March 18, 2024 • 52 mins
Why do brains dream, and why are dreams so bizarre? Why doesn't your clock work in your dreams? And even though you spend much of your working day looking at your cell phone and computer – why do they almost never make appearances in your dream content? Is dream content the same across cultures and across time? Are dreams experienced in black & white, or in color? Are dreams the strange love child of brain plasticity and the rotation of the planet? What is the relationship between schizophrenia and dreaming? In the future, will we be able to read out the content of somebody's dream? Join Eagleman this week to learn why and how we spend a fraction of our sleep time locked in different realities, swimming in plots which aren't real but which compel us entirely nonetheless.
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Speaker 1 (00:04):
Why do brains dream? And what's going on with the
bizarreness of dreams? Why doesn't your clock work in your dreams?
And even though you spend a lot of your day
working on cell phones and computers, why do those almost
never make appearances in your dream content? There are so
many cool questions that we're going to address today. Is
(00:27):
dream content the same across cultures and across time? Are
dreams experienced in black and white or in color? Why
do I think about dreams as this strange love child
between brain plasticity and the rotation of the planet. What
is the relationship between schizophrenia and dreaming? And in the
(00:47):
future will we be able to read out the content
of somebody's dream? Welcome to Inner Cosmos with me David Eagleman.
I'm a neuroscientist and author at Stanford and in these
episodes we sail deeply into our three pound universe to
understand why and how our lives look the way they
(01:09):
do and how we experience our life includes our nocturnal life.
We spend a third of our lives with our eyes closed,
lying still and horizontal, like a meat robot that's been
switched off. But why in the last episode, we talked
(01:33):
all about sleep, why brains do that, and why all
animals do that, and what is happening in the brain
during sleep. Today we're going to zoom in on one
of my favorite subjects, a very strange thing the brain does,
which we call dreaming. We spend a fraction of our
sleep time locked in a different reality, swimming around in
(01:57):
plots which aren't real, and they're often not even realistic,
but which nonetheless convince us entirely. And today we're going
to see what that's all about. Humans have been writing
about dreams and pondering about them for a long time,
and essentially we have evidence of this from the beginning
(02:17):
of writing. We see detailed dream reports from ancient Egyptians
and Romans and Chinese. The Bible is full of dreams.
Every culture in the world has been fascinated by these
strange nocturnal journeys that we go on. And as we'll
see shortly, there's an interesting surprise, which is that dream content,
(02:39):
in other words, the kind of things that people dream about,
is essentially the same across cultures and across time, and
that serves as a clue that will allow us to
unlock some mysteries about what otherwise feels like a deeply
mysterious experience that we enjoy or suffer every night of
(02:59):
our life lives. So strap in for an episode full
of surprises. So let's start with a poem that Lord
Byron wrote in eighteen sixteen called The Dream. He wrote,
sleep hath its own world and a wide realm of
wild reality. And dreams, in their development have breath and tears,
(03:22):
and tortures and the touch of joy. They leave a
weight upon our waking thoughts. So dreams are indeed a
wild reality. The thing we all find so amazing about
dreaming is its bizarreness. You're seeing new things, you hold
strange beliefs, and you fall for it all hook line
(03:45):
and sinker. Whatever your brain serves up to you, you
believe it entirely. So we'll talk about all this, But
let's first zoom in on what's happening inside the brain.
Dreaming occurs during rapid eye moos movement or rem sleep,
where your eyes are darting back and forth. There's nothing
(04:05):
coming in the eyes, of course, they're shut, so all
the activity is internally generated. For good housekeeping, all just
note that rem sleep isn't necessarily equivalent to dream sleep,
but that's when most dreaming occurs. Now, how do we
know that, Well, it's because if you wait until someone
enters rems sleep, their eyes are going back and forth,
(04:27):
and then you shake them awake and you say, hey,
what were you just experiencing? They'll tell you WHOA, I
was just panicking because I was at work but realized
I had forgotten to put on pants, and I was
hiding behind the plant pots and figuring out how to
escape before the meeting started. But if you wake them
up during the rest of the ninety minute sleep cycle,
(04:50):
during the stages that we call slow wave sleep, and
you say, hey, what were you just experiencing, they'll generally
say nothing, I wasn't there. Now, for completeness, I'll mention
that sometimes people report some form of mental activity during
slow wave sleep, but when they do, this is usually
just a thought or making a plan. But it lacks
(05:15):
the visual vividness and the hallucinatory components of typical dreams.
So dreaming of the sort we're interested in today happens
during rem sleep. Now, although dreams seem so untethered and ethereal,
there are specific things happening under the hood. Dreaming depends
(05:36):
on the normal functioning of a particular network of brain areas.
This is primarily in the limbic and paralymbic and association areas.
Now we know that from brain imaging, but also because
damage in this network can produce temporary or permanent dream
loss or impairment like loss of visual dream imagery. Now,
(05:59):
not all of those areas might sound familiar to you,
but you've probably heard of the limbic system, which sits
at the heart of your emotions. So presumably this is
why dreams are so overloaded with high emotion. And I
also want to mention a brain era that is suppressed
during rem sleep, and that is the hippocampus. This is
(06:20):
an area that's required to convert short term memory into
long term memory. And this is why when you wake
up from a dream, you can remember it so clearly,
but after about fifteen minutes it just slips away from you.
You just can't hold on to what happened. This is
because you have the short term memory just fine, but
(06:42):
you're not converting it into long term memory, and so
it simply fades before your eyes. And by the way,
I think this experience that we have every morning can
enhance our empathy about what it would be like to
have something like Alzheimer's disease, because a person with Allsheimers
says on the phone, Okay, I'll be right down there
(07:03):
in a moment, and they hang up, and then the
memory of that just slips away. So even though you
might tell a relative with Alzheimer's, come on, just try
harder to remember. Just think about somebody telling that to
you about your dreams in the morning. So back to
the Byron poem, the line that I thought was interesting
(07:23):
was they leave a weight upon our waking thoughts because
they don't directly interact with our waking thoughts, but instead
they can just put a spin on our mood, even
if we don't remember why. Okay, so what do we
see in the brain when dreaming begins, Well, just before
(07:44):
the onset of your eyes darting back and forth, you
have a group of neurons in the brain stem, specifically
in an area called the ponds, and these crank up,
and these trigger several consequences. The first is that your
major muscle groups get paralyzed. This is called atonia. So
(08:04):
you've got this elaborate neural circuitry that keeps the body
paralyzed during dreaming. And by the way, the very elaborateness
of this circuitry emphasizes the biological importance of dream sleep.
You don't get this kind of complexity by accident. Presumably,
dreaming would be unlikely to evolve and remain without an
(08:27):
important function behind it. So why do we get this
paralysis of the muscles. It allows the possibility for the
brain to experience things and simulate reality without actually moving
the body. The second consequence of these neurons in the
ponds is that they trigger these waves of activity known
as PGO waves, and these are key to the experience
(08:51):
of dreaming. These PGO waves travel to a tiny area
called the geniculate nucleus and from there these waves of
activity slam into the occipital cortex at the back of
your head. In other words, they drive activity into the
visual system. So that's why these are called PGO waves.
Because they start in the ponds, p move to the
(09:14):
geniculate g and go to the occipital cortex. Oh pgoh
I mention all this detail. Because PGO waves are the
neural correlate of dreaming, the visual areas become alive with
activity allowing us to see our dreams. You blast activity
into the visual cortex and you enjoy visual experience even
(09:37):
though your eyes are closed. Now, interestingly, when you measure
electrical activity across the brain with EEG, when you do
this during rem sleep, it looks really similar to that
during the waking state. You see similar patterns in both states,
for example, lots of gamma wave frequency, which is generally
(09:58):
thought to reflect something about cognitive processing, with the exception
of the paralyzed muscles and the lack of external visual
input because your eyes are closed, the states of rem
sleep and of wakefulness they kind of resemble one another.
And this is what we might expect from a state
of consciousness that's altered. But it's some sort of consciousness nonetheless. Okay,
(10:24):
so that's what's happening in the brain when we dream.
But why do we dream? Well, there are various hypotheses
about this, and I mentioned one last week, which is
that maybe dreams allow us to simulate rare situations. In
other words, these nocturnal neural simulations might allow us and
(10:44):
all animals to test out activities without the danger and
risk of doing so in the real world. So you
can practice through different scenarios with your muscles all shut down.
So people who advocate this theory suggest that the periodic
stimulation of the cortex in this semi random and non
(11:05):
specific manner this can maintain circuits that are really important
for survival, but they rarely get activated because you don't
run into emergencies that often. So the idea is that
you're just sending in random activity, keeping the engine oiled
in case you need one of these programs sometime, and
some researchers suggest that it's even more specific than that.
(11:27):
A version of this framework called threat simulation theory, suggests
that dreams exist to simulate threatening events and to rehearse
what to do in the face of threat, and that
seems on its surface at least consistent with the high
prevalence of violence and aggression in dreams. But I want
to note that there's no data that directly supports this idea,
(11:51):
and I mentioned last week that this theory suggests that
people exposed to more survival threats in waking life might
have a more common experience of threat dreams at night,
but the data do not support that. Also, the threat
perception theory doesn't explain the fact that most dreams are
totally meaningless and bizarre instead of involving any meaningful threat
(12:15):
perception or threat avoidance. So back to the question of
why we dream. A few years ago, my colleague Don
Vaughan and I proposed a new theory which is the
only one that makes quantitative predictions across species. And if
you heard episode eleven you may remember about this. That
theory has to do with brain plasticity. And here's the idea.
(12:37):
In a nutshell, we know that if a person goes blind,
other senses start to take over what was the visual cortex.
In other words, the territory of the visual system is
not fixed permanently, but instead the wiring of the brain
is quite fluid, and there's a takeover that happens. Okay, now,
it turns out that if you take a normally cited
(12:58):
person and you blindfold, you can start seeing the beginnings
of this takeover in neuroimaging starting in about one hour.
And that really surprised us because of how fast the
takeover starts to happen. So what does this rapidity of
the takeover of the cortex have to do with dreaming?
(13:20):
While in the incessant competition for territory in the brain,
the visual system has a special challenge because of the
planet's rotation, we experience darkness for about twelve out of
every twenty four hours. And obviously I'm talking about our
evolutionary history, not the recently electrically blessed times. In other words,
(13:42):
our ancestors all spent their lives as inadvertent participants in
a blindfold experiment every single night. So how did their
visual cortex defend its territory when you've got no data
coming in through the eyes. So our proposal is that
the visual corret tex preserves its territory by finding a
(14:03):
way to remain active at night. And we call this
the defensive activation theory. And the purpose of dreaming here
is to keep cells in the visual cortex active, and
that's how it resists conquest by the territories of the
other senses. Vision is the only one of the senses
that's disadvantaged by darkness. You can still touch and smell,
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and taste and hear in the dark, and so it's
the only sense that needs internally generated activity to maintain
its borders during the long night. So, as a result,
about every ninety minutes you get this internally generated activity
that blasts exclusively into the visual cortex, and so dreams
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are experienced as primarily visual. So several predictions immediately fall
out of the defensive activation theory. First, because brain plasticity
diminishes with age, this would suggest that the amount of
time spent in REM sleep should also decrease as one
moves through the lifespan, and that turns out to be
(15:08):
exactly what happens. REM sleep in humans accounts for half
of an infant's sleep time, but as a person grows older,
the percentage of remsleep decreases steadily. In other words, diminishing
plasticity of the brain correlates with less REM sleep. But
more importantly, we made a more quantified prediction. We said, hey,
(15:30):
maybe the more flexible and animal's brain is the more
REM sleep it requires to defend its visual cortex. So
Don and I studied the plasticity in twenty five species
of primates and we found that the species with more
plastic brains spend more time in REMS sleep every night.
(15:51):
So you'd think that these two measures REM sleep and
brain plasticity they would be totally unconnected, So it was
very surprising to find that they are tightly linked. So
dreaming defends the visual cortex. Now, the circuitry that underpins dreaming.
This is so ancient and deeply wired that even people
(16:12):
who are blind have it. But note that blind people
don't have visual dreams. Instead, their nighttime hallucinations involve the
other senses, like feeling their way around an oddly arranged
kitchen or hearing strangers speaking. Why because other sensory errors
have annexed the underused visual cortex. So think about it
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this way. People who can see and those with visual impairments,
they both have activity shooting into their occipital lobe during dreaming,
but the senses processed by that territory are different. The
defensive activation theory also makes more general predictions. If dream
sleep is triggered by the absence of visual input during
(16:56):
the night, we might presume that a person deprived of
vision while awake could similarly experience dreamlike visual hallucinations. And
that is exactly what happens when people have degenerating vision,
or they end up in solitary confinement or even just
in a dark float tank. Any situation in which vision
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gets deprived, the brain starts fighting back and having hallucinations.
So that's the idea. Dreams are a screensaver. The brain
puts activity into the visual cortex to prevent it from
getting ruined during the night. Okay, so you might say, fine,
your hypothesis seems plausible, But why do dreams seem to
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be stories? After all, we don't just see random snow
like on an old television. We experience stories, and in fact,
there are various stories of someone discovering something in dreams,
like Kurkule thinking of the structure of the Benzene ring
based on a dream he had of two snakes biting
each other's tails, or Paul McCartney dreaming the melody for
(18:02):
the song Yesterday. So what's up with dream content? The
key is that the brain is a storytelling machine. Your
brain is deeply carved with roadways that represent your experience
in the world, and these are stored in what are
called associative neural networks, which means that everything connects to
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other things based on how they relate. So if I
ask you to think of a mouse that's physically connected
in your brain's networks to your concept of cheese or
exterminators or mickey mouse or mazes, or running wheels, or
mouse traps or pet stores everything else you've ever associated
with a mouse. So all concepts are related and linked
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physically to what happens during sleep and dreaming. Well, the
synapses that are used during the day tend to be
slightly more chemically active, say, they're more hot from the
activity of the day, and so your dreams usually involve
something from the day or something that's on your mind.
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They often involve the memories and desires and fears and
hopes that are brewing in your inner life. But the
associations are much looser. So maybe you have something about
your boss or something that happened in a class or whatever,
but the dream quickly goes off in some weird direction.
The associations are looser, and so we end up dreaming
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stories with looser associations, following paths along the associative neural
network that we might not otherwise take. But things make sense,
at least in the light of dream logic. So even
if the visual cortex is just getting volleys of random activity,
you get meaning out of it. You get some sort
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of story. Now people often wake up and say, no, way,
that wasn't random, That was a metaphor. I'm trying to
decide if I should quit this job, and I had
a dream that I went into the office and the
floor was tilted at forty five degrees and no matter
what I did, I kept slipping back down. And that
was a metaphor about the impossibility of my advancement. There,
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that was a sign from my unconscious. Okay, so maybe
the interesting thing about interpreting the content of dreams is
that they might be one hundred percent random, but they
act like a Rorshack blot, which is to say, you
can assign any sort of meaning to them. You remember
a Rorshack blot, which is where you squish some ink
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between two pages, and then you pull the pages apart
and you get some random shape, and you ask people
to interpret what they're seeing to assign meaning to it.
And it's easy enough to say, yeah, that looks like
this thing in my life, maybe this issue that's been
chewing at me. And that's how doctor Rhorshak used this
to determine what had meaning in a person's mind. But
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you would never say the blob of ink carried meaning.
It's all about the imposition of meaning by the viewer.
And this, I suggest could be what happens with dreams
as well. You interpret the ink blob, and that interpretation
might have significance to your life, but you imposed that
meaning instead of it being inherent in the dream. Here's
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an interesting parallel. Pablo Picasso once said, we all know
that art is not truth. Art is a lie that
makes us realize the truth, and that could be the
same thing with dreams. They are a lie that makes
us realize the truth. So in this sense, it's the
same thing. If you're thinking about some problem and you
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go to the bookshelf and you pull off any random
book and turn to a random page and you read
the sentence. Often it will very tangentially give you some
push to the thing that you're trying to solve. But
that doesn't mean the awe of the book cared about
you and wrote that sentence with that future moment in mind.
It simply tells us that lots of things in the
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world are like lots of other things and can therefore
be interpreted. And I do just want to add one
more word of caution to the game of dream interpretation.
By the time you turn to the person next to
you and say, oh my gosh, I just had the
strangest dream and you tell them, you are forced to
add another layer of narrative scaffolding so that it makes
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sense as a story that you're telling. So a narrative
that's very thin can seem to have more flesh after
you've pushed it through your storytelling machinery. In other words,
we layer on narrative structure to give our dreams a
shape that they didn't actually have. And so especially if
you've had a dream that you've told over and over,
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it usually has more of a scaffolding than it actually
started with. Nonetheless, the content of dreams has always fascinated humans,
spurring societies to invent cultural uses for dreams in religious
ceremonies and medicinal practices, or doomed attempts to predict the future.
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Sigmund Freud, who lived decades before modern brain science, he
thought that dreams provided an inroad into the underlying functions
of the brain and especially the subconscious. He suggested, as
had many before him, that dreams concealed hidden meanings that
were just at the threshold of breaking through the barrier
(23:32):
to consciousness. More specifically, he proposed that dreams constitute a
disguised attempt at wish fulfillment. Similarly, Carl Jung positive that
dreams may offset features of a character personality that you
might ignore while you're awake. In general, both those theories
have been criticized because they can't be proven wrong, and
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critics have pointed out that the wish fulfillment interpretation seems
improbable in view of the recurring nightmares that attend post
traumatic stress disorder. So I am, of course not the
first to propose that dreams might have no inherent meaning.
The psychiatrists j al And Hobson and Robert McCarley suggest
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that dreams may have no meaning at all, and they
have a model they call the activation synthesis model, which
proposes that random activity from the brain stem goes to
the cortex, which tries to turn it into motor output.
But given the paralysis of the major muscle groups, the
brain has to explain the paradox between outgoing motor signals
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and a lack of expected sensory feedback. So in this situation,
the cortex synthesizes an explanation, essentially weaving a story from
the random inputs. Now Hobson and McCary faced criticism for
this aspect of their theory because dreams often do have
a relation relationship to life experience. So in that light,
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they made modifications to allow that dream content relates to
memories and fears and desires and hopes and so on,
but that these provide the background context and not the
exact content of the cortexas interpretation of the random activity.
So which is it, Does dream content tell us anything
at all? Or nothing? Well, here's how we can approach
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the problem. When you look at one person's dreams like
you think about your own dreams, you may not be
able to use the content as a key to unlock
much about the brain. But as you move from considering
one dreamer to doing the science and looking at thousands
of dream reports and hundreds of thousands from all over
the world, you can start to see the fence lines.
(25:48):
You see that dreams aren't a wild unleashing where anything
can happen. Instead, dreams have particular rules to the stories,
and that gives us hints. So what are those rules? Well,
I recently read a very cool new book by my
colleague Rahul John day Al called This Is Why You Dream,
and he outlines a series of studies that demonstrate a
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remarkable consistency of themes. Across cultures and across decades, the
same kinds of dreams are reported, for example, being unable
to find one's way or being late for an important event.
In dreams, both men and women usually experience more aggression
than friendliness, although men in almost all societies have greater
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physical aggression in their dreams than women do. Everyone experiences
more misfortune than good fortune. People experience more negative emotions
than positive emotions. So the cross cultural research suggests that
dreams are similar across a wide range of cultures in
terms of the subject matter, the level of aggression, familiarity
with the people in the dreams. For example, let me
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zoom in on this. Jandeal points out that in the
nineteen fifties there were ques given to college students in
America and college students in Japan, and the questionnaire asked
them what they had dreamt about, like showing up somewhere
with no clothes or flying or trying to do something
again and again, or being buried alive, or something involving
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school and their teachers or whatever. And as it turns out,
although American and Japanese students were living pretty different lives,
their answers were essentially the same. So for the Americans,
the top five dreams were falling, being attacked or pursued,
trying again and again to do something, a dream involving
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school or teachers, or studying, and sexual experiences. And when
you compare this to the Japanese students, it was essentially
the same. Their dreams were ranked as being attacked or pursued, falling,
trying again and again to do something, dreams about school
or teachers or studying, and being frozen with fright, and
sexual experiences were number six. So halfway across the world,
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very different cultures, same dream content. Now, fifty years after
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that study, similar questions were given to students in China
and Germany, and they came up with the century the
same answers. Again, you find people dreaming of being chaste,
or pursued, or arriving too late, like missing an airplane
or a final exam. Now you might say, fine, but
these are all industrialized countries and maybe their lives are
sort of similar. But in fact people have also studied
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indigenous societies in Brazil and Mexico and Australia and they
find extremely similar results. The cultures are quite different. But
the plots of the dreams are not. So there have
been lots of studies on this sort of thing now,
and they all conclude that dream content is a century
same across cultures and across time. As one example, wherever
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you are in the world, men dream more about other men,
while women dream equally of men and women, and all
people across cultures are more likely to be victims of
violence rather than perpetrators. So dreams cover similar themes across
the world, irrespective of language and culture and time. It
doesn't seem to matter how rich you are, how poor
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you are. So what does that mean? Well, what's the
one thing we all have in common? Our organs on
the inside and specifically the brain. As easy as it
is to look at different cultures around the world, with
different governments and different religions and different costumes, this variability
has cropped up in the last millisecond of human history.
And if you look just under the skin and the bone,
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you find the same brain in us all. It's the
same engine under the hood. So whenever we find something
clear like oh, everyone dreams about the same thing, that
we are looking at something fundamental and ancient and universal,
and we find all sorts of other interesting answers by
looking across thousands of dreams. For example, what if dreams
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are a way to live out fantasies like sexual fantasy.
That seems consistent with how we talk about dreams a
way of acting out our desires. But in studies across
all cultures, it turns out that fewer than ten percent
of dreams are sexual, which I find fascinating given the
way we talk about dreams. If a young single person
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says to another single person, oh, I had a dream
about you last night, then everyone titters, makes assumptions about that,
and we have terms like dream girl or dream guide,
But in fact, ninety percent of our dreams have nothing
to do with that. So the content is remarkably similar
across the world. But where things get really interesting is
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when we zoom in one more level and really examine
what dreamscapes look like like in detail. And I'm not
asking about what's in the dream script here, but if
you look very closely across thousands of dream reports, you
can ask what is not in the script. So I
want to return to a question I posed at the beginning,
which is that we live in a society where we
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are constantly hunched over our cell phones and our laptops.
How come these essentially never show up in our dreams?
Isn't that weird? And even in the era before computers,
back when people read a lot more books, how come
no one sits around reading books in their dreams. Why
can't you even see any text in your dreams? Why
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do you spend so much time writing stuff down in
real life but you never can write stuff down in
a dream. How come you never do math in a dream,
like calculating a tip for a restaurant bill, Even if
that comes up in a dream plot, it feels totally
impossible to get the right answer. Well, all of this
serves as a big clue into the networks that are
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active during a dream, and this is pretty well worked
out with brain imaging now, although anyone who is being
very observant probably could have guessed this all even a
century ago. What reading and writing, and cell phones and
computers all have in common is that they require the
use of a network in the brain that we summarize
as the executive network, which involves a lot of activity
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largely distributed in the frontal lobes and the parietal lobes,
and you need this for rule based problem solving and
for making decisions when you've got a particular goal in
front of you that you're trying to solve. And the
key is that activity in the executive network is reduced.
I'll just say it's shut down while you are dreaming,
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so you're not able to read and write and launch
an app on your cell phone screen and so on,
because that work requires the executive network, and that network
is off duty for the night. But what is on
is an network we summarize as the default mode network,
which is what kindles to life when you shut your
(33:07):
eyes and you're not involved in gathering information and acting
on some other task. So this is called the default
mode network, but many scientists are renaming this the imagination
network because this is what lets your storehouse of experiences fly.
You can piece ideas together and come up with new
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hypotheses and thoughts, and this is what's firing on all
cylinders when you dream. So the executive network has reduced,
the imagination network is enhanced, and this is what gives
dreams their very untethered character. There are other clues you
can also gather from looking at detailed dream reports, which
(33:51):
is that sometimes objects will turn into other objects, but
they're always related in some way. What I mean is
you might have your bicycle turn into a motorcycle, or
your small house becomes a mansion, or the cafeteria becomes
a restaurant, or the hammer becomes a screwdriver, but you
(34:11):
don't find the bicycle turning into a restaurant or your
house turning into a hammer. What does that tell us? Well,
under the hood, we have what are known as semantic maps,
and more than associations, which I mentioned before, semantic maps
refer to the way that all the stuff in your
brain is laid out in terms of relationships between concepts.
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For example, in your semantic map, you have the concept
of an animal, which might include categories like mammals and
birds and reptiles and so on, and within one of
those categories you might have more specific concepts like dog
and cat and eagle and salmon and snake and frog
and so on. Things are laid out in your brain
(34:56):
based on their conceptual meaning. And what we find is
that dreams follow the semantic maps. In other words, they
stay local in the little clusters of the maps. So
this is why you see the bicycle turning into the
motorcycle because they're both forms of transportation, but not into
the screwdriver, which is a tool and in a totally
(35:18):
different category. These things live in different little neighborhoods of
the semantic map. So again, a careful look at dream
reports tells us important clues about what is going on
under the hood, and that tells us that while the
themes are universal strife and falling and attempting to do
something over and over, the details are filled in with
(35:41):
the specifics of your semantic maps. And this all brings
me back around to a question I had since I
was a kid about whether dreams are experienced in black
and white or in color. Now. When I was a child,
I remember at some point that my parents told me
that we dream in black and white, and I was
(36:01):
confused by this because I didn't seem to dream in
black and white. As far as I could tell, my
dreams were in color, so I thought I must be
somehow assessing that incorrectly. Because they were both very smart
and educated. My mother was a biology teacher, my father
was a medical doctor, and as I grew older, I
asked my friends about this, but I couldn't find anyone
(36:22):
who thought that their dreams were not in color. Now,
because I genuinely knew that my parents were brilliant, I
thought maybe there was something they knew that I didn't like.
Maybe we were dreaming in black and white but didn't
realize it. And then I found several large scale surveys
that reported what my parents had said, that most people
(36:43):
dream in black and white. One study was from nineteen
fifty eight and they said only nine percent of people
dream in color, and a paper in nineteen forty two
reported that only ten percent claimed to frequently or very
frequently dream in color, and a report in nineteen fifty
one had the highest percentage. They said that twenty nine
percent of dreams are in color. But even this didn't
(37:05):
make things clear what was going on, because dream reports
from earlier, like Freud's reports of dreams in nineteen hundred,
often had explicit color descriptions in them. So somehow it
seemed to be only my parents' generation that dreamed in
black and white. And it turns out if you run
(37:27):
the study now, almost everyone says they dream in color.
As you may have guessed by now. The hypothesis on
this is that people were influenced by watching black and
white television and black and white movies and black and
white photographs, and once the technology changed to color, then
so did dreams. I'm putting a very nice paper by
(37:51):
Eric Schwitzkeebel on my site that compiles all these studies
through the years and the change in the reports. Again,
this demonstrates that the content of our dreams has to
do with the experiences that we have now. I'll tell
you an interesting side note on this. I happened to
live in California and during COVID, everyone in my neighborhood
(38:11):
wore masks, and it was a very weird time, and
so we rarely saw other human beings for a couple
of years without everyone being in masks. And one of
the things I remember from that time was that we
would sometimes watch a movie on TV, and it was
so shocking that people in the movie would push their
way through a dense crowd and sit so close to
their friends and the people they were talking with, and
(38:32):
they were indoors with such density. And it became in
twenty twenty so noticeable and so shocking when we were
in the middle of COVID. Interestingly, it's a little hard
to remember that now, but I remember it well because
I was taking careful notes on what was going on
with my dreams during this time, and specifically, since my
real life involved the very thinned out crowds and everyone
(38:55):
in masks, did that show up in my dreams? And
the answer was is no. The thing that struck me
the entire time during lockdown is that my dreams were
totally normal. In my dreams, I was at a big
party and there were lots of people around, and no
one ever had masks in my dreams, which struck me
as weird when I would wake up. Why didn't my
(39:16):
dreams reflect my daily experience? Now, this is just a
single person's report, and I didn't think to study this
carefully at the time by doing a big online survey
of everyone. But if it's generally true that other people
were having these very salient daily experiences of lockdown and
masks and yet it wasn't appearing in their dreams, the
(39:38):
only interpretation I can make is that our dreams reflect
pathways that get laid down over our youth when we're young.
And if that's the case, then maybe we could still
find some black and white dreaming among older people. Now,
in other words, maybe you'd still see some of that now,
even though those people have been watching color television for
(40:01):
sixty years. Now, with all the things on my plate,
I'm not going to have time to pull off that study.
But I would love it if listeners could ask their
oldest living relatives they a parent, or grandparent or great grandparent,
how they dream and determine if anyone still dreams in
black and white and what their age is. Okay, so
(40:37):
that story of black and white dreaming correlated with black
and white television. That seems like a clean story, But
there's one thing that still bugs me about it. Although
television and movies were in black and white, obviously the
world wasn't. When my parents walked outside, they saw green
trees and blue skies and red cardinals and yellow sunflowers
and so on. So why didn't their dreams reflect that? Well,
(41:01):
there are two things to say here. First, not everyone
dreamed in black and white. Instead, it was between let's
say seventy to ninety percent. So had I been alive
in the nineteen fifties, I would have studied the issue
of how many hours of television people watched each day,
and perhaps some measure of how many black and white
movies they saw on how many newspapers with black and
white photos and so on, and correlated that to whether
(41:23):
or not they had black and white dreams. Second, I
have a totally speculative hypothesis. I don't have any evidence
for this, but I'm going to say it anyway. What
if some part of the brain knows, at least in part,
that dreams are like a fake movie, and in that
way it takes on the property of fiction, which in
(41:43):
those days was black and white. Because note that even
when you're in the middle of a movie, some part
of your brain still knows you're watching a movie. And
this is why when the train comes at the camera,
you don't actually duck and scream. So even though we're
compelled by fiction, we don't fall for it completely. Could
it be that to the brain, dreams are more like movies.
(42:06):
I don't know, because I missed that era, so the
opportunity seems gone to study that. But I'm wondering if
we're going to have another shot at studying this question
once virtual reality becomes ubiquitous and pervasive, and whether a
big chunk of the population will report dreams that are
more like synthesized virtual reality worlds than like our daily life.
(42:29):
To me, this would shed light on the mystery of
the black and white dreams and the details by which
your dreams are determined by your experiences in the world. Now,
there's still lots of stuff that I think we don't understand.
One is why we can have false, implanted memories inside
a dream. This is something I've wondered about for years.
(42:52):
For example, I had a dream many years ago about
my brother's wedding and he was yelling at me and saying,
I can't believe you said that to Jenny and ruined
my wedding, and I felt horrible. I felt as guilty
as I ever felt. Why did I do that? Why
was I so insensitive? And then I woke up. As
it turns out, my brother had a lovely wedding that
went just perfectly, and I of course never said anything
(43:14):
bad to his bride, my lovely sister in law Jenny. Ever,
there was never trouble of any sort there. So why
did I fall for the false memory? Why couldn't I
access my real memories of the wedding while I was
inside the dream? In other words, the issue is that
not only did I have a false memory. But also
(43:35):
I had no access to my real memory of the wedding.
One set of memories was replaced by another. And this
is what freaks me out, not just about dreams, but
about our sense of reality. We buy whatever our brains
serve up to us at every moment. We buy the
plot of a dream completely. And by the way, this
(43:58):
is one interpretation of what happened in schizophrenia. The way
psychiatrists used to describe this about a century ago is
that psychosis is essentially an intrusion of the dream state
into the waking state. So the next time you see
a man talking to himself on the street and having
an argument with someone who is not there in front
(44:20):
of him, interpret it through this lens that he is
having an awake dream, and you might understand what's happening
in a fresh way. So what we see here, and
what we've seen in many of these episodes, is that
we accept whatever reality is served up to us. And
by the way, I think this is why literature works
(44:41):
with our species, because we can so easily adopt a
different reality. We can read a book and we laugh
and we weep. We are effortlessly deluded. And to understand
this I think we shouldn't use the term suspension of disbeliefs.
It's the wrong term because an applies that disbelief is
(45:02):
the standard disbelief is the normal operating mode. In fact,
it might be just the opposite. Our brains are perfectly
willing to accept whatever they are fed. Now, I want
to hit one more question in today's episode, which is
where is dreaming headed? Would it be possible to read
out the content of somebody's dreams? Well, if you happen
(45:27):
to have heard my episode number twenty seven, you'll know
that the answer is already yes, at least to some degree.
Different research groups have been working since at least twenty
eleven to see if they can measure brain activity in
the visual cortex to assess what somebody is seeing in
front of their eyes. In other words, if you're looking
at a building, there's a different activity in your visual
(45:50):
cortex than if you're looking at a puppy or a
cup of coffee and so on, and so the research
question is can you tell what a person is seeing
just by measuring the pasterns in their visual cortex? And
the answer is that you can pretty well tell what
somebody is seeing this way. After that research came out,
people realized we might be able to measure dreams because
(46:12):
dreams are activity in the primary visual cortex. Dreams are
experienced as visual because it's activity in the visual cortex,
and your brain understands that as visual experience. So Yuki
also Comma Tani and his colleagues published a paper a
few years ago in which he took this same approach.
(46:32):
He had people look at a bunch of pictures and
watch a bunch of videos while they were in the
brain scanner, and then he used machine learning to decode
how the picture out there corresponds to the activity patterns
in the brain. And now you let people go to
sleep in the scanner, and you measure their visual cortex,
(46:53):
and you use the machine learning model to decode what
that activity would correspond to, in other words, what they
were presumably seeing in their dream. And once the machine
learning model gives an answer, then you can make a
little video reconstruction of their dream, and you can watch
what presumably was the experience for the dreamer, albeit with
(47:17):
very low resolution. Now, when you're decoding pictures or videos,
it's easier to know if you're getting it right. When
you're decoding dreaming, it's harder to know for sure that
you got the right answer. You have to wake up
your participants and say, hey, what do you remember, and
then you compare that to what you think you might
have decoded. But even with those caveats, this gives the
(47:40):
rough start to a dream decoder that could tell you
what you were dreaming about. And presumably this will only
become higher resolution with time. So it maybe that in
the future we are able to know what you dreamed
even if you can't remember it. You could keep a
digitized dream diary that way, or you could share your
(48:03):
dreams with a girlfriend or boyfriend, or less likely, a
dream could be used in a court of lossome day.
Who knows where this will all go, but we can
imagine that in two hundred years from now, dreams may
be a very different sort of thing than the entirely
private experience that we enjoy now. So let's wrap up.
(48:26):
To my mind, the biggest issue that freaks me out
about dreams is this issue that we believe patently impossible situations,
and we accept false memories even when they contradict events
that we know to be true in waking life. This
represents a deeper question about why we can be so
easily fooled, but many other questions about dreams can be answered.
(48:50):
In the meantime, we're in a moment of using the
tools of neuroscience to tie specific details of the biology
to the experience of dreaming. We still have a lot
long way to go, but some promising leads can come
from the way that dream content changes with drugs. For example,
dreams can be made more vivid and frightening by drugs
(49:11):
that affect the dopamine system or by alkaloids. Antidepressants tend
to reduce the amount of dream sleep. Medications to reduce
epileptic seizures also seem to reduce nightmares. So we can
imagine in the near future having systematic studies to work
out the effects of different drugs on dream content, and
(49:33):
to do this in conjunction with brain imaging, and we
might be able to further nail down the relationships between
dream content and specific bits of the dream generation network.
And beyond drugs, we can also look to disease because
specific problems lead to the loss or impairment of dreaming.
(49:55):
People can lose dreaming with injuries to the inferior paride
lobe on either side. Patients with certain forms of dementia
report bland dreams, involving less aggression and less narrative complexity
and less emotional content. So by looking at changes to
the brain and corresponding changes in dreaming, we can better
(50:19):
map out the landscape of what is involved. And fundamentally,
studying dreaming may help us to comprehend consciousness. Why because
there are so many similarities between rem sleep and the
awake conscious state. Now there are major differences as well,
but it's important to note that we find both waking
(50:39):
life and dreaming equally compelling and believable, which tells us
that all you need to do is strike the right
notes on the neural piano and you have your totally
believable experience. But what would be cool is if there
were something like consciousness during a dream state that was
even close to our daily, normal conscious experience. And that's
(51:05):
what we're going to talk about next week. We're going
to talk about the very rare circumstance when you are
dreaming and you realize that you are dreaming, and you
take control of your dream and become an active director
of the plot. You are essentially conscious but living inside
(51:25):
the walls of your skull. So join me next week
as we sail into the very strange and amazing territory
of lucid dreaming. Go to eagleman dot com slash podcast
for more information and find further reading. Send me an
email at podcast at eagleman dot com with questions or discussion,
(51:49):
and check out and subscribe to Inner Cosmos on YouTube
for videos of each episode and to leave comments. Until
next time, I'm David Eagleman, and this is in our
car is miss
Why do brains dream? And what's going on with the
bizarreness of dreams? Why doesn't your clock work in your dreams?
And even though you spend a lot of your day
working on cell phones and computers, why do those almost
never make appearances in your dream content? There are so
many cool questions that we're going to address today. Is
(00:27):
dream content the same across cultures and across time? Are
dreams experienced in black and white or in color? Why
do I think about dreams as this strange love child
between brain plasticity and the rotation of the planet. What
is the relationship between schizophrenia and dreaming? And in the
(00:47):
future will we be able to read out the content
of somebody's dream? Welcome to Inner Cosmos with me David Eagleman.
I'm a neuroscientist and author at Stanford and in these
episodes we sail deeply into our three pound universe to
understand why and how our lives look the way they
(01:09):
do and how we experience our life includes our nocturnal life.
We spend a third of our lives with our eyes closed,
lying still and horizontal, like a meat robot that's been
switched off. But why in the last episode, we talked
(01:33):
all about sleep, why brains do that, and why all
animals do that, and what is happening in the brain
during sleep. Today we're going to zoom in on one
of my favorite subjects, a very strange thing the brain does,
which we call dreaming. We spend a fraction of our
sleep time locked in a different reality, swimming around in
(01:57):
plots which aren't real, and they're often not even realistic,
but which nonetheless convince us entirely. And today we're going
to see what that's all about. Humans have been writing
about dreams and pondering about them for a long time,
and essentially we have evidence of this from the beginning
(02:17):
of writing. We see detailed dream reports from ancient Egyptians
and Romans and Chinese. The Bible is full of dreams.
Every culture in the world has been fascinated by these
strange nocturnal journeys that we go on. And as we'll
see shortly, there's an interesting surprise, which is that dream content,
(02:39):
in other words, the kind of things that people dream about,
is essentially the same across cultures and across time, and
that serves as a clue that will allow us to
unlock some mysteries about what otherwise feels like a deeply
mysterious experience that we enjoy or suffer every night of
(02:59):
our life lives. So strap in for an episode full
of surprises. So let's start with a poem that Lord
Byron wrote in eighteen sixteen called The Dream. He wrote,
sleep hath its own world and a wide realm of
wild reality. And dreams, in their development have breath and tears,
(03:22):
and tortures and the touch of joy. They leave a
weight upon our waking thoughts. So dreams are indeed a
wild reality. The thing we all find so amazing about
dreaming is its bizarreness. You're seeing new things, you hold
strange beliefs, and you fall for it all hook line
(03:45):
and sinker. Whatever your brain serves up to you, you
believe it entirely. So we'll talk about all this, But
let's first zoom in on what's happening inside the brain.
Dreaming occurs during rapid eye moos movement or rem sleep,
where your eyes are darting back and forth. There's nothing
(04:05):
coming in the eyes, of course, they're shut, so all
the activity is internally generated. For good housekeeping, all just
note that rem sleep isn't necessarily equivalent to dream sleep,
but that's when most dreaming occurs. Now, how do we
know that, Well, it's because if you wait until someone
enters rems sleep, their eyes are going back and forth,
(04:27):
and then you shake them awake and you say, hey,
what were you just experiencing? They'll tell you WHOA, I
was just panicking because I was at work but realized
I had forgotten to put on pants, and I was
hiding behind the plant pots and figuring out how to
escape before the meeting started. But if you wake them
up during the rest of the ninety minute sleep cycle,
(04:50):
during the stages that we call slow wave sleep, and
you say, hey, what were you just experiencing, they'll generally
say nothing, I wasn't there. Now, for completeness, I'll mention
that sometimes people report some form of mental activity during
slow wave sleep, but when they do, this is usually
just a thought or making a plan. But it lacks
(05:15):
the visual vividness and the hallucinatory components of typical dreams.
So dreaming of the sort we're interested in today happens
during rem sleep. Now, although dreams seem so untethered and ethereal,
there are specific things happening under the hood. Dreaming depends
(05:36):
on the normal functioning of a particular network of brain areas.
This is primarily in the limbic and paralymbic and association areas.
Now we know that from brain imaging, but also because
damage in this network can produce temporary or permanent dream
loss or impairment like loss of visual dream imagery. Now,
(05:59):
not all of those areas might sound familiar to you,
but you've probably heard of the limbic system, which sits
at the heart of your emotions. So presumably this is
why dreams are so overloaded with high emotion. And I
also want to mention a brain era that is suppressed
during rem sleep, and that is the hippocampus. This is
(06:20):
an area that's required to convert short term memory into
long term memory. And this is why when you wake
up from a dream, you can remember it so clearly,
but after about fifteen minutes it just slips away from you.
You just can't hold on to what happened. This is
because you have the short term memory just fine, but
(06:42):
you're not converting it into long term memory, and so
it simply fades before your eyes. And by the way,
I think this experience that we have every morning can
enhance our empathy about what it would be like to
have something like Alzheimer's disease, because a person with Allsheimers
says on the phone, Okay, I'll be right down there
(07:03):
in a moment, and they hang up, and then the
memory of that just slips away. So even though you
might tell a relative with Alzheimer's, come on, just try
harder to remember. Just think about somebody telling that to
you about your dreams in the morning. So back to
the Byron poem, the line that I thought was interesting
(07:23):
was they leave a weight upon our waking thoughts because
they don't directly interact with our waking thoughts, but instead
they can just put a spin on our mood, even
if we don't remember why. Okay, so what do we
see in the brain when dreaming begins, Well, just before
(07:44):
the onset of your eyes darting back and forth, you
have a group of neurons in the brain stem, specifically
in an area called the ponds, and these crank up,
and these trigger several consequences. The first is that your
major muscle groups get paralyzed. This is called atonia. So
(08:04):
you've got this elaborate neural circuitry that keeps the body
paralyzed during dreaming. And by the way, the very elaborateness
of this circuitry emphasizes the biological importance of dream sleep.
You don't get this kind of complexity by accident. Presumably,
dreaming would be unlikely to evolve and remain without an
(08:27):
important function behind it. So why do we get this
paralysis of the muscles. It allows the possibility for the
brain to experience things and simulate reality without actually moving
the body. The second consequence of these neurons in the
ponds is that they trigger these waves of activity known
as PGO waves, and these are key to the experience
(08:51):
of dreaming. These PGO waves travel to a tiny area
called the geniculate nucleus and from there these waves of
activity slam into the occipital cortex at the back of
your head. In other words, they drive activity into the
visual system. So that's why these are called PGO waves.
Because they start in the ponds, p move to the
(09:14):
geniculate g and go to the occipital cortex. Oh pgoh
I mention all this detail. Because PGO waves are the
neural correlate of dreaming, the visual areas become alive with
activity allowing us to see our dreams. You blast activity
into the visual cortex and you enjoy visual experience even
(09:37):
though your eyes are closed. Now, interestingly, when you measure
electrical activity across the brain with EEG, when you do
this during rem sleep, it looks really similar to that
during the waking state. You see similar patterns in both states,
for example, lots of gamma wave frequency, which is generally
(09:58):
thought to reflect something about cognitive processing, with the exception
of the paralyzed muscles and the lack of external visual
input because your eyes are closed, the states of rem
sleep and of wakefulness they kind of resemble one another.
And this is what we might expect from a state
of consciousness that's altered. But it's some sort of consciousness nonetheless. Okay,
(10:24):
so that's what's happening in the brain when we dream.
But why do we dream? Well, there are various hypotheses
about this, and I mentioned one last week, which is
that maybe dreams allow us to simulate rare situations. In
other words, these nocturnal neural simulations might allow us and
(10:44):
all animals to test out activities without the danger and
risk of doing so in the real world. So you
can practice through different scenarios with your muscles all shut down.
So people who advocate this theory suggest that the periodic
stimulation of the cortex in this semi random and non
(11:05):
specific manner this can maintain circuits that are really important
for survival, but they rarely get activated because you don't
run into emergencies that often. So the idea is that
you're just sending in random activity, keeping the engine oiled
in case you need one of these programs sometime, and
some researchers suggest that it's even more specific than that.
(11:27):
A version of this framework called threat simulation theory, suggests
that dreams exist to simulate threatening events and to rehearse
what to do in the face of threat, and that
seems on its surface at least consistent with the high
prevalence of violence and aggression in dreams. But I want
to note that there's no data that directly supports this idea,
(11:51):
and I mentioned last week that this theory suggests that
people exposed to more survival threats in waking life might
have a more common experience of threat dreams at night,
but the data do not support that. Also, the threat
perception theory doesn't explain the fact that most dreams are
totally meaningless and bizarre instead of involving any meaningful threat
(12:15):
perception or threat avoidance. So back to the question of
why we dream. A few years ago, my colleague Don
Vaughan and I proposed a new theory which is the
only one that makes quantitative predictions across species. And if
you heard episode eleven you may remember about this. That
theory has to do with brain plasticity. And here's the idea.
(12:37):
In a nutshell, we know that if a person goes blind,
other senses start to take over what was the visual cortex.
In other words, the territory of the visual system is
not fixed permanently, but instead the wiring of the brain
is quite fluid, and there's a takeover that happens. Okay, now,
it turns out that if you take a normally cited
(12:58):
person and you blindfold, you can start seeing the beginnings
of this takeover in neuroimaging starting in about one hour.
And that really surprised us because of how fast the
takeover starts to happen. So what does this rapidity of
the takeover of the cortex have to do with dreaming?
(13:20):
While in the incessant competition for territory in the brain,
the visual system has a special challenge because of the
planet's rotation, we experience darkness for about twelve out of
every twenty four hours. And obviously I'm talking about our
evolutionary history, not the recently electrically blessed times. In other words,
(13:42):
our ancestors all spent their lives as inadvertent participants in
a blindfold experiment every single night. So how did their
visual cortex defend its territory when you've got no data
coming in through the eyes. So our proposal is that
the visual corret tex preserves its territory by finding a
(14:03):
way to remain active at night. And we call this
the defensive activation theory. And the purpose of dreaming here
is to keep cells in the visual cortex active, and
that's how it resists conquest by the territories of the
other senses. Vision is the only one of the senses
that's disadvantaged by darkness. You can still touch and smell,
(14:27):
and taste and hear in the dark, and so it's
the only sense that needs internally generated activity to maintain
its borders during the long night. So, as a result,
about every ninety minutes you get this internally generated activity
that blasts exclusively into the visual cortex, and so dreams
(14:47):
are experienced as primarily visual. So several predictions immediately fall
out of the defensive activation theory. First, because brain plasticity
diminishes with age, this would suggest that the amount of
time spent in REM sleep should also decrease as one
moves through the lifespan, and that turns out to be
(15:08):
exactly what happens. REM sleep in humans accounts for half
of an infant's sleep time, but as a person grows older,
the percentage of remsleep decreases steadily. In other words, diminishing
plasticity of the brain correlates with less REM sleep. But
more importantly, we made a more quantified prediction. We said, hey,
(15:30):
maybe the more flexible and animal's brain is the more
REM sleep it requires to defend its visual cortex. So
Don and I studied the plasticity in twenty five species
of primates and we found that the species with more
plastic brains spend more time in REMS sleep every night.
(15:51):
So you'd think that these two measures REM sleep and
brain plasticity they would be totally unconnected, So it was
very surprising to find that they are tightly linked. So
dreaming defends the visual cortex. Now, the circuitry that underpins dreaming.
This is so ancient and deeply wired that even people
(16:12):
who are blind have it. But note that blind people
don't have visual dreams. Instead, their nighttime hallucinations involve the
other senses, like feeling their way around an oddly arranged
kitchen or hearing strangers speaking. Why because other sensory errors
have annexed the underused visual cortex. So think about it
(16:35):
this way. People who can see and those with visual impairments,
they both have activity shooting into their occipital lobe during dreaming,
but the senses processed by that territory are different. The
defensive activation theory also makes more general predictions. If dream
sleep is triggered by the absence of visual input during
(16:56):
the night, we might presume that a person deprived of
vision while awake could similarly experience dreamlike visual hallucinations. And
that is exactly what happens when people have degenerating vision,
or they end up in solitary confinement or even just
in a dark float tank. Any situation in which vision
(17:16):
gets deprived, the brain starts fighting back and having hallucinations.
So that's the idea. Dreams are a screensaver. The brain
puts activity into the visual cortex to prevent it from
getting ruined during the night. Okay, so you might say, fine,
your hypothesis seems plausible, But why do dreams seem to
(17:39):
be stories? After all, we don't just see random snow
like on an old television. We experience stories, and in fact,
there are various stories of someone discovering something in dreams,
like Kurkule thinking of the structure of the Benzene ring
based on a dream he had of two snakes biting
each other's tails, or Paul McCartney dreaming the melody for
(18:02):
the song Yesterday. So what's up with dream content? The
key is that the brain is a storytelling machine. Your
brain is deeply carved with roadways that represent your experience
in the world, and these are stored in what are
called associative neural networks, which means that everything connects to
(18:24):
other things based on how they relate. So if I
ask you to think of a mouse that's physically connected
in your brain's networks to your concept of cheese or
exterminators or mickey mouse or mazes, or running wheels, or
mouse traps or pet stores everything else you've ever associated
with a mouse. So all concepts are related and linked
(18:48):
physically to what happens during sleep and dreaming. Well, the
synapses that are used during the day tend to be
slightly more chemically active, say, they're more hot from the
activity of the day, and so your dreams usually involve
something from the day or something that's on your mind.
(19:08):
They often involve the memories and desires and fears and
hopes that are brewing in your inner life. But the
associations are much looser. So maybe you have something about
your boss or something that happened in a class or whatever,
but the dream quickly goes off in some weird direction.
The associations are looser, and so we end up dreaming
(19:32):
stories with looser associations, following paths along the associative neural
network that we might not otherwise take. But things make sense,
at least in the light of dream logic. So even
if the visual cortex is just getting volleys of random activity,
you get meaning out of it. You get some sort
(19:53):
of story. Now people often wake up and say, no, way,
that wasn't random, That was a metaphor. I'm trying to
decide if I should quit this job, and I had
a dream that I went into the office and the
floor was tilted at forty five degrees and no matter
what I did, I kept slipping back down. And that
was a metaphor about the impossibility of my advancement. There,
(20:16):
that was a sign from my unconscious. Okay, so maybe
the interesting thing about interpreting the content of dreams is
that they might be one hundred percent random, but they
act like a Rorshack blot, which is to say, you
can assign any sort of meaning to them. You remember
a Rorshack blot, which is where you squish some ink
(20:38):
between two pages, and then you pull the pages apart
and you get some random shape, and you ask people
to interpret what they're seeing to assign meaning to it.
And it's easy enough to say, yeah, that looks like
this thing in my life, maybe this issue that's been
chewing at me. And that's how doctor Rhorshak used this
to determine what had meaning in a person's mind. But
(21:01):
you would never say the blob of ink carried meaning.
It's all about the imposition of meaning by the viewer.
And this, I suggest could be what happens with dreams
as well. You interpret the ink blob, and that interpretation
might have significance to your life, but you imposed that
meaning instead of it being inherent in the dream. Here's
(21:25):
an interesting parallel. Pablo Picasso once said, we all know
that art is not truth. Art is a lie that
makes us realize the truth, and that could be the
same thing with dreams. They are a lie that makes
us realize the truth. So in this sense, it's the
same thing. If you're thinking about some problem and you
(21:46):
go to the bookshelf and you pull off any random
book and turn to a random page and you read
the sentence. Often it will very tangentially give you some
push to the thing that you're trying to solve. But
that doesn't mean the awe of the book cared about
you and wrote that sentence with that future moment in mind.
It simply tells us that lots of things in the
(22:07):
world are like lots of other things and can therefore
be interpreted. And I do just want to add one
more word of caution to the game of dream interpretation.
By the time you turn to the person next to
you and say, oh my gosh, I just had the
strangest dream and you tell them, you are forced to
add another layer of narrative scaffolding so that it makes
(22:30):
sense as a story that you're telling. So a narrative
that's very thin can seem to have more flesh after
you've pushed it through your storytelling machinery. In other words,
we layer on narrative structure to give our dreams a
shape that they didn't actually have. And so especially if
you've had a dream that you've told over and over,
(22:51):
it usually has more of a scaffolding than it actually
started with. Nonetheless, the content of dreams has always fascinated humans,
spurring societies to invent cultural uses for dreams in religious
ceremonies and medicinal practices, or doomed attempts to predict the future.
(23:12):
Sigmund Freud, who lived decades before modern brain science, he
thought that dreams provided an inroad into the underlying functions
of the brain and especially the subconscious. He suggested, as
had many before him, that dreams concealed hidden meanings that
were just at the threshold of breaking through the barrier
(23:32):
to consciousness. More specifically, he proposed that dreams constitute a
disguised attempt at wish fulfillment. Similarly, Carl Jung positive that
dreams may offset features of a character personality that you
might ignore while you're awake. In general, both those theories
have been criticized because they can't be proven wrong, and
(23:56):
critics have pointed out that the wish fulfillment interpretation seems
improbable in view of the recurring nightmares that attend post
traumatic stress disorder. So I am, of course not the
first to propose that dreams might have no inherent meaning.
The psychiatrists j al And Hobson and Robert McCarley suggest
(24:17):
that dreams may have no meaning at all, and they
have a model they call the activation synthesis model, which
proposes that random activity from the brain stem goes to
the cortex, which tries to turn it into motor output.
But given the paralysis of the major muscle groups, the
brain has to explain the paradox between outgoing motor signals
(24:39):
and a lack of expected sensory feedback. So in this situation,
the cortex synthesizes an explanation, essentially weaving a story from
the random inputs. Now Hobson and McCary faced criticism for
this aspect of their theory because dreams often do have
a relation relationship to life experience. So in that light,
(25:02):
they made modifications to allow that dream content relates to
memories and fears and desires and hopes and so on,
but that these provide the background context and not the
exact content of the cortexas interpretation of the random activity.
So which is it, Does dream content tell us anything
at all? Or nothing? Well, here's how we can approach
(25:25):
the problem. When you look at one person's dreams like
you think about your own dreams, you may not be
able to use the content as a key to unlock
much about the brain. But as you move from considering
one dreamer to doing the science and looking at thousands
of dream reports and hundreds of thousands from all over
the world, you can start to see the fence lines.
(25:48):
You see that dreams aren't a wild unleashing where anything
can happen. Instead, dreams have particular rules to the stories,
and that gives us hints. So what are those rules? Well,
I recently read a very cool new book by my
colleague Rahul John day Al called This Is Why You Dream,
and he outlines a series of studies that demonstrate a
(26:10):
remarkable consistency of themes. Across cultures and across decades, the
same kinds of dreams are reported, for example, being unable
to find one's way or being late for an important event.
In dreams, both men and women usually experience more aggression
than friendliness, although men in almost all societies have greater
(26:33):
physical aggression in their dreams than women do. Everyone experiences
more misfortune than good fortune. People experience more negative emotions
than positive emotions. So the cross cultural research suggests that
dreams are similar across a wide range of cultures in
terms of the subject matter, the level of aggression, familiarity
with the people in the dreams. For example, let me
(26:55):
zoom in on this. Jandeal points out that in the
nineteen fifties there were ques given to college students in
America and college students in Japan, and the questionnaire asked
them what they had dreamt about, like showing up somewhere
with no clothes or flying or trying to do something
again and again, or being buried alive, or something involving
(27:15):
school and their teachers or whatever. And as it turns out,
although American and Japanese students were living pretty different lives,
their answers were essentially the same. So for the Americans,
the top five dreams were falling, being attacked or pursued,
trying again and again to do something, a dream involving
(27:36):
school or teachers, or studying, and sexual experiences. And when
you compare this to the Japanese students, it was essentially
the same. Their dreams were ranked as being attacked or pursued, falling,
trying again and again to do something, dreams about school
or teachers or studying, and being frozen with fright, and
sexual experiences were number six. So halfway across the world,
(27:58):
very different cultures, same dream content. Now, fifty years after
(28:20):
that study, similar questions were given to students in China
and Germany, and they came up with the century the
same answers. Again, you find people dreaming of being chaste,
or pursued, or arriving too late, like missing an airplane
or a final exam. Now you might say, fine, but
these are all industrialized countries and maybe their lives are
sort of similar. But in fact people have also studied
(28:41):
indigenous societies in Brazil and Mexico and Australia and they
find extremely similar results. The cultures are quite different. But
the plots of the dreams are not. So there have
been lots of studies on this sort of thing now,
and they all conclude that dream content is a century
same across cultures and across time. As one example, wherever
(29:04):
you are in the world, men dream more about other men,
while women dream equally of men and women, and all
people across cultures are more likely to be victims of
violence rather than perpetrators. So dreams cover similar themes across
the world, irrespective of language and culture and time. It
doesn't seem to matter how rich you are, how poor
(29:26):
you are. So what does that mean? Well, what's the
one thing we all have in common? Our organs on
the inside and specifically the brain. As easy as it
is to look at different cultures around the world, with
different governments and different religions and different costumes, this variability
has cropped up in the last millisecond of human history.
And if you look just under the skin and the bone,
(29:48):
you find the same brain in us all. It's the
same engine under the hood. So whenever we find something
clear like oh, everyone dreams about the same thing, that
we are looking at something fundamental and ancient and universal,
and we find all sorts of other interesting answers by
looking across thousands of dreams. For example, what if dreams
(30:11):
are a way to live out fantasies like sexual fantasy.
That seems consistent with how we talk about dreams a
way of acting out our desires. But in studies across
all cultures, it turns out that fewer than ten percent
of dreams are sexual, which I find fascinating given the
way we talk about dreams. If a young single person
(30:34):
says to another single person, oh, I had a dream
about you last night, then everyone titters, makes assumptions about that,
and we have terms like dream girl or dream guide,
But in fact, ninety percent of our dreams have nothing
to do with that. So the content is remarkably similar
across the world. But where things get really interesting is
(30:54):
when we zoom in one more level and really examine
what dreamscapes look like like in detail. And I'm not
asking about what's in the dream script here, but if
you look very closely across thousands of dream reports, you
can ask what is not in the script. So I
want to return to a question I posed at the beginning,
which is that we live in a society where we
(31:16):
are constantly hunched over our cell phones and our laptops.
How come these essentially never show up in our dreams?
Isn't that weird? And even in the era before computers,
back when people read a lot more books, how come
no one sits around reading books in their dreams. Why
can't you even see any text in your dreams? Why
(31:37):
do you spend so much time writing stuff down in
real life but you never can write stuff down in
a dream. How come you never do math in a dream,
like calculating a tip for a restaurant bill, Even if
that comes up in a dream plot, it feels totally
impossible to get the right answer. Well, all of this
serves as a big clue into the networks that are
(32:01):
active during a dream, and this is pretty well worked
out with brain imaging now, although anyone who is being
very observant probably could have guessed this all even a
century ago. What reading and writing, and cell phones and
computers all have in common is that they require the
use of a network in the brain that we summarize
as the executive network, which involves a lot of activity
(32:24):
largely distributed in the frontal lobes and the parietal lobes,
and you need this for rule based problem solving and
for making decisions when you've got a particular goal in
front of you that you're trying to solve. And the
key is that activity in the executive network is reduced.
I'll just say it's shut down while you are dreaming,
(32:46):
so you're not able to read and write and launch
an app on your cell phone screen and so on,
because that work requires the executive network, and that network
is off duty for the night. But what is on
is an network we summarize as the default mode network,
which is what kindles to life when you shut your
(33:07):
eyes and you're not involved in gathering information and acting
on some other task. So this is called the default
mode network, but many scientists are renaming this the imagination
network because this is what lets your storehouse of experiences fly.
You can piece ideas together and come up with new
(33:29):
hypotheses and thoughts, and this is what's firing on all
cylinders when you dream. So the executive network has reduced,
the imagination network is enhanced, and this is what gives
dreams their very untethered character. There are other clues you
can also gather from looking at detailed dream reports, which
(33:51):
is that sometimes objects will turn into other objects, but
they're always related in some way. What I mean is
you might have your bicycle turn into a motorcycle, or
your small house becomes a mansion, or the cafeteria becomes
a restaurant, or the hammer becomes a screwdriver, but you
(34:11):
don't find the bicycle turning into a restaurant or your
house turning into a hammer. What does that tell us? Well,
under the hood, we have what are known as semantic maps,
and more than associations, which I mentioned before, semantic maps
refer to the way that all the stuff in your
brain is laid out in terms of relationships between concepts.
(34:35):
For example, in your semantic map, you have the concept
of an animal, which might include categories like mammals and
birds and reptiles and so on, and within one of
those categories you might have more specific concepts like dog
and cat and eagle and salmon and snake and frog
and so on. Things are laid out in your brain
(34:56):
based on their conceptual meaning. And what we find is
that dreams follow the semantic maps. In other words, they
stay local in the little clusters of the maps. So
this is why you see the bicycle turning into the
motorcycle because they're both forms of transportation, but not into
the screwdriver, which is a tool and in a totally
(35:18):
different category. These things live in different little neighborhoods of
the semantic map. So again, a careful look at dream
reports tells us important clues about what is going on
under the hood, and that tells us that while the
themes are universal strife and falling and attempting to do
something over and over, the details are filled in with
(35:41):
the specifics of your semantic maps. And this all brings
me back around to a question I had since I
was a kid about whether dreams are experienced in black
and white or in color. Now. When I was a child,
I remember at some point that my parents told me
that we dream in black and white, and I was
(36:01):
confused by this because I didn't seem to dream in
black and white. As far as I could tell, my
dreams were in color, so I thought I must be
somehow assessing that incorrectly. Because they were both very smart
and educated. My mother was a biology teacher, my father
was a medical doctor, and as I grew older, I
asked my friends about this, but I couldn't find anyone
(36:22):
who thought that their dreams were not in color. Now,
because I genuinely knew that my parents were brilliant, I
thought maybe there was something they knew that I didn't like.
Maybe we were dreaming in black and white but didn't
realize it. And then I found several large scale surveys
that reported what my parents had said, that most people
(36:43):
dream in black and white. One study was from nineteen
fifty eight and they said only nine percent of people
dream in color, and a paper in nineteen forty two
reported that only ten percent claimed to frequently or very
frequently dream in color, and a report in nineteen fifty
one had the highest percentage. They said that twenty nine
percent of dreams are in color. But even this didn't
(37:05):
make things clear what was going on, because dream reports
from earlier, like Freud's reports of dreams in nineteen hundred,
often had explicit color descriptions in them. So somehow it
seemed to be only my parents' generation that dreamed in
black and white. And it turns out if you run
(37:27):
the study now, almost everyone says they dream in color.
As you may have guessed by now. The hypothesis on
this is that people were influenced by watching black and
white television and black and white movies and black and
white photographs, and once the technology changed to color, then
so did dreams. I'm putting a very nice paper by
(37:51):
Eric Schwitzkeebel on my site that compiles all these studies
through the years and the change in the reports. Again,
this demonstrates that the content of our dreams has to
do with the experiences that we have now. I'll tell
you an interesting side note on this. I happened to
live in California and during COVID, everyone in my neighborhood
(38:11):
wore masks, and it was a very weird time, and
so we rarely saw other human beings for a couple
of years without everyone being in masks. And one of
the things I remember from that time was that we
would sometimes watch a movie on TV, and it was
so shocking that people in the movie would push their
way through a dense crowd and sit so close to
their friends and the people they were talking with, and
(38:32):
they were indoors with such density. And it became in
twenty twenty so noticeable and so shocking when we were
in the middle of COVID. Interestingly, it's a little hard
to remember that now, but I remember it well because
I was taking careful notes on what was going on
with my dreams during this time, and specifically, since my
real life involved the very thinned out crowds and everyone
(38:55):
in masks, did that show up in my dreams? And
the answer was is no. The thing that struck me
the entire time during lockdown is that my dreams were
totally normal. In my dreams, I was at a big
party and there were lots of people around, and no
one ever had masks in my dreams, which struck me
as weird when I would wake up. Why didn't my
(39:16):
dreams reflect my daily experience? Now, this is just a
single person's report, and I didn't think to study this
carefully at the time by doing a big online survey
of everyone. But if it's generally true that other people
were having these very salient daily experiences of lockdown and
masks and yet it wasn't appearing in their dreams, the
(39:38):
only interpretation I can make is that our dreams reflect
pathways that get laid down over our youth when we're young.
And if that's the case, then maybe we could still
find some black and white dreaming among older people. Now,
in other words, maybe you'd still see some of that now,
even though those people have been watching color television for
(40:01):
sixty years. Now, with all the things on my plate,
I'm not going to have time to pull off that study.
But I would love it if listeners could ask their
oldest living relatives they a parent, or grandparent or great grandparent,
how they dream and determine if anyone still dreams in
black and white and what their age is. Okay, so
(40:37):
that story of black and white dreaming correlated with black
and white television. That seems like a clean story, But
there's one thing that still bugs me about it. Although
television and movies were in black and white, obviously the
world wasn't. When my parents walked outside, they saw green
trees and blue skies and red cardinals and yellow sunflowers
and so on. So why didn't their dreams reflect that? Well,
(41:01):
there are two things to say here. First, not everyone
dreamed in black and white. Instead, it was between let's
say seventy to ninety percent. So had I been alive
in the nineteen fifties, I would have studied the issue
of how many hours of television people watched each day,
and perhaps some measure of how many black and white
movies they saw on how many newspapers with black and
white photos and so on, and correlated that to whether
(41:23):
or not they had black and white dreams. Second, I
have a totally speculative hypothesis. I don't have any evidence
for this, but I'm going to say it anyway. What
if some part of the brain knows, at least in part,
that dreams are like a fake movie, and in that
way it takes on the property of fiction, which in
(41:43):
those days was black and white. Because note that even
when you're in the middle of a movie, some part
of your brain still knows you're watching a movie. And
this is why when the train comes at the camera,
you don't actually duck and scream. So even though we're
compelled by fiction, we don't fall for it completely. Could
it be that to the brain, dreams are more like movies.
(42:06):
I don't know, because I missed that era, so the
opportunity seems gone to study that. But I'm wondering if
we're going to have another shot at studying this question
once virtual reality becomes ubiquitous and pervasive, and whether a
big chunk of the population will report dreams that are
more like synthesized virtual reality worlds than like our daily life.
(42:29):
To me, this would shed light on the mystery of
the black and white dreams and the details by which
your dreams are determined by your experiences in the world. Now,
there's still lots of stuff that I think we don't understand.
One is why we can have false, implanted memories inside
a dream. This is something I've wondered about for years.
(42:52):
For example, I had a dream many years ago about
my brother's wedding and he was yelling at me and saying,
I can't believe you said that to Jenny and ruined
my wedding, and I felt horrible. I felt as guilty
as I ever felt. Why did I do that? Why
was I so insensitive? And then I woke up. As
it turns out, my brother had a lovely wedding that
went just perfectly, and I of course never said anything
(43:14):
bad to his bride, my lovely sister in law Jenny. Ever,
there was never trouble of any sort there. So why
did I fall for the false memory? Why couldn't I
access my real memories of the wedding while I was
inside the dream? In other words, the issue is that
not only did I have a false memory. But also
(43:35):
I had no access to my real memory of the wedding.
One set of memories was replaced by another. And this
is what freaks me out, not just about dreams, but
about our sense of reality. We buy whatever our brains
serve up to us at every moment. We buy the
plot of a dream completely. And by the way, this
(43:58):
is one interpretation of what happened in schizophrenia. The way
psychiatrists used to describe this about a century ago is
that psychosis is essentially an intrusion of the dream state
into the waking state. So the next time you see
a man talking to himself on the street and having
an argument with someone who is not there in front
(44:20):
of him, interpret it through this lens that he is
having an awake dream, and you might understand what's happening
in a fresh way. So what we see here, and
what we've seen in many of these episodes, is that
we accept whatever reality is served up to us. And
by the way, I think this is why literature works
(44:41):
with our species, because we can so easily adopt a
different reality. We can read a book and we laugh
and we weep. We are effortlessly deluded. And to understand
this I think we shouldn't use the term suspension of disbeliefs.
It's the wrong term because an applies that disbelief is
(45:02):
the standard disbelief is the normal operating mode. In fact,
it might be just the opposite. Our brains are perfectly
willing to accept whatever they are fed. Now, I want
to hit one more question in today's episode, which is
where is dreaming headed? Would it be possible to read
out the content of somebody's dreams? Well, if you happen
(45:27):
to have heard my episode number twenty seven, you'll know
that the answer is already yes, at least to some degree.
Different research groups have been working since at least twenty
eleven to see if they can measure brain activity in
the visual cortex to assess what somebody is seeing in
front of their eyes. In other words, if you're looking
at a building, there's a different activity in your visual
(45:50):
cortex than if you're looking at a puppy or a
cup of coffee and so on, and so the research
question is can you tell what a person is seeing
just by measuring the pasterns in their visual cortex? And
the answer is that you can pretty well tell what
somebody is seeing this way. After that research came out,
people realized we might be able to measure dreams because
(46:12):
dreams are activity in the primary visual cortex. Dreams are
experienced as visual because it's activity in the visual cortex,
and your brain understands that as visual experience. So Yuki
also Comma Tani and his colleagues published a paper a
few years ago in which he took this same approach.
(46:32):
He had people look at a bunch of pictures and
watch a bunch of videos while they were in the
brain scanner, and then he used machine learning to decode
how the picture out there corresponds to the activity patterns
in the brain. And now you let people go to
sleep in the scanner, and you measure their visual cortex,
(46:53):
and you use the machine learning model to decode what
that activity would correspond to, in other words, what they
were presumably seeing in their dream. And once the machine
learning model gives an answer, then you can make a
little video reconstruction of their dream, and you can watch
what presumably was the experience for the dreamer, albeit with
(47:17):
very low resolution. Now, when you're decoding pictures or videos,
it's easier to know if you're getting it right. When
you're decoding dreaming, it's harder to know for sure that
you got the right answer. You have to wake up
your participants and say, hey, what do you remember, and
then you compare that to what you think you might
have decoded. But even with those caveats, this gives the
(47:40):
rough start to a dream decoder that could tell you
what you were dreaming about. And presumably this will only
become higher resolution with time. So it maybe that in
the future we are able to know what you dreamed
even if you can't remember it. You could keep a
digitized dream diary that way, or you could share your
(48:03):
dreams with a girlfriend or boyfriend, or less likely, a
dream could be used in a court of lossome day.
Who knows where this will all go, but we can
imagine that in two hundred years from now, dreams may
be a very different sort of thing than the entirely
private experience that we enjoy now. So let's wrap up.
(48:26):
To my mind, the biggest issue that freaks me out
about dreams is this issue that we believe patently impossible situations,
and we accept false memories even when they contradict events
that we know to be true in waking life. This
represents a deeper question about why we can be so
easily fooled, but many other questions about dreams can be answered.
(48:50):
In the meantime, we're in a moment of using the
tools of neuroscience to tie specific details of the biology
to the experience of dreaming. We still have a lot
long way to go, but some promising leads can come
from the way that dream content changes with drugs. For example,
dreams can be made more vivid and frightening by drugs
(49:11):
that affect the dopamine system or by alkaloids. Antidepressants tend
to reduce the amount of dream sleep. Medications to reduce
epileptic seizures also seem to reduce nightmares. So we can
imagine in the near future having systematic studies to work
out the effects of different drugs on dream content, and
(49:33):
to do this in conjunction with brain imaging, and we
might be able to further nail down the relationships between
dream content and specific bits of the dream generation network.
And beyond drugs, we can also look to disease because
specific problems lead to the loss or impairment of dreaming.
(49:55):
People can lose dreaming with injuries to the inferior paride
lobe on either side. Patients with certain forms of dementia
report bland dreams, involving less aggression and less narrative complexity
and less emotional content. So by looking at changes to
the brain and corresponding changes in dreaming, we can better
(50:19):
map out the landscape of what is involved. And fundamentally,
studying dreaming may help us to comprehend consciousness. Why because
there are so many similarities between rem sleep and the
awake conscious state. Now there are major differences as well,
but it's important to note that we find both waking
(50:39):
life and dreaming equally compelling and believable, which tells us
that all you need to do is strike the right
notes on the neural piano and you have your totally
believable experience. But what would be cool is if there
were something like consciousness during a dream state that was
even close to our daily, normal conscious experience. And that's
(51:05):
what we're going to talk about next week. We're going
to talk about the very rare circumstance when you are
dreaming and you realize that you are dreaming, and you
take control of your dream and become an active director
of the plot. You are essentially conscious but living inside
(51:25):
the walls of your skull. So join me next week
as we sail into the very strange and amazing territory
of lucid dreaming. Go to eagleman dot com slash podcast
for more information and find further reading. Send me an
email at podcast at eagleman dot com with questions or discussion,
(51:49):
and check out and subscribe to Inner Cosmos on YouTube
for videos of each episode and to leave comments. Until
next time, I'm David Eagleman, and this is in our
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I’m Jay Shetty host of On Purpose the worlds #1 Mental Health podcast and I’m so grateful you found us. I started this podcast 5 years ago to invite you into conversations and workshops that are designed to help make you happier, healthier and more healed. I believe that when you (yes you) feel seen, heard and understood you’re able to deal with relationship struggles, work challenges and life’s ups and downs with more ease and grace. I interview experts, celebrities, thought leaders and athletes so that we can grow our mindset, build better habits and uncover a side of them we’ve never seen before. New episodes every Monday and Friday. Your support means the world to me and I don’t take it for granted — click the follow button and leave a review to help us spread the love with On Purpose. I can’t wait for you to listen to your first or 500th episode!
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations. Follow now to get the latest episodes of Dateline NBC completely free, or subscribe to Dateline Premium for ad-free listening and exclusive bonus content: DatelinePremium.com
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.