1,743 words · auto-generated from the episode video
48:34always talk about which is all of these discoveries and these movements are cumulative. They're not happening in a vacuum. So the immediate thing I just thought of was you know Vera Rubin and the massive amount of data that's going to be there uh in combination with JWST and some of the instruments that are looking at exoplanet atmospheres like there are data sets that have answers >> that we already have in our possession. Yeah. >> Some are proprietary some are open source whatever >> but that >> once we find and unlock >> all of a sudden makes these data sets incredibly valuable. >> Uh and this is sort of maybe a scout type of mission. Yeah. to be able to create some of that better understanding to get rid of the baseline of the planet
49:15so we can better read. And so that's again the exoplanet stuff I'm always such a huge fan of. >> We are going to come back into our main story number two of three and this one is going to be a an interesting combination. It's neuroscience, >> sleep and marine biology. >> Yes. Uh this is in nature communications published on January 7th. Why do jellyfish need sleep? The ancient origins of our nightly rest. This is from Bar Ilhan University. And the hook here is imagine a creature without a brain.
49:55>> Yep. >> That sleeps just like you. And scientists have discovered that jellyfish do exactly that. >> Do exactly that. >> They have no brain, but they sleep like us. >> Yes. Um, it's a core paradox in biology to be honest. It's like why do we sleep, >> right? >> It's a very simple question, but if you think about it from an evolutionary point of view, it seems naively really dumb to do. [laughter] Okay? Because sleep is a state there's behavioral vulnerability. You're not you're not like aware of stuff. Something could come and kill you. Um, you're vulnerable to predation. It ceases foraging. You're not getting food. And also, you're not having sex,
50:36>> so you're not really procreating. Yes. Right. So, what's the point? And yet, it's conserved across 600 million years of evolution. >> We have whales doing it, humans do it, and now we've got jellyfish do it, right? And the traditional view was it's a neuroscentric view, meaning it has to do with complicated neuro mechanisms, right? this idea of this synaptic homeostasis hypothesis, which is the idea that over the day your neurons are constantly learning and your synapses are growing. And if you just let it just keep growing and growing and growing, then you're going to get this runaway interaction kind of like last episode we were talking about in deepseek, right? If you have these matrices that just
51:18start blowing up, then you're going to get a very chaotic system. So, you need some way to constrain them. And maybe sleep was one way to constrain our synapses such that the signals don't propagate in a chaotic way. But now we've got this new finding which shows that sleep is actually a fundamental cellular requirement because of DNA repair and it's happening even in these brainless basil metazzoans. So in this case jellyfish but they also did the experiments on sea anemone and they found very similar results. Okay. So let's get into some of the historical context [snorts] for sleep research. Pre-1980s there was this guy Hans Berger in 1929. He invents the EEG which is the
52:00electroinsphlogram. And what he showed was that people that are see sleeping they've got these cortical oscillations alpha waves and other types of brain waves. And he said okay sleep is basically the state when we get that >> right. >> All right. Now that's fine, but that totally excludes invertebrates because invertebrates don't I can't do an EEG on an invertebrate, right? I need some kind of centralized brain. So I can do this on mammals, but are you saying that like you know lower order organisms don't sleep? So in the 1980s there was this neuroscientist Irene Toblar at the University of Zurich. She came up with the behavioral
52:42criterion. Okay. She showed that actually insect sleep, scorpion sleep and there were three def three things that she wanted to classify something as sleep. She was a pioneer in her field. The three things are the following. First, reversible immobility. That makes sense, right? When we sleep, we're stillish, but somebody can wake us up. So, that's the reversible part. >> Okay. >> Okay. The second one is increased arousal threshold. If I poke you when you're awake, >> you can sense it. But if I poke you when you're asleep, you probably can't. I need to poke you really hard in order to wake you up. >> Okay? Like I need to like slap you >> and then you're going to wake up.
53:22>> The the amount of effort needed to uh >> elicit a behavioral response >> is higher >> is higher when you sleep. Okay. And the third thing is homeostatic regulation. This means that if I deprive you of this sleep, then the next time you sleep, you're going to sleep longer. >> We've all had this, right? Like if you're if you've had a night out, the next day you're quote hung over, but what you're really doing is homeostatic regulation on top of the fact that you don't have any electrolytes, but you know, you're sleeping way longer than you should be. >> Yes. >> So, those are the three sort of behavioral definitions that I need in order to characterize sleep. >> I don't think I've ever thought about how do you define sleep before in my
54:03life. Like, but that's, >> you know, it becomes obvious when you talk about humans. You can just ask them like, did you sleep with mammals? Again, you could hook up a EEG, but now when we're getting into something like jellyfish, >> it's like how do we define sleep for an organism that's just doing this the whole time, >> right? >> Yes. >> So, but these three criteria actually we can translate. >> Okay. So, the model organisms in this paper are Nigerians, jellyfish, and sea anemone. Okay. It's a paper that came out of nature communications and these organisms actually diverged from the bilaterals which are us the the you know bilateral meaning to the symmetric kind of thing
54:44instead of the round symmetry. >> Yes, >> they diverged from us 600 million years ago. >> Okay, >> it's even thought that maybe the nervous system of these Nigerians >> is completely separately evolved from us. There's a little bit of debate on that because if you look at the neurons of these guys, the genes that they express are very similar to the neurons the genes that our neurons express. So perhaps there's a little bit of independence, but also at the same time a little bit of the same >> genes going forward. But what's very cool is these guys don't have a brain. They have nerve nets. There's no centralized repository. >> Okay? It's a bunch of nerves that are just in a net together and they're
55:26making decisions together and it's very unclear how they're doing it. [laughter] Okay, but in any case, very different from our centralized nervous system that we have with a central hub and it branching out to create motor functions. There's a decision-m that happens in our brain and then the rest of the neurons carry it out. Here we've got a very decentralized decision-m process. Is this the idea of like there's like no executive function in these uh like because there's not very related >> there's not like a there's not an authority who decides and then everyone else has to follow a better way to put it. >> Okay. Very very much so. So the the challenge now becomes okay we've got these two organisms that we want to
56:08study. Let's try to define sleep for them right using those three criteria. So what they did was just make videos of these organisms in their natural not natural habitat but in lab conditions. They used infrared light because if you use normal light then you're just messing with their rhythm, right? It's like you you still need a night and day cycle. So instead you use high resolution infrared light. So this is infrared light. And here you see the jellyfish that are pulsating, right? This is Cassiopia Andromeda, the jellyfish. And what they could do is analyze these videos and figure out basically classify two behavioral
56:48states. >> Okay, >> based on those three rules that we had about what sleep is, they did the same thing for the starlet anemone. That's the neat neatella vectennis, right? These are they they're like hydra looking things. This is a 20 minute time lapse. They're much slower moving. So, it's actually harder to classify immobility. But what you could do is actually classify the no even even when they're awake, they have a little bit of jitter. And they could they could really hone in on that jitter and classify >> rest just 5 minutes of rest versus actual sleep. >> Sleep. Okay. >> Okay. And and that's that's that that's what was really cool about how they did
57:28this, right? They they actually figured out a way to move beyond just these arbitrary dimensions and used um threshold-based optimization algorithms that were custom made for this use case. Right? >> Yes. Yes. >> And it's a rigorous definition. So they come up came up with these rigorous definitions. And now let's go ahead and try to analyze the sleep. When you analyze the sleep, one thing that's really cool is the um Cassopia Andromeda, which is the dellifish. Yes. >> Yeah. That's the one that actually it so in the light phase it was highly active. So during the day it's very active. That's the high on the y-axis. And then during dark times it was very inactive. But what's very cool is during the day
58:08right in the middle it takes a siesta. >> It takes a midday nap. >> They're very European. I see. >> Yeah. Yeah. These jellyfish are Spanish. In fact. >> In fact. [laughter]