Ep 198 Sleep Part 1: Sleeping with one eye open

Sleep is a universal experience. It’s not just the lion that sleeps tonight - it’s also the butterfly, the chicken, the jellyfish, the dog, the snake, the worm, and of course the human. What is this widespread physiological process whose spell we are all under? What purpose (or purposes) does it serve? Why do we sleep the way we do? These are just some of the questions we’re going to get into in this week’s episode, the first half of our two-parter on sleep. We break down the different components of sleep in humans before diving deep into how animals sleep and what drives the different patterns we see. Night owl or daybird? Light sleeper or deep slumberer? Frequent naps or one big chunk? One eye open or both eyes closed? Tune in as we unravel some of the mysteries of sleep. Support this podcast by shopping our latest sponsor deals and promotions at this link: https://bit.ly/3WwtIAu See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

• 0:01Speaker 00

  This is exactly right.

• 0:06Speaker 01

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• 1:03Speaker 02

  Hey, I'm Niall Rogers. This fall, I'll be driving across the country, meeting some of today's coolest and most fascinating artists. We'll explore the stories before the moments that changed everything. Because every musician remembers the moment where it all began. Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.

• 1:35Speaker 03

  Hey, everyone. It's Stephen Ray Morris. I'm here to tell you a little bit about sleep paralysis and lucid dreaming and where the two meet in the middle, which is me. Sleeping has always been, especially lately, has been pretty difficult. But for most of my life, I've had pretty stressful dreams, to the point where I feel like sleep isn't very restful for me. When I was younger, it used to be really easy for me to fall asleep, but then the actual dreams and things themselves wouldn't be very restful. And that, I think, like a common theme in my dreams is that I have to do a task in a limited amount of time, and there's an obstacle getting in the way.

• 2:17Speaker 03

  And some of my favorite examples of this are I am like a manager at a brothel Christmas party, and I have to make sure everybody gets their gifts, but all the gifts are unlabeled. I have to catch a train, but I keep running into people I haven't seen in a long time. So, oh, hey, nice to see you. Actually, I gotta catch that train. And then I run into somebody else. In college, I started getting sleep paralysis. I still do from time to time, but it was really bad where, you know, it's your, your brain is awake, but your body is asleep. So there's usually some sort of demon like Nascol Dementor style thing in the corner of the room. And it just causes this intense fear and terror.

• 3:00Speaker 03

  And so I usually wake up like everyone I've ever, whatever spent the night with have always had to deal with me waking up and screaming from these forces. In college, I met my roommate, my buddy Evan, who's from the Bay Area. And, you know, we all watched Waking Life. And in that movie, they talk about lucid dreaming, which is, you know, the ability to be aware that you're dreaming and control your dreaming, et cetera, et cetera. The two main things that I took away from it are, you know, like AI, look at your hands. Or look at clocks because dreams can't represent either of those things very well. So if you see them, that means you know you're dreaming. So I'd started continuing these dreams where just this intense fear is this dark figure is looming in the corner.

• 3:45Speaker 03

  And I, after all this lucid dreaming, training or whatever, I started to like wriggle a little bit, you know, because I was so scared that I like was really trying to get away. And then one night, as it got right over my bed, was looming down at me. I just remember this feeling of, ah, you know, like full like superhero movie, like the strain. And I, I reached my hand out and grabbed this sleep process demon by the wrist. And then I woke up and I didn't have sleep process again for a few years. I still remember this so clearly, like it was yesterday, even though this was maybe like, I don't know, almost 20 years ago. The sleep process still happens every once in a while, but I think my lucid dreaming training

• 4:30Speaker 03

  still serves me well occasionally. So I'm prepared basically anytime sleep paralysis demons come at me.

• 5:22Speaker 04

  Steven.

• 5:24Speaker 01

  Steven!

• 5:25Speaker 04

  I mean, first of all, terrifying, but also, secondly, what a joy to hear your voice.

• 5:30Speaker 01

  Thank you so much for sharing your sleep and sleep dreams, sleep paralysis stories with us.

• 5:35Speaker 04

  It is so scary. I've had sleep paralysis just a few times in my life, and I truly thought I was dying.

• 5:41Speaker 01

  I know. I don't know that I've ever had it, but all of the stories that I hear are really terrifying.

• 5:45Speaker 04

  Yeah, yeah.

• 5:48Speaker 01

  So, thank you. We appreciate it.

• 5:50Speaker 04

  Hi, I'm Erin Welsh.

• 5:52Speaker 01

  And I'm Erin Allman-Uptake.

• 5:53Speaker 04

  And this is This Podcast Will Kill You.

• 5:55Speaker 01

  Welcome to the Exactly Right Studios!

• 5:58Speaker 04

  Yes, where we will be discussing in two episodes...

• 6:02Speaker 01

  Sleep!

• 6:05Speaker 04

  I'm excited for this.

• 6:07Speaker 01

  Very much so.

• 6:08Speaker 04

  What are we going to be talking about? There's a lot that we're going to cover and...

• 6:12Speaker 01

  A lot that we will miss.

• 6:13Speaker 04

  ...that we will not cover. So, we are going to be talking... This first episode, we're focusing on what sleep is, essentially. Like, what does it entail? What is your brain doing? A little bit about why sleep is important, or what we think sleep is important for. I'm going to be talking about sleep in animals.

• 6:32Speaker 01

  I'm so excited.

• 6:32Speaker 04

  A lot.

• 6:33Speaker 01

  I'm really excited about that.

• 6:34Speaker 04

  I'm excited about it, too. I did not know where it was going to go.

• 6:37Speaker 01

  Right.

• 6:38Speaker 04

  And then, next episode, we're going to talk about some of the consequences of sleep deprivation. And also, we're going to be talking about the history of human sleep.

• 6:49Speaker 01

  I'm really excited about that, too. I think the second episode is going to be a lot of interesting discussion about how we think about sleep today.

• 6:55Speaker 04

  I think so, too. I personally felt a lot better about sleep.

• 7:00Speaker 01

  Oh, good. That's great. Happy to hear it.

• 7:02Speaker 04

  Thank you. Thank you.

• 7:03Speaker 01

  Hopefully, everyone else will, too. But not this week.

• 7:06Speaker 04

  No.

• 7:07Speaker 01

  This week, you'll just learn a lot about sleep.

• 7:09Speaker 04

  Yeah.

• 7:10Speaker 01

  I'm excited.

• 7:11Speaker 04

  Um, and you'll also have a really delicious.

• 7:14Speaker 01

  Beverage.

• 7:14Speaker 04

  Beverage.

• 7:15Speaker 01

  To go along with it.

• 7:16Speaker 04

  Right.

• 7:16Speaker 01

  Cause it's quarantine-y time.

• 7:17Speaker 04

  It is. In this case, it's placebo-rita time.

• 7:19Speaker 01

  It is.

• 7:20Speaker 04

  Because alcohol, spoiler alert, makes you sleep badly.

• 7:23Speaker 01

  It's not good for your sleep.

• 7:24Speaker 04

  It's not good for your sleep.

• 7:25Speaker 01

  Even though lots of people use it as a sleep aid.

• 7:27Speaker 04

  Oh, it's bad.

• 7:27Speaker 01

  Or an anxiolytic.

• 7:29Speaker 04

  Mm-hmm.

• 7:29Speaker 01

  Uh, it's not good for either of those.

• 7:31Speaker 04

  I mean, alcohol's not good for anything, period.

• 7:33Speaker 01

  It's not good for your body.

• 7:35Speaker 04

  Yeah, there's no safe amount. Anyway.

• 7:37Speaker 01

  Anyways.

• 7:37Speaker 04

  So, we're doing a placebo-rita.

• 7:39Speaker 01

  Our placebo-rita is, is basically like a really nice version of a chamomile tea.

• 7:44Speaker 04

  But what is it called, Erin?

• 7:45Speaker 01

  It's called Pillow Talk.

• 7:49Speaker 04

  Yeah.

• 7:50Speaker 01

  The long pause of you trying to remember.

• 7:52Speaker 04

  Well, cause we had a few different options.

• 7:55Speaker 01

  We did.

• 7:55Speaker 04

  There was also bedtime story.

• 7:57Speaker 01

  Story, which this, what would work.

• 7:58Speaker 04

  It's a great one, yeah.

• 7:59Speaker 01

  Pillow Talk.

• 8:00Speaker 04

  Yeah, it's a chamomile tea.

• 8:02Speaker 01

  Mm-hmm.

• 8:02Speaker 04

  Plus ginger honey syrup.

• 8:04Speaker 01

  Yum.

• 8:05Speaker 04

  So good.

• 8:05Speaker 01

  A little.

• 8:06Speaker 04

  And a little bit of lemon.

• 8:07Speaker 01

  In there.

• 8:07Speaker 04

  Yeah.

• 8:08Speaker 01

  Kinda wish we had that to drink.

• 8:10Speaker 04

  Sounds nice. Sounds good for your throat.

• 8:12Speaker 01

  Yeah.

• 8:12Speaker 04

  Yeah.

• 8:13Speaker 01

  Anyways, but you can make one and drink along with us. We'll post the full recipe on our social media channels, for sure.

• 8:20Speaker 04

  Mm-hmm.

• 8:20Speaker 01

  Um, maybe on our website. Erin, walk us through the website.

• 8:23Speaker 04

  Oh, the website.

• 8:24Speaker 01

  Sorry for throwing it at you.

• 8:25Speaker 04

  What a treat. Yeah. The website is a real joy to discover.

• 8:29Speaker 01

  It is.

• 8:29Speaker 04

  You can find things like transcripts, you can find things like the sources for each and every one of our episodes. You can find links to our bookshop.org affiliate page, Goodreads list, merch, some pretty sweet merch. Uh, you can find links to music by Blood Mobile, to a contact us form, a firsthand account form, and probably some other things. There's an about us page, too.

• 8:50Speaker 01

  There is. It's got like four lines.

• 8:52Speaker 04

  Yep. Does not contain a lot of information.

• 8:55Speaker 01

  Oh, so check that out.

• 8:57Speaker 04

  Check it out.

• 8:58Speaker 01

  Make sure you are rated, rated, make sure you are ra, make sure you have subscribed.

• 9:03Speaker 04

  And rated.

• 9:04Speaker 01

  And like to.

• 9:04Speaker 04

  And reviewed.

• 9:05Speaker 01

  And review the podcasts. We would appreciate that.

• 9:07Speaker 04

  We're doing great.

• 9:08Speaker 01

  We're really killing it today.

• 9:09Speaker 04

  Yeah.

• 9:10Speaker 01

  Um, and if you are a fan of watching things, uh, we're on YouTube, on the Exactly Right Network channel.

• 9:16Speaker 04

  So you can see some sweet PJs that we're wearing.

• 9:19Speaker 01

  We're pretty excited about these.

• 9:20Speaker 04

  I really like, I really like yours. It's very Beetlejuice.

• 9:24Speaker 01

  Love yours, too. It is very Beetlejuice.

• 9:25Speaker 04

  Thank you.

• 9:25Speaker 01

  I love it. Um, we took a long time picking these out, everyone, so.

• 9:29Speaker 04

  We did.

• 9:29Speaker 01

  Okay. Well, with that, Erin?

• 9:33Speaker 04

  Shall we take a break?

• 9:34Speaker 01

  Business completed?

• 9:37Speaker 04

  Business complete.

• 9:38Speaker 01

  Let's move on to learning about sleep.

• 9:40Speaker 04

  Love it.

• 9:41Speaker 01

  Okay. What is one thing many of us deal with every single day, but rarely talk about? Dry hands. Whether you frequently wash your hands or deal with harsh weather, your hands can be left feeling dry, rough, cracked, and even uncomfortable. That's where O'Keefe's Working Hands Hand Cream comes in to help. The fast-absorbing formula goes on smoothly, and it won't leave behind a greasy residue, so you can get back to your busy day without ever missing a beat. And because a little will go a long way, O'Keefe's Working Hands Hand Cream is effective, dependable, and economical, too. Whether you're dealing with harsh weather outside, demanding work, or everyday wear and tear, O'Keefe's Working Hands works just as hard as you do. So keep your hands hydrated, smooth, and feeling comfortable all season long.

• 10:27Speaker 01

  Visit okeefescompany.com today. That's O-K-E-E-F-F-E-S company.com for guaranteed relief. O'Keefe's Working Hands. Yeah, it works.

• 10:40Speaker 00

  Hello, hello. I'm Malcolm Gladwell, host of Smart Talks with IBM. Imagine your business depends on a system you didn't build and don't fully control. For years, it works perfectly. It's fast, reliable, affordable. So over time, more and more of your operations rely on it. Then one day, the terms change. What once felt flexible now feels difficult to leave. Moving to another provider or bringing those capabilities back under your own control could take years, cost millions, and disrupt the business in the process. That's the challenge of digital sovereignty. Businesses today rely on all sorts of third-party systems: cloud platforms, data pipelines,

• 11:24Speaker 00

  AI models, software tools. Most days, these systems operate quietly in the background. But when something changes, like costs go up or rules shift, organizations are forced to confront how much control and flexibility they actually have. So to understand the challenge up close, I traveled to Paris to speak with IBM's Annapola Assis and Access CIO, Giovanni Daniele, two people who think about these questions every day.

• 11:56Speaker 00

  Hear the full conversation at ibm.com/smarttalks or wherever you get your podcasts.

• 12:20Speaker 01

  We all sleep. All of us, humans. And Erin, I know that you are going to walk us through some of the many different ways that animals sleep, which I'm quite excited about. Like, what does that mean in animals?

• 12:33Speaker 04

  What does it mean?

• 12:34Speaker 01

  And there's such a variety there.

• 12:35Speaker 04

  What does it mean in humans?

• 12:36Speaker 01

  Well, let me tell you about it. And that's an interesting question. It's because, like, because we all sleep. I think that we all know what it means to sleep. One could even go so far as to say, much like the Supreme Court Justice Potter Stewart said in 1964 when trying to define hardcore pornography. I know it when I see it.

• 12:57Speaker 04

  Know it when you see it. Yep, yep.

• 13:01Speaker 01

  We all know what sleep is. But what is sleep? If we're trying to put like a label on it, what are our brains doing when we sleep? And these are the questions that I'm going to try and answer today. But the biggest question is one that we cannot really answer with what we know.

• 13:22Speaker 04

  Why do we sleep?

• 13:23Speaker 01

  Exactly. Why do we sleep? We don't really know truly the function of sleep. But we do have a lot of thoughts and hypotheses which have various levels of support. So we'll get into some of that as well. And then next week, like we said, we'll talk more about what makes good sleep good and what makes bad sleep bad.

• 13:41Speaker 04

  It's so, and then what about like the quantities of sleep?

• 13:44Speaker 01

  And all of that stuff. And the consequences. We'll get into all of that.

• 13:46Speaker 04

  And the architecture of sleep.

• 13:47Speaker 01

  Oh, we'll get into all of it. Okay. So what is sleep? If we define it.

• 13:51Speaker 04

  Sure.

• 13:52Speaker 01

  A simplified definition is like a reduced state of voluntary motor activity. So you're not moving. You've got a decreased response to stimulation. And in general, there's a stereotypic posture associated with sleep. I know you'll talk more about that, Erin.

• 14:08Speaker 04

  No, I just love the thought of the stereotypic posture.

• 14:10Speaker 01

  I know, right?

• 14:11Speaker 04

  It's very cute.

• 14:11Speaker 01

  In humans, we lay down, right?

• 14:13Speaker 04

  Yeah.

• 14:13Speaker 01

  That's what we do for sleep. And in contrast to other states that might be similar to sleep, like say, a coma, sleep is easily reversible. Okay? But in reality, in medicine, we have defined sleep based on specific patterns of electrical activity in our brains.

• 14:30Speaker 04

  EEG.

• 14:31Speaker 01

  EEGs. So let's get into it. We talked about EEGs, or electroencephalograms, in our epilepsy episode.

• 14:38Speaker 04

  Oh, gosh, that was a long time ago.

• 14:39Speaker 01

  It was a while back, and at that time, I was just like, I don't want to get into it. Goodbye. And we just didn't talk about it.

• 14:45Speaker 04

  We'll do it someday. Today is that day.

• 14:46Speaker 01

  Today's the day. So EEGs measure the electrical activity happening in our brains. And the readouts of EEGs, when you see them on paper or on a computer, are these wave patterns. Kind of like, if you've ever edited, like, a sound file, you see these little wave patterns. They look very similar to that. And waves, if anyone hasn't taken physics in a long time, are measured by two main measurements, and that is amplitude, which is the height of the waves, and frequency, which is the number of waves per second or per unit of time.

• 15:20Speaker 04

  Right.

• 15:20Speaker 01

  Okay? So the higher the frequency, that means the faster the waves, the closer together the waves are. And we call that a high frequency. And then lower frequency are slower waves.

• 15:33Speaker 04

  Okay.

• 15:34Speaker 01

  So longer wavelength, longer frequency. Okay? Depending on what our brain is doing, our EEG makes a number of kind of predictable patterns, some of which we only see when we're awake, and some of which we only really see when we're asleep. So when we're awake, our EEG pattern shows these fast frequency.

• 15:55Speaker 01

  Low amplitude waves.

• 15:57Speaker 04

  Fast frequency, low amplitude.

• 16:00Speaker 01

  High frequency, low amplitude.

• 16:01Speaker 04

  Yeah, yeah, yeah.

• 16:02Speaker 01

  So they're like close together waves and they're, they're not they're just little, little baby waves.

• 16:08Speaker 04

  Yeah.

• 16:08Speaker 01

  And the most common two types of waveforms are called alpha waves and beta waves. There's a few others too.

• 16:14Speaker 04

  Uh huh.

• 16:14Speaker 01

  Um, alpha rhythms are like calm, eyes closed, like meditation type of vibes. And then beta waves are what we see more with like activity of the brain.

• 16:24Speaker 04

  Sorry. So we're talking about, these are sleep.

• 16:26Speaker 01

  Awake.

• 16:26Speaker 04

  Sleep. Oh, these are.

• 16:27Speaker 01

  These are awake.

• 16:27Speaker 04

  Okay, okay.

• 16:28Speaker 01

  This is what we're doing right now.

• 16:29Speaker 04

  Yeah, yeah.

• 16:29Speaker 01

  We're probably beta waving.

• 16:31Speaker 04

  We're definitely beta waving.

• 16:33Speaker 01

  Not calm at all.

• 16:36Speaker 01

  Um, but during sleep, our EEG patterns change. And we can measure more than just the brain electricity, actually. So when we're measuring sleep, there's three main sets of measurements that we're looking at. The EEG, which is your brain electrical activity. The EMG or electromylogram, which records activity in our skeletal muscles.

• 16:58Speaker 04

  Okay.

• 16:59Speaker 01

  And then the EOG or electro oculogram.

• 17:02Speaker 04

  Yes.

• 17:02Speaker 01

  Which is measuring.

• 17:04Speaker 04

  Rapid eye movement.

• 17:05Speaker 01

  Yes, horizontal eye movement. Um, and if we put all three of these together, they result in what's called a polysomnogram or PSG. So you can look up a picture of a PSG, but it's like a lot of wires all over.

• 17:18Speaker 04

  Yeah.

• 17:19Speaker 01

  And sometimes there's more if you're measuring like your pulse ox and your heart rate and things like that.

• 17:23Speaker 04

  Okay, I've always wondered this about sleep study things.

• 17:27Speaker 01

  Yeah.

• 17:27Speaker 04

  I feel like I would sleep terribly.

• 17:29Speaker 01

  I know. It's a, it's a valid concern. I don't have an answer for it.

• 17:33Speaker 04

  Okay, so like how, okay, another question then. How many nights will you sleep with wires, et cetera, to get like a good model of what your sleep is like?

• 17:43Speaker 01

  That's a great question. I don't know. A lot. A lot of times, it might just be one night.

• 17:51Speaker 04

  Just one night?

• 17:52Speaker 01

  Yeah, but it totally depends on like what the scenario is, what the study is, and like what information they get from that, kind of a thing.

• 17:58Speaker 04

  I find that so interesting because I feel like sleep is so variable.

• 18:01Speaker 01

  Oh, it's so variable, Erin. It can totally be so variable.

• 18:05Speaker 04

  Yeah.

• 18:06Speaker 01

  No, so I don't have a great answer to that.

• 18:07Speaker 04

  Okay.

• 18:08Speaker 01

  Yeah, yeah, totally, totally depends on the study and what they're doing, what they're looking for. But, based on these PSG readings, what we've done over the years in studying many people for longer periods and in the lab, etc., we now can divide sleep into two main phases. There's REM sleep.

• 18:25Speaker 04

  Just two?

• 18:26Speaker 01

  Well, two main like divisions.

• 18:28Speaker 04

  Yeah, yeah, yeah.

• 18:28Speaker 01

  There's phases within these. But the two main divisions are REM, or rapid eye movement sleep, and non-REM, or non-rapid eye movement sleep.

• 18:36Speaker 04

  Yeah.

• 18:37Speaker 01

  Within non-REM sleep, there are three different phases, sometimes four, sometimes stage three and four are separated.

• 18:44Speaker 04

  And this is just depending on classification, not like...

• 18:46Speaker 01

  Yeah, the older, the older literature kind of says there's four stages of non-REM, and the newer literature is like, realistically, deep sleep is all deep sleep. We'll just call it phase three.

• 18:57Speaker 04

  Oh, interesting, okay.

• 18:58Speaker 01

  Yeah, so anyways, doesn't really matter. But let's walk through what a night of sleep looks like, together, because we fall asleep in relatively predictable patterns. And as we fall asleep, our brainwaves kind of get slower and slower as we go. So, like I said before, as we're awake and relaxed, our brain is in this alpha wave pattern, which is low amplitude, relatively high frequency waves.

• 19:26Speaker 01

  Then, as we fall into stage one sleep, which is one of the stages of non-REM, we call it kind of drowsiness, we'll slip into this pattern called theta waves, which is slightly lower frequency, still low amplitude.

• 19:44Speaker 04

  Slightly lower frequency, okay.

• 19:46Speaker 01

  So a little longer wavelength and a little longer frequency than the alpha waves.

• 19:53Speaker 04

  Yep.

• 19:53Speaker 01

  But still low amplitude.

• 19:55Speaker 04

  Okay, little just chilling down there.

• 19:57Speaker 01

  Muscle-wise, you might have these little like twitches or muscle jerks, as we all know.

• 20:02Speaker 04

  Why?

• 20:03Speaker 01

  I don't know.

• 20:06Speaker 01

  And then, stage two, is when you start to truly fall asleep. This is when conscious awareness is gone. Your muscle activity decreases substantially. And your brainwaves will continue in this theta wave pattern. But then we see them punctuated by these really weird little bursts of activity. These short little bursts of super-high-frequency events that are called spindles, followed by what's called a K-complex, which is this very, it's a low-frequency, high amplitude, just like one-two punch.

• 20:39Speaker 04

  Low-frequency, high amplitude.

• 20:40Speaker 01

  So like, wide.

• 20:42Speaker 04

  Yeah.

• 20:42Speaker 01

  And tall.

• 20:44Speaker 04

  Weird.

• 20:44Speaker 01

  But just one, and that's a K-complex.

• 20:46Speaker 04

  Okay.

• 20:47Speaker 01

  And that's like, stage two. So we see this mostly like, slightly chiller pattern, then awake, and then little bursts of brrr, pa, pa.

• 20:55Speaker 04

  Yeah, yeah. Almost like a heartbeat, kind of.

• 20:58Speaker 01

  Yeah. Sure, I know, we'll say sure.

• 21:01Speaker 04

  Yeah.

• 21:02Speaker 01

  And then, after stage two, we fall into deep sleep, or slow-wave sleep. Stage three of non-REM.

• 21:09Speaker 04

  So I'm guessing, frequency goes down?

• 21:11Speaker 01

  Yes.

• 21:11Speaker 04

  Tell me about amplitude.

• 21:13Speaker 01

  Amplitude goes up. So we see this high amplitude, low, low-frequency, slow waves that we call delta waves.

• 21:21Speaker 04

  Um, what, what is, what does it mean to have high amplitude? You know?

• 21:26Speaker 01

  Yeah. So the waves are created essentially by this like, activity of our neurotransmitters happening all at once.

• 21:34Speaker 04

  Okay.

• 21:34Speaker 01

  And so, really, it's that the, the activity patterns in various parts of our brain have slowed down, essentially, is what we're seeing.

• 21:43Speaker 04

  For the frequency?

• 21:44Speaker 01

  Right.

• 21:44Speaker 04

  And what about the amplitude?

• 21:45Speaker 01

  I don't know the answer about amplitude. Yeah, I really don't. This is why I'm like, not an EEG expert, and maybe someone who is can let us know. Because I don't. But that is deep sleep, or slow-wave sleep. So we'll stay in that sleep for a period of time. Don't know how long, depends on you. And then, we pop up quickly to stage two. We pass through that pretty quickly. And then we enter our first REM sleep of the night.

• 22:13Speaker 04

  So, uh, deep sleep is one? That's stage, that's the first thing that we encounter?

• 22:19Speaker 01

  No, we go, we go stage one.

• 22:21Speaker 04

  Stage one.

• 22:21Speaker 01

  Stage two, stage three, which is deep sleep.

• 22:23Speaker 04

  Oh, okay.

• 22:24Speaker 01

  We'll stay there for a little while, and then we'll go stage two, REM.

• 22:28Speaker 04

  Got it.

• 22:29Speaker 01

  Okay. And in contrast to all these other sleep patterns where waves are getting longer and

• 22:36Speaker 04

  Yeah.

• 22:37Speaker 01

  In REM sleep, your brain EEG pattern looks like you're awake.

• 22:41Speaker 04

  Right.

• 22:41Speaker 01

  It is an awake beta wave, so not even like a calm alpha wave pattern. It's like a beta wave.

• 22:46Speaker 04

  Zzzzz, zzzzz, zzzzz.

• 22:48Speaker 01

  Type of pattern.

• 22:49Speaker 04

  Like we're recording an episode in our sleep.

• 22:51Speaker 01

  In our sleep.

• 22:54Speaker 01

  And REM sleep is also characterized by like a more awake type of physiology. Our blood pressure is higher, our heart rate is higher, our respiratory rate is higher compared to non-REM sleep.

• 23:04Speaker 04

  What about our temperature, our body temp?

• 23:06Speaker 01

  Oh, that's a good question. I think our body temperature goes up as well, too.

• 23:09Speaker 04

  Okay.

• 23:09Speaker 01

  Still probably not quite as high as it is because in general, our body temperature falls with sleep, but it's going to go up compared to deep sleep.

• 23:15Speaker 04

  Okay.

• 23:17Speaker 01

  However, we have two weird things happening in REM sleep that we do not see when we're awake, and that is these rapid horizontal eye movements.

• 23:26Speaker 04

  Yep.

• 23:26Speaker 01

  That happen. And our skeletal muscle activity is essentially atonic. We really do not move.

• 23:34Speaker 04

  We don't, so we move even less than we do in our falling asleep twitchy.

• 23:38Speaker 01

  Correct.

• 23:38Speaker 04

  Yeah.

• 23:38Speaker 01

  You might still have occasional muscle twitches.

• 23:41Speaker 04

  Right.

• 23:41Speaker 01

  But in general, your skeletal muscles, so like arms and legs, are not really moving.

• 23:46Speaker 04

  I know that this is all foundational so that someday we will talk about sleep disorders in more detail.

• 23:51Speaker 01

  Yes.

• 23:52Speaker 04

  But it is making me want to ask 1,001 questions.

• 23:55Speaker 01

  Yeah.

• 23:56Speaker 04

  About, about like what happens when sleepwalking. Anyway, we, yeah.

• 24:00Speaker 01

  Yeah. Sleepwalking is something you'd see more in the deep sleep.

• 24:02Speaker 04

  In the deep sleep.

• 24:03Speaker 01

  Right.

• 24:03Speaker 04

  Okay.

• 24:04Speaker 01

  Because you're, again, in REM sleep, your muscles are not moving.

• 24:07Speaker 04

  You're right.

• 24:07Speaker 01

  So in REM sleep, we can see things like sleep paralysis. We think that that's like your.

• 24:12Speaker 04

  In REM sleep. Yeah, because you can't move.

• 24:14Speaker 01

  You're having basically REM sleep muscle activity, but with an awake brain where you actually do wake up. And that's what we think is happening in sleep paralysis. And that's all I'm going to talk about when it comes to dreams.

• 24:27Speaker 04

  Yeah.

• 24:27Speaker 01

  FYI.

• 24:28Speaker 04

  Yeah.

• 24:29Speaker 01

  So, in a night of sleep, we cycle through both non-REM and REM sleep in a pretty typical pattern. We go from stage one to two to three, that quick pick stop at two, and then back up to REM.

• 24:41Speaker 04

  Mm-hmm.

• 24:41Speaker 01

  And that, once we end that REM cycle, is considered one sleep cycle. And in adults, a sleep cycle lasts between like 90 and 100 or so minutes.

• 24:52Speaker 04

  Okay.

• 24:53Speaker 01

  So depending on how long you sleep at night, we might go through like four or five or more of these cycles.

• 25:00Speaker 04

  Okay, I have a question about-

• 25:01Speaker 01

  Give it to me.

• 25:02Speaker 04

  Um, the REM, like, deep sleep. So I remember reading that deep sleep happens early on in the night.

• 25:10Speaker 01

  Correct, yes.

• 25:11Speaker 04

  Um, why? And, but REM sleep happens throughout?

• 25:15Speaker 01

  We tend to have more deep sleep early in the night.

• 25:18Speaker 04

  Mm-hmm.

• 25:19Speaker 01

  And then like shorter periods of REM sleep earlier in the night, and longer periods of REM sleep later in the night. And then it's possible that you might not, like, later in the night, drop all the way down to that deep sleep, like, stage three and REM. You might maybe just go to stage two, then up to REM a couple of times in your later sleep cycles.

• 25:39Speaker 04

  Hmm.

• 25:40Speaker 01

  Yes, that is true. Why? I don't know, Erin. It's also really interesting because like, the amount of deep sleep that you get also correlates to how much sleep you got, say, the night before. So if you are sleep deprived and you're running off of like, sleep debt, as they sometimes call it, um, then your next night of sleep will likely have more of that slow wave or deep sleep compared to the night before.

• 26:03Speaker 04

  Recovery sleep, kind of. So, the, in terms of the breakdown of, like, I'm, the sleep cycle, not even like the number, but just the proportion overall, oh, I'm getting ahead of things.

• 26:14Speaker 01

  You are, yeah.

• 26:15Speaker 04

  Because, but I'm like-

• 26:16Speaker 01

  You can ask it.

• 26:16Speaker 04

  What, what proportion of sleep, quote-unquote, should be REM, should be deep sleep, should be whatever, stage two?

• 26:24Speaker 01

  Yeah. It depends on your age and your stage of life and things like that. So babies have like a lot more REM sleep than adults. They've got like over 40% REM sleep. Adults, it's usually 20 to 30% is considered typical. Um, and then 20, I think it's like 15 to 20%, it's in my notes from next episode.

• 26:42Speaker 04

  Okay, okay.

• 26:42Speaker 01

  We'll get more into it. But yeah, it's usually like 15 to 20% or so is deep sleep.

• 26:47Speaker 04

  Oh, wow.

• 26:47Speaker 01

  Or should be deep sleep, typical deep sleep.

• 26:49Speaker 04

  Oh, my gosh. I mean-

• 26:50Speaker 01

  And then the rest is that like stage two type of sleep. Or bouncing between, you know, stage one and stage two.

• 26:57Speaker 04

  Sort of like, which is not, I mean, I feel like deep sleep and REM are like the stars of the show.

• 27:01Speaker 01

  Yeah, they get, they get the cred, even though they're not the majority of your sleep.

• 27:05Speaker 04

  Right, which is also important.

• 27:07Speaker 01

  It is, it is.

• 27:08Speaker 04

  Yeah.

• 27:09Speaker 01

  But that is like how your sleep cycle goes throughout the night. And it is going to depend how much time you spend in each one of these from night to night, from person to person. And anybody who has one of those rings or one of those watches that's monitoring your sleep knows that these things are going to vary night to night.

• 27:29Speaker 04

  Yeah.

• 27:29Speaker 01

  So, speaking of which, I just wanted to.

• 27:32Speaker 04

  Good, yeah, I'm glad you're talking about this.

• 27:34Speaker 01

  Just wanted to talk about these real quick because there is so much out there right now that's like, you need one of these rings to monitor your sleep and you need to be monitoring your sleep. And these are, this one is the best one to be monitoring it, etc.

• 27:50Speaker 01

  I found a paper that was not sponsored by the manufacturer of any of these devices. Just the one.

• 27:57Speaker 04

  Just one.

• 27:58Speaker 01

  There's a lot of other papers that are sponsored by, that were like funded by the manufacturing of these things, who will say like, oh, these are like 75 to 80% accurate compared to PSGs. Like, these are super, super accurate.

• 28:07Speaker 04

  Yeah.

• 28:08Speaker 01

  So I found one paper that was comparing a number of different rings. It wasn't as much looking at the watches. That was trying to figure out, could these be as good as PSGs that we do in clinic? Which is really important because especially to diagnose a lot of sleep disorders, like we do need this data.

• 28:25Speaker 04

  And it's like accessibility and ease and all of these things, yeah.

• 28:28Speaker 01

  Right, so it's like if we could use these clinically, that would be really awesome.

• 28:31Speaker 04

  Right, and then you're not having to wear all of these tubes that make you sleep poorly. And then you're like, you're a terrible sleeper, you need all these things. And it's like, I was just had hooked up to wires all night.

• 28:40Speaker 01

  Well, and like the ability to be able to do it at home.

• 28:43Speaker 04

  Yeah.

• 28:44Speaker 01

  Is so, yeah, so there's so much that would be great if these things were really great. The problem is that they're not. And it's not that they're not. Decent.

• 28:54Speaker 04

  Yeah.

• 28:55Speaker 01

  But I will quote here because I think that this quote kind of summarizes it all. What they said was that even the ones that correlate very strongly with the PSGs, who like on average agree with what the PSG readings are. They said that, quote, "This agreement masks substantial individual level inaccuracies, prohibiting their use in clinical sleep medicine as accurate assessment of individual nights, including both nights with exceptionally low or high quality and quantity is essential for patient care."

• 29:30Speaker 04

  Mm-hmm.

• 29:30Speaker 01

  So like on average, if you're just looking like population wide, sure, they decently, they do decently well, but on a night to night basis, there's a lot of variability in how well it's capturing you as an individual.

• 29:42Speaker 04

  That makes sense. So you can't wake up in the morning and go, "How was last night?"

• 29:46Speaker 01

  Right.

• 29:46Speaker 04

  Oh, yeah, I see what happened. Yes. Yeah, yeah, yeah. Like we did this morning.

• 29:51Speaker 01

  Like we did, like we've been doing the last couple of weeks.

• 29:53Speaker 04

  Mm-hmm.

• 29:54Speaker 01

  So, yeah, so that's just what I want to say about those. It's like, they're not...

• 29:58Speaker 04

  I have heard that like, so they're not great at distinguishing between, among the stages of sleep.

• 30:03Speaker 01

  Correct.

• 30:04Speaker 04

  But they are okay at distinguishing awake and sleep.

• 30:08Speaker 01

  Yes. So like to get like total duration, they're pretty decent.

• 30:11Speaker 04

  Right.

• 30:12Speaker 01

  But again, if you're trying to like understand, especially like quality, what we call quality, and like differentiating between the different stages and things like that, or even if you're trying to, and this paper was specifically more looking at people who have, say, like obstructive sleep apnea or some other kind of sleep disorder where you really want to be able to get that fine detail.

• 30:31Speaker 04

  Yeah.

• 30:31Speaker 01

  They weren't going to be effective for that.

• 30:34Speaker 04

  I see.

• 30:34Speaker 01

  And most of the studies funded by the manufacturers are looking at like the general population, so like healthy people without any diagnosed sleep disorders or anything. So it's also a different population level that we're looking at.

• 30:45Speaker 04

  Right, right.

• 30:46Speaker 01

  So, yeah, so that's what we know about those devices. Moving on, before I get too deep into like why, what is happening, we know now what our brains are doing as we monitor them, but before we get into the maybe why of it, I want to touch base really quickly on kind of how we sleep, like what is driving our sleep?

• 31:07Speaker 04

  Okay.

• 31:07Speaker 01

  Okay.

• 31:08Speaker 04

  Sleep drive.

• 31:08Speaker 01

  Sleep drive. That's the answer. We did talk a little bit about this in our circadian rhythm episode. Yes. Because our circadian rhythm is one of the drivers of our sleep. So as a recap, so that you don't have to listen to that episode again. There's a collection of cells deep in like the center front of our brain, behind our eyes. Mm hmm. Deep in our brain. That's called the suprachiasmatic nucleus. That is the clock of our brain. The SCN. The SCN. Yep. And it basically generates this close to 24 hour rhythm. All of our cells do this to one degree or another. Which is really cool. It's so cool, but this is like the master clock that keeps all of our body functions in sync, mostly using signals from light and dark from the sun. Right?

• 31:52Speaker 01

  And this circadian clock of ours drives things like hormone production, among many other things, that help to promote sleep and awake at the right times of day and night for us as diurnal creatures. But our brain also has other mechanisms aside from just the circadian clock that help to promote both sleep and wakefulness, or what's called arousal in the literature. Yeah. And it's mostly parts of our brain stem. Right. And our brain stem is like the deep back part of our brain that connects to our spinal cord. The stem. The stem. And it parts of our brain stem release a whole bunch of neurotransmitters

• 32:34Speaker 01

  that are involved mostly in promoting wakefulness. And wakefulness. Right, so promoting us being awake. Yeah. And active during the day. These are things like histamine, dopamine, noradrenaline, serotonin. All of these types of things that act in other parts of our brain to be like, go do things. Be awake. Yeah. That's what I imagine they're saying. And we think that sleep ends up happening from a couple of things changing in our brain. One is that there's other parts of our brain closer towards the front of it that send signals to start to inhibit those awake signals. So like at some point in the day, other parts of our brain will send signals and be like, hey, listen, histamine, chill out a little bit. You've done enough today.

• 33:19Speaker 01

  So they'll start to inhibit the release of histamine or orexin or other signals that are saying, be awake, be awake, right? And so, okay. And then the other part. I'll wait. Yeah. The other part is that, and this I think is really interesting. We also, during the day, like just with our normal metabolism, how our brain is functioning all day long, we are making a bunch of stuff. And some of those things, we think, act as like sleepy substances. Where as they build up in our brains throughout the day, as the concentration of this substance, or these substances really, accumulate in our body tissues, including our brain, they increase sleep pressure.

• 34:03Speaker 04

  Yeah.

• 34:04Speaker 01

  One of the classic ones of these is adenosine.

• 34:07Speaker 04

  Mm-hmm.

• 34:08Speaker 01

  And adenosine, we produce just as a byproduct of metabolism. But as we produce that and it builds up in our brain, it makes us more sleepy. Caffeine, which we talked about.

• 34:18Speaker 04

  I was just about to ask about caffeine.

• 34:20Speaker 01

  Yeah. Caffeine inhibits the adenosine receptors. So it tricks our brain into thinking that we don't have a buildup of this sleepy substance.

• 34:29Speaker 04

  Right.

• 34:29Speaker 01

  When we actually do. And that's how it works to keep us awake.

• 34:32Speaker 04

  What about, like, morning, though? Because if we're starting, are we starting the day fresh? Everything's cleared out?

• 34:38Speaker 01

  Mm-hmm.

• 34:38Speaker 04

  Tell me again about caffeine. It's been way too long since that episode.

• 34:41Speaker 01

  So caffeine, basically, like, we, because we're making adenosine, just like from metabolism, we break down ATP, and we make adenosine.

• 34:48Speaker 04

  Yeah.

• 34:48Speaker 01

  So throughout the day, it's just gonna build up, build up, build up, build up. And it's gonna bind to these receptors that do inhibition stuff. That's like, go to sleep, go to sleep. Caffeine binds to those receptors.

• 34:59Speaker 04

  Right.

• 34:59Speaker 01

  So it doesn't matter how much adenosine you have, there's nothing for them to bind to.

• 35:02Speaker 04

  Got it.

• 35:03Speaker 01

  Because caffeine is blocking them. And so it tricks our brain into being like, there's no adenosine here, I don't need to go to sleep. And it is quite effective. Like, there's so many studies on, like, caffeine helping to alleviate sleepiness.

• 35:14Speaker 04

  I, I think that, like, what is so interesting, okay, speaking for myself.

• 35:19Speaker 01

  Yeah.

• 35:20Speaker 04

  I feel like, when, if I am sleepy during the day, or in the evening, or whatever, just at, at any point in the day, I'm like, I didn't get good sleep, I'm really tired. And I feel like I, I expect that if, to get really good sleep, or getting really good sleep, makes me have no sleep drive, and that's the ideal.

• 35:40Speaker 01

  Oh, that's so interesting.

• 35:41Speaker 04

  You know what I mean?

• 35:41Speaker 01

  Yeah, yeah, like, you shouldn't ever be sleepy if you're getting good sleep.

• 35:44Speaker 04

  I shouldn't be sleepy until it's right before bed, and now I just lay back, close my eyes, and I'm out.

• 35:48Speaker 01

  Boom.

• 35:48Speaker 04

  And I'm like, that would be great.

• 35:49Speaker 01

  That would be great.

• 35:50Speaker 04

  But like.

• 35:51Speaker 01

  It's not realistic.

• 35:51Speaker 04

  It's not realistic. So sleep drive is so important, is what I'm saying.

• 35:54Speaker 01

  It is. Well, and it's also, it's interesting, too, because there is this, um... There's like a buildup of our sleep drive versus our circadian rhythm. And so sometimes those kind of cross paths at a weird time where we can get more sleepy than we expect in like the middle afternoon or something like that. Yeah. And so that's part of why we might feel sleepy at times of day where we think like, I don't understand why I feel sleepy right now. Right. And it's just maybe because things are, you know, it hasn't overlapped in exactly the right way today, kind of a thing. But it doesn't necessarily mean that your sleep was terrible the night before. Right. So it is really interesting and I'm probably not doing it justice. But there's obviously a lot, and it's not just adenosine, right? There's a lot of other substances that we think are involved in this.

• 36:38Speaker 01

  So there's a lot that goes into when and how we're sleepy. And some of it too is genetics. So we know that some of our sleep drive and a lot of our circadian rhythm, like whether we are a night owl or a morning bird. Morning lark. Morning lark. Like some of that is genetics. There's also some genetic markers that we think are associated with like very short sleep, where people sleep very little but are totally fine. Oh, yeah. Right? And our need for and our pattern of sleep also changes drastically over our lifetime. It does. My favorite example of this are tiny babies. Oh, yeah. Because even though fetuses sleep when they are still in utero, they do that like

• 37:23Speaker 01

  mostly in sync with the human who's housing them. But once a baby is born, they do not have a well-defined circadian clock. It's a mess. It is a disaster. Yeah. Their circadian clock is much less than 24 hours. And their sleep pattern, like I said, a sleep cycle is like 90 minutes. It's much shorter in babies. So they're also cycling through a whole cycle of sleep in much less time. Yep. And their sleep pattern is totally random. Yeah. Completely random. And they'll sleep up to like 16 hours a day.

• 38:00Speaker 04

  Like a dog.

• 38:01Speaker 01

  And not in any pattern that's compatible with adult sleep patterns. And it's not until the first like six to 12 months of life that they start to consolidate their sleep into these 24 hour patterns. And because I fell into what is very common these days of being very obsessive about my infant sleep when my first child was born, I have data that you can check out if you're watching the YouTube of my kid's sleep pattern when he was an infant and you can see that it is literally all over the place.

• 38:33Speaker 04

  I don't think anyone listening is surprised that you collected data for how many months of your first kid's life?

• 38:39Speaker 01

  So many months.

• 38:40Speaker 04

  So many.

• 38:41Speaker 01

  I mean, the first probably 15 months.

• 38:42Speaker 04

  And that's just one aspect of it.

• 38:43Speaker 01

  I had all of the data.

• 38:44Speaker 04

  The amount of proof I remember too.

• 38:45Speaker 01

  There was so much.

• 38:46Speaker 04

  Yeah.

• 38:46Speaker 01

  Yeah, the second one, I didn't do any of that. But you can then see that by 11 or 12 months, even though sleep wasn't great, you can see this 24 hour pattern emerge where there's like a nap in the middle of the day or maybe two naps, but then the majority of sleep is happening over the nighttime period. And that is because that's how long it really takes for infants to develop this 24 hour pattern, which I think is just so interesting. And then the amount of sleep that we need over our lifetime changes too. Kids need a lot more sleep. Teenagers, we talked about in our circadian rhythm episode, do actually have a shift in their circadian rhythm towards night owl tendencies.

• 39:25Speaker 04

  Yeah.

• 39:26Speaker 01

  And so they tend to sleep later and wake up later. And that can put them out of sync with our modern society. And then as adults, especially older adults, a lot of times we don't need quite as much sleep. So the amount of sleep that we actually need varies.

• 39:43Speaker 01

  So why do we need this much sleep? Like, why? I'm asking you, but I'm not. It's a rhetorical question that I'm going to try and answer.

• 39:53Speaker 04

  Are we asking the room?

• 39:54Speaker 01

  We're asking, does anybody know?

• 39:56Speaker 04

  Does anyone know?

• 39:59Speaker 01

  We still, like, we still don't really know.

• 40:02Speaker 04

  We don't.

• 40:03Speaker 01

  Exactly what our brains are doing in terms of the function of our sleep.

• 40:07Speaker 04

  Like, we know what happens, we know there are bad things that happen when we don't get enough sleep.

• 40:11Speaker 01

  Correct, and we'll talk a lot about that.

• 40:13Speaker 04

  That's what guides a lot of our assumptions about why sleep is important.

• 40:17Speaker 01

  Yes, and like, what our brains are really, like, doing during sleep.

• 40:20Speaker 04

  Yeah.

• 40:20Speaker 01

  So, we do see, and one of the, one of the hypotheses, I'll kind of walk through the biggest ones. One of the hypotheses is that it is kind of energy conservation during sleep.

• 40:30Speaker 04

  Yeah.

• 40:30Speaker 01

  And that is because we do see a relative decrease in metabolism during sleep.

• 40:35Speaker 04

  Mm-hmm.

• 40:35Speaker 01

  However...

• 40:37Speaker 04

  Not really, I mean, especially... Yeah, yeah, yeah.

• 40:39Speaker 01

  Especially if you're looking at total body metabolism, like, during REM sleep, our metabolism is essentially the same as when we're awake. Our brain metabolism does decrease substantially, especially during non-REM sleep. But again, that's only a portion of our total sleep.

• 40:55Speaker 04

  Right.

• 40:56Speaker 01

  And it's nothing, like, like, our sleep is nothing like hibernation, or torpor, or something, where we're truly decreasing metabolism.

• 41:02Speaker 04

  Yeah.

• 41:03Speaker 01

  So that's clearly not the whole story, could be part of it. There is a lot of evidence that we see changes in things like gene expression. So, like, certain things turn on and certain things turn off when we're asleep. That only happens when we're asleep, so we think that must be important. But why exactly, we don't know.

• 41:22Speaker 04

  I mean, yeah.

• 41:23Speaker 01

  Because I talked about these, like, sleepy substances and things like that, we do think that there's sort of, like, a clean out of the buildup of these neurotransmitters that happens during the day.

• 41:33Speaker 04

  Detox.

• 41:34Speaker 01

  Yeah, brain detox, I hate that word, it's not accurate. But, but we do see, like, an increase of cerebral spinal fluid flow during sleep and things like that.

• 41:42Speaker 04

  Washes over the brain, is how I've just heard it described, yeah.

• 41:46Speaker 01

  Getting rid of all these neurotransmitters and replenishing others as well.

• 41:49Speaker 04

  It's very, like, it's a very satisfying image to think about, just like, whoosh, just like a gentle washing of the brain.

• 41:56Speaker 01

  That's what you're hearing as you fall asleep, anyways.

• 41:59Speaker 04

  Great white noise.

• 42:02Speaker 01

  How much of, is that the function of sleep? Maybe.

• 42:06Speaker 04

  Yeah.

• 42:07Speaker 01

  And then one of the biggest hypotheses is that sleep is required for consolidation of our memory.

• 42:12Speaker 04

  Memory consolidation.

• 42:15Speaker 01

  Why do we have to whisper?

• 42:16Speaker 04

  I don't know.

• 42:18Speaker 01

  And we do know there's something called sleep-dependent memory processing, where there's done, we've done a bunch of studies where if you give humans or animals a task and then deprive them of sleep, they never really learn that task to the same degree that they would if you let them sleep after it. But even this, the data is a little, it's a little bit controversial still, that like, is this truly the function of sleep? Especially because it's like, we're trying to compare human brains to like, well, we don't have, like, lots of animals sleep that don't, we don't know anything about their memory. Oh, you'll get to it. You'll get to it with those eyebrows. Sorry. I love it. But, but yeah, that's, that is one of the kind of big hypotheses, that like, sleep really is essential for our memory.

• 43:01Speaker 04

  What, okay, but like, I don't understand why that's controversial, only in that if it's overstated that this is the function.

• 43:09Speaker 01

  That's what it is. That's what it is. It's that, like, we know that it's essential.

• 43:12Speaker 04

  It is a function.

• 43:13Speaker 01

  It is a function. But I think, I think that it's just that people are so obsessed with this idea that there is like, a reason for things.

• 43:20Speaker 04

  Nah. That's just, sorry.

• 43:24Speaker 01

  But that's true, right? Like, it's not, we're not gonna get to, oh, oh, blah, like, this like, glorious.

• 43:32Speaker 04

  Enlightenment will not, will not arrive.

• 43:33Speaker 01

  It's, a bunch of different things happen when we sleep.

• 43:36Speaker 04

  I know. It's not, it's not as satisfying as, we found it. Here is the answer.

• 43:41Speaker 01

  The reason for sleep.

• 43:43Speaker 04

  Right.

• 43:43Speaker 01

  The singular function of sleep.

• 43:46Speaker 04

  Yeah.

• 43:46Speaker 01

  That's ridiculous. We sleep for a bunch of different reasons. And as we'll see in next episode, if we don't, there's a problem.

• 43:52Speaker 04

  A lot of different things happen.

• 43:53Speaker 01

  A bunch of problems.

• 43:54Speaker 04

  Beyond memory.

• 43:56Speaker 01

  But, that's for next episode. So Erin, what I'd like to know from you, please, is like, obviously, I know my dog sleeps. My cat, all he does is sleep.

• 44:08Speaker 04

  Yeah.

• 44:09Speaker 01

  Do, do all animals sleep? Like?

• 44:10Speaker 04

  Oh, do they?

• 44:12Speaker 01

  Do they?

• 44:13Speaker 04

  Do they? I'll tell you.

• 44:15Speaker 01

  Okay.

• 44:18Speaker 01

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• 45:16Speaker 00

  Hello, hello. I'm Malcolm Gladwell, host of Smart Talks with IBM. Imagine your business depends on a system you didn't build and don't fully control. For years, it works perfectly. It's fast, reliable, affordable. So over time, more and more of your operations rely on it. Then one day, the terms change. What once felt flexible now feels difficult to leave. Moving to another provider or bringing those capabilities back under your own control could take years, cost millions, and disrupt the business in the process. That's the challenge of digital sovereignty. Businesses today rely on all sorts of third-party systems:

• 45:59Speaker 00

  cloud platforms, data pipelines, AI models, software tools. Most days, these systems operate quietly in the background. But when something changes, like costs go up or rules shift, organizations are forced to confront how much control and flexibility they actually have. So to understand the challenge up close, I traveled to Paris to speak with IBM's Anupala Assis Anaxas CIO, Giovanni Daniele, two people who think about these questions every day.

• 46:33Speaker 00

  Hear the full conversation at ibm.com/smarttalks or wherever you get your podcasts.

• 46:57Speaker 04

  In 1971, renowned sleep researcher Alan Rixshoffin wrote that, quote, "If sleep does not serve an absolute vital function, then it is the biggest mistake the evolutionary process has ever made," end quote.

• 47:13Speaker 01

  I love that.

• 47:15Speaker 04

  Right?

• 47:15Speaker 01

  Yeah.

• 47:15Speaker 04

  Okay, so let's, let's break that statement down. First, why would sleep be a mistake? It leaves us vulnerable

• 47:22Speaker 01

  Super.

• 47:23Speaker 04

  to predators and bugs and parasites transmitted by bugs. And it takes up precious time that we could be using to do something else, like forage, or mate, or socialize, or read a book, or do your taxes, or play with your kids, or exercise, or cook a nice meal, or work more hours at the office.

• 47:38Speaker 01

  So true.

• 47:39Speaker 04

  So many things. I know that many tech bros view sleep as a mistake.

• 47:42Speaker 01

  Oh, yeah. You don't even need it.

• 47:44Speaker 04

  You don't need it.

• 47:45Speaker 01

  You could just wake up at 3 a.m. Sorry.

• 47:49Speaker 04

  Wow.

• 47:52Speaker 04

  I think something just happened there.

• 47:53Speaker 01

  I flipped.

• 47:54Speaker 04

  I liked it. But I mean, that aside, though, I do think that most of us have, at one point in our lives, wished that we didn't have to sleep as much as we did. Because like, we could get so much more done. I know that I have wished that. Like, gosh, I could just, if I didn't have to sleep as much, I could do things I wanted to do. It is undeniable that sleep is costly. But it would only be a mistake if we didn't get anything out of it.

• 48:20Speaker 01

  Right.

• 48:21Speaker 04

  Okay, so second, does sleep serve a vital function? From what you just told us, Aaron, it serves multiple vital functions. We may not know precisely how sleep helps us and the pathways that it works along. But we know from experimental and observational research that sleep deprivation is harmful. And that when we lose out on sleep, our body compensates by increasing sleep. There's like sleep homeostasis, kind of.

• 48:45Speaker 01

  Totally.

• 48:46Speaker 04

  Okay, so now, why would sleep be the biggest mistake that the evolutionary process ever made? Because sleep is ubiquitous across the animal kingdom.

• 48:55Speaker 01

  Love this.

• 48:56Speaker 04

  At this point, in our understanding of sleep, it would be much harder to prove that an animal doesn't sleep than determine that it does.

• 49:04Speaker 01

  Okay.

• 49:05Speaker 04

  Even cavefish species, like the Mexican blind cavefish, which has lost eyes and pigmentation and much of their circadian rhythm patterns.

• 49:12Speaker 01

  Because they're in the complete black darkness.

• 49:15Speaker 04

  Complete darkness.

• 49:15Speaker 01

  Yeah.

• 49:16Speaker 04

  They still retain some sleep.

• 49:18Speaker 01

  Wow.

• 49:18Speaker 04

  It's reduced as much as like 80%, but still, there are indications of sleep. What does indications of sleep mean?

• 49:25Speaker 01

  Especially in a fish.

• 49:26Speaker 04

  I know. Okay. So for us to recognize and measure sleep in non-human animals, we have to step outside of our human box.

• 49:34Speaker 01

  Right.

• 49:34Speaker 04

  So for one, there's the logistical challenge of recording an EEG on a Mexican blind cavefish. Like, that's...

• 49:40Speaker 01

  Can you do it?

• 49:40Speaker 04

  Can you do it? I don't know. It's pretty difficult, challenging. And then for two, we want to be able to observe sleep in more natural settings. And for three, it's important to step back from our tendency to make humans like the ideal, the norm, right? Like, oh, if you don't sleep like a human, are you sleeping?

• 49:58Speaker 01

  Are you even sleeping at all?

• 50:01Speaker 04

  So we can measure sleep electrophysiologically using EEGs, and we have done that for a number of animal species. And we can measure it behaviorally. So researchers use five criteria to say that an animal sleeps. Number one, and it's very similar, like you mentioned some of these. Number one, prolonged behavioral quiescence. Basically, stop doing stuff.

• 50:21Speaker 01

  You're not doing stuff.

• 50:23Speaker 04

  Not doing it.

• 50:23Speaker 01

  Okay.

• 50:24Speaker 04

  Number two, reversible upon stimulation, unlike, like you said, torpor or a coma.

• 50:29Speaker 01

  Okay.

• 50:30Speaker 04

  Three, a species-specific posture. It's not just humans, like laying down or tucking your antenna away. And then I have a picture of my dog in bagel formation, which is a very...

• 50:41Speaker 01

  Bagel.

• 50:41Speaker 04

  He's one of his favorites. Number four, increased arousal threshold. So you need a louder or like more substantial stimulus, like a noise to get you to respond that if you're awake.

• 50:53Speaker 01

  Decreased response to stimulation, same idea.

• 50:55Speaker 04

  You may be like whispering like, hey, wake up now.

• 50:57Speaker 01

  Could you please roll over?

• 50:59Speaker 04

  Right.

• 50:59Speaker 01

  Might not do it.

• 51:00Speaker 04

  You're snoring.

• 51:03Speaker 04

  So like your senses are dulled.

• 51:05Speaker 01

  Right.

• 51:05Speaker 04

  And number five, rebound. After being sleep deprived, you sleep more. And so these are the things that we can use to say that animal is sleeping.

• 51:12Speaker 01

  Okay.

• 51:12Speaker 04

  Because it's doing all these things.

• 51:14Speaker 01

  Okay.

• 51:15Speaker 04

  And so using these criteria, we can describe and define sleep in a huge array of species like pond snails, octopus, cuttlefish, which may even exhibit REM sleep.

• 51:26Speaker 01

  Sorry, snails.

• 51:28Speaker 04

  Snails. Oh, it gets even more extreme.

• 51:30Speaker 01

  Keep going, keep going.

• 51:31Speaker 04

  Lobsters, mice, armadillos, flies. And funnily enough, whether animals truly sleep is kind of a more recent question. Ancient scholars like Aristotle fully believed that animals sleep.

• 51:42Speaker 01

  Like, of course.

• 51:42Speaker 04

  Yeah, of course they sleep. And there's an adorable quote I'm going to read to you from an 1865 book called Yearbook of Facts. Quote, "An insect composes itself to sleep with its antennae folded. Some of the beetles adjust them to their breast. The butterfly seeks some particular aspect of a tree and folds vertically its wings, throws back the antennae, and remains motionless and insensible to all external circumstances. When caterpillars, which are insatiable feeders, are observed resting immovable with their heads down, they are asleep."

• 52:15Speaker 01

  I love it.

• 52:16Speaker 04

  End quote.

• 52:16Speaker 01

  Isn't that cute? They're like, we don't need an EEG, bro. Just look at the bugs.

• 52:19Speaker 04

  Look at their little antennae. They're all beep boop.

• 52:22Speaker 01

  Yeah. And you can hear them quietly snoring.

• 52:24Speaker 04

  Oh, yeah. So sweet.

• 52:26Speaker 01

  So cute.

• 52:28Speaker 04

  But it's still helpful to have these specific standards for what counts as sleep because we can then also try to trace the genetic basis and neurological pathways of sleep.

• 52:36Speaker 01

  Okay.

• 52:37Speaker 04

  Okay, so for example, sea elegans, the research world's favorite worm, contains a mere 302 neurons.

• 52:45Speaker 01

  Wow.

• 52:45Speaker 04

  Compared to an adult fruit fly, which has 250,000.

• 52:48Speaker 01

  Wow, okay.

• 52:49Speaker 04

  So, right? And since sea elegans sleeps, we can map out the neural pathway of sleep, at least in that critter, because there are so few neurons.

• 52:57Speaker 01

  Wow, that's really cool.

• 52:59Speaker 04

  Okay, really cool. But what's even more amazing is that this isn't the quote unquote, like, simplest creature to sleep.

• 53:05Speaker 01

  Okay.

• 53:06Speaker 04

  Using those behavioral criteria, researchers concluded that the upside down jellyfish in the genus Cassiopea sleep.

• 53:14Speaker 01

  Jellyfish. Jellyfish.

• 53:16Speaker 04

  Jellyfish. Unlike sea elegans, these jellyfish, they don't have a central nervous system. No. Just a nerve net, like rings of neurons.

• 53:24Speaker 01

  Yeah.

• 53:24Speaker 04

  And so scientists observed that when the jellyfish is active, their nerve net contracts and causes pulsing behavior that lets them feed and get nutrients. But at night, the pulsing behavior reduces and they become less responsive to external stimuli. And then when you disrupt their resting time, like you keep splashing them with water or waves or whatever, they will pulse even less the next day, indicative of sleep rebound.

• 53:49Speaker 01

  Oh, my gosh.

• 53:50Speaker 04

  Right?

• 53:51Speaker 01

  I love it.

• 53:51Speaker 04

  Isn't that wild?

• 53:52Speaker 01

  Yes.

• 53:53Speaker 04

  And so this means that sleep likely evolved before a central nervous system.

• 53:58Speaker 01

  That is so interesting.

• 54:00Speaker 04

  Huge, huge.

• 54:02Speaker 01

  Especially the context of memory and stuff like that, right?

• 54:05Speaker 04

  Well, I mean, OK, yeah.

• 54:07Speaker 01

  OK.

• 54:07Speaker 04

  Yeah, yeah, yeah, yeah.

• 54:10Speaker 04

  But like, this is, this is an ancient and widespread thing.

• 54:13Speaker 01

  Right.

• 54:13Speaker 04

  And so, given how ancient and widespread it is, it doesn't really seem like sleep is, it's, is a mistake.

• 54:19Speaker 01

  No.

• 54:20Speaker 04

  And as far as, I mean, sleep doesn't get fossilized because it's a behavior. But as far as we can tell, no species has entirely lost the capacity for sleep, meaning that it is still so vital to

• 54:30Speaker 01

  You can't get around it.

• 54:31Speaker 04

  Continued existence.

• 54:32Speaker 01

  Yeah.

• 54:32Speaker 04

  Yeah. Sleep disturbances or a lack of sleep can have profound effects on health and overall performance, vulnerability to infections, attentiveness, reaction time, memory formation. Mollusks that have been deprived of sleep cannot form new memories. So like, it goes deep.

• 54:50Speaker 01

  How do you measure a mollusk's memory?

• 54:52Speaker 04

  I don't know. I didn't go that deep.

• 54:55Speaker 01

  Now I need to.

• 54:56Speaker 04

  Oh, I will find the paper for you and send it your way.

• 54:59Speaker 01

  OK, I love it.

• 55:00Speaker 04

  And then there are a few gruesome experiments where rats that were completely deprived of sleep for like, a long period of time, died.

• 55:07Speaker 01

  Oh, my gosh.

• 55:08Speaker 04

  They died, yeah. The world record for no sleep, sleep deprivation in a human, is 11 days.

• 55:14Speaker 01

  I heard that.

• 55:15Speaker 04

  264 hours, held by a San Diego teenager named Randy Gardner, who in 1965 played basketball throughout the night to stay awake. But apparently, like, I think in, I don't know how they determine this, but they were discovering that he was taking like micro naps.

• 55:31Speaker 01

  Of course he was.

• 55:32Speaker 04

  And so was it truly 264 hours?

• 55:34Speaker 01

  No.

• 55:35Speaker 04

  You know, yeah.

• 55:35Speaker 01

  I mean, his brain was falling asleep, he just did not know it.

• 55:38Speaker 04

  He didn't know it. And no one else knew that he was.

• 55:40Speaker 01

  Right.

• 55:41Speaker 04

  Yeah. But in any case, that's like a do not try that at home situation.

• 55:43Speaker 01

  No.

• 55:44Speaker 04

  Yeah. So even though we all sleep in some capacity, we don't all sleep the same. Elephants sleep about half the time that humans do, four hours compared to our eight, which is really more like six to seven. Brown bats sleep about 19 hours a day, similar to armadillos. Koalas sleep even longer, 20 to 22 hours. Meanwhile, donkeys sleep about three hours. Cats sleep 12 and a half hours a day, which seems like an underestimate.

• 56:10Speaker 01

  Absolutely an underestimate.

• 56:11Speaker 04

  Goats, 5.3 on average. Guinea pigs, 9.4. I mean, just to show you, it's all over the map.

• 56:17Speaker 01

  Yeah.

• 56:18Speaker 04

  And really, many of these sleep duration estimates, we do have to take with a grain of salt because like we're measuring sleep in the lab.

• 56:24Speaker 01

  Right.

• 56:24Speaker 04

  And so there tends to be a bias towards like longer sleep because they're like, I don't have to worry about predators.

• 56:32Speaker 01

  What else am I gonna do?

• 56:32Speaker 04

  I've got food here.

• 56:33Speaker 01

  Yeah.

• 56:33Speaker 04

  I've got water. I'm chilling.

• 56:35Speaker 01

  Might as well take a nap.

• 56:36Speaker 04

  Might as well just nap all the time. But even still, we do have this huge variation in how much sleep different species need. But duration is just one component of sleep, as we talked about. There's also whether you sleep in one big chunk or multiple times throughout the day or throughout the night. Like monophasic sleep is one big chunk, which is what humans usually do, big asterisk on that. Biphasic sleep, which is two chunks, which is what humans maybe used to do, asterisk on that. Or polyphasic sleep, like multiple chunks, like my dog who sleeps constantly.

• 57:12Speaker 01

  The cat.

• 57:12Speaker 04

  Yep. Whether you tend to sleep during the nighttime during or during the day is another big component of this, like a red-tailed hawk versus a barn owl, for instance, if we're talking birds. And not all owls are nocturnal, a lot are crepuscular. So it took me a while to find one that I was like, is a barn owl?

• 57:29Speaker 01

  Such a great word, crepuscular.

• 57:30Speaker 04

  I love crepuscular. Yeah, it's very good. There's also whether or not you have REM sleep. So generally speaking mammals and birds are the only animals with REM sleep, except for maybe the cuttlefish.

• 57:41Speaker 01

  That's so weird.

• 57:42Speaker 04

  I know, I know. And not all mammals have REM sleep.

• 57:45Speaker 01

  Really?

• 57:46Speaker 04

  Yeah.

• 57:46Speaker 01

  Okay.

• 57:47Speaker 04

  Um, so side note, REM sleep evolved after non-REM sleep, as far as we can tell. And it's thought to have emerged in mammals and birds independently.

• 57:55Speaker 01

  Oh, that's interesting.

• 57:57Speaker 04

  Yeah, so, which indicates that it might be really important for cognitive activities or warm-bloodedness, like, AKA endothermy.

• 58:05Speaker 01

  Oh, interesting, okay.

• 58:08Speaker 04

  Cuttlefish, I don't know.

• 58:09Speaker 01

  Goodness. Cuttlefish are weird ones.

• 58:11Speaker 04

  They are.

• 58:12Speaker 01

  I love them. They're so cute.

• 58:15Speaker 04

  But if you do have REM sleep, you know, how long are your sleep cycles between REM and non-REM? So for instance, you said human is 90 minutes or so. The chinchilla is six minutes.

• 58:25Speaker 01

  Six minutes? They go through a whole sleep cycle in six minutes?

• 58:28Speaker 04

  Yeah.

• 58:28Speaker 01

  Oh my gosh.

• 58:30Speaker 04

  They're like, done.

• 58:32Speaker 01

  And up.

• 58:34Speaker 04

  There's also whether you sleep with all of your brain or half of it.

• 58:38Speaker 01

  That's, I think, one of my favorite facts I learned in a children's book accidentally before we were... It was called Sleepy. And that is where I learned about uni-hemispheric sleep.

• 58:46Speaker 04

  Uni-hemispheric sleep, yep. It's a real thing, sleeping with one eye open. It is a real thing. Aquatic mammals, like whales, dolphins and seals, as well as some bird species, especially those that are undergoing like, long migrations.

• 58:59Speaker 01

  Ah, like the, um, what's the one that never touches the land?

• 59:01Speaker 04

  Albatross?

• 59:02Speaker 01

  Yeah, is that it?

• 59:03Speaker 04

  Oh gosh, I don't know. Woo, sorry, sorry ornithologists. But yeah, uni-hemispheric sleep. And, uh, we've got a little, uh, thing here that shows like, the EEG of what it looks like when you have like, one part of the brain.

• 59:18Speaker 01

  So it's like, part of your brain is on and part of your brain is off?

• 59:20Speaker 04

  Yeah.

• 59:20Speaker 01

  Oh my gosh, that's so interesting.

• 59:22Speaker 04

  It's amazing.

• 59:23Speaker 01

  In the right and the left. Oh wow.

• 59:26Speaker 04

  And what's even weirder about this is that whales, dolphins and porpoises who do this uni-hemispheric sleep, they don't seem to have REM sleep. Or if they do, it's not in a form that we recognize.

• 59:37Speaker 01

  Oh, that's so interesting.

• 59:38Speaker 04

  Yeah. So it's like, did they lose REM sleep?

• 59:41Speaker 01

  Right. When they went back to the oceans.

• 59:44Speaker 04

  Right. I don't know. I don't know. Okay, but why do aquatic mammals sleep with just one half of their brain?

• 59:51Speaker 01

  I mean-

• 59:51Speaker 04

  There's a few different possible reasons, right? So one is because they need to breathe.

• 59:55Speaker 01

  Right.

• 59:55Speaker 04

  And so they need to be able to come up and have that more active thing. Another is to reduce heat loss, apparently. It's supposed to help with like thermo generation.

• 1:00:02Speaker 01

  Interesting.

• 1:00:03Speaker 04

  And a third is to be on the lookout for predators. And a fourth is to stay close to one another because you can really drift apart because the water.

• 1:00:11Speaker 01

  Yeah, if you're just drifting.

• 1:00:12Speaker 04

  Yeah.

• 1:00:12Speaker 01

  Yeah.

• 1:00:12Speaker 04

  Like, have you seen those amazing videos of sperm whales all sleeping vertical-

• 1:00:16Speaker 01

  Vertical?

• 1:00:17Speaker 04

  And like a forest of sperm whales? Yeah. Uh, sea otters, of course, hold hands when they sleep, which is just, ugh, it's so cute.

• 1:00:25Speaker 01

  You know how I feel about sea otters.

• 1:00:27Speaker 04

  Yep. Uh, and unlike terrestrial mammals, newborn dolphins and orca whales are on the move from the first moment.

• 1:00:35Speaker 01

  Right.

• 1:00:36Speaker 04

  And unlike human babies, which sleep, like you said, so much, so randomly, all over the place, these, um, baby dolphins and orca whales are continuously active for like four weeks, like no sleep.

• 1:00:47Speaker 01

  They don't sleep at all?

• 1:00:48Speaker 04

  No sleep, along with mom, yeah.

• 1:00:49Speaker 01

  Fascinating.

• 1:00:50Speaker 04

  Yep, yep. And it's only after those weeks that sleep gradually returns. And this might be because it's just a really vulnerable time for those babies.

• 1:00:58Speaker 01

  They can't afford it.

• 1:00:59Speaker 04

  Yeah.

• 1:00:59Speaker 01

  Huh.

• 1:01:00Speaker 04

  And even when sleeping, these, uh, aquatic mammals are moving quite a bit. So dolphins make counterclockwise circles regardless of which half of the brain is sleeping.

• 1:01:09Speaker 01

  Counterclockwise circles?

• 1:01:10Speaker 04

  Mm-hmm.

• 1:01:11Speaker 01

  Why?

• 1:01:13Speaker 04

  Uh, great question. I do not know. I do not know.

• 1:01:18Speaker 01

  Counterclockwise circles regardless of which part of their brain is sleeping?

• 1:01:21Speaker 04

  Yeah.

• 1:01:22Speaker 01

  That is so interesting.

• 1:01:23Speaker 04

  I know.

• 1:01:24Speaker 01

  Do they sleep, um, sorry, I'm gonna ask more details.

• 1:01:27Speaker 04

  Uh-huh.

• 1:01:27Speaker 01

  Do they sleep, like, obviously it's one half at a time, but is it like consolidated, like at nighttime, they're gonna like, okay, 40 minutes on this half and then 40 minutes on this half or whatever?

• 1:01:36Speaker 04

  That's a good question. I don't know. I don't know.

• 1:01:38Speaker 01

  Okay, I'm so curious.

• 1:01:39Speaker 04

  I can say, there's a really great paper that I have, I'll shout out at the end.

• 1:01:42Speaker 01

  Excellent.

• 1:01:43Speaker 04

  That has like a lot more information on this and even like pictures of dolphins sleeping at the bottom of like enclosures.

• 1:01:49Speaker 01

  Oh, wow.

• 1:01:49Speaker 04

  And whales and stuff like that. Yeah, yeah.

• 1:01:51Speaker 01

  I love it.

• 1:01:52Speaker 04

  Uh, okay, fur seals, listen to this description, it's very cute. "When fur seals sleep in water, they usually float on their sides, holding one front and two hind flippers in the air. The front flipper in the water constantly paddles." Isn't that cute? And the rest are just like up in the air. Uh, one eye is open and the other is closed.

• 1:02:12Speaker 01

  Wow.

• 1:02:13Speaker 04

  Mm-hmm. Fur seals also are one of these creatures that spend some time on land. And guess what their sleep is like on land?

• 1:02:20Speaker 01

  Uh, like a dog.

• 1:02:21Speaker 04

  Like any other terrestrial mammal.

• 1:02:23Speaker 01

  But when they're in the water, they unihemispheric?

• 1:02:25Speaker 04

  They unihemispheric sleep.

• 1:02:26Speaker 01

  What?

• 1:02:27Speaker 04

  And when they're on land, both eyes are closed and they cycle through REM and non-REM.

• 1:02:32Speaker 01

  But when they're in the water, they don't?

• 1:02:34Speaker 04

  Nope.

• 1:02:35Speaker 01

  Oh, that is so interesting.

• 1:02:37Speaker 04

  I know, I know.

• 1:02:39Speaker 01

  Oh, wow.

• 1:02:39Speaker 04

  It makes me like, I never, I mean, I have like thought about sleep, mostly in like a very selfish, like, am I sleeping enough? Oh, my gosh, my sleep kind of away, but this is maybe more interested in REM sleep than like.

• 1:02:52Speaker 01

  Ever.

• 1:02:53Speaker 04

  Yeah.

• 1:02:53Speaker 01

  Yeah, same.

• 1:02:54Speaker 04

  Yeah.

• 1:02:54Speaker 01

  I did not know any of that.

• 1:02:56Speaker 04

  Yep. Me either.

• 1:02:57Speaker 01

  How interesting.

• 1:02:59Speaker 04

  It's amazing.

• 1:03:00Speaker 01

  Yeah.

• 1:03:00Speaker 04

  Okay, so that, but the fact that sleep comes in all shapes and sizes across the animal kingdom and is even variable, like you said, within an individual's life, it shows us that sleep is not random, right? How a species sleeps is the outcome of millennia of adaptations. Nor is sleep rigid, right? There may be times when we need to go with less sleep than we, you know, ideally like to have. Migration, midterms, having a newborn.

• 1:03:28Speaker 01

  Migration or midterms?

• 1:03:29Speaker 04

  Equal.

• 1:03:30Speaker 01

  I love it.

• 1:03:31Speaker 04

  Socializing, stress, you know, there's a lot of different reasons that might affect our sleep duration. And we can do that, we can sleep with, we can have less sleep than we'd like for a limited, like a certain amount of time. And then our bodies know to recover from that sleep debt. So if the way that we sleep is not random, what determines how species sleep? Why is a chinchilla have a six-minute? That I can't answer that. I don't know about that. But it is, it is a great question overall.

• 1:04:00Speaker 01

  Right.

• 1:04:00Speaker 04

  And we don't exactly know. And so there are some general patterns that I'll, I'll take you through, but to every pattern, there's an exception.

• 1:04:07Speaker 01

  Exceptions, yeah.

• 1:04:08Speaker 04

  So if we take all that we know about sleep in animals and we look for similarities after controlling for how related they are, a few strong drivers emerge.

• 1:04:18Speaker 01

  Okay.

• 1:04:19Speaker 04

  Predation, metabolism, immune function, gestation length, brain mass, and neuroanatomical regions like the amygdala.

• 1:04:27Speaker 01

  So these are all the parts of things that are contributing to how long and how an animal is sleeping?

• 1:04:33Speaker 04

  Um, mostly, I would say like how long and the polyphasic versus...

• 1:04:39Speaker 01

  Got it.

• 1:04:39Speaker 04

  Yeah, yeah. Monophasic, et cetera.

• 1:04:41Speaker 01

  Okay.

• 1:04:42Speaker 04

  And I don't like, there are some aspects of REM and non-REM, but like, that seems, I mean, it's just like, it's really difficult to draw any sort of...

• 1:04:51Speaker 01

  Yeah.

• 1:04:52Speaker 04

  Like parallels.

• 1:04:53Speaker 01

  Well, and I feel like it's so interesting because one of the books that I read, it was like, how you define sleep in animals, like with this behavioral thing, then also affects how we think about and look at the why of sleep, right? If you define it in slightly different ways, then you might come to a different conclusion as to the function of sleep.

• 1:05:11Speaker 04

  It's a little bit of a guiding hypothesis kind of a thing.

• 1:05:13Speaker 01

  Yeah.

• 1:05:14Speaker 04

  You're like, well, if, if REM is really, the questions that you're asking are driving that, yeah, how you're looking for data.

• 1:05:20Speaker 01

  If you're only counting REM sleep as sleep, then your conclusions are going to be totally different versus if you...

• 1:05:25Speaker 04

  Or if like, is more REM sleep better?

• 1:05:27Speaker 01

  Right.

• 1:05:27Speaker 04

  Yeah.

• 1:05:28Speaker 01

  It's so interesting.

• 1:05:29Speaker 04

  It's really interesting. Okay, so let's talk about some of these, some of these different factors. When you're sleeping, you are in a vulnerable state.

• 1:05:37Speaker 01

  Yeah.

• 1:05:37Speaker 04

  Your senses are dulled, so you can't hear that twig snap, and you're laying there motionless, looking like a nice tasty snack for that tiger that's, you know, just caught your scent and creeping away from you, creeping towards you, actually. Creeping away would be great.

• 1:05:51Speaker 04

  So you might be a little better off if you had like a burrow or a tree hole to nestle into. But if you just plop down in an exposed area, you're you're playing a very risky, very risky game.

• 1:06:02Speaker 01

  Yeah.

• 1:06:02Speaker 04

  And so to lower that risk, you might sleep less.

• 1:06:05Speaker 01

  Okay.

• 1:06:06Speaker 04

  And that is what we tend to see. Prey species or species that sleep in more vulnerable locations, like on the ground as opposed to like in the tree. They tend to have shorter sleep durations.

• 1:06:16Speaker 01

  Interesting.

• 1:06:16Speaker 04

  And in one experiment, rats that encountered a predator got less sleep afterwards, both rem and non-rem.

• 1:06:22Speaker 01

  They were like on edge.

• 1:06:23Speaker 04

  You're just on edge. You've got to be like, you're in lighter sleep, I guess.

• 1:06:26Speaker 01

  Yeah.

• 1:06:27Speaker 04

  Some research actually, some researchers actually suggest that light sleepers and people with insomnia might have those predator or biting insect vigilance mechanisms on overdrive. So if you're like someone who has really hard time getting into like, you're awake at the drop of, like, just a little rustle.

• 1:06:44Speaker 01

  Yeah.

• 1:06:44Speaker 04

  You might be.

• 1:06:45Speaker 01

  It's just evolution.

• 1:06:46Speaker 04

  It's adaptive. Not anymore, though.

• 1:06:49Speaker 01

  You won't get eaten.

• 1:06:50Speaker 04

  It once was adaptive, yeah. And so sleeping in larger groups, like larger social groups, that might help counteract some of the vulnerability to predators while you're sleeping. But then there's also the trade off of social disturbances and parasite transmission because you're just like all together.

• 1:07:06Speaker 01

  All in a group.

• 1:07:06Speaker 04

  Yeah. But it's like, sleep alone and be easier prey, or sleep in a group and get less sleep. Not necessarily worse, but like, and maybe it's more efficient sleep, but it does seem like sometimes it's shorter sleep.

• 1:07:17Speaker 01

  Okay, interesting.

• 1:07:19Speaker 04

  Or you could sleep while your predators also sleep. Okay. And predators tend to get more sleep on average.

• 1:07:26Speaker 01

  You're like, it's fine, bro.

• 1:07:27Speaker 04

  Right, like, I'm chilling. And metabolism might also play a role in that when it comes to predators versus prey. Because herbivores, which are more generally, more often prey, they need to eat more frequently because they have faster metabolisms or like their food is less calorically dense.

• 1:07:46Speaker 01

  Yeah.

• 1:07:46Speaker 04

  And so they have to spend a good chunk of their time foraging, especially if their food is, their preferred food is dispersed across the landscape. Like, oh, I have to get fruit trees and I have to go far to find them. And so you're like, your commute is long.

• 1:08:00Speaker 01

  Got it.

• 1:08:01Speaker 04

  And you're like, I gotta get back to my, my little burrow.

• 1:08:03Speaker 01

  Yes.

• 1:08:05Speaker 04

  Yeah. Animals with faster metabolisms relative to body size also sleep less, and smaller animals tend to sleep throughout the day. They're polyphasic sleepers.

• 1:08:14Speaker 01

  Interesting.

• 1:08:15Speaker 04

  Immune function. So we all know that not getting enough sleep leaves us more vulnerable to infections. And some studies suggest that species with longer sleep durations have higher white blood cell counts and are less likely to be parasitized.

• 1:08:28Speaker 01

  Interesting.

• 1:08:29Speaker 04

  I think this is a very big generality.

• 1:08:31Speaker 01

  Correlation, causation, all of that, yeah.

• 1:08:33Speaker 04

  And finally, oh, there's also gestation length. So longer gestations are associated with shorter sleep.

• 1:08:39Speaker 01

  So that's why, like, elephants, you said, get only four hours?

• 1:08:42Speaker 04

  Yeah.

• 1:08:43Speaker 01

  That's really weird, though. Why? Maybe it's just a correlation.

• 1:08:46Speaker 04

  Yeah, it could be.

• 1:08:48Speaker 01

  They're all down to metabol- I don't know.

• 1:08:51Speaker 04

  I mean, that's like a lot. This is like a very much an I-don't-know.

• 1:08:53Speaker 01

  Yeah, yeah, yeah.

• 1:08:54Speaker 04

  Episode.

• 1:08:55Speaker 01

  How interesting, though.

• 1:08:56Speaker 04

  And then finally, bigger brains, like-

• 1:09:00Speaker 01

  Per body size.

• 1:09:01Speaker 04

  Per body size, yeah. In proportion to body size, equals a bigger chunk of time spent in REM sleep.

• 1:09:06Speaker 01

  In REM sleep specifically. Okay.

• 1:09:09Speaker 04

  But again, this is all messy. So there was a cool paper, though, I read, that showed how vastly different sleep could be for two closely related species and how similar it could be for distantly related species. So for instance, the domestic cat and its relative, the genet, a cat gets around 12 and 1/2 hours of sleep, like I said, a day, with 3.2 hours REM. And a genet gets about half that, 6.3 hours with 1.3 hours REM. And those are like closely related species.

• 1:09:36Speaker 01

  Yeah.

• 1:09:37Speaker 04

  Yeah.

• 1:09:37Speaker 01

  And is that just like because domestic cats are just chilling in their houses?

• 1:09:40Speaker 04

  They might be just domestic cats, yeah. But then there's also a golden mantled ground squirrel-

• 1:09:45Speaker 01

  Okay.

• 1:09:46Speaker 04

  And a dago, again closely related. The squirrel's 15.9 hours of sleep-

• 1:09:50Speaker 01

  Wow, good for them.

• 1:09:51Speaker 04

  With 3 in REM, and 7.7 for the dago with 0.9 in REM.

• 1:09:55Speaker 01

  How interesting.

• 1:09:56Speaker 04

  So it's not just about like domestication, although I'm assuming that is a decent part of it for the cat.

• 1:10:01Speaker 01

  Yeah.

• 1:10:01Speaker 04

  Then take a guinea pig and a baboon, not closely related, but their sleep architecture is, or they're not architecture, their sleep, like, duration and REM proportion is very similar. They each get about 9.4 hours of sleep and one of REM.

• 1:10:16Speaker 01

  That's so interesting.

• 1:10:18Speaker 04

  And in case you were wondering, for humans, humans, we humans get the same amount of sleep as an Eastern American mole.

• 1:10:28Speaker 04

  We get seven to eight hours and we both have about two hours sleep REM.

• 1:10:31Speaker 01

  Oh my gosh, interesting.

• 1:10:32Speaker 04

  Isn't that funny?

• 1:10:33Speaker 01

  Yeah.

• 1:10:33Speaker 04

  It's really funny. But among primates, though, humans are the exception. We are at the very extreme end of sleep duration with some of the shortest sleeps of all primate species.

• 1:10:45Speaker 01

  Oh, interesting.

• 1:10:46Speaker 04

  The shortest sleeps, yeah.

• 1:10:47Speaker 01

  The shortest sleep of all primates?

• 1:10:48Speaker 04

  Yep.

• 1:10:49Speaker 01

  Huh.

• 1:10:49Speaker 04

  Yep, yep. On the other end of the spectrum are owl or night monkeys, owl monkeys or night monkeys, which sleep about 17 hours, but they get the same amount of REM sleep as humans.

• 1:11:02Speaker 01

  That is so interesting.

• 1:11:03Speaker 04

  Yeah.

• 1:11:04Speaker 01

  Oh, I do want to look so much more into REM now.

• 1:11:06Speaker 04

  I know, right?

• 1:11:08Speaker 01

  What is up with that?

• 1:11:10Speaker 04

  I know, what is up with that? Sleep, what is up with that?

• 1:11:15Speaker 01

  Yeah.

• 1:11:16Speaker 04

  Based on our human body size, body, or brain size, body mass, predation, risk, foraging needs, sexual selection dynamics, diet, and what we know about other primates, like researchers have kind of compiled this model to be like, how should we, how should we expect humans to sleep based on what we know about all other primates?

• 1:11:33Speaker 01

  Okay.

• 1:11:34Speaker 04

  And that comes out to nine and a half hours a night.

• 1:11:36Speaker 01

  That's how much we should be getting based on?

• 1:11:38Speaker 04

  Based on these. That is not, but we, on average, it's six to seven hours for humans.

• 1:11:43Speaker 01

  Yeah.

• 1:11:44Speaker 04

  And this does not mean that we should all be sleeping nine and a half hours.

• 1:11:47Speaker 01

  No, no, no, no.

• 1:11:47Speaker 04

  It's just what the model predicts based on other primates.

• 1:11:50Speaker 01

  So it shows that we are weirdos.

• 1:11:52Speaker 04

  Yes. Because evidence, I mean, evidence points to six to seven as normal sleep, or six to eight as normal sleep in humans. And it might just be that we somehow squeezed our sleep into a shorter duration, like we're more efficient or intense sleepers.

• 1:12:05Speaker 01

  Interesting.

• 1:12:06Speaker 04

  Other great apes sleep a bit more than humans, but less than like night owl or night monkeys. And like chimpanzees get about 10 hours with similar REM as humans. And gorillas sleep about 12, orangutans sleep about nine, slightly less than humans. But when it comes to humans and, and other great apes, we do share other characteristics. So like, we have this high proportion of REM sleep and we have nesting behavior.

• 1:12:33Speaker 01

  Mm-hmm.

• 1:12:34Speaker 04

  Which I just think is adorable. Many of the over 400 primate species that exist sleep in trees. Whether that's in tree holes or on bare branches, just like balancing up there. Even if they spend like much of their waking time on the ground, they will sleep, you know, up in the trees. And this might help with like predator avoidance, probably. Other species might sleep individually, or they might sleep in groups, or they might sleep on bare ground, or on cliffs, like baboons sleep on cliffs and on bare grounds. And some build nests, mostly in trees. In fact, all great apes build nests, all of them.

• 1:13:13Speaker 01

  I did not know that.

• 1:13:14Speaker 04

  Yeah, me either. Yeah. And so this suggests that the behavior emerged about 14 to 18 million years ago.

• 1:13:20Speaker 01

  Interesting.

• 1:13:20Speaker 04

  They are built individually. They take between one to seven minutes to construct. And they're usually built every night with occasional reuse.

• 1:13:30Speaker 01

  So they just make their own new nest every night?

• 1:13:32Speaker 04

  They make their own new nest, yeah, with a bunch of different materials. There is so much more about nest building, and I have a paper too.

• 1:13:37Speaker 01

  That's so cute.

• 1:13:38Speaker 04

  And so, why did we start to build nests? It's thought that as body size got bigger in these great ape species, they probably helped to make sleeping more comfortable overall, and to protect against damage if you like fell out of a tree, then like your body was just like, "coo-choo."

• 1:13:53Speaker 01

  You got that little cushion there?

• 1:13:54Speaker 04

  You got some cushion. So like, yeah, it makes it more comfortable. And so this also helped to avoid predation. So, research suggests that chimpanzees build nests higher and in closer proximity to each other in places where there are more predators.

• 1:14:09Speaker 01

  Ah.

• 1:14:10Speaker 04

  And also thermoregulation, so you can decide, okay, is your nest placement going to be higher up or lower down? Do I need more insulation? Do I need to pack in some more leaves?

• 1:14:18Speaker 01

  Is it a cold night?

• 1:14:19Speaker 04

  Is it a chilly night? Is it nice and warm? You know, like, I want to get a breeze up in there.

• 1:14:23Speaker 01

  Yeah.

• 1:14:23Speaker 04

  And finally, nests may also help to deter biting insects. So researchers found that some orangutans built their nests near naturally mosquito-repellent tree species when mosquitoes were abundant.

• 1:14:35Speaker 01

  I love this so much.

• 1:14:37Speaker 04

  I know. I mean, if you think about it, nest building is an incredible behavior, and there are some researchers that categorize it under tool use, which would make it the most pervasive among great apes.

• 1:14:48Speaker 01

  Wow.

• 1:14:48Speaker 04

  Yeah. It's environmental problem solving when it comes down to it. Did great apes build nests because they were smart? Or did building nests help evolve smartness, evolve enhanced cognition?

• 1:15:02Speaker 01

  Such an interesting question.

• 1:15:04Speaker 04

  Yeah, chicken or egg. I don't know.

• 1:15:05Speaker 01

  Yeah.

• 1:15:05Speaker 04

  I don't know. But so like I mentioned, most of these nests are in trees, but humans have long slept on the ground, despite the ground making us more vulnerable to predators. And some researchers have suggested that this ground sleeping with its more stable surface would have enabled even deeper sleep, which then allowed us to sleep more intensely.

• 1:15:26Speaker 01

  Because we're not gonna fall out of a tree.

• 1:15:28Speaker 04

  Right. We don't have to have that increased vigilance as much. And so that's what maybe allowed us to shorten our sleep duration. And then, once humans developed the ability to control fire, that would have cut down on the risk of predators and biting insects, and it would have increased our thermoregulation capacities, while allowing us longer hours to socialize into the night, exchanging ideas and storytelling, maybe even promoting the evolution of language. And so, in short, sleeping on the ground helped to make us become human.

• 1:16:00Speaker 01

  Oh, my God.

• 1:16:03Speaker 04

  Right? Once we made it there, on the ground, what happened then? Did we just stick to our six to eight hours a night with no breaks? Or is the story slightly more complicated than that? I'm leaving you on a cliffhanger, so you'll have to tune in next week to find out. But I hope you liked this little hodgepodge of a tour through animal kingdom sleep.

• 1:16:26Speaker 01

  I loved it.

• 1:16:27Speaker 04

  It's not a mistake.

• 1:16:29Speaker 01

  No.

• 1:16:29Speaker 04

  Sleep is not a mistake.

• 1:16:30Speaker 01

  Not an evolutionary mistake.

• 1:16:32Speaker 04

  I think that was mostly said tongue in cheek.

• 1:16:34Speaker 01

  I totally sounded like it.

• 1:16:35Speaker 04

  Yeah, yeah, yeah.

• 1:16:37Speaker 01

  Oh, that was really fun. And it made me really excited to find out what humans did with our sleep.

• 1:16:42Speaker 04

  I can't wait to tell you.

• 1:16:44Speaker 01

  I mean, I don't sleep on the floor.

• 1:16:46Speaker 04

  I don't sleep on the floor. I have slept on floors.

• 1:16:48Speaker 01

  Many times.

• 1:16:49Speaker 04

  Yeah.

• 1:16:49Speaker 01

  It's not my preferred method.

• 1:16:51Speaker 04

  Airports benches. It's horrible.

• 1:16:52Speaker 01

  Yeah. So I can't wait to hear what we did with sleep.

• 1:16:57Speaker 04

  Well, in the meantime, there's a lot more reading that you can do. Shall we tell the people where to read?

• 1:17:03Speaker 01

  Let us tell them.

• 1:17:05Speaker 04

  I have many sources, many sources for this one.

• 1:17:08Speaker 01

  I can't wait.

• 1:17:08Speaker 04

  Because I just kept going down rabbit holes.

• 1:17:10Speaker 01

  I loved them all. We didn't even talk about rabbit sleep.

• 1:17:13Speaker 04

  We didn't.

• 1:17:13Speaker 01

  But I'm.

• 1:17:14Speaker 04

  I actually did have a section where I was, I went through each of the animals on my PJs to be like, raccoons sleep this amount, possums sleep this amount, my favorite animal, besides the Tasmanian devil, squirrels, et cetera. And I cut it because I was like, it's way too many animals.

• 1:17:31Speaker 04

  Okay, you can find more information. There's a book about a lot of animal sleep called Evolution of Sleep: Philogenetic and Functional Perspectives by McNamara et al. from 2010. Then there's a great paper I loved from 2008 called "Unearthing the Philogenetic Roots of Sleep" by Alada and Siegel from 2008, I think I already said 2008 multiple times, by Lyman et al. from 2008 as well, "Cetacean Sleep: An Unusual Form of Mamalian Sleep", and finally by Fruth and Stewart, "Sleep and Nesting Behavior in Primates: A Review."

• 1:18:06Speaker 01

  Love it.

• 1:18:07Speaker 04

  Great stuff.

• 1:18:09Speaker 01

  I had, most of this information that I shared came from a book from 2012 that was called "Sleep: A Very Short Introduction" from Oxford University Press. It covers all the bases. But I also enjoyed a paper from Physiological Reviews from also 2012, that's weird, that was called "Control of Sleep and Wakefulness" by Brown et al. And then the paper that was not funded by industry about the wearable finger tracker ring sleep measures was from Scientific Reports, published this year, 2025.

• 1:18:42Speaker 04

  Trying so hard not to say any brand names.

• 1:18:44Speaker 01

  I know. You know the ones. I guess 2025 is last year by the time this comes out, doesn't matter. Anyways, it was by Herberger et al. and it was titled "Performance of Wearable Finger Ring Trackers for Diagnostic Sleep Measurement in the Clinical Context." But I have other ones as well too, and so many more papers. So you can read them all and find them all on our website, thispodcastwillkillyou.com.

• 1:19:07Speaker 04

  We will post them all there. Stephen Ray Morris, thank you again. What an absolute delight.

• 1:19:14Speaker 01

  It was really, thank you so much for sharing your story.

• 1:19:17Speaker 04

  Also, sorry that you've had sleep paralysis. We're not saying your sleep paralysis was a delight. Hearing your voice, hearing you share your story. It was wonderful, thank you. And thank you also to Blood Mobile for providing the music for this episode and all of our episodes.

• 1:19:29Speaker 01

  Thank you, thank you. Thank you to everyone here at Exactly Right Studios, as well as everyone who helps make this podcast possible.

• 1:19:36Speaker 04

  Yes, including you listeners. Thank you for listening. Patrons, thank you for patroning. Your patronage.

• 1:19:44Speaker 01

  Your patronage. That feels...

• 1:19:46Speaker 04

  Yeah. Thank you for everything.

• 1:19:48Speaker 01

  Thank you.

• 1:19:49Speaker 04

  Wow. Until next time, wash your hands.

• 1:19:52Speaker 01

  You filthy animals.

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