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Why do we dream?
287 Plays1 month ago
Why do we dream, and what is the meaning of our dreams? Rolf and Joe talk about several ideas about dreaming, including a new theory by David Eagleman called the "defensive activation theory", which proposes that dreams are like a screen saver to keep the visual parts of the brain from being overtaken by other senses.
Eagleman, D. M., & Vaughn, D. A. (2020). The Defensive Activation theory: dreaming as a mechanism to prevent takeover of the visual cortex. bioRxiv, 2020-07.
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Transcript
Return from Summer Break
00:00:07
Speaker
Welcome to Cognation. I'm your host, Rolf Nelson. And I'm Joe Hardy. And it is good to be back. I know we've had a little bit of a break. um We've been enjoying our summers and getting getting been getting back into work and things like that, but um it's nice to be back for another episode. But yeah, it's good to get get back in the studio talking about things related to consciousness and cognition and all the things that we like to talk about.
Introduction to Dreams
00:00:40
Speaker
I think today we're going to talk a little bit about dreams. Um, you know, we've been interested in a variety of different ways to approach the topic of consciousness and, and we're interested in thinking about dreaming just because it's an area that we haven't touched on much.
00:00:59
Speaker
on the show so far. And it's a very rich area, both in terms of just phenomenological experience, but also in terms of research. And we wanted to approach a few topics in dreaming, starting with a basic question of why do we dream?
Theories on Why We Dream
00:01:18
Speaker
Yeah, so there's a lot of different ideas about this. And one of the reasons why we're doing this podcast is to talk about a relatively recent idea about dreaming that we'll get into in a bit from David Eagleman. um But there's there's a whole bunch of um ideas about why we dream. and And some of them work on different levels, so why the brain you know why Why does the brain need to dream? Why do you know we need to dream? um So thinking about it at different levels. And that sort of the maybe the most well-known and popular idea about dreaming is is thinking of dreams as having symbols and having some some meaningful content to it. So ah the Freudian view of dreaming, and he thought dreaming was a ah ah really important process. He called it the royal road to the unconscious.
Freud's Dream Analysis
00:02:08
Speaker
Freud thought that dreams had um both a manifest and a latent meaning, meaning that they were ah disguised for something else that was going on in your life, that your unconscious was trying to tell you.
00:02:23
Speaker
um so Everything you know all the weird stuff that you dreamed was is weird because it's a it's a symbolic representation of something different and I think a lot of people find this ah view of dreams appealing that you know this this you know has some real relevance and and my subconscious is trying to tell me something and From my dream, right? Yeah, exactly. I mean, we we might have a dream about, you know, forgetting that a final is tomorrow and we haven't studied or maybe we didn't even take the class.
00:03:00
Speaker
um And, you know, that obviously that's not about. a final exam or even a class because like, certainly in my case, I haven't been in school in a, in a very long time. Um, and so it's not about that particular class or that particular exam, but there may be some other source of anxiety in my life. And so the, the manifest content is, is about this, uh, thought of, Oh, I know I have to take this test tomorrow that I'm not prepared for.
00:03:32
Speaker
But the latent content might have something to do with something in my life that I'm otherwise anxious or stressed about. And so the idea would be that this is my unconscious trying to tell me something about something going on in my life.
00:03:46
Speaker
So this presents, I mean, I think it presents a really appealing view of the unconscious as sort of an act of unconscious that you know sort of monitors what you're doing, cares about what's going on in your life, and and brings things to the surface in your dreams. um So this is a very psychodynamic kind of theory of dreams. um And there are there are a couple other theories that have come up over the years
REM vs Non-REM Dreams
00:04:10
Speaker
too. um Specifically, so um we know now, and I think most people are familiar with the idea that most dreams happen during REM sleep, during rapid eye movement sleep. But this is something that's relatively recently discovered, maybe 70 or 80 years ago. um People discovered that sleep wasn't just a uniform thing and and that there are different components to it. So there's you know more deep wave sleep, and then there's rapid eye movement sleep. And during rapid eye movement sleep,
00:04:43
Speaker
essentially your body is paralyzed and your mind is acting um you know in a manner that's that looks more similar, or your brain waves at least look a little more similar to what it looks like when you're awake. And during that time, your mind is a little more active, and it's it can be quite bizarre, but it's a little bit more like real waking life. You can also have dreams, by the way, in non-REM sleep. They just tend to be more boring kinds of dreams. So if you've ever woken up and thought, you know oh,
00:05:16
Speaker
You just have that thought, just, oh, I got to do the laundry. I forgot to do the laundry. I need to do the laundry. Some boring thought like that might be a non-REM kind of dream or a non-REM, maybe more of a mentation than an actual dream, whereas dreams during REM sleep tend to be much more vivid and specifically very visual if you're a sighted person.
00:05:39
Speaker
Yeah. And so another kind of idea about dreams is that maybe it's a way to integrate information that you've processed during the day. So maybe in terms of consolidation of memories, for example, or you If you think about the predictive coding ah approach that we've discussed a few times on the show where the brain is trying to develop models of how the world works so that you can make sense of the world and make better predictions about what's going to happen in the world, maybe some of that integration of information is happening during dreams.
00:06:17
Speaker
And there seems to be a lot of um interest in that aspect of sleep and dreaming in the last few years too, the idea that it serves that function of consolidating memory. ah Though i don't know I don't know if we can say for certain whether that's happening, but there is some interesting evidence there. Right, for sure. And so you have to then disentangle that just sleeping from dreaming in that context because certainly sleeping is important for consolidating memories seems to be for sure. So but you know to the extent that ah dreams and particularly rapid eye movement sleep is important for that is a related but kind of separate ah area of just ah research.
Threat Simulation Theory
00:07:06
Speaker
And ah one interesting theory for is something called threat simulation theory, which basically suggests that we dream to confront threats in our environment in a safe space, um that that we're just sort of simulating the ah things that are happening to us. So this is sort of like when you see your cat kind of poking around, and it looks like maybe it's hunting a little bit when it's sleeping, the idea that it it's some simulating and getting a chance to practice in environments. And that seems like a reasonable, I mean, certainly that seems like a reasonable idea. And, you know, like I said, some of these theories exist on different levels too. We might think of one as sort of more evolution, you know, evolutionary, you know, what's the evolutionary utility of this, which is a little different than the way that Freud was thinking about his theory of latent and and manifest content and dreams.
00:08:03
Speaker
Right, yeah, there's sort of this epistemic question of what do what do we mean by why when we say why why do you dream? And it's not the case that they arere these things are mutually exclusive either, right? Right, that's right, yeah. and Yeah, certainly across levels, that they're not mutually exclusive, but even within a level,
00:08:20
Speaker
uh, of analysis, for example, evolutionary, there could be multiple benefits to that's right. Yeah. Yeah. And when we're looking at evolutionary benefits like that, it's hard to distinguish among them because we're not, you know, we weren't present when they were actually adapted for. So exactly, exactly.
Dreams as Screensavers?
00:08:39
Speaker
But yeah, there's ah is an interesting new theory that has come out and we're going to talk about that a little bit today, um, to call the defensive activation theory.
00:08:49
Speaker
of REM sleep. Bob, do you want to introduce that? Yeah. so this is a really this is ah To me, this is kind of out of nowhere, and I was i was surprised when I heard about this, but it's a really interesting idea. so The basic idea behind this is by David Eagleman, who's a prominent neuroscientist that's done lots of other interesting stuff.
00:09:07
Speaker
Basic idea is that dreams act as kind of a screensaver for the mind. Basically, that um we have very plastic brains, meaning um different brain areas can be used for different things depending on their need. And some research indicates that if you're not using your visual cortex, which is the area in the back of your head that processes vision,
00:09:36
Speaker
if you're not using it, then it gets overtaken by other senses. And people might be familiar with the idea that parts of your brain get used ah so in blind individuals that ah that part of your brain doesn't just go dormant, it gets utilized as a way to um navigate around the spatial world, even though it's not the same as sight, it's still a useful piece of cortex, it still gets um that gets used, right?
00:10:08
Speaker
um so Yeah, so so the idea is,
00:10:14
Speaker
human beings are, you know, for about half the time, maybe a third of the time, depending on how much sleep you get. When you close your eyes, you don't get any visual input. So as a protective measure, your brain sends signals to the visual cortex and activates it every 90 minutes or so during sleep to just sort of preserve the visual functioning of that region of of the brain.
00:10:40
Speaker
right Does that sound about right? Am I getting the- Yeah, I think that's exactly exactly the the the model ah that they've presented. The idea is just knowing that if visual input is removed from the brain, you know most typically this happens when someone goes is blinded by some something that happens to them. So they go blind.
00:11:06
Speaker
You can observe the activity in the visual cortex changing from responding to visual information, which it's no longer receiving, to now responding to a stimulation from other senses, most prominently auditory information, but also information from other senses and spatial information. So um the idea just that is that the the cortex in general
00:11:35
Speaker
in the brain is is able to do different kinds of
Brain Plasticity and REM Sleep
00:11:40
Speaker
things. Different parts of the brain tend to develop to process certain kinds of information most predominantly, but they have this potential to do different kinds of things. And our biology is very good at taking advantage of the resources that it has. Right. So it's not going to just leave that section of the brain totally unused. So all right exactly all brain matter is, you know, I mean, essentially, I mean, this sort of goes to the this fallacy that we only use 10 percent of our brain. Right. Or this this idea that got passed down that we only use 10 percent of our brain, which is totally false.
00:12:24
Speaker
um All of our brain is essentially working all of the time. It's just modulating and changing how fast it's firing in response to different things. But it's not like some of it's just sitting there dormant, not doing anything. And yeah the idea is this acts as a as a protective way of sort of holding that territory, holding the fort down while you're sleeping and not getting any visual input so that it can be used and and stays visual, I guess.
00:12:52
Speaker
Right. And this so-called plasticity is something that has been studied extensively over about the past 50 years or so. And but some of the things that that neuroscientists have learned about the way that plasticity works are kind of interesting. One of them is that it happens relatively quickly and more quickly than you would imagine in the sense that, let's say that you cut off input to the visual cortex either by blindfolding someone or they lose their sight.
00:13:26
Speaker
input from other parts of the brain other senses and other ah sensory inputs start to be responded to by the visual cortex within just a matter of a day or a couple of days. there was even some And this is maybe a different sort of plasticity, but there's even some evidence that um is presented that you do get visual cortex activation after only about 40 or 50 minutes of being blindfolded too.
00:13:53
Speaker
Maybe that's not full fledged activity, but there's something still starting to go on after i and it just a relatively short amount of time. Right, right. So the idea is that this part of the brain has that latent potential to respond to other types of information. And the term that's used in neuroplasticity is unmasking. So when you take away the stimulus from the eyes, the inputs and the ability to respond to other sorts of information is unmasked.
00:14:22
Speaker
So and disinhibited, there's some sort of inhibition that's preventing that part of the brain from responding to auditory information, sensory. So there's already connections laid down. There's already connections there. yeah Yeah. Exactly. So it's all ready to go ah to to use, to be used in that way. And actually those connections may be used in kind of a low key way all the time, um but they're just not so predominant. It's not, you know,
00:14:52
Speaker
the dominant responsivity of that part of the brain. Only once you cut off vision entirely do you see that sort of encroaching in. Right, exactly. So that kind of thinking is supportive of this kind of wild idea that maybe in order to prevent other input sources like audition, spatial information from touch and proprioception and other sorts of sensory input,
00:15:22
Speaker
or just any other kind of input in general. In order to to maintain the predominance of visual processing in that part of the brain, you may need to see send signals that are visual in nature to the visual cortex um to keep it all keep it going, basically, as you say, like a screensaver, to prevent it from ah for being captured, as it were, by these other other inputs.
00:15:52
Speaker
Yeah. um And I think this this does relate to another prominent theory of dreams that we that i I guess I didn't mention, but which is also another um player, which is ah Alan Hobson, who's a longtime sleep researcher, had a model called the activation synthesis model.
00:16:13
Speaker
which is basically that um you get random firings from the lower parts of the brain from the pons that go into the cortex and the cortex makes a story out of them. So, you know, if you have a dream where, you know, this sort of accounts for some of the bizarre imagery and dreams and some of that sort of nonsensical nature of things, you know, like i you know I was walking along and I yeah slipped on a purple banana and of fell into a pile of jelly and then my grandma was there, but she was really like a dog or you know something like that where things just reg progress all strangely. Well, Hobson says, okay, that's because essentially you've been hit with an activation of you know your grandmother and and jelly and
00:17:02
Speaker
a whole bunch of these random things, and your brain is furiously struggling to put them all together and make a coherent story out of them. um There's nothing there underneath it, really. It's just it just random activations. and And we are amazing at somehow rationalizing and creating stories out of out of these random things.
Hobson's Dream Model
00:17:22
Speaker
um And I think um this this um defensive activation theory that the screens Maybe we should just call it the screensaver theory because I feel like that's the easiest way to remember this, right? well Yeah. Yeah, for sure. I mean, but I guess when I think of screensaver, I think a little bit more of just so that parts of the screen don't get bleached. Right. Less than keeping it awake necessarily, right?
00:17:49
Speaker
defensive act Well, defensive activation theory is a good name, too. You're defensively sort of protecting your initial cortex. Just call it that. that Okay, that. I think that works kind of within the framework of Ellen Hobson's theory of this random firing to the cortex um because um it's it's the same he ah Eagleman relies on the same kinds of processes. you get waves of This is why um REM sleep is so visually oriented is because you get waves of activation um that come from the ponds, go through the lateral geniculate nucleus, and then back to the occipital lobe. So those are the PGO waves that that give you this really visual sensation in dreaming.
00:18:40
Speaker
Yeah, when you have your eyes open, the information's going from your retinas through this lateral geniculate nucleus or LGN thalamus. So this is like a different route that activates this visual visual information. Instead of getting information from the outside, you're just getting it from your pons, which is just sending waves of visual stimulation.
00:19:03
Speaker
So we could talk a bit about what their sort of evidence is. yeah i mean what What they're basically arguing is, well, if this is true and that is correct, would it be the case that different animals that have more or less plasticity in their brains would need more or less REM sleep. So in other words, the theory being humans need a lot of REM sleep because our brains are very plastic. Other animals have brains that are somewhat less plastic. They might need less REM sleep and it might be proportional. So you might see that animals that need very little
00:19:49
Speaker
ah have very little plasticity, need very little REM sleep. And if there was some cor kind of correlation between these things, it might provide some evidence for for their model. That's that's the the basic argument of the paper. I think it's a nifty argument, too. I think um it's not bulletproof, but I think it's ah it's an interesting connection that It is. it is it's It's certainly stimulating to think about.
Animal Development and REM
00:20:14
Speaker
And you know I think also just the the proxies that they use for plasticity are interesting as you think about what we mean by plasticity because and why plasticity might exist in the first place. right um you know Because it's not very easy to say for a lot of different species um know how much plasticity there is in the brain because those types of studies
00:20:39
Speaker
as comparisons are a little bit challenging to do, and they haven't been done in all these different species. yeah So they use some proxy measures for for thinking about how plastic or not a brain would be. And they basically, so all of these proxy measures basically rely on development time. That creatures with a more plastic brain take longer to develop. Right, exactly. So they they use things like Uh, when, uh, from when a baby is born to when it's able to walk. So time to locomotion in days is one proxy where humans is like average of like 318 days, almost like ah a year from the time that a baby is born to when it can start to, to walk.
00:21:29
Speaker
And that's on the on the way upper end too, by the way. there's yes That's like almost almost twice as much as other animals. Yeah. you know Most of these monkey these animals that they're comparing to are um our primates. um So ah other types of monkeys and apes.
00:21:47
Speaker
So if you look at ah the vervet monkey, for example, it's walking around within 21 days. So within three weeks, all good to go. It's all, it's brains all ready to go within 21 days yeah in terms of locomotion and and moving around. Um, you know, another one that they used is, uh, time to weaning. So how long until it's, you know, these are all mammals. So they're, they're weaned from their mothers. Um,
00:22:12
Speaker
the time to weaning. So for humans, it would be 1,095 days. And there are a couple, there are a couple of primates with slightly longer weaning periods too. I thought that was interesting though. That is interesting, isn't it? I mean, you look at the Bornean orangutan, 1637 days. Yeah. So it's with its mother for a long time. Almost five years. Yeah. Yeah. Really very long time. And the chimpanzee even longer than us too. Yep. Yep.
00:22:44
Speaker
1393 days for a chimpanzee. Yeah. Yeah. And then the the the third thing that they looked at is time to adolescence. What what do they mean to hear about adolescence? How are they defining that? ah Well, let's see with humans, it's 162 months. So, you know,
00:23:05
Speaker
Is that just basically the amount of time nominally that it takes until an animal is is able to go out on its own and and live ah away from its parents? Is that the idea? I don't know how you, I'm not sure exactly how you calculate that, but yeah, I'm assuming that's the thing, because I guess you're going for when when it's independent enough. Right, right, exactly. And so then, yeah, then they look at, then they they basically correlate all of these against
00:23:36
Speaker
against percentage of sleep in REM. So of the time that you're sleeping, how much of it is REM sleep, which they then you know, say is corresponding to how much presumably how much you're doing dreaming that involves visual information in particular. And humans are right at the top of that. And other animals, you know, like dreams are like, but if you observe them, it looks like they're, they're dreaming and seeing things. They behave like that or, you know, when they're in REM sleep. So
00:24:12
Speaker
we assume that that they're similar in that way. And yeah, exactly. ah Humans are right at the top in terms of how much REM sleep we get as ah as a function of how much sleep overall we get. So 21% of our sleep is REM sleep. As opposed to the low end here is about 6%, so somewhere between 6 and 21%. Chimpanzees are pretty close to us at about 16%, but we seem to take the most REM sleep.
00:24:39
Speaker
Yep. Yep. Yeah, exactly. And and you know, the idea is of this plasticity thing. And you you know, an interesting another interesting proxy might have been um proportion of cortex to brainstem, for example, how much of your brain is this cortex versus brainstem would have been would have been an interesting one to look at.
00:25:04
Speaker
Uh, but they didn't look at anything anatomical like that yeah behavioral things. Well, you also, like I mean, one of the things I wonder about these comparisons too, are the, uh, differences in size. Cause you get some of these, as you get some of these primates that are really small yes and that have a short lifespan too, right? might Imagine their brains are fairly plastic, but they also, um, develop very fast.
00:25:31
Speaker
Yes. And that yeah the the argument in that that this is sort of what I was getting at. It's interesting the types of proxies that they use and what that means for the assumptions they're making about what plasticity is doing and why we think that humans have very plastic brains compared to other animals, other primates even. And the idea is that Animals that are behaviorally relatively simple have brains that are somewhat less complex and require less organization after birth as more of their behaviors are inborn, if you will. As they need to develop more flexible behaviors outside of the womb and respond to their environment more.
00:26:27
Speaker
Yes, so so animals that need to to develop more outside of the womb, have less inborn traits and behaviors, their brains need to be more plastic. And so the idea is the reason why humans take so long to develop outside of their mothers is that their brains need to continue developing in the context of the environment. So in response to what they're seeing and then what we're what we're seeing in the environment, seeing, reacting to, hearing all of these things behaviorally, our brains are able to adapt to those different environments and actually become structurally different ah depending on what we're experiencing.
00:27:22
Speaker
yeah And so humans are thought to be extremely good at this relative to other animals. and I mean, I think that's that seems to be a reasonable, I don't know, what do you think Rob? is that Is that like fair? Is that, can we just take that as like- That human brains are more plastic than other animals?
Human vs Animal Brain Plasticity
00:27:38
Speaker
Yeah. Or how do we feel about that? I don't know. I mean, what would be the mechanism here? I'm not sure how this what would actually work. I mean,
00:27:48
Speaker
um i mean development I like the the angle of looking at it from a developmental point of view, because I think that sort of simplifies things from um what's the plasticity of an adult human brain, for example. or right you know yeah i mean Because that's what we're kind of interested in. We're and interested in what's the plasticity of an adult human brain so that it you know to what extent does it plastically recede from the visual cortex.
00:28:17
Speaker
Right. I guess that's another assumption that they've made here, right? That there's a relation between those kinds of plasticities. yeah Exactly. That the plasticity in development is related to the plasticity in adulthood, that animals that are more plastic in childhood and adolescence are then going to have be more plastic in adulthood. Which is again, I mean, who knows i mean that seems to me a reasonable assumption, but it's certainly one that you would have to defend if you really wanted to make a really robust argument, basically. Yeah, you might want to do the blindfold test and on all of these you know across all of these species and get ah see what's going on in their cortex, how long it takes these intrusions from other areas to affect their visual cortex. Right, exactly, exactly. Yeah, and and they they they they did suggest to do that. They did suggest to do that. um but yeah i mean listen So we can talk about the data a bit. I mean, when they did these correlations,
00:29:14
Speaker
They did see that there were correlations so that, um, the time to locomotion, the time to weaning, the time to adolescence are all correlated with the sleep time and REM as a percentage of overall sleep time with the highest correlation being, uh, for time to locomotion, uh,
00:29:36
Speaker
where humans have the most time to locomotion and longest time to locomotion and the most sleep time in REM. But even then, these correlations are significant, but they're not enormous. They're not massive, but they're not nothing. No. I mean, this is like an R squared of 0.32 for time to locomotion versus sleep time in REM. And that's like 32%, basically saying 32% of the variance Uh, in the time to locomotion is explained by sleep time and REM, which is, yeah, I mean, that's not, that's certainly me to give it how complex all these things are. That's, that's a relationship. Let's just say that there, there's a relationship there for sure. Um, at least in this dataset. Yeah. Yeah. So I guess, you know,
00:30:25
Speaker
with that in mind, that there is this correlation. They say, well, that's some good evidence for for our theory. And it ah it it is evidence for their theory. Yeah, it's not not evidence for their theory. No, yeah, exactly, exactly. It doesn't argue against their theory. I guess it'd be interesting to think a little bit about what other implications of their theory might be. My thought was I was- You mean other ways to test it or? or No, I guess more just like, um as we think about the robustness of the theory, what else you would imagine being true and what else you could look at. oh Okay. So one of the things I was thinking was why is it just about vision? And they say in here that, um,
00:31:16
Speaker
auditory stimulus is still being processed when you're asleep or it's still available. So you can still so you still if someone is next to you while you're sleeping and talking to you, it's still processed to some degree. Right, exactly. you could if you so For example, if you if someone says your name, you're more likely to wake up than if they say something else. Whereas when your eyes are closed, you're getting nothing. Yeah, I mean, you're you know not getting nothing. but saying I mean, if it's dark, you're not getting anything. But you're certainly not getting um images. Yeah, you're not getting images.
00:31:52
Speaker
But here's here's what why my mind went to that thought was, but I'm still processing, I'm still hearing sounds in my dreams. Do you hear sounds in your dreams? You know, I don't know. It's sort of a tough question. yeah I can't tell if it's something I'm adding after I've woken up or not. i ah It's hard to understand the phenomenology of your dreams because all you have is your recollection of them.
00:32:22
Speaker
Yeah, I, I, it's interesting cause I mean, I, I have the same thought about vision in dreams as well visuals and dreams in the sense that because I was, you know, we were talking about this, um, this, this idea of a Fantasia, which is the idea of like some people are better and worse at
Aphantasia and Dreams
00:32:44
Speaker
imagining things. This is in the, in the waking state. And just when you're awake, people are better and worse at imagining things visually, visualizing things.
00:32:52
Speaker
Aphantasia being the quality of not being able to image things or imagine things. Right, exactly. Visually. yeah and i'm i um have I have like a fairly extreme form of Aphantasia. I don't see anything when I close my eyes and I can't see anything when visual. visualize try to think about what something looks like. I don't see anything at all. Just nothing. Um, occasionally I can see phosphenes just like, you know, little spots of, um, brightness, but they're not correlated to any image. Um, but I see, I think I see pretty robust, like full scenes, visual scenes in my sleep, but then I wonder,
00:33:35
Speaker
when I think about it, is that is that true? yeah Or is that a function of my memory of the dream? and And did you just sort of have the conceptual thought that you're seeing something? Right, exactly. like And what is the difference? What would the difference be of having an experience of a conception of seeing something in a dream and actually seeing something in a dream?
00:34:05
Speaker
Well, here's where I think the evidence can actually separate this out a bit. I mean, it seems as though these signals that are going from the pawns to the visual cortex are really very specifically targeting vision. And um i mean we can corroborate with this with what a lot of people report, which is you know visually very vivid dreams during REM sleep.
00:34:31
Speaker
But they also have other aspects, this is my point, is that there they're more like, they're not just visuals, like imagine, um you know, just a kaleidoscopic. Like just, just ah right. so It's like a kaleidoscopic hallucination or, you know, visual hallucination. Random bits of light. it's it's It's a whole storyline, right, usually.
00:34:57
Speaker
And it may not be it may be a fairly abstract storyline, but it has characteristics like ah spatial information, auditory information, whether or not you're hearing it or not hearing it. or but I don't know. hu But you have you have some sense of space and you can even see people will sometimes, you know, move or kick or, you know, punch or whatever, you know. Yeah. So it's not like just pictures. Not just not just pictures. It's it's it's a whole big, robust storyline, and in more or less robust in different states of of ah brain activity and sleep. So that's where it's like, I get the idea of wanting to preserve the functions of different parts of your brain, but i it's it's harder for me to buy into that it's just vision. This this feels to me like, I don't know, as Eagleman, a vision scientist, I feel like vision scientists always
00:35:53
Speaker
want everything to be about vision. but Yeah, i think he I think he does some vision stuff. i mean i had a similar I had a similar thought about this, which is, if that i mean if that's the simple story about what's going on with dreams, that it's a screensaver, that you're just getting some sort of visual activation in there, why do we experience, like you say, all the detail we do in the dreams? We experience you know people and objects, and we don't just experience random visual stimulation. so why Why do we experience all those details and dreams if it's really just about um keeping it visual? Why isn't it just um abstract visual things? So i think I'm thinking there's more to the story than just this. if this you know If this is a part of the story, there's more to it. Right, right. Yeah, exactly. And I guess also another thing that is popping into my head now about this argument is
00:36:51
Speaker
um If it's about plasticity and the relationship is is a function of plasticity being correlated with REM sleep and dreams, that's not inconsent that same argument is not inconsistent with some of these other models for why we dream. Right. you know So for example, it could be a bonus it could be a bonus that comes along with some of these other things.
00:37:16
Speaker
Yeah, exactly. So like this predictive processing kind of approach of, you know, integrating information about your world so that you're more able to make good predictions in the morning when you wake up. Yeah. Also relies on plasticity, right? Yeah. Because you're these mental models, the ability to maintain them, to change them in response to new information is a function of the plasticity and of your brain.
00:37:46
Speaker
Well, I mean, yeah I guess another thing this brings up too is if this is what's going on in dreaming, then what's happening in lucid dreaming when you're able to control things, if it's not just a random, if it's not just random input that you're responding to, that you can actually have some effortful control over what's going on in your dreams. How does that happen? Right. Exactly. How do you, how do you, how do you take those random firings and make something meaningful out of them?
00:38:12
Speaker
ah Yeah, presumably that's not just driven by the pawns, right? Which is like a deep brain, stretch right I mean, a deep brainstem structure. Yeah. Not so associated with conscious control. That there's something going on in and other parts of the cortex also. Yeah. Yeah.
00:38:31
Speaker
Well, I mean, I think it's cool. I mean, it's a cool theory. Um, it's thought provoking for sure. Um, I think it's highly original. I think it's highly original. I would have never, I would have never thought that, right. Come up with the concept that the reason we dream is just to protect our visual areas during sleep. Right. Right. Right.
Dreams and Visual Processing
00:38:52
Speaker
Yeah. There's some interesting predictions there, like, um,
00:38:57
Speaker
the idea that if you don't sleep, if you don't dream much, for whatever reason, your visual processing might be less efficient.
00:39:08
Speaker
Huh. Yeah. Right. I think they you know that's and that's a testable thing. That's hard to test, but it's it is testable. I mean, it's one of those things you might be able to take advantage of some natural experiments where people have um challenges for whatever reason, somehow their their REM sleep is disrupted. you could I was thinking about the idea of just like really simple stuff like contrast threshold detection, you know various basic aspects of visual processing, would you see worse sensitivity to to contrast in people who have disrupted REM sleep for whatever reason. So with the with the idea that you are getting some intrusion, on I mean. Because you could have the idea is that, I mean, though if if if it's that, if it's about protecting, right, protecting that functionality, that the reason for protecting that functionality
00:40:06
Speaker
and preserving it for vision is so that your vision stays really sharp and efficient. Not just like, you know, but not just like visual acuity crisp, but like efficient and...
00:40:19
Speaker
yeah I'm trying to think of a simple story of how something like this evolves. that You've got you know some guys who are sleeping well, they get lots of REM sleep, they got a nicely delineated visual cortex, and they're just functioning well. They're more likely to be able to you know able to re remind the find the mates that they need. the fruit or yeah exactly whatever Where this one guy can't get much REM sleep and he's exhaust all the time. He's having intrusions from you know auditory stuff. It's a mess. You can't find the the nice, juicy apples. They're a little bit hidden. He's confused because his visual cortex isn't very well delineated. Exactly. Maybe. i mean
00:41:02
Speaker
Does that seem like a plausible evolutionary story? we can You can make up anything you want about evolution sometimes. Yeah, these as we call these just-so stories. those stories yeah yeah this is i mean i it says I think just-so stories should be judged at least and in part by how interesting they are. Yeah. because And this is an interesting one. Because we're never going to know right one way or the other what it really is. Yeah. And maybe maybe the question doesn't even make sense really when you think about how evolution works. But <unk> I think it's useful in the sense of thinking about what we mean by different types of functions in the brain. Like when we say a brain, part of the brain or the brain does something, what does that mean? What is that like? I think it's it's a useful way of thinking about that.
00:41:50
Speaker
Yeah, and so I think it's it's a generative at least in that in this context we're we're we're never gonna know whether it's a real thing or not, but It's interesting to think about and you know, this is a you know, I think something is a good example of just a way that dreams Can be a window into thinking about consciousness thinking about the way that the brain works as an interesting aspect and one that is relatively under discussed I mean, it's not that it's not discussed, but it is, but it's relatively disproportionately under-discussed in the neuroscience and and and psychology literatures these days anyway. Yeah. I mean, back when Freud was was the big psychology guy that was talked about a lot. but Yeah. so wrap up So wrap up question here. So do you think this makes dreams sort of
Do Dreams Have Meaning?
00:42:42
Speaker
meaningless? I mean, it's kind of fun to make sense out of your dreams, right?
00:42:46
Speaker
Yeah, I mean, I i think that you know ah dreams are great. thing to project on, right? you know I think it has that characteristic, a little bit of astrology, right? right right um you know You can make meaning from it. It doesn't mean that it it's not, I think dreams are more or less abstract. And so I think it's like, when something is, when you're like stressed because you think someone is mad at you and in the dream, this person is mad at you,
00:43:19
Speaker
Like it's not hard to think about what that dream is about. Right. And people think like that all the time. That's, yeah, that those dreams happen. Things like that happen all the time in dreams. But the one where you're like, it's somehow abstractly related to something that's going on in your life. It's interesting to think about, but you know, you can project onto that. Like, you know, the dream that I have all the time that I was saying about I'm in a class, I took this class in college and I forgot that I had it or I never studied for it and then the exam is tomorrow. And all kinds of different details and and different versions of this come up for me. And you know like one of them is like, you know I can't find the exam. So I'm gonna actually get up and ready to go to the test. I'm like, I'm gonna take this test even though I have no idea what's on it or what we even studied. Then I can't find the location of the exam room.
00:44:19
Speaker
So okay, so does that...
00:44:23
Speaker
I mean, you know, sometimes you feel some personal meaning. I mean, it's a bunch of stuff, right? Like, I mean, this is a dream that I have because I went to a lot of, I went to college for a long time. I went to college for four and a half years. And then I went to graduate school for my PhD for five years. And then I went to physical school for another three years. So I went to way too much college and took way too many exams. So that's the thing about me for sure. Right. So there's some meaning in that just there within like, that's part of the way you think in a way, it's just getting out of the way that you think.
00:44:51
Speaker
Yeah, and but why am I having this dream when it times now when I'm stressed? What does that mean about like, why I'm stressed? I mean, there's, I can make meaning of that, like whether that is has any independent meaning or not. I don't know that that's even but like a, a reasonable question to ask. I don't know. What do you think?
00:45:10
Speaker
Yeah, I mean i think i I tend to agree. I think the the way that you said it is probably about the same way that I think about it too, that dreams can can be given meaning because they maybe represent some of the ways that you think.
00:45:25
Speaker
But i don't I don't believe that dreams have um some hidden meaning that's manufactured by another part of your brain, that there's some force, some active unconscious force that that's trying to get these things to the surface because they're important in a symbolic kind of sense. I think they can be interesting to analyze and you might you might sort of key into you know what you're thinking of if you're not noticing it in in everyday life. But I don't think they're messages from the deep.
00:45:56
Speaker
Right, right. Well, that's cool.
Future Exploration of Dreams
00:45:59
Speaker
i Well, I think that's a good place to wrap it up. And and you know I think we'll hopefully have a chance to come back to dreams um in a few different contexts as we bring in some guests that have different perspectives on dreams and and their relationship to consciousness. So I think it's an interesting topic.
00:46:19
Speaker
And I think it's also worth, if you're interested in so you know sleep and dreams, a good episode of ours to go back to is the episode with Eric Prather, who's a sleep researcher at UCSF University of California, San Francisco. Lots of great info on that one. Yeah.
00:46:35
Speaker
Yeah. Lots of great info about how to fall asleep and make sure that you are able to fall asleep and stay asleep, which is I think a very important thing. Sleep to me is like so precious. if yeah I notice very, very much when I don't get enough of it. For sure. Yeah. Yeah. That's the worst. All right. All right. Well, thanks for joining us again on an episode of Cognition. Yeah. And if you're interested in you know, any kind of comment about what we are have on the show or eat something you'd like to hear on the show or you'd like, you'd personally like to be on the show. You can reach out to us at cognationpodcast at gmail dot.com.