is going to be different than the ideal brain state for processing motor activity. And so we probably evolved these different brain states to say just like you have, you know, you get the high school you get a different teacher for chemistry than you have for English because they don't understand each other's specialties. The brain basically is putting us into different classrooms, if you will, as we go across the night, to help us learn to improve our knowledge about different subjects.
Nick Jikomes 7:34
So what are those different classrooms that we go into? You mentioned rapid eye movement sleep, but can you walk through the different sleep stages and how they look different in terms of the underlying neurophysiology?
Robert Stickgold 7:44
Yes, so do you want me to pop up some slides or no,
Nick Jikomes 7:52
um, I would say,
Robert Stickgold 7:54
No, of course, it's going to be video audio only.
Nick Jikomes 7:57
A lot of people will be on audio only Okay. Sorry.
Robert Stickgold 8:02
So the most obvious changes that we see are in the electrical activity of the brain, which is basically recording of all the nerve cells as a as an aggregate and their firing rates in their activity. And what we see is that as we've gotten into deeper and deeper stages of sleep of non REM sleep, the firing rates of these brain cells become synchronized and slower. So that early and sleep, you start to see these oscillations in the eg the recording of the brain activity, going at about six to eight bump cycles per second. And then as we go into deeper sleep, we see those waves getting bigger and slower, slowing down to just one or two waves perspective, but a much higher magnitude. And the higher magnitude means that more of the cells of their brain are in this pattern of firing together. And that takes us into our deepest sleep, which we also call slow wave sleep, because of these large slow waves. And then the process reverses. And the sleep becomes lighter, becomes easier to wake us up, the oscillations become faster, and then we transition into REM sleep. And in REM sleep, the eg is completely desynchronize you don't see much have any wave activity at all. In fact, it looks very much like it does during wake. And of course your eyes start hopping back and forth at the same time. And so you have some ramps here, and then you go back down through the stages of non REM sleep and you come back up for another REM period. And this goes on all night long. Now that's the eg but we're seeing other things change too. If you look at the major neuromodulators in the brain, you know these guys, it's serotonin it's dopamine, it's it's epinephrine, norepinephrine acid, you're calling these modulators of brain activity they're shifting to. So levels of norepinephrine, release and, and serotonin release. And of course, we know serotonin from the SSRIs, which enhancer activity. A lot of antidepressants work to enhance norepinephrine activity, when you go into REM sleep, their release is completely shut off. It just the brain is switching to a different program. It's like you're coming out of Excel and going into Word, I don't know quite how to describe it. But the hallway that neurons in the brain are talking to each other, is globally changed. And when we look at the memory processing, we see that in slow wave sleep, and you've got those large, synchronous firing of huge proportions of the neurons in the brain, when that's happening, the brain is really good at at stabilizing, and what we call consolidating facts that we've learned during the day. So those French verbs, that's when my knowledge of the French verbs gets locked into my brain reliably. But if I've learned other things like how to play some puzzle game that I haven't quite mastered, yet, whether I'm still trying to figure out, how do all these pieces that I learned during the day fit together. That's what gets processed during REM sleep. REM sleep is about creative processing. and creative just means you know, taking information and finding new ways that it fits together. It does creative processing, that does emotional processing. Because emotional processing isn't just about remembering French verbs. It's about understanding all of the implications of some evoke emotional event for me and for my life. And so this basic division between non room and room seems to be non rooms good for like straightforward, strengthening, consolidating, maintaining stabilizing memories about facts, or even how to do things like that piano playing. And REM sleep, which, by the way, involves much, much later in the animal world. REM sleep is about how things fit together. And that's a very different process. In fact, you know, in your own life, that there are times, you know, when you're, when you're tired in the evening, you might not want to be memorizing verbs, you might want to be just trying to think more globally about things because your brain states are shifted.
Nick Jikomes 12:55
So we have these different brain states, within sleep, you've got non REM sleep, you've got REM sleep, they have different patterns of brain activity, and they have different amounts of neurotransmitters that are active at those times. So to use your classroom analogy, it's like two completely different classrooms that you go into. And you're really good at learning one type of thing in one classroom, you're much better at learning another type of thing in a different classroom. It also strikes me that it's important, you know, important for learning is not only remembering things that are useful, but forgetting things that are not useful. So what role do these processes play in helping us forget or get rid of the things that are not important?
Robert Stickgold 13:36
That's a wonderful question. There's still there's still disagreement or confusion about this because of its complexity. We know, for example, that if you have people looking at slides, slides that have some background scene, with an emotional central object on it, maybe a car crash, or, or dead cat in the middle of the street. Over the day, if you look at these pictures in the morning, over the day, you tend to forget all of that detail, you forget the backgrounds, you forget the central features central objects, you forget about your ability to recognize them again drops by about 10 to 15% across the day, across a native sleep. Interestingly, you hold on to those central emotional objects, and forget the background. Now, whether this is an active process, whether their brain is sort of saying okay, I want to forget this, and then do something to cause that memory to be forgotten, or whether the brain is just saying, okay, I care about this central object. I'm going to preserve it. I don't care about The other parts and so they just get forgotten by sort of passive process. We're not sure whether that forgetting is active or passive. But but a lot of forgetting occurs across the night. My pipe brother once told me, he knew why he slept, he said, I seem to forget where I parked yesterday. So at the end of my day, today, when I come out of work, I'm not confused about where I parked, I forgotten yesterday's parking spot. And I remember where I parked today. So whether that forgetting is just the exigencies of time and our memory story get forgotten, and they get forgotten across sleep as well. Or whether sleep is actually picking out memories and seeing you out. We don't know how to tell that we certainly don't ever see faster forgetting across the night, than we do across just a period of wakefulness.
Nick Jikomes 16:00
So we don't know yet if there's active and selective forgetting, what about active and selective remembering. So you mentioned that certain stages of sleep are good for consolidating certain forms of learning. Can you talk a little bit about the phenomenon of replay and the idea that some of the actions or things that we're learning are actually replayed at night to help consolidate?
Robert Stickgold 16:23
Yes, but let me first answer what you started to go through us, which was selective consolidation. We know that, remember, I talked to you about playing the piano, we actually have a task where we just teach people to type a nasty little five digit sequence for 1324 on their keyboard, and that's a task in which they improve actually, over in native sleep, they're better, they're faster and more accurate in the morning than they were the night before. And if we tell them before they go to bed, by the way, we're done with that task, you're never going to see again, tomorrow morning, we're going to teach you some French verbs. They don't get better on the finger tapping overnight. So the brain decides, calculates, uses some algorithms to determine which memories are going to get processed during sleep and which aren't. And the basic rule in a nutshell is, the brain thinks I'm going to need it again. It's going to work on it, the brain thinks I'm done with it, it could care if I couldn't care less, it can care less. So So there is this selectivity. And again, before we get to your fascinating, RepRap question, you can watch this process of selection as you're falling asleep. Tell me what you think about it. You're lying there in bed, trying to fall asleep.
Nick Jikomes 17:58
I'm usually thinking about the things that I need to do tomorrow, right,
Robert Stickgold 18:03
and the things that didn't get finished today. And the things that that happened today that you don't fully understand that you haven't fully processed, but not everything. If you called, if you sent an email to someone during the day, when you're lying in bed, you don't say, Oh, I forgotten his email address, what was his email address? You don't worry about that. As you're falling asleep, it's things that are unfinished, it's things that need more work that are going through your mind. And they're probably going through your mind because that state, and if you pay attention, it's a weird little state that you're in. It's actually queuing up those topics. For later processing during the night. It is selecting, if you will, what you're going to dream about, and what aside from German, but your brain is going to be working on outside of your awareness entirely. So if if you're going to be tested on that finger tapping task in the morning, you're going to say, Oh, geez, I wonder if I'll still you know, and your brain will work on it. But it's also not it's also the conversation you had with someone where they said so I hear you're going to try to get this up onto YouTube tonight had good luck. And it's like, was he saying good luck in that sort of do well sound the community mean by that? Right? You get these Ed SCOTUS leftover comments from people, these leftover things you saw you watch the news and there was a story that bothered you know, where you didn't get to think of at the time it comes back as you're falling asleep. So that's a time that your brain is sifting through the day to decide what to work on later at night. And the way it works on it in many cases, is to bring the memory backup. This is the replay you were talking About with that finger tapping task, it can be shown to various degrees depending on whether you're working in animals or humans, or an end the exact task you're doing that the brain replays the actual experience. So if you run a mouse through a maze, before they go to bed, the the part of the brain called the hippocampus actually comes up with identify specific cells that reflect the position of the mouse in the maze. And if you record with electrodes in the brain of this mouse, you can just watch the electrodes on your computer screen the electrical activity, and know where the mouse is in the maze. Oh, it's halfway around, like it's halfway around, okay, that cell stopped firing this though sales started praying, he's moved around to hear that mass falls asleep. And they're running the race again, in their brain, you can see those brain cells firing in that same pattern again.
Nick Jikomes 21:08
And so yeah, if you disrupt that process, do you prevent the memory from forming,
Robert Stickgold 21:14
it's hasn't been done at that level in the mouse, because usually with those rodent studies, to get the effect strongly enough that you can see if they've been run through it many times, and they've basically learned it. But we know from human studies, that you can reactivate memories by cueing them while they're asleep. I mentioned at the start that some sensory information still gets into the brain, even though we're asleep. And people at the University of Northwestern University of Chicago did this wonderful study, where they had people sitting at a computer, they had a computer screen, and they pop different items up on the screen in different locations, and told people that they had to memorize the location of each of the objects, a little bit like that old game of concentration, where you had to remember where the different cards were. And the brilliance of the experiment is that each object which they would see multiple times, and always in the same location, came with a sound. So cat appears up here, and they hear me now. And a horn appears down here, and they hear Hong Kong and a hammer appears over here, and they hear Bang, bang. And they're learning the locations of the objects. And then when they're asleep, the researchers play half the sounds to them. They reactivate the memories by playing the sounds again. And when they do that, after sleeping, and they test the subjects again, they are better on placing the items whose sounds they had heard while they slept. Then the other half of the objects whose sounds they had in third. So must be that when you play that sound of the horn, the brain is hearing that sound remembering that it was connected to the picture of the car, and the car was down here. And so that kind of replay. And now they have some sophisticated brain imaging techniques that actually say, yes, the brain activity associated with that item in that location was in fact being reactivated when we played that sound to them in their sleep, that that reactivation seems to be key to the brain processes that strengthen that memory?
Nick Jikomes 23:58
And what about dreaming? What stage of sleep is dreaming normally taking place in? And do we know if the content of dreams just just from my own experience? Sometimes it feels like the content of dreams contains things that are important and that I'm potentially trying to remember my brain is trying to consolidate. And sometimes it seems like the content is completely supperclub has nothing to do with it. So are is the content of dreams. Functionally important in any way? Is it epi phenomenal? Is it just all of the is it just an after effect of what else is going on in the brain?
Robert Stickgold 24:35
Well, two months ago in January, I published a book with Norton titled brain brains stream that discusses exactly this question. So to take your questions in order we probably dream we definitely do in all stages of sleep in that night light non REM in that deep slow wave portion of the night. And especially during REM. And especially in the first few minutes of sleep, what we call the hypnagogic. Sleep onset period, the very latest stage of, of non REM sleep, in REM sleep. And in that light sleep onset period, if we wake someone up about 80% of the time, though, we call it dream content. But for deeper stages of non REM sleep, it's still a 50 60%. So we're probably in fact dreaming all night long, that the content of the dreams and probably the function of the dreams very subtly. So to live to the end, and then work back. We've come up with a model for the function of June that we call Next up, which stands for network expiration to understand possibilities. And the argument is that during most of the night, when we're doing that kind of memory processing that I talked about earlier, this is happening outside of conscious awareness outside of our dreams. And it's all about convergent processes trying to answer questions that we understand, okay, how did I type that sequence? What was that for? form? How do I understand all these different things I learned about this game? How do I put them together into some general rules? When we train, we're doing divergent rather than convergent processing? We're not looking for answers to questions. We're doing what we refer to as exploring the solution space. So say you got a job offer? And you know, there's no simple answer, How many times should I take the job or not? And in fact, it's not even clear what factors are important in that decision? Is it just about salary is about prestige, chance for improvement, chance for advancement? Or is it about how my spouse will respond to having to move how my kids would do with a change in schools, what my friends will think of me taking this new job, but my parents will think of my take me this new job, all of these, all of these aspects are part of that decision. And we don't know how to weigh them. And we don't you know, you can make that sheet of paper, right? Take the job, don't take the job, pluses minuses and write all these things down. And that never helps. Instead, you sleep on it. Right? And you wake up in the morning, and you say, I can't take that job, it's just wrong for me. And we're just see if you watch that person now, when they're dreaming, they're dreaming about a piece of it. They're exploring memories, often weakly related, just memories that might be relevant to the decision making. So they might, you know, they're trying to decide whether to take this job, they're looking at their scientists, typically how many square feet of lab space, they're going to be provided their teacher, they're looking at how many classes and how large the classes are going to be. But what do they dream about their dream about a fight they had with their father, 20 years earlier.
A fight in which the father was complaining about something the son was doing, or you don't even know, in the dream, it's just there is your father. And he's saying, why don't you ever do what your mother says, and you don't even know what he's talking. And you don't know what's going on in the dream, and it doesn't seem particularly relevant. But your brain when you dream is sort of like a venture capitalist. It's not looking for every investment to pay off big. It's looking for a future payoff big and it's happy if others don't. So maybe, you know, maybe you come out of that thinking, and not even realize that you think that my fault, I should talk to my father, before I make this decision. or, excuse me, screw it. I don't care what my father thinks about this. And you might not even remember the dream. You might not even know why you're thinking about him in relationship to the job. But your brain has identified this older memory which in some ways is connected to this decision that you're trying to make to your current concern. And in this weight case, it's connected because your father and you've had a lot of discussions about what you should and shouldn't do. Not so much with your whole life. But maybe you know, it's $5 at the amusement park, but it's you It seems, Bob, that you care a lot about what your father thinks about your decisions. Let's run that bind, see how that plays out. So the only way the brain has to determine whether this sort of newly remember Association, but your father, my father, and decision making, is to literally play it out in a story. That's what we do when we're awake. If you're awake, and someone says, hey, there's a good movie tonight, you want to go see it. He said, You say, wow, I got a lot of work to get done. And then you have this little movie that runs through your brain. You imagine going to the movie, and then coming back and trying to do the work afterwards, and being too tired to do it. And that's not good. And you imagine going to the movie, and just not even trying to do the work because it doesn't really need to be done. That doesn't feel good. And then you decide, well, I can get that work done in time before I go to the movie. And then you say, yeah, and you say, Yeah, because you've played out the scenarios. And you found one that feels good. Okay, when you play out these stories in your mind, there's always an emotional reaction to it. I like that, oh, that's not good. I don't like that, Oh, is this gonna work that makes me happy. And that's part of your decision making. That's how you decide whether to go that movie. I mean, it happens like that. And you say, Now, I really can't, I've got to break out. But scenario played out in your mind, the emotional response came to it. You looked at the emotional response and said, Nope, can't do it. Your brain is doing the same thing at night, with very specific differences. You remember I said, that release of norepinephrine is shut off when you're in REM sleep. When that happens, your brain's ability to find associations shifts from obvious focal associations, like, Okay, this job, I had this other job teaching in classrooms, okay, I've taught in big classrooms and smart classrooms, it shifts from these tight associations to much more distant, weaker associations. And so it's a privilege time, when in fact, your brain can probably find associations that you'd never think of when you were awake. And it doesn't in a way that also biases the shut off of serotonin probably biases, your brain towards thinking that those associations are important. It has to do with a bias in terms of salience and significance in it looks like, it's possible that when that serotonin gets shut off, your brain is more likely to say, Oh, this is important, I should strengthen this association. And you need that when you're dreaming, because half of the dreams you have they're so wacky if you were functioning normally, you'd say, Well, this is a totally useless dream, why would I want to strengthen that association and so so the brain is in a state where it's
it's finding weaker associations, is biased towards finding significance in the brain, by the way, in REM sleep is also shut off from actually remembering the memories from the day. So if you dream about something that happened today, tonight, you don't dream what happened, you don't actually remember what happened in the dream. You wake up in the morning, and you say, Oh, that must have been about that podcast recording this bout. But in your dream, you don't replay that podcast, because literally the connections between the hippocampus where those recent memories are being stored, and the rest of the brain where they can be perceived, that communication is shut off. So it looks like the brain is throwing you into a therapy session. It's saying don't don't tell me about what this guy you were dating. Know how he was a jerk and how he he left you and you don't tell tell me what, how that feels to you. Tell me what it reminds you of? Tell me what you think it means, you know, widen your associative networks and say, No, have you ever felt this way before. So it's almost like that except in spades. It's just doing it in And in a more powerful way, and in a more reliable way, I mean, you're guaranteed two hours a night, when your brain will do this kind of dreaming Association exploration of associations to find the ones that are passively useful.
Nick Jikomes 35:20
So it sounds like dreaming, especially during REM sleep has a lot to do with contextual processing, trying to figure out things that have a lot of contextual complexity associated with them. And you mentioned that we were, the brain is sort of exploring the space of possibilities more than so perhaps the bizarre, weird content of dreams is a consequence of that, that your brain is sort of trying out different possibilities in relation to different memories that may or may not be related to whatever is trying to be worked out.
Robert Stickgold 35:56
Absolutely. And, and again, there's room and there's not room and it's kind of fun, because for the last 20 or 30 years now, it's been clear that if you wake people up from REM sleep, and you ask them for a dream report, and then you ask them, so why do you think you've jumped that are not the whole dream, but like, you just had a dream about flying saucers? Or do you think you jumped about flying saucers? So this person is awakened from REM sleep? They're likely to answer they might answer Oh, I just have a love affair with pizza. I just love pizza so much, you know, Peters Peters in my mind all the time and has been forever. Sorry, I think I was really just dreaming about pizza. Okay, now you wake someone else from non REM sleep. And they tell you they were dreaming about flying saucers. And you asked them, Why do you think that was? And the answer is, oh, I had pizza last night. So when you wake someone from non REM, and they find they try to find the waking correlates or causes of their dream elements. They tend to give you recent events. Oh, I had pizza for dinner last night. Oh, I wish my son wanted to play frisbee and I couldn't find the Frisbee. Oh, I don't know we had pancakes for breakfast. Maybe the pancakes reminded me of flying saucers, but it'll be recent events. And you wake the people from REM sleep, they tend to be older memories. And they tend to be what we call semantic memories. Things like I just love pizza. Or I was never any good at flying frisbees, not specific events. But But general categories of knowledge. And that fits with the idea, right that we know from our memory experiments that non REM sleep is really good for stabilizing strengthening memories of actual things that you learned during the day, the French verbs as my example. And REM sleep is more about figuring out those puzzles that you couldn't figure out how to solve where you're trying to put things together in a more general way. And so that dreaming probably has this different overall function of trying to do exploration without coming to a conclusion about the right answers, just exploring the possibilities, but still locked by the physiology to be more remote and semantic during REM sleep and more recent and episodic events during during non REM sleep.
Nick Jikomes 39:04
Do we know what happens? If you selectively deprive someone of one type of sleep or another? For example, are there drugs that inhibit REM sleep or non REM sleep? And what sort of impact might that have?
Robert Stickgold 39:19
Um, well, if you look at specific memory tests, in the laboratory, you see exactly what you expect. If you give drugs to enhance REM sleep, then those puzzle solving or emotional memories, show more enhancement than they would otherwise show in proportion to the increasing amount of REM sleep. And if you're we're learning those French verbs, drugs or other methods that increase that deep slow wave sleep will enhance your memory for those those words. perished. If you're talking more globally, it's really hard to do, you can try to deprive people of REM sleep, and you can do it for a night or two, not easily with with drugs at all. But you can do it by literally waking them up. Every time they're eg in the case that they're starting to go into REM sleep. And whereas Normally, you don't hit your first REM period until about 90 minutes into the night, an hour to 90 minutes into the night, if you selectively REM deprive someone for a couple of nights, they'll start going into REM sleep, as soon as they fall asleep, their brain will fight back. So it's really hard on any sort of continued period of time to block any sleep stages that the brain will fight back and bring them back in. So we don't know very early on. Back in the 50s, when they first discovered REM sleep. They tried to do these REM deprivation experiments and and had some suggestion that people started to act crazy like, but in retrospect, it's probably because after a couple of nights, they had to wake people up five minutes after they fell asleep, because they were going in through so fast. And they were really doing total sleep deprivation. And if you've ever pulled an all nighter, you know, you get a little crazy The next day, and it's interesting, you get a little depressed. And no one wants to be around you after you've only gotten an hour of sleep before. And you start to get a little bit wacky, you become emotionally labile. But that's probably more about total loss of sleep at any particular stage.
Nick Jikomes 41:52
What's the connection between Sleep Sleep deprivation and a common neuro psychiatric problem like depression, say I've heard previously, that a an acute treatment for major depression is actually acute sleep deprivation. So is that true? And what do we know about that? And how to things like SSRIs that you previously mentioned, affect sleep architecture.
Robert Stickgold 42:16
So you raised one of the best or worst questions, I can't decide. There are a number of studies over the years that have shown if you have someone who has very severe treatment resistant depression, they've been tried on a half dozen antidepressants, and nothing works. If you think depression, they get a amazing recovery, not a recovery, but a relief. From the depression. They say oh my god, I don't feel depressed anymore. And that feeling will remain as long as you keep them awake. And that's not very useful. Because after a couple of days being awake, you know, they're gonna fall asleep no matter what you try to do. And by that second day, or third day, they're not very functional in any other ways. But from a medical and scientific point of view, it's a fascinating question, why would sleep deprivation do that? And the totally consensual agreed upon answer is we don't have a clue. We've got no idea. In fact, some of the earlier studies showed that just doing REM deprivation was enough to cause this relief. And to add to the story, I mentioned that you usually don't go into REM and tone hour an hour and a half after you fall asleep. People with major depression go into REM earlier. And we don't know why that happens. And we don't know if it's functional. We don't know if it's the brain trying to cope with that depression somehow, which would sort of argue against the data that suggests that REM deprivation makes them feel better. But what we can say is that there's a really strong connection between sleep and depression. anti depressants have varying effects. Most of them most of the SSRIs suppress REM sleep, they can also suppress that deepest slow wave sleep of the night. And sort of leave you mostly with sort of undifferentiated lighter and non REM sleep. Is that related to its beneficial effects? We don't know is that impairing its potential benefits. We don't know. But but they are because they're all acting on these same neuromodulators that I was telling you about earlier. They affect what sleep stages you end spending your time.
Nick Jikomes 45:03
I want to talk a little bit about sleep and health. Generally speaking, I think, going back to the very first question, everyone understands intuitively that sleep is very important for health. We've all had experiences of how wacky and dysfunctional you can be with just one night of sleep deprivation, or even just a few hours of sleep deprivation. But what? What would you say? And I know there's no one answer to this question. But what is the optimal amount of sleep that someone needs? And how does someone know if they're getting the right amount?
Robert Stickgold 45:39
wonderful questions. The optimal amount of sleep is a bad question. Because it's, I have to ask you, optimal amount of sleep for what if you're an adolescent 70% of your growth hormone is secreted during that deep slow wave sleep, and the deep slow wave sleep comes entirely in the first half of the night, you've got most of your REM in the second half mixed with that night or non REM, you have all of your slow wave sleep, mixed with a little bit of REM and low that lighter non REM in the first half of the night. So if you're just worried about growing taller, four hours of sleep a night is probably okay. If you want to deal with emotional issues, which tends to happen in REM sleep, most of that REM sleep comes too late in the night, you're probably wanting to get eight hours. On the other hand, we also know that if you put someone on four hours of sleep a night, for five nights, they start looking pre diabetic, their insulin regulation goes completely off. So are you talking about enough sleep, to remember those French verbs are to secrete growth hormone or to regulate your endocrine function. And by the way, everybody listening, I single night of sleep deprivation after getting a flu vaccine cuts in half the amount of antibody you produce to the vaccine. So if you're going to get the COVID vaccine, you want to get good sleep the night after especially. But other studies have shown again four hours of sleep a night for several nights before the vaccination severely reduces the amount of antibody you end up producing. So asking how much sleep is optimal is that is like asking how much vitamins is optimal. Or you don't want to say 50 milligrams, because that might be what you want for vitamin C, but that's 1000 times more than you want for vitamin K. And you don't want to say 10 micrograms, which may be all you need for vitamin K, because you need 1000 times more of vitamin C. So it's not a good question. I would turn step two, your second half of the question, how can you tell if you're getting enough sleep? Because what most everybody does, and this is both people on their own and scientist is sleep clinicians do is they trust in the brain's own homeostatic mechanism. Right? I tell people, if the thought of going to noon without a cup of coffee, or the thought of waking up in the morning, without an alarm clock, strike you as terribly bad ideas, then you're not getting enough sleep. If you're getting enough sleep, you should be able to wake up fine without your alarm clock. You shouldn't need caffeine until mid afternoon. So there's these signals that your brain and body give you you few wake up and you feel exhausted, well, you didn't get enough sleep. And it doesn't matter whether you got six hours or eight hours, or 10 hours. If you still need that coffee in the morning, if you still need that alarm clock, if you still feel half asleep when you wake up, you're not getting enough sleep.
Nick Jikomes 49:36
And is it possible So how much does it matter. When in the sleep cycle you wake up is that important if you wake up during REM versus non REM sleep?
Robert Stickgold 49:48
Probably not. So by morning time, you're not going to have deep sleep waking up from deep sleep is ugly. If you feel hungover you've woken up in the middle of the night. And have this experience of almost not knowing where you are, we've just been totally disoriented, that's waking up from that deep sleep. By morning is going to be light non REM, or rim. They're both easy to wake up from and I think you feel equally good from both. There have been some suggestions that you will feel more alert if you wake up from REM sleep. And so there are a bunch of apps you can get out that try to figure out when you're in REM sleep, and wake you up while you're in REM sleep. And if you're a non REM sleep, you know that you sleep longer until you go into REM. I haven't seen any evidence that they're they're very effective in improving your, your condition in the morning. And certainly, in regards to any of the deep functions of sleep, whether it's immune or endocrine memory, or emotional, which that you wake up from doesn't matter at all.
Nick Jikomes 51:00
That's exactly what I was gonna ask you Next is all of these sleep apps that claim to track exactly what stage you're in? And everything? How How well are those working? Do they do a reasonably good job at differentiating between how much REM and non REM you're getting? Or is it really just marketing at this point,
Robert Stickgold 51:18
there seem to be some devices, some wearable devices coming on the market, low end products that can actually do a decent job of telling them run from that run. That's only been in the last few years, and the data is still coming in from them. I think the main advantage of wearing Fitbit and such for from tracking your sleep, is to get a sense of how much sleep you're really getting. I mean, I talked to these people who say, how much sleep do you get? I asked them to say, Oh, I try to get eight hours a night? Uh huh. And how much did you get last night? They say, oh, last night was funny. I I have to get something done. I only got six. Oh, and then like before that? Well, that night, I went to bed fine. But I had to get up early because I had some work I had to do I maybe got seven hours. Oh, what am I the last time you actually got eight hours? And a partner say, Gee, I don't know. So. So the real value of those devices is to let you honestly see how much you're getting in there pretty good at that.
Nick Jikomes 52:25
Okay, and how much does sleep actually vary from person to person. So if you had a large population of adults, that were about the same age, and reasonably similar across any major demographic variables that might matter? How much do people vary in how much sleep that they naturally get every night, or should get out getting?
Robert Stickgold 52:45
If you let people sleep until they wake up. I don't have the numbers in front of me. But certainly much more than 90% will fall between six and 10 hours. And probably more than two thirds will fall between seven and eight and a half. That's really where people tend to fall. If you It's a hard experiment to do, because you have to let them sort of get over their sleep deprivation. So there's a wonderful study at NIH, where they had subjects come in for 21 nights in a row are not night days, they went to bed and they spent 15 hours I think in bed. And for the first several nights of this, they were sleeping 1213 even 14 hours. But after about two weeks, they were down on average to eight hours and 15 minutes. But you know, they're sort of recovering from all that earlier, sleep deprivation. And interestingly, when they get down to the eight hours and 15 minutes, they tell the researchers I've never felt this good in my life. It's the phenomenon of coming back from a vacation. And feeling like you're turbocharged that your your brain is functioning at twice its normal speed and everything is working so much better. I don't think that's about relaxing. I think that's about sleeping and catching up on your sleep. Finally.
Nick Jikomes 54:23
I'm glad that you brought that up the one of the things I wanted to ask about so So a couple things you said earlier struck me. What was your advice for people getting vaccinated. So if you're not getting enough sleep, it actually leads to problems in terms of your immune function. If you're not getting enough sleep, it leads to other problems for memory and other things. And you just mentioned going on vacation and getting recharged. I've actually had that experience. I've also had the experience of going on vacation and not feeling recharged. And I wonder how much of it has to do with things like taking a vacation where you're not getting enough sleep perhaps because you Going out and partying every night drinking alcohol. So what's the effect of alcohol on sleep architecture? And what do we know about the potential health consequences of drinking in the evening?
Robert Stickgold 55:15
There's almost nothing good to say about it. Alcohol will cause you to fall asleep faster. A lot of alcoholics use a lot of alcohol in the evening, because that period before sleep, when all your concerns, rush through your mind is so painful for them is so full of upsetting, depressing, worrying, thoughts that they just want to get through it. And in fact, whereas normally when you have those thoughts before sleep, your brain stays calm. Sometimes it gets agitated, and of course, then you have you have insomnia, right? You, you suddenly realize, Oh, my God, I had to submit that today, I didn't submit that what's going to happen, you know, you can feel the adrenaline rush and you say, Great can be 10 minutes before I can even consider falling asleep now. So a lot of people will use alcohol to get them more quickly through that pre sleep period, that sleep onset period. That might be seen as a good thing. But then it also causes a lot of awakening later in the night. A lot more awaking. So overall, they get enough sleep. And alcohol is also a REM suppressant. So insofar as the brain is trying through a process, all of that emotional material, it's not going to do as well. So yes, so a vacation where you're out partying late, so you get less sleep while you're drinking so you're getting less REM sleep, or even in an older age group, when you're going to you know, 10 countries in 14 days and getting up at six in the morning to get to the airport but eight to catch your flight to get you to your next destination by nine so you can have a whole day there. I suspect those are equally and relaxing or an unrelaxed in the sense of leaving you when you get back home with this sense of replenishment.
Nick Jikomes 57:31
Interesting the other drug I wanted to ask you about is caffeine. So how does caffeine affect sleep it obviously keeps you awake but if you're drinking a number of cups of coffee in the morning, is caffeine still able to affect your sleep the subsequent evening.
Robert Stickgold 57:49
The the general rule is you don't want caffeine after 4pm. assuming you're going to bed between 10 and 12 so that you want at least six to eight hours between your left caffeine and going to commit if you do that the caffeine is essentially out of your system and not a problem. Now having said that, I know people who have you know a double espresso with dinner and fall asleep in two minutes. When they go to bed. It varies dramatically from person to person, and probably with personal history. But you know, if you're getting in bed and can't fall asleep for a half hour and you're having caffeine in the afternoon or evening, late afternoon or evening, the first thing to do is cut that caffeine out.
Nick Jikomes 58:49
I see so if you're if you have a few hours in between your last cup and when you go to bed, it's probably fine because your body will have metabolized it but if you're drinking closer and having trouble sleeping that's an indication that
Robert Stickgold 59:02
right or if you're if you're drinking if you're taking caffeine at 4pm which is what we would call the last safe time and you can't fall asleep at night no I'd say what try a couple of nights we don't have any caffeine afternoon and see what happens and you might find Why are asleep easily at night but fall asleep at eight o'clock to fall asleep at nine o'clock to you know you're sort of between the two of distance so I'm sure there's you know, the some people will need that to get them through to the end of the day. And of course it becomes a vicious circle because they're losing sleep because they have caffeine in the evening. And then they're tired the next day so they need caffeine. So, you know doing a little bit of a purge would not be a bad way of self tie. gnosis
Nick Jikomes 1:00:02
interesting. So one of the things I did want to swing back to earlier, you mentioned briefly, that the amount of REM and non REM sleep, we get changes across development. And obviously, newborn babies sleep a lot more young children sleep a lot more than adults. But how does the amount and also the architecture of sleep, the ratio of REM to non REM change across development, and what what significance do we think that might have for learning at different stages of life?
Robert Stickgold 1:00:29
Well, infants have an adult, an adult will have something like 20%, REM sleep 20%, deep, slow wave sleep, and 60%, that lighter intermediate non REM sleep, infants can have up to 80% REM sleep, as sort of suggests that their brain, you know, if they're, that the main job of their brain at that point, is trying to figure out how things fit together. Not to memorize a sound they heard, but to understand, but sounds are all about. There's a lot of stage two, in a period where motor development is occurring. And indeed, we see increases in in stage two, when we do that finger tapping task, we see that the amount of improvement someone gets overnight depends on how much of that stage two, stage two sorry, light, non REM sleep they're getting. And as we get older, the amount of slow wave sleep we have starts to disappear. By the time you're 40 years old, half of that, or more is gone. And that seems to be related to the fact that you know, our memories start to go at that age to your ability to remember recent things starts to drop off. And Matt Walker out in Berkeley has shown that if you look at people like 50, to 70 years old, how well they do on these simple memory tasks is better predicted by how much slower they get them by how old they are. So so it might be that as you get older, your brain just doesn't memorize facts as well. And that might reflect a system breaking down. No, your brain can't produce this much slow wave sleep, or can be an evolved decision that once you get to a certain age, you're more concerned with being wise than being smart, you're more concerned with working and how the knowledge you already have, can be put to use and how it fits together, then I'm learning new things. And that that's, that's going to be a really hard question to try to sort out. But that's what we see, we see huge amounts of REM sleep in the first few years of life. And that pretty much drops down to normal levels. I think by somewhere between five and 10 years of age, and no slow wave changes the disappearance of slow wave sleep to actually start in your 30s. And just continue john, throughout the rest of your life.
Nick Jikomes 1:03:33
So it's it's not 100% clear whether or not the disappearance of slow wave sleep, say as you age is a consequence of not needing that slowly sleep as much because you already have things versus some sort of deterioration of the mechanisms that allow you to have it in other words, that it's this part of normal aging.
Robert Stickgold 1:03:53
Right? And, and it doesn't seem to happen late enough that if it was truly detrimental, evolution wouldn't have dealt with it. You know, you're still evolutionarily relevant through your 30s at least and and if this was impairing your survival, right, that you can't remember these things, these specific types of new information. Evolution could have taken care of that. It's very good at that. Let me just show you how good evolution is dealing with sleep problems. I will turn to the to the whales. You know, whales can't afford to sleep. Because if they do, they'll think and drown. They have to surface every few minutes. Take a breath. So what do these aquatic mammals do? And I'm talking whales, porpoises dolphins, all They have evolved to sleep on one side of their brain at a time. They let their left hemisphere go to sleep, and keep the right hemisphere awake. And then after a while, they let the right hemisphere go to sleep and the left hemisphere wakes up. So sleep is so critical for survival, that when an animal can't afford to sleep, it comes up with this kind of occludes. This kind of a workaround, which must have been phenomenally difficult to evolve. But it didn't evolve just one once. If you look at flack flock birds, like ducks, it turns out that at night, at a time, a flock of ducks will land on a pond. And so all bunched together and go to sleep. And the ducks on the outer edge of that flock will keep the half of their brain that gets input from the outward facing eye awake. And then after some period of time, they say, Excuse me, and they move into the middle of the flock and person other birds out to the edge. But again, they keep that situational awareness by evolving a mechanism to sleep half a brain at a time, depending on where they are in this in this flock of birds on the pond. So parallel evolution with the same goal. If the brain can evolve that mechanism, it could have evolved a mechanism that kept the slow wave sleep up.
Nick Jikomes 1:06:47
If you really needed it throughout,
Robert Stickgold 1:06:51
you're going to have to really need it in the sense that you really need to breed, I mean, a 1% selective advantage, you know, over 100,000 years is enough to guarantee that that 1% advantage will move through the entire population. So even a small advantage would be enough. So you know, from that sort of argument, you would say that it was okay, you know, that, excuse me that we evolved to sort of drop out some of that slow wave sleep. And parenthetically in that same line, even on a night by night basis, the amount of sleep we get in different stages depends on what kind of information we have to process. If we teach someone a task that is going to improve overnight, depending on how much REM sleep they get, they'll get more REM sleep at night. But if it's the French verbs, they'll get more of that deep slow wave sleep at night. So the brain on an night by night basis will adjust how much time you spend in what sleep stage, depending on where it calculates is optimal for the work that it has to get done.
Nick Jikomes 1:08:11
So you mentioned some animals that have unique sleep patterns based on the ecological reality that they face. I want to ask you about how old sleep is how evolutionarily old it is, when did when did it first evolve? Does every animal with the nervous system seem to go to sleep or is this something evolved later on
Robert Stickgold 1:08:35
every animal because they all have nervous systems, every animal sleeps. And in fact, the issue is not so much whether they sleep but how we measure sleep. So you know, you can't look at the eg of a sponge to try to figure out whether it's sleep. But you can notice that it has a quiet period every night that it's not only quiet, but it's less responsive to stimulation. And if you stimulate it and you keep it more alert more active, when it would normally be quiet. 24 hours later, it'll spend more time being quiet and it will be harder to get it moving again. So we can see these behavioral correlates of sleep. as far down as we can see, you can even go to the blue green algae you know, arguably the lowest single cellular animals or plants in that case, you know around and they have a 24 hour cycle. No they are more. Their photosynthetic system is cranked up during In the daytime when there's more light, and if you keep them in constant darkness, every time it's light outside every 24 hours, that cycle of increased activity of the photosynthetic system is seen. So so the circadian rhythm is certain, certainly seen across all living forms. Because, you know, because life evolved on a planet that has a 24 hour day, per night, and dark and warmer and darker. And so all organisms, organisms respond to that. And you know, that they not only have their own 24 hour cycle, but if you move them, you know, from Boston to California, they have jetlag, you know, and they slowly shift so that their, their 24 hour cycle adapts to the new location. And as early as we have, as early in evolution, as we have any way to get a hint of the possibility of sleep, that's what we see, we see sleep.
Nick Jikomes 1:11:09
And you mentioned earlier that sleep deprivation. And sleep itself can lead to changes in hormone levels. You mentioned growth hormone coming at certain stages of non REM sleep, I believe, you mentioned that sleep deprivation can affect things like your propensity to develop diabetes. And so I wanted to ask a more general question around sleep in the body? To what extent is sleep a brain and central nervous system phenomenon? And to what extent is sleep actually a phenomenon of the whole body and the rest of your physiology? Are there any interesting facts about human health and physiology in terms of things that are regulated by sleep?
Robert Stickgold 1:11:51
We're not scientists are very brainy people. So so we are often brain centered. And there is a there is a claim out there that sleep is of the brain and by the brain and for the brain. And that's clearly not true. So I was talking about circadian cycles. You see circadian cycles in the liver, in the intestine, in the lungs, in the pancreas, in almost all the Oregon systems, they have circadian rhythms of activity that are controlled from the brain, which sort of synchronizes everybody's circadian rhythm. But even in the absence of that, that brain input that nervous system input, all of our organs follow circadian rhythms, and their circadian rhythms have to do with left activity at one time of the day, or the other. We know that, you know, people who have sleep apnea, which is a sleep disorder, where you tend to wake up frequently, because your your, your throat collapses, and you can't get there that those people are at increased risk for heart disease. So we've got the endocrine system, we've got the immune system, we've got the cardiovascular system, I would guess that at some level, all of our organ systems have developed dependencies, and sleep. And this gets into a fun discussion about functions of sleep. And I distinguish between core functions and what I call housekeeping functions. So if you go into any large office building, you will discover that the offices are cleaned at night. And that's not because people who clean offices can only function at night. It's because that's when the building's empty and it's convenient. could have been done anytime within a day or night. That's just the most convenient. And so that's when it's done. And of course, once it's done there, it's impossible to change it because everybody's used to that system, and it just won't change. And so I think things like growth hormone, I think the brand said, hey, look, this guy's lying down for eight hours. What a great time to try to do a little bit of growing. I mean, if we want to get the spine to grow a little bit, probably would work better if they were lying down. They actually are standing up and pounding around and walking all day long. The immune system, you know, the endocrine system, it's like, Okay, if everything sort of shut down, okay, but she's not going to eat any food for the next eight hours. It's a good time to Work on Andrew can function got this stable condition here. Let's do it now. So these I think of as housekeeping functions, but I suspect that you know, every organ system has developed some functions that it has decided work better when you're asleep. Not that they had to evolve that way, but they did. And so now that's that's how we do it.
Nick Jikomes 1:15:27
One of the things we mentioned earlier, too, is and that you touched on just now are the endo, endocrine effects of sleep and sleep deprivation. One thing that you often hear people say is that you're not supposed to eat, you know, within an hour or two before going to bed. So can you talk a little bit more about the relationship between sleep and metabolism, and perhaps touch on like some of the do's and don'ts with respect to things like eating right before you go to sleep?
Robert Stickgold 1:15:58
Oh, I'm, I'm stern. I always eat before. My wife always says, Bob, you really don't want to be eating that. I know. I know. I'm just gonna have one more scoop. One more scoop. I don't know that literature. I don't know that that story. Um, I could understand why you don't want to go to bed with a very full stomach. It would certainly be uncomfortable. But I don't know anything about how food is metabolized. oversleep. It's slowed down, is it sped up? I just don't know.
Nick Jikomes 1:16:37
How did you first get into sleep research? Why did you choose to go into this area?
Robert Stickgold 1:16:44
Actually, because it's a memory piece and the dreaming piece. I've always been fascinated by James, I think for the same reason that everybody else is that they're just on the one hand so crazy. And at the on the other hand, sometimes so incredible power. Sources fascinated by them. And as a as a cognitive neuroscientist. No, we just didn't have a handle on it. So I was really curious about that. And I think that's what actually brought me in, I started out working with Alan Hopson who had published some major theoretical papers about dreaming back in the 70s. And actually, I got a PhD in biochemistry, I did my doctoral research on DNA replication bacteria. So I just completely moved my field of study. And I know I was fascinated by the memory question, but I don't know that I was thinking about it in relationship to sleep. So I might say that it was the dream issue. That really hooked me into it.
Nick Jikomes 1:17:59
And you mentioned earlier that REM sleep have evolved later in evolutionary time. So does that mean that that dreaming is also an evolutionarily newer phenomenon, and that only certain types of animals are likely to have sort of the classic bizarre, highly emotional dream states?
Robert Stickgold 1:18:19
Well, yeah, so So first of all, remember, we do dream through much of non REM sleep. So that would be available so mammals, and birds are pretty much it for color cut REM sleep. Lower animals and others, besides birds on that branch, don't seem to have REM sleep, although in the last few years, there's been talk of REM like sleep in other animals. Whether other animals dream, really is a subset of the question are other animals conscious? Right. I mean, this is, this is something we could spend the next three hours talking about if you want, but I often disconcert my students by telling them that there's never been an experiment conducted that demonstrated that humans are conscious. We have no way of showing that humans or any other species are conscious. Now, since you know that you're conscious and I know that I'm conscious to internal instead inspection. If we start saying, okay, humans are conscious, then we can say okay, well, this person is in a coma. They're not conscious, this person is asleep. If they're conscious, it's a very altered form of consciousness. And this person took these drugs and it knocked them up completely their unconscious now, but that all involves starting from the assumption that we're conscious. So you're not Get the dog, who shows every sign in the world have been conscious. And who shows every sign of dreaming with their feet running, and then whimpering while they're asleep. And we know actually during REM sleep, so they look like they're dreaming. And I think it's fair to sleep that if they're conscious say that if they're conscious when they're awake, they're dreaming. But that's no, you have to you have to make that assumption first. And then who all dreams. I wouldn't be surprised if, if all mammals end up turning up to dream, although the dreaming will be obviously very different as you go lower. In in the, in the orders. I mean, I doubt that rats have anxiety dreams about how they're going to perform on the maze tomorrow. And they certainly don't worry about what their mother would have thought about them being in this experiment, right? In fact, I guess you just have to say that you'd have to look at what a given species is dealing with in their world what their concerns would be, you know, and it's from that, that you wouldn't be able to guess what they dream about. So probably, you know, dogs probably dream about being predated. And cats probably dream about being predators. Because those are the those are the concerns of their day, where it might be worth identifying associated memories that could help them perform their tasks better the next day.
Nick Jikomes 1:21:52
On the subject of dreaming, I did want to ask you about unusual dream or sleep states, the one that really comes to mind that I don't think I've ever really experienced myself. But some people claim that this happens to them sometimes, is the phenomenon of lucid dreaming, where you're asleep, you're not moving, you are in a dream state, you're definitely not awake. But you're simultaneously aware that you are asleep and dreaming. Is this a genuine phenomenon? And do we know anything about how this particular phenomenon arises?
Robert Stickgold 1:22:27
It's a real thing. It's been demonstrated over and over in scientific experiments, despite the fact that many scientists who haven't experienced it themselves, insisted couldn't possibly exist. But it's very well documented. And, again, Ken powers lab at Northwestern University, has now come up with protocols where they can pretty much take students off the street, and get about a third of them to have a lucid dream in a single night. So whereas before, it was really thought maybe, you know, maybe only 5%, or 2% of the population can do this on a regular basis. It might be something that's trainable. That's what's definitely something that's trainable.
Nick Jikomes 1:23:21
How do they do that training?
Robert Stickgold 1:23:26
it largely involves learning to pay attention to cues. So the older methods, I haven't really read Ken pallars new technique carefully. And I'm not sure that he's published the whole technique. But what, what was classically dynasty they would say to you, okay, I want you to ask yourself, every 10 minutes all day long, whether you're asleep. And don't just say, am I asleep? No, obviously not. Stop for a moment and say, How do I know I'm not asleep? Okay. And if you do that over and over all day long, for a half dozen days, it becomes a concern. You start asking the question, and your dream. And that's what does it you know, you suddenly say, okay, Is this a dream? Well, actually, where am I?
How did I get here? What was I doing half an hour ago? I'm looking at a book, can I actually read the book?
So you learn to ask questions. First, you learn to question whether you're asleep to ask the question. And then if you do, it's not that hard to figure out that you're dreaming. In fact, that's the funny thing, right? You wake up in the morning and you say, like the Hulk Right not have known that I was tuning. I mean, I was in a parish with my father, and my father has been dead for 20 years. I was flying. I mean, these are not hard ones to figure out that I was, must have been dreaming. And, you know, I was in my bedroom at home, and the next moment I was at the beach. I mean, I obviously was dreaming. So it's not so much the difficulty of figuring it out, it's the difficulty of recognizing to ask the question. And so they'll do that by having you ask the question a lot during the day, you can also get these goggles, which will flash a green light in your eyes every once in a while while you're sleeping. And you'll start to see green flashes in your dream and that becomes awake, green flashes, I must be dreaming. So that that's what that that's how people are taught to be lucid dreamers. And then the big game is to try to stay in that state. Because lucid dreaming is a knife edge. It's a knife edge between waking up and falling back into non lucid dreaming. And it's a tricky edge to walk because if you get too excited by it, you'll wake yourself up. And if you say okay, don't get too excited, you're you're likely to slide back into non lucid to forget that you're dreaming. And so, you know, people who are lucid dreamers, become skilled that are holding their knife edge, what's actually happening, while the prefrontal cortex, which is involved in executive control, logical decision making serves the sort of the control center of center for cognitive activity. The prefrontal cortex, which is normally shut right down during REM sleep, starts to come back online. And so becomes a classic parasomnia where you're sort of part of your brain is awake, while the rest of your brain is asleep. And we see that with lucid dreaming, we see that with sleep paralysis. Sleep Paralysis is when you wake up in the morning, and you were literally paralyzed and hallucinating. And that's because when you are in REM sleep, your body is paralyzed, otherwise, you would act out your dreams in REM sleep. So you're paralyzed. And your brain, you know, now the frontal cortex is woken up completely and you're awake and you know you're lying in bed in your bedroom. But lower brainstem regions that are controlling that paralysis, haven't shut off yet. And in fact, the hallucinatory process is still going on. So you get these hallucinations with your eyes open, which means they're hallucinations that happen in your bedroom. they very often hear about seeing people or strangers or monsters come into your bedroom. In fact, there is very good data that suggests that are the alien abduction.
People are in fact, misinterpreting sleep paralysis. Because alien abductions always come with an awakening from sleep.
usually involve people been reporting that they've been paralyzed by these aliens. And they see these strange creatures in their, in their bedroom. Back in the dark ages, they saw the same things but they thought that they were that they thought that they were devils or angels. So the phenomenon is is robust across at least the last five or 600 years, but the interpretation of it is completely socially determined, but again, part of the brain is awake, or the rest of the brain is asleep. A parasomnia similar to sleep walking or sleep talking, again, when you're sleepwalking your brains awake enough that you can make it to the stairs and down the stairs and into the kitchen without waking up. But But, you know, huge parts of your brain remain asleep.
Nick Jikomes 1:29:36
I don't know the statistics, but I do know it's become more common over time for people to use pharmaceuticals to assist them in getting sleep. So sleeping pills, things like Ambien. Those clearly help people get to sleep and keep them knocked out. But do they differ at all? It's not true.
Robert Stickgold 1:29:58
Well, at least with the SF So our eyes, you get more awakenings. But you're talking there with the standard hypnotics. And being such helps you fall asleep faster, not all that much faster, but some faster, helps you stay asleep. And the cost is a real decrease in the amount of REM sleep you get. And often a decrease in the amount of slow wave sleep, deep sleep that you're getting. So from the point of view of a memory researcher, it's a disaster. Because those are the times when you're doing most of your memory processing. And there's been some studies with with Ambien and the like, that showed that sleep dependent memory consolidation can be impaired. And again, it's a funny story, because if you're talking about that finger tapping task, the amount of improvement you show depends on how much light non REM sleep you get late in the night. So if you take Ambien that suppresses REM sleep, you get more of that, like non REM sleep to make up for it. And you actually show more improvement and the finger tapping task. But if it was a remedy dependent task, you would be in deep trouble. And even more trouble is the fact that these drugs effectively clamp you into a sleep architecture said you can't your brain no longer has the ability to shift the amount of different sleep stages to match its needs. So I always push for cognitive behavioral approaches to to sleep problems, if at all possible.
Nick Jikomes 1:31:49
Interesting. That's good advice. What? What do you think are some of the most interesting areas of sleep research that are on the horizon over the next couple of years that we'll start to learn more about?
Robert Stickgold 1:32:04
You know, the worst one. So, course beer. So one of the big areas of research now are ways to manipulate three, non pharmacological and this can involve electrodes put on the scalp that inject very small amounts of current that might be delivered at those slow speeds of the slow waves of deep sleep. And that can increase the amount of slow wave sleep you get, that can increase your performance, and the French firms across the net, because that depends on how much flow we've seen, you get. Adam Horowitz of MIT at the Media Lab, has been working with me and has developed a method of doing what he calls targeted dream incubation, where he can manipulate the content of your dreams in that sleep onset period. And you remember I said, they get more than 80% reports of dream content, if they wake people up. And he's interested in using that to foster creativity. But chorus beer is using it too. And for the Superbowl, this year corps ran this advertisement where they tried to get people to watch a video about course beer and not in the streams and flowing water lakes and beautiful scenery, together with music, and then have people play that music again, while they slept. I would argue to try to get people to become trained to buy Coors beer. So a lot of Kafka esque work being done there. And there are a couple of other companies that are looking at this targeted dream incubation as ways to manipulate market share. And at the moment, it's sort of benign in the sense that you know, you have to agree to do it. You have to watch the video, you have to keep the tape running on night. But 30 million Americans have a Lexus in their bedroom now.
Nick Jikomes 1:34:39
This is literally like the movie inception.
Robert Stickgold 1:34:42
Little bit like that. I mean, here's a funny question. If you are someone who has an Alexa in your bedroom, what is it doing while you're asleep? And the answer is you have no idea and that could be scary. So No, there's there's a little chance for abuse there of sleep manipulation of dream manipulation. And a lot of potential for good Adams talking about working, he is starting to work with some clinical psychiatrist to see if it can be used with people with PTSD, to help them process those memories by queuing them up with three bouncer for later in that process. And the same thing for treating anxiety, nightmares. So it's potentially a valuable tool, as are all of these things. And as was most really valuable to secure a potential risk of misuse. So that's that's some of the, at least some of the sexiest work going on these attempts to manipulate sleep stages and June content. What else is going on? I think there's more work going on looking at these non brain based consequences of sleep, to try to help figure out how widely the body depends on on that sleep.
Nick Jikomes 1:36:16
And what about So you mentioned PTSD, one of the things I was curious about are neuropsychiatric conditions like PTSD, where one of the symptoms is highly disturbing, highly emotional dreams and nightmares that people might have. So we've mentioned a lot about the benefits of REM sleep with respect to certain types of memory processing, are there any cases like PTSD, where it might actually be beneficial to suppress either REM sleep or another stage of sleep in order to prevent bad dreams essentially happening?
Robert Stickgold 1:36:53
I think the exact opposite is true. I've actually written a couple of papers on this. I think PTSD is a sleep disorder. I think it's a breakdown of all those processes, which almost entirely happens in REM sleep. That we've, we've seen, we've seen that in REM sleep, the brain processes emotional memories, it can help the brain hold on to the core of a memory. But forget all the peripheral details, something that doesn't happen in PTSD patients, it can help the brain integrate new information, emotional information with existing networks of older memories, something that fails in PTSD might be that the kind of so PTSD is basically a memory disorder, I mean, you have a traumatic event and forms a memory. And it's the impact of that memory on you, it's the failure of you to get past it get past the memory. And what it means to get past the memory is to take it out of isolation and allow it to become integrated with all the other information you have about yourself, all your other memories, or your sense of self before that traumatic event. So that a you you become more relaxed in terms of who you are, relationship to trauma, but also more importantly, so that you understand going forward. How to be safe how to avoid a reenactment, you know, the future of PTSD dreams, is that people with PTSD report that they dream, the traumatic event over and over again, in their precise replication. And that's something that never happens in normal people, we actually have paper, no, less than, less than 2% of the time that people think they know the source of something in their dream. Is that dream element, does it work like even look like a replication of what happened during wake. And I think that that failure to metaphor lies, to, to abstract the the traumatic memory in the dream is a biological marker of the brain's failure to process if there are time, when it should be bringing up remote associates to this event, to think about other times you've been driving in a car, other times that you've been out with men where horrible things didn't happen, so you can sort of put that together with this traumatic event. Instead, you just keep replaying that trauma memory. That failure to let that kind of weak Association arise might be a significant contributor to the development of PTSD. And of course, we know as PTSD that your brain doesn't ever shut off the norepinephrine at night, the brain stays hyper alert, it knows or believes that it's not safe to relax. And so that norepinephrine stays even during REM sleep, which would block that ability of the brain to do that kind of work. And it's the same as, as if you're in therapy about this, you know, if you're in therapy about a trauma, you can't just keep telling your therapist for happening over and over again.
Nick Jikomes 1:40:44
I see I didn't know that about PTSD and norepinephrine. So you mentioned earlier in the discussion, that normally during REM sleep, norepinephrine basically shuts off or shuts away down. And for people who aren't familiar with neuro modulators, you can think of neuron norepinephrine, at least in a simplified way as the modulator that's very much responsible for paying attention and being alert and being focused on particular things right in front of you. And so is it fair to say that in PTSD, norepinephrine levels are staying up during REM, and more or less, you're in a state of hyper vigilance. And that's one of the physiological markers of it.
Robert Stickgold 1:41:24
Yeah. And so your brain can't go out and find when it's trying to construct the dream it's looking for. Okay, I've got this very important concern, this traumatic event. Let me look for associates to it. It keeps coming back to the trauma memory itself, rather than moving out through these, you know, these incredibly complex networks of associated memories to find other relevant information that might be helpful for learning to cope with and understand that trauma event.
Nick Jikomes 1:42:01
Are there any final thoughts about sleep that you want to leave people with before we tie this up?
Robert Stickgold 1:42:08
Yeah, it's an incredibly exciting time. First of all, to be a sleep researcher. 20 years ago, Alan Hopson, a noted sleep researcher, was quoted as saying that the only known function of sleep was to cure sleepiness. We literally had no idea at all, at the turn of the century, what sleep was for, which parents said, okay, it's sort of fascinating because all of our other major drugs know things like thirst, hunger, breathing, sex, all of these, we, you know, we do them because we feel a drive to do them, we feel we need to do them. I mean, it's a it's a, it's a conscious drive to do these things. But we knew their biological functions 1000 years ago. I mean, 1000 years ago, people understood you don't just eat to cure hunger. You eat because if you don't eat, you will be malnourished and your your body won't grow, and you won't have energy to do things. And we know that if you don't drink, you know, you'll become parched. And eventually, you know, you die of thirst. I mean, all of these things were well known 1000 years ago, and yet, you just 20 years ago, we had no agreed upon functions for sleep. So everything I've talked about, on your show, has been about the last 20 years worth of research, and I don't think we have a clue where it's going to go in the next 24 hours.
Nick Jikomes 1:43:50
Fascinating. Well, Professor stickle Thank you for taking the time. And it was it was a real pleasure talking to you. This was fascinating,
Robert Stickgold 1:43:58
and I enjoyed it as well. Take care
today. Well