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SPEAKER_3: Coming up on Star Talk Special Edition, it's all about sleep and we learn what it is, why we need it, how it impacts our perception of time, and how it is that we actually go crazy when our head hits the pillow as we drift off in slumber.
SPEAKER_3: Coming up on Star Talk, welcome to Star Talk, your place in the universe where science and pop culture collide.
SPEAKER_3: Star Talk begins right now.
SPEAKER_3: This is Star Talk, Neil deGrasse Tyson here, your personal astrophysicist.
SPEAKER_3: I got Chuck Nice, my co-host, Chuck.
SPEAKER_1: Hey, what's up Neil?
SPEAKER_3: All right, Gary O'Reilly.
SPEAKER_2: Hi Neil.
SPEAKER_3: All right, and this is a Star Talk special edition.
SPEAKER_3: All about sleep.
SPEAKER_3: Gary, what have you put together today?
SPEAKER_2: Well, sleep, Neil.
SPEAKER_2: We all do it.
SPEAKER_2: Some better than others, but why?
SPEAKER_2: And why have humans not evolved to do without it?
SPEAKER_3: I've been asking that my whole life.
SPEAKER_3: Here we go.
SPEAKER_3: What a waste of time this is.
SPEAKER_1: What a waste of time.
SPEAKER_2: Now we're gonna get somewhere, right?
SPEAKER_2: What are circadian rhythms and what are chronotypes?
SPEAKER_2: What actually defines a good night's sleep?
SPEAKER_2: What's it gonna be like sleeping in space?
SPEAKER_2: There is so much to understand.
SPEAKER_2: So let's go grab ourself an expert.
SPEAKER_2: Neil, if you would like to introduce our guest, and just because you sleep at night doesn't make you an expert, all right?
SPEAKER_2: We need a real expert.
SPEAKER_3: We got Dr.
SPEAKER_3: Matt Walker.
SPEAKER_3: Matt, welcome to Star Talk.
SPEAKER_4: Oh, it's a delight and a privilege.
SPEAKER_4: And I have to say, I'm a little intimidated by the intellectual horsepower that's on display across all three of you, but I am, it is such a privilege.
SPEAKER_4: You mean me.
SPEAKER_4: You mean me, Matt.
SPEAKER_4: Well, let me be agnostic in terms of where I'm...
SPEAKER_3: As soon as a professor at University of California, Berkeley, yes.
SPEAKER_4: I'm applying it.
SPEAKER_4: Oh no, don't be fooled by that, all the accent.
SPEAKER_4: Yeah, my, I think someone last week suggested that I'm, if I were any more stupid, you'd have to water me twice a week.
SPEAKER_4: So just be warned.
SPEAKER_4: That's hilarious.
SPEAKER_3: That's great.
SPEAKER_1: That's very funny.
SPEAKER_3: So you're a professor of neuroscience and psychology at University of California, Berkeley.
SPEAKER_3: That presumably means you have an official appointment in two departments, is that correct?
SPEAKER_4: I do indeed.
SPEAKER_3: And you're the founder and director of the Center for Human Sleep Science at UC Berkeley with center spelled C-E-N-T-R-E.
SPEAKER_3: Is that correct in my notes here?
SPEAKER_4: That is very correct.
SPEAKER_3: How evil of you.
SPEAKER_4: British nature, I know.
SPEAKER_1: Clearly somebody's not getting enough sleep to spell correctly.
SPEAKER_4: Oh, there are going to be so many instances of my faux pas that you'll be able to point out and say, this guy must be on for three hours of sleep based on his idiocy, so inbound.
SPEAKER_3: And author of the best seller, Why We Sleep, Unlocking the Powers of Sleep Plus Dream.
SPEAKER_3: And you're a Ted Talker, why wouldn't you be after all that?
SPEAKER_3: And you are the host of the boringly titled The Matt Walker Podcast.
SPEAKER_3: What's up with that?
SPEAKER_4: I know, you know, the team around me, we had one of these retreats, three or four days bashing around titles.
SPEAKER_4: And I think the innovation there was stunning.
SPEAKER_4: The Matt Walker Podcast.
SPEAKER_4: You can see that we're a creative bunch in this domain.
SPEAKER_4: So, deeply, deeply embarrassing.
SPEAKER_3: At the end, we're just going to agree that you need more sleep, okay?
SPEAKER_3: That's what's going to happen here.
SPEAKER_4: Yeah.
SPEAKER_3: I want to know why do we need sleep at all?
SPEAKER_3: I see that as a shortcoming of the human brain.
SPEAKER_3: If aliens came and they just watched us just lay down and be semi-comatose for one third of Earth's rotation, they'll wonder what's wrong with these people.
SPEAKER_4: Isn't it stunning?
SPEAKER_4: And when you think about it from an evolutionary perspective, it makes no sense.
SPEAKER_4: Because first, we're not finding food, we're not finding a mate, we're not reproducing, we're not caring for our young, and worse still, we're vulnerable to predation.
SPEAKER_4: So on any one of those five grounds, but especially all of them as a collective, sleep should have been strongly selected against in the course of evolution.
SPEAKER_4: But the fact that in every species that we've studied carefully, even evolutionary ancient old species, every species seems to sleep or have something like sleep.
SPEAKER_4: What that means is that sleep evolved with life itself on this planet, and then has fought its way heroically through every step along the evolutionary path, which must mean that sleep is absolutely vital.
SPEAKER_4: And in fact, it's once been said, to your point, Neil, that if sleep doesn't serve a critical set of necessary functions, it's the biggest mistake the evolutionary process has ever made.
SPEAKER_1: I'm going with the latter.
SPEAKER_4: Man after my own heart.
SPEAKER_4: No, no, no.
SPEAKER_4: Just let's get the honesty out on the table.
SPEAKER_3: Put it out up there, right out front.
SPEAKER_4: But we now have a huge collection of science that suggests that why Mother Nature did not make a spectacular faux pas in creating this thing called sleep.
SPEAKER_3: So do worms sleep?
SPEAKER_3: When you say animals, you're not just talking about just vertebrates or mammals.
SPEAKER_3: You mean all animals.
SPEAKER_4: Yeah.
SPEAKER_4: So even earthworms, which are so old from an evolutionary perspective, they have states of activity and inactivity.
SPEAKER_4: And if I were to show you on a video, it's really quite telling that they seem to have, it may not be sleep.
SPEAKER_4: We call it lethargicus in these species.
SPEAKER_4: It's the kind of fancy earthworm way of saying, you kind of look like you're asleep, but we can't ask you the question.
SPEAKER_4: But yes.
SPEAKER_1: It could be they're just lazy.
SPEAKER_4: That's right.
SPEAKER_4: They are lazy at very predictable times across the 24-hour period.
SPEAKER_4: But despite that, when they put their feet up, who knows what they're watching?
SPEAKER_4: Maybe it's Earthworm Netflix.
SPEAKER_4: I don't know.
SPEAKER_4: But they do it in a very stable, predictive way.
SPEAKER_3: So, I hate using this term, but you'll know exactly what I mean.
SPEAKER_3: Do higher level animals require more sleep than lower level animals?
SPEAKER_4: It's a very interesting question, which is can we understand the functions of sleep across phylogeny, across different species?
SPEAKER_4: And it's been fiendishly difficult because there are some species, such as the little brown bat.
SPEAKER_4: It's the rock star of sleep, sort of Keith Ritchie.
SPEAKER_4: That little brown bat can sleep up to 19 hours per day.
SPEAKER_4: Whereas if you look...
SPEAKER_1: Really, talk to my cat.
SPEAKER_2: Yeah, it's trying to challenge that.
SPEAKER_2: We've got cats that can do that.
SPEAKER_1: That bat has nothing on my cat.
SPEAKER_2: All animals ending AT can do at least 19 hours a day.
SPEAKER_4: Yeah, it seems to be.
SPEAKER_4: But then if you look at elephants, for example, they sleep maybe just two to three hours.
SPEAKER_4: And you think, well, is there a correlation between size then?
SPEAKER_4: Absolutely not.
SPEAKER_4: There is no correlation.
SPEAKER_4: Is it about the size of the brain?
SPEAKER_4: Nothing to do with the size of the brain.
SPEAKER_4: Is it about prey versus predator and your status on that hierarchy?
SPEAKER_4: Not at all.
SPEAKER_4: Is it about the complexity of your nervous system?
SPEAKER_4: A little bit, but not much.
SPEAKER_4: Omnivore, herbivore, carnivore, does that present?
SPEAKER_4: No, it doesn't.
SPEAKER_4: If you are temperature-regulated, thermoregulatory, or you're nothing.
SPEAKER_3: So warm-blooded or cold-blooded?
SPEAKER_4: Warm-blooded, cold-blooded.
SPEAKER_4: But we're starting to understand that it's actually a complex set of all of these different things.
SPEAKER_4: Metabolic rate does seem to be predictive and such that if you have a higher metabolic rate, your idea would be, well, then you need to sleep more to sort of restore that.
SPEAKER_4: It's the opposite.
SPEAKER_4: Higher metabolic rate, you need to stay awake for longer so you can get in enough calories to support your higher metabolic rate.
SPEAKER_4: So it's a very complex question.
SPEAKER_4: But to your point, no, there is no simple correlation that explains the vast variance of sleep across species.
SPEAKER_3: One question before I hand over to my co-host here.
SPEAKER_3: So we've heard things about sleep rhythms and maybe leading the pack there is circadian rhythms.
SPEAKER_3: Could you just shed some light on that?
SPEAKER_3: I think Chuck had a question about that too.
SPEAKER_1: Yeah, well, no, I was wondering if the earthworms had a circadian rhythm because that's one of the defining attributes of sleep is the fact that you actually do it at kind of the same time in the cycle of the day.
SPEAKER_4: You're absolutely right.
SPEAKER_4: So let me start with what circadian rhythms are and sort of break the term down.
SPEAKER_4: Circa, sort of around, approximately, and rhythm, we all know what that term is.
SPEAKER_4: So in other words...
SPEAKER_3: Circa, that's the same Latin word when circa 1832.
SPEAKER_4: Yeah.
SPEAKER_3: Okay, cool.
SPEAKER_4: Exactly.
SPEAKER_4: And then you've got dian from the Latin derivative of day.
SPEAKER_4: So in other words, it's a rhythm of around or approximately one day.
SPEAKER_4: Why is it not precisely one day?
SPEAKER_4: Well, when we've done studies where we take human beings, there's a famous study with a professor, Nathaniel Kleitman, and they went off down to Mammoth Cave, deepest cave in America.
SPEAKER_4: In America, yeah, and where there is no light.
SPEAKER_3: And they just lived whatever day they wanted, right?
SPEAKER_4: And they just lived and they wanted to see what happens to their sleep-wake rhythms.
SPEAKER_4: Do they just abandon all timing?
SPEAKER_4: And the answer was no.
SPEAKER_4: They stuck to a very close timing.
SPEAKER_4: But it was close to 24 hours.
SPEAKER_4: It wasn't precisely 24 hours.
SPEAKER_4: When they cut themselves off from the outside world, specifically the most predictable thing on this planet, which is that since the dawn of time, unless you want to correct me, the sun has always risen and the sun has always set.
SPEAKER_4: And it's set in that 24-hour rhythmic nature.
SPEAKER_4: And when they decoupled themselves from that rhythmic signal, the body still kept its 24-hour rhythm almost.
SPEAKER_4: It was just a little bit laggy.
SPEAKER_4: And it ran about 24 hours and about 30 minutes.
SPEAKER_4: And now we figured this all out in big studies.
SPEAKER_4: And it's about 24 hours and 12 minutes that we run a little bit late if we're disconnected from the outside world.
SPEAKER_3: That's why I always want to sleep an extra 30 minutes after the alarm clock.
SPEAKER_3: Please do that.
SPEAKER_4: Please do that.
SPEAKER_4: Or better still, remove the alarm clock and just add an extra half hour.
SPEAKER_4: But you will just, yeah.
SPEAKER_4: But if I were to disconnect you like they did in Mammoth Cape, you just drift forward in time.
SPEAKER_4: You keep adding on about 50 minutes.
SPEAKER_4: So that's why we define it as about 24 hours.
SPEAKER_4: But beautifully, when we're living in the real world, we have cues of that 24 hour period like light, but also feeding at certain times.
SPEAKER_4: Those cues, which are what we call zeitgebers from the German term time giver, act like little fingers to pop out the dial on your wristwatch and reset it to 24 hours each day so you don't drift.
SPEAKER_4: But coming back to Chuck's question, that's one of the ways that we define sleep in species where it's hard to sort of place electrodes in or place electrodes on their heads.
SPEAKER_4: So we can look to see, do they do that activity and inactivity state in a 24 hour predictable rhythm?
SPEAKER_4: Yes.
SPEAKER_4: Also, another one is, is it reversible?
SPEAKER_4: Because that's what differentiates, it's one of the things that differentiates sleep from death, which is that when an organism goes into this state of activity, yeah, yeah, I was going to say, it's not the only one, don't worry.
SPEAKER_4: But if you prod the earthworms, then they seem to come back to life as if they were absent this waking state.
SPEAKER_2: So Matt, when you've got circadian rhythms and it's trapped into a 24 hour-ish cycle by obviously clinical experiment, what happens if you're an early bird or a night owl?
SPEAKER_2: And you call those chrono types.
SPEAKER_3: You know, they're early people, and they're morning people, and they're night people.
SPEAKER_2: So how are we, I mean, is that disruptive?
SPEAKER_2: Or is that just, you know, some people have software uploaded that does that, other people have this.
SPEAKER_1: There are party people, and then there are...
SPEAKER_3: And plus, Gary, the term for your brain is not software, it's wetware.
SPEAKER_3: We have different wetware.
SPEAKER_2: Sounds like I'm scuba diving, but I'll go with that.
SPEAKER_4: Scuba diving with Matt Walker on Star Talk.
SPEAKER_4: And we are defined by our chrono type.
SPEAKER_4: And our chrono type, by the way, whether you're an evening type, morning type, or somewhere in between, it's about a third, third split across the population.
SPEAKER_4: It is not your fault.
SPEAKER_4: It is genetically determined, largely, and there are at least 22 different genes that we now know will dictate your chrono type destiny.
SPEAKER_4: It's gifted to you at birth.
SPEAKER_4: You can't really change it very much, unfortunately.
SPEAKER_4: But how does this fit in with that strange sort of circadian rhythm?
SPEAKER_4: I just told you everyone has.
SPEAKER_4: But these chronotypes, as I said, there are essentially three types, and it's genetically determined.
SPEAKER_4: What's interesting about those is how it changes what I just told you about the 24-hour clock face, the circadian rhythm.
SPEAKER_4: I told you that we have a rise, we're a dienyl species, we're active during the day, and then we're asleep at night, active during the day.
SPEAKER_4: So how does chronotype fit into your innate circadian rhythm?
SPEAKER_4: Chronotype dictates where that sort of sine wave, where that oscillation of rising activity and then the lull of sleep, where that sits on the 24-hour clock face.
SPEAKER_4: So we all have a circadian rhythm, but if you are a morning type, your peak activity will arrive earlier on the clock face, whereas if I'm a neutral, which I am, I'm just going to sit somewhere in the middle, and then the party people, Chuck, not saying anything, their peak of activity won't start happening or rising until the afternoon.
SPEAKER_4: Everyone has a 24-hour rhythm.
SPEAKER_4: Where that rhythm sits on the clock face and is positioned is dictated by your chronotype.
SPEAKER_4: Does that make any sense?
SPEAKER_1: So the chronotype is like a dial that sets the place where you fall on that weight.
SPEAKER_4: Beautiful.
SPEAKER_4: Yes, exactly that.
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SPEAKER_3: So, Matt, I get it.
SPEAKER_3: You can describe what you already see in us, and that sounds very erudite, but scientifically, what I really want to know is what the hell is going on inside of us while we're asleep.
SPEAKER_4: And we now know that.
SPEAKER_4: And we know it from a broad perspective in terms of whole brain activity, and we also know it right down inside of a cell itself in terms of the expression of genes and everything in between.
SPEAKER_4: I mean, we have sliced and diced sleep in all sorts of ways, but I'll just give you some highlights.
SPEAKER_4: Upstairs in the brain, it is stunning.
SPEAKER_4: It is a spectacular display of electrical symphonic ballet.
SPEAKER_4: And trust me, if you saw it, you would be stunned.
SPEAKER_4: And in fact, we've even extracted these brain waves from the sleeping brain, and we've converted them into sound files.
SPEAKER_4: And it's amazing.
SPEAKER_4: So what happens is that when we're awake, we have very fast frenetic activity.
SPEAKER_4: Your brain wave patterns are going up and down many, many times per second, maybe 50, 60 times per second.
SPEAKER_4: As you start to fall asleep, those brain waves start to slow down.
SPEAKER_4: And when you go into the deepest stage of what we call a non-rapid eye movement sleep, so you have two main types of sleep, non-REM sleep and REM sleep, non-rapid eye movement sleep, rapid eye movement sleep.
SPEAKER_4: And non-REM sleep, you can split it up into light non-REM, deep non-REM.
SPEAKER_4: When you go into deep non-REM, something incredible begins.
SPEAKER_4: All of a sudden, hundreds of thousands of brain cells all decide to synchronize in their firing in unison.
SPEAKER_4: So they all fire together, and then they all go silent together.
SPEAKER_4: And they all fire together.
SPEAKER_4: It's almost like this mantra chant.
SPEAKER_4: And it produces these huge, powerful, deep, slow, rhythmic brain waves that have riding on top of them, these incredible bursts of electrical activity called sleep spindles.
SPEAKER_4: And so this is stunning.
SPEAKER_4: And then you go into REM sleep, and then the brain becomes once again frenetic.
SPEAKER_4: In fact, if all I had was your brainwave activity, Neil, during REM sleep, and I was in the other room, and you're in my sleep center, I could not tell in the bed, are you awake or are you in REM sleep?
SPEAKER_4: In fact, some parts of your brain are up to 30% more active when you are in REM sleep and dreaming, which is stunning.
SPEAKER_4: And then downstairs in the body, gosh, as you go into deep sleep, it provides almost the very best form of naturalistic blood pressure medication that you could ever wish for.
SPEAKER_4: Heart rate drops, your blood pressure lowers, your immune system kicks into high gear.
SPEAKER_4: Upstairs, coming back to your brain, there is a cleansing system that starts to pulse and it flushes out all of the toxins.
SPEAKER_4: So it's literally a power cleanse for the brain at night.
SPEAKER_4: There are so many stunning things.
SPEAKER_4: These are just a few that I could regale you with.
SPEAKER_1: All right, well, listen, I got to go take a nap.
SPEAKER_4: My work here is done, Chuck.
SPEAKER_2: Given that these things are happening, Matt, is the brain able to improve mental health?
SPEAKER_2: Is it having an effect on things like dementia?
SPEAKER_4: It does.
SPEAKER_4: It radically alters both what we call your cognitive functions, so learning, memory, and also your emotional and your mental health processes.
SPEAKER_4: So in terms of emotional and mental health, we've done a lot of work, and we do a lot of work at my sleep center on this.
SPEAKER_4: Firstly, sleep, and particularly dream sleep, seems to provide a form of almost overnight therapy where it will take difficult, painful experiences, and it will essentially act almost like a nocturnal soothing balm and just take the sharp edges off those painful experiences so that you come back the next day and you don't feel as bad.
SPEAKER_4: They don't feel as painful anymore.
SPEAKER_4: And so it's not time that heals all wounds, but it's time during sleep, and specifically dream sleep, that offers that emotional convalescence, as it were.
SPEAKER_4: So that's one of the mental health benefits.
SPEAKER_4: There was a great quote, by the way, E.
SPEAKER_4: Joseph Cosman, an American entrepreneur, he once said that the best bridge between despair and hope is a good night of sleep.
SPEAKER_4: And that's exactly what we've discovered in the laboratory.
SPEAKER_4: Your other question, Gary, is very interesting about cognitive function and Alzheimer's disease.
SPEAKER_4: What we have discovered is that, so there are at least two toxic proteins underlying the disorder of Alzheimer.
SPEAKER_4: One is amyloid protein, beta amyloid protein, and the other is called tau protein.
SPEAKER_4: And what we've discovered is that during sleep, and particularly deep sleep at night, there is this pulsing sewage system.
SPEAKER_4: It's called the glymphatic system.
SPEAKER_4: You have one in your body, it's called the lymphatic system in the brain.
SPEAKER_4: It's called the glymphatic system.
SPEAKER_4: And it only kicks into high gear during deep sleep.
SPEAKER_4: And it sort of washes out all of the metabolic detritus of the day.
SPEAKER_4: Two of the proteins, the toxic proteins, that sleep will wash away every night, if you are getting enough of it, are these two Alzheimer's proteins, amyloid and tau protein.
SPEAKER_4: And that's why we found such strong links between insufficient sleep across the lifespan and your risk for developing Alzheimer's disease.
SPEAKER_4: So from that perspective, it's a form of almost, you know, good night sleep cleaning.
SPEAKER_1: So is there any work being done to figure out how you might induce that artificially or is the cleaning of this amyloid plaque by your brain not significant enough that it might be able to ward off Alzheimer's altogether?
SPEAKER_1: But the mechanism itself, is it something that we could replicate artificially to either aid in that process or just do it?
SPEAKER_4: Fantastic question.
SPEAKER_4: And in fact, it's a question that we have addressed.
SPEAKER_4: We started to develop a technology based on something called transcranial direct current stimulation.
SPEAKER_4: It sounds like the stuff of science fiction, more your stuff than the mind, but I promise you it's not.
SPEAKER_4: You apply electrodes to the head and you insert a small amount of voltage into the brain and it's so small you typically don't feel it, but it has a measurable impact.
SPEAKER_4: And if you apply that stimulation during sleep, during those big, powerful, deep, slow brainwaves when we get this cleansing, you can amplify the size of those deep sleep brainwaves and we can almost, for example, double the benefit that deep sleep brainwaves give to your memory the next day.
SPEAKER_3: So that would mean you can hijack a shorter sleep to make you feel like you had a longer sleep.
SPEAKER_4: Well, that we don't know.
SPEAKER_4: We don't know if by improving the size of these brainwaves, does that reduce your overall sleep need?
SPEAKER_4: And if we could, to your point, Neil, it would suggest that we're almost able to buy compressing sleep through increasing quality.
SPEAKER_4: It's almost as though I am sort of like zip filing sleep.
SPEAKER_4: I just compress down your sleep need by improving the quality and it's a short-term end.
SPEAKER_4: I mean, that would be spectacular.
SPEAKER_4: We haven't found evidence for that yet, but we have found the ability to manipulate this brainwave activity and we've now since split it out into a startup company to develop the device.
SPEAKER_3: What intrigues me, the way you described the different parts of the sleep cycle, the sleep session, I hadn't thought about this before this moment that if you sleep for less time than the full allocation or you're on some travel regimen where there's a time zone shift and whatever, you can get some sleep serving only some parts of that portfolio of need, leaving out other parts of that very portfolio.
SPEAKER_3: So are there effects?
SPEAKER_3: I mean, you mentioned Alzheimer's, but overall, why can't I just sleep a little longer later?
SPEAKER_3: I gotta stay up and pull an all nighter tonight.
SPEAKER_4: It is a very interesting question.
SPEAKER_4: Can you essentially catch up on sleep when you've missed it?
SPEAKER_1: Catch up, catch up.
SPEAKER_4: We say that all the time.
SPEAKER_4: I've got a tough week this week, but at the weekend, don't worry, I'm going to catch up.
SPEAKER_4: Unfortunately, many of the processes of sleep, not all of them in truth, but many of them, do not work like the bank.
SPEAKER_4: So you can't accumulate a debt and then hope to pay it off at some later point in time.
SPEAKER_4: Sleep in many ways, and learning in memory is a good example, is an all-or-nothing phenomenon, meaning if you don't sleep within the 24 hours after learning those facts, you can lose the chance to consolidate and hit the save button on those memories.
SPEAKER_4: So you end up forgetting the information rather than remembering it.
SPEAKER_1: Yeah.
SPEAKER_1: I read the abstract on a study that was talking about that, and what they did was they measured the cognitive retention of people who sleep right after learning something as opposed to those who didn't.
SPEAKER_1: And oddly enough, if you want to do well on a test, go to bed, study and go to bed.
SPEAKER_1: It's incredible.
SPEAKER_3: But suppose you go to sleep during the class.
SPEAKER_4: Well, you know what?
SPEAKER_4: The funny thing is, in my course, I teach a large course here of about 500 or 600 students on campus, the science of sleep, and at the start of the semester, I say based on what I know regarding the benefits of sleep on learning and memory, it's the greatest form of flattery for me to see people like them not being able to resist the urge to strengthen what I'm telling them by falling asleep in the class.
SPEAKER_4: So feel free just to ebb and flow through consciousness throughout my course.
SPEAKER_4: I'll take absolutely no offense.
SPEAKER_2: Matt, is there a connection between dreams and time?
SPEAKER_2: Because we've had this question pop up before on previous episodes, but without a sleep expert.
SPEAKER_3: We all saw the Christopher Nolan movie, Inception, right?
SPEAKER_3: Which embedded time frames within dreams.
SPEAKER_2: And Matt may have had a part in that.
SPEAKER_4: Did you have a part in that, Matt?
SPEAKER_4: I can neither confirm or deny that, but what I'm about to tell you is very congruent with the movie.
SPEAKER_4: So time is so fascinating when it comes to sleep, because it's a total paradox.
SPEAKER_4: On the one hand, you lose all sense of time, meaning that if you fall asleep on a plane, you know, let's say a transatlantic flight, when you wake up, what's the first thing that you do?
SPEAKER_4: Typically, you look at your clock and you say, how long have I been asleep?
SPEAKER_4: Why didn't you?
SPEAKER_4: Weren't you able to track time in your sleep?
SPEAKER_4: No.
SPEAKER_4: So you've lost your sense of time during sleep at one level.
SPEAKER_4: But then the second level is that when we fall asleep and we go into dream sleep, there, something different happens with time.
SPEAKER_4: And we've got a neural explanation that I'll come on to.
SPEAKER_4: But what is different about dream sleep is that you can get what we call time dilation.
SPEAKER_4: And this comes on to the movie Inception, where at the first level down, five minutes in the real world is maybe 50 minutes in the first level of the dream.
SPEAKER_4: And then maybe it's five years in the second level.
SPEAKER_4: And then maybe it's 50 years in the third level.
SPEAKER_4: Now, we don't actually have these levels, as it were.
SPEAKER_4: We really just go into the dream state.
SPEAKER_4: But it is fitting because when you go into dream sleep, and here's a good example, let's say that you have a snooze button and your arm goes off and your snooze button is for three minutes.
SPEAKER_4: So you hit it and you go back to sleep and you go back into the dream that you are having.
SPEAKER_4: And then the alarm goes off again three minutes later.
SPEAKER_4: But you could absolutely tell me, no, that wasn't three minutes.
SPEAKER_4: I was dreaming for what felt like 15 minutes.
SPEAKER_4: And so time is stretched and dilated, which means that, yes, inception-like, you have more time as you go into dream sleep.
SPEAKER_4: Why would this be?
SPEAKER_4: If you look at rats running around a maze as they learn the maze, the memory centers of the maze code the maze.
SPEAKER_4: So it's sort of like, ba-ba-ba-bum, ba-ba-ba-bum, if you were to listen to the brain cells as it's learning the signature of the maze.
SPEAKER_4: And then scientists have let those rats sleep and then they've listened back in to the firing of those brain cells.
SPEAKER_4: And what's stunning is that when you go into REM sleep, unlike non-REM sleep where things speed up, in REM sleep, it goes from ba-ba-ba-bum, ba-ba-ba-bum, to bum-bum-bum-bum, bum-bum-bum-bum.
SPEAKER_4: It's about 0.5 times, it's like taking this podcast and hitting on your podcast player, play it at 0.5 times for me.
SPEAKER_4: That's what dream sleep is actually like and maybe provides an explanation for why we have time dilation and why you can create beautiful movies like Inception.
SPEAKER_1: And now at what level does it go to bum-bum-bum-bum?
SPEAKER_4: The one that I'm most worried about is the one that goes bum-bum-bum-bum-bum, bum-bum-bum-bum-bum.
SPEAKER_4: I'm trying to be fitting with the current music of the program.
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SPEAKER_2: All right, Matt, how about premonitions?
SPEAKER_3: Because I've got into this before about a premonition I've had, but do we have the ability to see into the future while we dream, or quite literally, are we just dreaming?
SPEAKER_2: The answer is no, no, no, no.
SPEAKER_2: Really?
SPEAKER_4: We want it to be true, books are written about it, it's in religious texts.
SPEAKER_4: Oh, Neil, I'm so glad you are in the world.
SPEAKER_4: Well, at first glance, you're right, and then if you look at some of the data, you start to think, ah, is he right?
SPEAKER_4: Because there are some cases where people, and this is what people will tell me, say, look, the FBI has a documented person who two days before called them and said, look, there is going to be, unfortunately, a plane crash, it's going to be this specific line, and it's going to crash in this state.
SPEAKER_4: It's going to crash here in the United States.
SPEAKER_4: And they think, it's a cracked pod.
SPEAKER_4: And yeah, they just think this person is out of their mind.
SPEAKER_4: And then lo and behold, two days later, and now that person seems like a culprit, and they find out that it's not.
SPEAKER_4: How is that?
SPEAKER_4: That seems deeply prophetic when that person then tells you during the interview, I had this dream.
SPEAKER_4: It was a dream that told me this was going to happen.
SPEAKER_4: And it felt so real.
SPEAKER_4: And now I've just seen it happen, and I want to go back to my phone call.
SPEAKER_4: And you think, okay, there's got to be something in this.
SPEAKER_4: Well, this is where there are lies, damn lies, and statistics.
SPEAKER_4: Because if you think about firstly, we have about four to five REM cycles every night.
SPEAKER_4: And let's just say that for every REM cycle, we only have one dream.
SPEAKER_4: It's probably not true, but let's be conservative in our calculation.
SPEAKER_4: So that's about four to five dreams per person, per night across the current six billion human beings.
SPEAKER_4: So if you do eight, eight, eight billion, right.
SPEAKER_4: And let's assume that of those, you know, seven are at the stage of development where they actually are dreaming.
SPEAKER_4: So I become conservative again.
SPEAKER_4: That math, that mathematics, as we would say, if you calculate it means that it is highly probable by just statistical chance alone that someone somewhere on the planet tonight is going to have a dream that turns out to have some degree of prediction of something that will happen in the world tomorrow.
SPEAKER_4: It is just statistical chance.
SPEAKER_4: Unfortunately, Neil, you're a gem.
SPEAKER_4: You're absolutely right again.
SPEAKER_3: And we remember the hits and not the misses, right?
SPEAKER_3: Do you call up the FBI every time you have some kind of crime premonition?
SPEAKER_3: You know, it's...
SPEAKER_1: I had a dream that someone killed my wife and it has not happened.
SPEAKER_1: What is going on?
SPEAKER_1: What is happening?
SPEAKER_4: Why I can't get away with this type of stuff?
SPEAKER_2: You're in so much trouble with the good lady.
SPEAKER_2: So you've bust that myth by statistics and damn lies, in my opinion, man.
SPEAKER_2: So when we enter a dream state and we sleep, is there a point where we are entering into a psychotic state?
SPEAKER_4: By all definition, yes.
SPEAKER_4: Because when you start to dream, you begin to see things which are not there, so you're hallucinating.
SPEAKER_4: You believe things that couldn't possibly be true, so you're delusional.
SPEAKER_4: You become confused about-
SPEAKER_3: Like the monster chasing me.
SPEAKER_4: Correct, and that feels immensely real.
SPEAKER_4: Ask your heart rate, and it will confirm that very much.
SPEAKER_4: And so you lose your sense of time, place, and person, so you're suffering from disorientation.
SPEAKER_4: You have wildly fluctuating emotions that we call being affectively labile.
SPEAKER_4: And then how wonderful, you woke up this morning, and you forgot most, if not all, of that dream experience, so you're suffering from amnesia.
SPEAKER_3: What does labile mean?
SPEAKER_3: What does that phrase mean?
SPEAKER_4: Labile means unstable, almost pendulum-like, in an unpredictable manner, where you're just unstable.
SPEAKER_4: So it's a very labile state.
SPEAKER_4: And in that way, across all of those five things, hallucinating, you're delusional, and you're amnesic, if you were to report any one of those symptoms when you're awake, to me, you would be seeking serious psychological, psychiatric treatment.
SPEAKER_4: But for reasons that we're now only just understanding, it seems to be both a perfectly normal biological and psychological sleep.
SPEAKER_4: But you are essentially entirely psychotic when you drink.
SPEAKER_2: Nice to know.
SPEAKER_1: Well, it's good to see that things don't change when I go to sleep.
SPEAKER_4: PS, you're welcome.
SPEAKER_4: You know, you invite a guest onto the show, and what they end up doing is accusing you of becoming utterly psychotic.
SPEAKER_4: Thanks.
SPEAKER_4: Great.
SPEAKER_3: I got a question.
SPEAKER_3: In zero G, you know, I think of a nice cozy night's sleep.
SPEAKER_3: It's a fluffy pillow, nice cozy comforter blankets.
SPEAKER_3: In zero G, your body doesn't lean in any one direction.
SPEAKER_3: You just float there.
SPEAKER_3: So, do you think your brain knows?
SPEAKER_3: You can ask astronauts this, of course, but I never thought to do so.
SPEAKER_3: Does your brain have to have some sense of a gravity vector while you're asleep, do you think?
SPEAKER_1: Yeah, like your inner ear.
SPEAKER_3: For proper dreaming.
SPEAKER_4: It's a fascinating question.
SPEAKER_4: We've done some work with NASA with sleep.
SPEAKER_4: It's a really important challenge for a number of reasons.
SPEAKER_4: But firstly, what we found is that that gravitational vector, as you described it, isn't thankfully hugely influential, such that any one particular stage of sleep or your entire sleep becomes ungeneratable, as it were.
SPEAKER_4: Not a word, but it's not necessarily a problem there.
SPEAKER_4: However, there are some other problems.
SPEAKER_4: The first is just simply pragmatic, that if you are floating around and you're asleep, you're going to start bumping into things, you're always going to be waking up.
SPEAKER_4: So firstly, you have to carabiner yourself against this.
SPEAKER_3: Well, they strap them in on the...
SPEAKER_3: They're not just bodies floating by.
SPEAKER_4: Well, the people who are working the night shift, the typing way there, who's that?
SPEAKER_4: Oh, it's Gary floating by, you know?
SPEAKER_3: And the people who snore, you know, there's extra propulsion.
SPEAKER_4: Correct, yeah, could you imagine?
SPEAKER_4: Well, actually, it would be great because what you could do is, since there's no gravity, hopefully that means that you could not have the airway collapsing and snoring would be less.
SPEAKER_4: That's actually a really interesting hypothesis.
SPEAKER_4: One that I don't know.
SPEAKER_3: Is there snoring in space?
SPEAKER_3: Yes.
SPEAKER_2: These are the questions we need answers to.
SPEAKER_4: Great hypothesis.
SPEAKER_4: I love it.
SPEAKER_4: There's the first grant.
SPEAKER_4: But yes, so you have to carabini yourself against this sort of large cylindrical metal cigar that you're floating around in.
SPEAKER_4: That's the first thing.
SPEAKER_4: The second weird thing is that when you, in sort of zero G, when you exhale, if there wasn't sufficient circulation and you're strapped in and you're in the same position, what begins to happen is you get this buildup, this cloud of carbon dioxide around you.
SPEAKER_1: A CO2 bubble.
SPEAKER_4: And it can obviously lead to a very quick final popping you out of the gene pool.
SPEAKER_3: Just to be clear, the space station has air currents in it.
SPEAKER_3: So it would cycle through the air.
SPEAKER_3: And other than the CO2 coming out at body temperature, which is presumably warmer than air temperature.
SPEAKER_1: It would rise away.
SPEAKER_3: It would rise on earth and not rise in the space station.
SPEAKER_3: So there are air currents.
SPEAKER_3: And so much so that if you leave something, if you let something go, it will eventually go to the vent.
SPEAKER_3: So that's why everything is velcroed in.
SPEAKER_3: If you misplace something, check the vent.
SPEAKER_2: So Matt, talking to the space station, how many sunsets and sunrises do you get in space in a 24-hour period for an hour?
SPEAKER_2: For an astronaut or on a space station?
SPEAKER_2: And how are you working with that?
SPEAKER_4: Here's the challenge.
SPEAKER_4: This is the main reason, not the loss of the gravitational vector, but the fact that your circadian rhythm that we spoke about is now thoroughly confused.
SPEAKER_4: Because let's say that you're on the International Space Station as an example.
SPEAKER_4: You are going to see every 24 hours 16 sunrises and 16 sunsets.
SPEAKER_4: And so your body is getting the signal that we all get in a nice predictable fashion.
SPEAKER_4: Once during the day, once sunrise, once sunset.
SPEAKER_4: It's getting the signal of, okay, it's time to be awake.
SPEAKER_4: Oh, no, now it's sleep.
SPEAKER_4: Oh, no, and you're awake.
SPEAKER_4: No, no, no, back to sleep.
SPEAKER_1: I'm sorry.
SPEAKER_3: How connected are we to the sun?
SPEAKER_3: We live in a fully lit nighttime.
SPEAKER_3: I live in New York City.
SPEAKER_1: I never take my eyes off my phone.
SPEAKER_3: I mean, are we farmers?
SPEAKER_3: No, we're not all just up, time to go to sleep, then on the second, time to wake up.
SPEAKER_3: So do we think it really matters anymore in modern society?
SPEAKER_3: I'll still give you the 24 hours, but do you really give a rat's ass about the sun anymore?
SPEAKER_4: You would think based on...
SPEAKER_2: I'm not sure I heard you say that right.
SPEAKER_2: You wrote a rat's ass about the sun.
SPEAKER_4: Take that, song!
SPEAKER_4: Well, speaking about the rodent derriere, as you just described it, yes, it does matter.
SPEAKER_4: And in fact, it's part, it's one of the contributing reasons why there is so many, well, there's so much sleep disruption and sleep problem, such a sleep problem that we see in society right now.
SPEAKER_4: We have become dislocated from this natural edict of the rising and setting of the sun.
SPEAKER_4: We are a dark, deprived society in this modern era, and we need darkness at night in particular to help regulate the hormone release called melatonin, which augments your human sleep.
SPEAKER_4: And in part, we can do this with natural light when we come in in the evenings.
SPEAKER_4: No wonder why our sleep disrupted, because our brain is thoroughly confused.
SPEAKER_4: It's in constant low level light.
SPEAKER_3: I really have a couple more minutes.
SPEAKER_3: Matt, I might be a good subject for your sleep studies, because I can sleep anytime, anywhere, in practically any position for almost any length of time.
SPEAKER_3: So much so that I would say, you know, the power nap that people talk about, I can either have that or not.
SPEAKER_3: If I got a couple minutes, I say, let me sleep for 20 minutes and I'll get up and go.
SPEAKER_3: Let me sleep for an hour and a half.
SPEAKER_3: Let me sleep for 45.
SPEAKER_3: And I'll do this.
SPEAKER_3: And at night, I can sleep for eight hours or five hours, depending on what I need to do in that day.
SPEAKER_3: So, and I can go to sleep within minutes of laying down, you know, in some kind of comfortable position.
SPEAKER_3: And I met so many people that have a hard time sleeping.
SPEAKER_3: I say, what do you mean you have a hard time?
SPEAKER_3: Just go to sleep.
SPEAKER_3: Or stay awake and do something productive.
SPEAKER_3: Don't lay in bed and say, oh, I can't get to sleep.
SPEAKER_3: Then go do something, mow the lawn.
SPEAKER_2: Yeah, 11.30 at night, get the lawnmower out.
SPEAKER_2: Your neighbors are going to love you.
SPEAKER_3: Is it true that people who sleep anytime, anywhere, and I don't drink coffee, I don't have a relationship with caffeine, so I don't depend on that for me to be awake or asleep.
SPEAKER_3: I think that's unusual based on people I speak to.
SPEAKER_4: It is unusual.
SPEAKER_4: And it's especially unusual the older that you get.
SPEAKER_4: I'm not suggesting that you're old, but as we get older.
SPEAKER_3: No, I'm an old fart.
SPEAKER_3: I'm an old crusty man.
SPEAKER_4: I'm right there with you in the foothills of middle age, at least right now.
SPEAKER_4: It is inbound.
SPEAKER_4: What I would say is that firstly, you could just be one of those unique people who have an incredible appetite and hunger and drive for sleep, such that the alacrity of your sleep with which it arrives is stunning and that you're in the top 1%.
SPEAKER_4: The other thing that sometimes we would want to do, however, is check the quality of your sleep, because if you are constantly able to fall asleep anytime, anywhere, for any duration, which is what you just described to me, at that point, I may be getting a little bit worried that you're carrying a lingering sleep quality debt because there's something about your sleep that may not be quite sufficient, such that with that debt, you are constantly craving.
SPEAKER_4: Your brain has this constant hunger because you are constantly in a fasted state, as it were, when it comes to quality sleep.
SPEAKER_4: So no wonder whenever you give your brain the chance, it thinks, time to feast, because my goodness, I'm so sort of sleep macronutrient deficient right now.
SPEAKER_3: Giving it the little bit that it will take.
SPEAKER_1: Or it could have been that you're just a closet narcoleptic.
SPEAKER_3: I mean, so, but also when I wake up, I'm pretty perky when I wake up.
SPEAKER_3: I'm not one of these...
SPEAKER_4: That's right.
SPEAKER_1: Yeah.
SPEAKER_4: And there is, unfortunately, there is not necessarily a strong alignment between your subjective sense of how well you slept last night.
SPEAKER_4: So I would say that when it comes to that sleep need, we would just want to check the quality of your sleep to make sure that you're sleeping okay.
SPEAKER_4: And if that's the case...
SPEAKER_3: Well, next time in Berkeley, put me on electrodes, okay?
SPEAKER_4: I will bring you in anytime.
SPEAKER_4: We'll fly out.
SPEAKER_4: We'll come and apply them tonight.
SPEAKER_4: Tell me where you live.
SPEAKER_4: And once I know where you live, I'll be careful.
SPEAKER_3: Well, Matt, this has been a delight.
SPEAKER_3: Neil deGrasse Tyson here, coming from a Star Talk special edition on sleep.
SPEAKER_3: We'll see you again, provided you continue to look up.