The Neuroscience of Consciousness – with Anil Seth

The Neuroscience of Consciousness – with Anil Seth

[APPLAUSE] – Two out of the three
fundamental mysteries about our place in the universe
have already been resolved. The first is literally about
our place in the universe. Many years ago Copernicus told
us that we were not at its centre, that we were just a
tiny dot suspended in the abyss. This is an image of the earth
taken from the probe Voyager 1 as it was leaving the
solar system from about six billion kilometres away. All of human history, all of
the history of life on Earth, has taken place on
that pale blue dot. The second mystery,
Darwin then revealed that we humans are just
one branch, or one twig, of a beautifully rich and
delicate evolutionary tree. And that much of the
machinery of life is shared even with the lowliest
of our fellow creatures. The third mystery is
that of consciousness, our inner universe. Now earlier this year, for
the third time in my life, I ceased to exist. As the propofol anaesthetic
flowed from the cannula in my wrist into my bloodstream
and then into my brain, there was a falling apart. A blackness. An absence. And then, I was back. Drowsy and disoriented,
but definitely there. And when you wake
from a deep sleep, you might be confused what
time it is, especially in flying somewhere, but you’ll
know that some time has passed. There seems to be
some basic continuity between your consciousness then,
and your consciousness now. But coming around from
a general anaesthetic, it could have been five minutes. It could have been five hours. It could have been five
days, or five years. I was simply not there. A premonition of the
oblivion of death. And general anaesthesia doesn’t
just work on your brain. It doesn’t just
work on your mind. It works on your consciousness. By altering the delicate
electrochemical circuitry inside your head, the
basic ground state of what it is to be is
temporarily abolished. And in this process lies one
of the greatest remaining mysteries in science
and philosophy. How does consciousness happen? Why is life in the first person? It is going away,
and coming back. The modern incarnation
of this problem is usually traced to Descartes,
who in the 17th century distinguished between matter
stuff, res extensa, the stuff that these desks are made
of, that clothes are made of. But also the brains and bodies
and made of, material stuff. And res cogitans, the stuff
of thought, of feelings. The stuff of consciousness. And in making this
distinction, he gave rise to the now infamous
mind/body problem, and life has never
been simple ever since. But Descartes actually
generated even more mischief with his doctrine of
the beast machine, which I’m going to mention now,
because it anticipates where I’m going to end up as the bell
rings when I finish in an hour. Before Descartes, people
commonly believed in something called the great chain of
being, with rocks and plants at one end, and other
non-human animals, a bit higher up than humans, and then angels
and gods at the very top. And this great scale
of being was also a scale of moral virtue, so that
humans had more moral virtues than animals and plants,
and then rocks and so on. Now Descartes, in making
this division between mind and matter, argued that only
humans had minds, and therefore moral status, while other
animals didn’t have minds. They were merely physiological
machines, or beast machines, morally equivalent to
plants, and to rocks. And in this view, the
physiological mechanisms that give rise to the
property of being alive were not relevant
to the presence of mind or consciousness. Now I’m going to propose, at the
end of this talk, the opposite. That our conscious sense of
self arises because of, and not in spite of, the fact that
we, too, are beast machines. So to get there, let’s return
to the apparent mystery of consciousness. Now as recently as 1989, which
is quite a while ago, but not that long ago,
Stuart Sutherland, who was founding professor
of experimental psychology at my university of
Sussex, had this to say. “Consciousness is a fascinating
but elusive phenomenon. It is impossible to specify
what it is, what it does, or why it evolved. Nothing worth reading
has been written on it.” [LAUGHTER] It’s quite a pessimistic
point of view. And that may have
been true then. I don’t think it was true
then, but in any case things have changed a lot since. And more or less, about
the time that Sutherland made these remarks, we can
see the birth, or the rebirth, of the study of consciousness
within the neurosciences. And a good landmark
is this paper by Francis Crick and Christof
Koch, published in 1990. And they start their paper by
saying that it is remarkable that most of the work
in cognitive sciences, and the neurosciences, makes
no reference to consciousness or awareness at all. And then they go on to
propose their own theory of what the neural correlates
of consciousness are. What it is in the brain that
is responsible for being conscious. And since then, over
the last 25 years, there’s been first a trickle,
and now a deluge of research on the brain basis of
conscious experience. Some of this work
is being carried out in my laboratory, the Sackler
Centre, the consciousness science, which was founded
six years ago with Hugo Critchley, my co-director. And there are now even
specialised academic journals, The Neuroscience
of Consciousness, which I started last year
with Oxford University Press. And this is a real
change of the tide. When I started out
more than 20 years ago, it was thought to be a
very– it was thought to be career suicide to
want to study consciousness, scientifically. And it may still
be, we don’t know. Let’s see. So while the brain
basis of consciousness is still a mystery,
it is, in some sense, an accessible mystery. And the author, Mark Haddon,
put this very nicely, I think. He said the raw material
of consciousness is not on the other
side of the universe. It didn’t happen 14
billion years ago. And it’s not squirrelled
away deep inside an atom. The raw material
of consciousness is right here, inside
your head, and you can hold the brain in your hands. But the brain won’t deliver
its secrets very easily. What’s extraordinary
about the brain is not so much the
number of neurons, though there are
about 90 billion. It’s not even the
number of connections, though there are so many that
if you counted one every second, it would take you about
three million years to finish counting. What’s truly extraordinary
are the patterns of connectivity, which
to a large extent, are still not known, but within
which are inscribed everything that makes you, you. The challenge is then this,
at least the the way I see it. How can the structure
and dynamics of the brain, in connection with
the body and the environment, account for the subjective
phenomenological properties of consciousness? And considering
things this way, we come up against what
the philosopher David Chalmers has often called the
hard problem of consciousness. And the idea is this. There is an easy problem. The easy problem is to
understand how the combined operations of the brain and the
body give rise to perception, to cognition, to thinking,
to learning, to behaviour. How the brain works,
in other words. The hard problem
is to understand why and how any of this
should have anything to do with consciousness at all. Why aren’t we just robots,
or philosophical zombies, without any in a universe? Now there’s a tempting
intuition here, which is that, even if we solve
the hard problem, even if we solve the easy problem, the
hard problem would still remain as mysterious as it seems now. But this just seems
wrong-headed to me. It may not be necessary to
explain why consciousness exists at all, in order to
make progress in understanding its material basis. And this for me, is the real
problem of consciousness; how to account for its
various properties in terms of biological mechanisms without
pretending that it doesn’t exist at all, as you do if
you solve the easy problem, and without trying to
account for why it’s parts of the universe in
the first place, which is the hard problem. And in the history
of science, we’ve been somewhere similar before. It’s hard to say if it’s
exactly the same situation. But in our
understanding of life, eminent biochemists of the time
found it entirely mysterious how biological mechanisms
could give rise to the property of being alive. And there were
proposed of things, like elan vital
and essence vital, and all sorts of other stuff. And although we don’t
yet understand everything about life, this initial
sense of mystery about life has, to a large
extent, dissolved as biologists have just
got on with the business of understanding the properties
of living systems in terms of mechanisms. An important part
of this story was the realisation that life
is not just one thing, but rather a constellation of
partially dependent, partially separable, processes, like
metabolism, homeostasis, and reproduction. In the same way,
to make progress on the real problem
of consciousness, it can be useful to distinguish
different aspects or dimensions of what it is to be conscious. The space of possible
minds, if you like. And one simple classification
is into conscious level, which is the property of
being conscious at all. For example, the
difference between being in a dreamless sleep, or
under general anaesthesia, and being awake and
conscious as you are now. And the conscious content,
when you are conscious, you’re conscious of something. The myriad of sights, sounds,
smells, emotions, feelings, and beliefs that populate your
inner universe at any one time. And one thing you are conscious
of when you are conscious, is the experience, the specific
experience, of being you, and this is conscious self. And it’s the third
dimension of consciousness. Now I don’t claim
these distinctions mark completely independent aspects
of what it is to be conscious, but they’re a pragmatically
useful way of breaking down the problem a bit. So let’s start with
conscious level. What are the fundamental
brain mechanisms that underlie our ability
to be conscious at all? And we can think of this, at
least a first approximation, as a scale from being
completely unconscious, as if you were in a coma, or
under general anaesthesia, to being awake, alert, and
fully conscious as you are now. And there’s various states
in between being drowsy, being mildly sedated and so on. What’s important is that, while
being conscious and being awake often go together, this
is not always the case. For instance, when you are
dreaming you are asleep, but you are having
conscious experiences. The conscious experience
of your dreams. And on the other
side of this diagram, there are pathological states,
like the vegetative state, where physiologically you will
go through sleep/wake cycles, but there is nobody at home. There is no
consciousness happening. So what are the
specific mechanisms that underlie being conscious
and not simply being physiologically awake? Well there are a number
of possibilities. Is it the number of neurons? Well actually, probably not. There are more neurons
in your cerebellum, this bit at the
back of your brain, than in the rest of
your brain put together. In fact are about four times
more neurons in your cerebellum than in the rest of your cortex. But if you have damage
to your cerebellum, yeah, you’ll have some problems
with coordination and other things, some
cognitive problems, but you won’t lose
consciousness. It’s not just the
number of neurons. Doesn’t seem to be
any particular region. In fact, there are regions
that, if you suffer damage, you will permanently
lose consciousness; in thalamina, the
nuclei, and the thalamus deep inside the brain. But these seems to be
more like on/off switches than actual generators
of conscious experience. It’s not even neural
activity, at least not simple kinds of neural activity. Your brain is
still highly active doing unconscious
states, during the sleep. And even if your brain
is highly synchronised, one of the first
theories of consciousness was it depended on neurons
firing in synchrony with each other. If your brain is
too synchronised, you will lose consciousness,
and this happens in states of absence epilepsy. What seems to be the case is
that, being conscious it all, depends on how different
brain regions talk to each other in specific ways. And this was some groundbreaking
work by Marcello Massimini in Milan about 10 years ago. And what he did here,
was he stimulated the cortex of the brain
with a brief pulse of electromagnetic energy,
using a technique called transcranial magnetic
stimulation or TMS. And then he used EEG
electroencephalography to listen to the brain’s echos. A little bit like
banging on the brain and listening to its
electrical response. And what he noticed
when you do this, and you can see on
the left is asleep, and on the right is awake. And this is very
much slowed down. When you stimulate the
brain in a sleep condition, there is still a response. There’s still an echo, but
the echo stays very localised to the point of stimulation. It doesn’t travel
around very much, and it doesn’t last very long. But when you stimulate
a conscious brain, there’s a spatial
temporally complex response. This echo bounces around
all over the cortex in very interesting ways. What’s more, the complexity of
this echo can be quantified. You can apply some
simple algorithms to describe how
complex, how rich, this pattern of
interactivity is. This is also from
the Milan group. And what they’ve done here is,
they basically look at the echo as it moves around the brain. And they see the extent to
which you could describe it, the minimum description length. How much can you compress
the image of that echo? Much the same way
that algorithms make compressed files from
digital images in your phone. And they came up
with an index called the perturbational
complexity index. And what you find
is, you now have a number that you can attach
to how conscious you are. This is, I think,
really intriguing, because it’s a first
step towards having an actual measurement
of conscious level. This graph on the bottom
shows this measure applied to a variety
of conscious states, ranging from pathological
conscious states, like the vegetative
state, where there is no consciousness at all,
all the way through locked in syndrome, and
then healthy waking. And you can immediately
see that techniques like this might already have
clinical value in diagnosing potential for
consciousness patients might have after
severe brain injury. Now at Sussex, we are continuing
work along these lines. We actually look,
instead of bashing on the brain with a
sharp pulse of energy, we want to see whether we can
get something similar just by recording the spontaneous
activity of the brain. So we look at
spontaneous dynamics from, in this case, waking
states and anaesthesia. This is work with my PhD
students Michael Schartner and Adam Barrett. We measure its
complexity, and indeed, we find that we can
distinguish different levels of consciousness just by
the spontaneous activity of the brain. In a way this isn’t
that surprising, because we know
various things change. The balance of
different frequencies of your brain activity changes
when you lose consciousness. But this doesn’t
have to do with that. This is independent of that. There’s something specific
that is being detected by these changes in complexity. More recently we’ve applied
the same measures to sleep, in this case taking
advantage with colleagues in Milan of recordings
taken from directly within the human
cerebral cortex. These are implanted electrodes. And we see much the same story. If you compare where
the two areas are, you compare the complexity
of wakeful rest, and early non-rem sleep, where
you are not dreaming very much. You see that complexity
fools a great deal. What’s interesting here is, if
you compare wakeful rest to REM sleep, where people will often
report dreams if you wake them up, the level of
complexity is very much as it is during
the wakeful state. There’s something
else going on here, which is that the complexity in
the frontal part of the brain seems to be higher than in
other parts of the brain. And that’s something we still
don’t understand fully, yet. I just wanted to
give you something hot off the press, so to speak,
which is where you’ve also been applying these
measures now to data taken from people under the
influence of psychedelic drugs; psilocybin, ketamine, and LSD. And what we find, at least in
our hands to start with here, is that the level of
complexity actually increases as compared to the
baseline state, which is not something we’ve seen before
in any other application of these measures. So what’s important about
this way of looking at things is that, it’s grounded
in a theory that tries to explain why certain
sorts of brain dynamics go along with being conscious. And put very simply,
the idea is this– and it goes back to Guilio
Tononi and Gerald Edelman, people that I went to work with
in America about 18 years ago– the idea is very simple. Consciousness is
extremely informative. Every conscious experience
you have, or have had, or will have, is different
from every other conscious experience you have had,
are having, or will have. Even the experience
of pure darkness rules out a vast repertoire
of alternative possible experiences that you could have,
or might have in the future. There’s a huge amount of
information for the organism in any conscious experience. At the same time every
experience that you have is highly integrated. Every conscious scene is
experienced, as all of a piece, is bound together. We don’t experience colours and
shapes separately in any way. It’s conscious experiences
at the level of phenomenology combine these properties. They are the one hand
highly informative, composed of many different parts. On the other, bound
together in a unified whole. And this motivates us to search
for mathematical measures which have the same property,
which are neither lacking in information. On the left, you
see a system which is all connected together,
so it can’t enter very many different states. On the right is a system which
is completely dissociated, so they can enter states,
but it’s not a single system. We want measures that track
this middle ground of systems, that combine both integration
and differentiation. And a number of these
measures now exist. There are some
equations here, which we can talk about
later if you like, that try to target
this middle ground. And time will tell whether,
by applying these more phenomenologically
grounded measures, we come up with even more
precise practical measures of consciousness. Now why is this business
of measurement important? And I want to make a
general point here, which is that, if you’re
trying to naturalise a phenomenon which
seems mysterious, the ability to measure it
is usually one of the most important steps you can take. And we’ve seen numerous
examples of this. The history of our understanding
of heat and temperature is one very good example
Here’s an early thermometer from the 18th century, which
used the expansion of air. But of course there
are many problems in generating a
reliable thermometer and a scale of temperature,
if you don’t already have fixed points. And if you don’t
know what heat is you get trapped in a kind
of vicious circle that took a long
time to break out of. But people did
break out of this, and the development
of the thermometers catalysed our
understanding of heat from being something that flowed
in and out of objects, to being something that was identical
to a physical property. The mean molecular kinetic
energy of molecules in a substance. And having that
concept of heat now allows us to talk
about temperature far beyond the realms
of human experience. We can talk about
the temperature on the surface of
the sun, in a sense, the way we can talk about the
temperature of interstellar space, close to absolute zero. None of these things
make any sense and in our phenomenological
experience of hot and cold. So this brings me to my
first take-home message. Measurement is important, and
consciousness, conscious level, depends on a complex balance of
differentiation and integration in brain dynamics,
reflecting the fact that conscious
experiences themselves are both highly informative
and always integrated. Now when we are conscious, we
are conscious of something. So what are the brain
mechanisms that determine the content of consciousness? And the hero for this
part of the story is the German physicist and
physiologist Hermann Von Helmholtz. And he proposed the
idea that the brain is a kind of prediction machine. That what we see,
hear, and feel are nothing other than the brain’s
best guess about the causes of sensory inputs. And the basic idea is,
again, quite simple. The brain is locked inside
its bony skull home, and has very indirect access
to the external world. All it receives are ambiguous
and noisy sensory signals, which are highly
and directly related to this external world
of objects, and so on, if there is an external world
of objects out there at all. They know about that. Perception in this
view is, by necessity, a process of inference in
which the brain interprets these ambiguous and noisy
sensory signals with respect to some prior
expectations or beliefs about the way the world is. And this forms the
brain’s best guess of the causes of the
sensory signals that are impacting our sensory
surfaces all the time. What we see is the brain’s
best guess of what’s out there. I want to give you
a couple of examples that illustrate this process. It’s quite easy to do, in a way. This first example is a
well-known visual illusion called Edelstein’s Checkerboard. Now here, you’ll
see two patches. You’ll see patches A and B. And
I hope to you they look to be different shades of grey. Do they? They look to be
different shades of grey. Of course they are exactly
the same shade of grey. I can illustrate that by
putting an alternative image, and joining up
those two patches. You’ll see that’s it’s
the same shade of grey. You may not believe
me, so what I’ll do is, I’ll shift it along, and
you’ll see even more clearly. There are no sharp edges. It’s the same shade of grey. What’s going on
here, of course, is that the brain is unconsciously
applying its prior knowledge that a cast shadow dims
the appearance of surfaces that it casts onto. So we therefore see
the patch B as being lighter than it
really is, in order to account for that effect. And this is of course
an illustration of the success of the visual
system, not its failure. The visual system is a very
bad physical light metre, but that’s not what
it’s supposed to do. It’s supposed to, or one
thing it’s supposed to do, is to interpret the
causes of sensory signals in terms of meaningful
objects in the world. It’s also an example
of what we sometimes call cognitive impenetrability. Even if you know the patches
are the same shade of grey, when I take that bar away,
they again look different. Can’t do much about that. The second example
just shows you how quickly the brain can
take in new prior information to change the nature of
conscious perception. This is a so-called
Mooney image. And if you haven’t seen
it before, hopefully what you will see here
is just a passing of black and white splotches. Does everybody kind of get that? Black and white splotches? Some of you might
have seen this before. And now what I’m going
to do is fill it in, and you see something
very different. What you’ll see is a very
meaningful scene here involving at least two objects, a
woman, a hat and a horse. Now if you stare at
this for a while, I won’t leave it
up for too long– but if you just look
at it for a little bit, and then I take that
image away again, you should still be able to see
the objects within that image. Now for me this is
quite remarkable, because the sensory information
hasn’t changed at all. All that’s changed are your
brain’s prior expectations about what that
sensory data signifies. And this changes what
you consciously see. Now this also works in
the auditory domain. Here are two spectrograms. This is something
called sine wave speech, and what you see here are two
time frequency representations of speech sounds. The one on the top has all the
sharp acoustical features that provide normal speech removed. A little bit like
thresholding an image. And the bottom is
something else. So I’m going to
play the top first, and let’s see what
it sounds like. [STRANGE BEEPS AND NOISES] And now I’ll play
you something else. (BOTTOM SOUND – A MAN’S
VOICE): Jazz and swing fans like fast music. – So I hope you all understood
that piece of sage advice. And now if I play the
original sound again– [BEEPS AND WHISTLES THAT SOUND
LIKE THE SENTENCE] – Yeah? This is exactly the same. Again, all this
change is what we expect that sound to signify. [SAME SOUND PLAYED AGAIN] – One more time, just for luck. It’s not just a bunch of
noisy whistles, it’s speech. Now this typical
framework for thinking about these kinds of effects
is Bayesian Inference. And this is a form of
probabilistic reasoning, which is applicable in all
sorts of domains, not just in neuroscience,
in medical diagnosis, and all sorts of things,
like finding lost submarines. But in neuroscience, we talk
about the Bayesian brain. And it’s a way of
formalising Helmholtz’s idea that perception is a
form of best guessing. And the idea is that sensory
signals and prior beliefs can be represented as
probability distribution. So for instance,
this yellow curve is the probability of
something being the case, maybe that you’ve got a brief
glimpse of an object moving to the right. The sensory data may
say something different. It may have a
probability that peaks at a different
angle of movement. Maybe it’s drifting in
a different direction. And the optimal
combination of the prior, and the likelihood, the yellow
curve and the red curve, is this green curve, which
we will call the posterior distribution. And that represents the
best optimal combination of these two sorts of evidence. And the idea is, well
that’s what we perceive. Thinking about
perception in this way does something rather
strange to the way, classically in
neuroscience, people have thought about perception. The classical view
is that the brain processes sensory
information in a bottom-up, or feed-forward direction. This is a picture of the
visual system of the monkey, and the idea is that information
comes in through the retina, then goes through the thalamus. It then goes to the
back of the brain. And as the sensory signals
percolate deeper and deeper and deeper into the
brain, they encode or represent progressively
more sophisticated features of objects. So you start out at early
levels the visual cortex with response to
luminance, and edges, and then higher up to objects,
including other monkeys. What’s important here is
the perceptual heavy lifting is done by information
flowing in this bottom-up or feed-forward direction. Now the Bayesian brain idea
says something very different. It says that what’s really
important are the top-down or inside-out connections
that flow from the centre of the brain back out. And we’ve known for
a long time there’s a large number, a very large
number of these connections, and some descriptions more
than flow the other way around. But the function has
been rather mysterious. Thinking about
the Bayesian brain gives us a nice way
to interpret this. Which is that it’s exactly
these top-down or inside-out connections that
convey predictions from high levels of the brain to
lower levels, to lower levels, back out to the
sensory surfaces. So these blue arrows convey
the brain’s predictions about the causes
of sensory signals. And then what flows in the
feed-forward or bottom-up direction, from the outside-in,
that’s just the prediction area, the difference between
what the brain expects and what it gets at each
level of description. So this is often called
predictive coding, or predictive processing,
in some formal frameworks. And the idea is that
minimization of prediction error occurs across all
levels of this hierarchy at the same time,
and what we then perceive is the consequence
of this joint minimization of prediction error. So you can think of
perception as a sort of controlled
hallucination, in which our perceptual predictions are
being reined in at all points by sensory information from
the world and the body. Now there’s quite a
lot of experiments that show that
something like this is probably going
on in the brain. These are a couple of examples. And since they’re– I was looking for
the best example so they don’t come
from my lab at all. [LAUGHTER] This is from Lars
Muckli in Glasgow. He’s shown using advanced
brain reading techniques, which I won’t describe, that you
can decode the context of what a person is seeing from parts
of the visual cortex that isn’t even receiving any input. And what’s more, you
can decode better when you decode from the top
part of the cortex, which is supposed to receive
predictions from higher levels. So that suggests there are
predictions being fed back. And another study by Andre
Bastos and Pascal Fries in Germany, they used a method
called Granger causality, which is sensitive to information
flow in systems. And they find that top-down
signals and bottom-up signals are conveyed in
different frequency bands in the cortex,
which is what you’d predict from predictive coding. One last experiment which I
find particularly interesting is an experiment from a Japanese
group of Masanori Murayama. And they used to
optigenetics, which is a way of using lights
to selectively turn on or off neural circuits. And in this
experiment they showed that by just deactivating
top superficial levels of somatosensory
cortex in a mouse brain, the part
of the mouse brain that’s sensitive to
touch, they could affect how well that
mouse was able to do tactile discriminations. Those top-down connections were
coming from a motor cortex. So there’s a lot of evidence
that top-down connections in the brain are
important for perception, is the basic message there. But what’s rather strange,
and what I’m going to tell you next is that all this
stuff is all very good, but predictive processing is
not a theory of consciousness. Nothing I’ve said has anything
to do with consciousness, at all. It has to do– it’s a
very general theory of how brains do what they do. How they do
perception, how they do cognition, how they do action. So somewhat
counter-intuitively, I think this is exactly why it’s
a great theory of consciousness. And the reason I think
this is because it allows us to ask all
sorts of questions about the real problem. About what it is,
what happens in brains that underlies what you happen
to be conscious of right now, without getting sucked into the
metaphysical pluckhole of why you are conscious
in the first place. In other words, it provides
a powerful approach to looking for neural
correlates of consciousness, those things in the brain that
go along with being conscious. Because we can
now take advantage of a very general theory
of how brains do what they do, rather
than just looking at this region or that region. So what does
predictive processing, or the Bayesian brain say about
consciousness, specifically? Well many years ago, some
influential experiments revealed a very
strong connection between top-down signalling
and conscious contents. In this example by Alvaro
Pascual-Leone and Vincent Walsh, what they
did was they had people look at visual motion,
examples of visual motion. And they used TMS, this
interventional technique where you can zap the
brain very briefly. I mentioned it before. But they used it
here, specifically to interrupt the
top-M down signalling that was evoked by this
perception of visual motion. And the result was that, if
you interrupted specifically the top-down feedback,
you would abolish the conscious perception
of visual motion, even if you left the
bottom-up signalling intact. So that was an early key. Now, more recently, in our
lab and in many other labs all over the place, we’ve been
asking some other questions about the relationship
between what you expect and what you
consciously experience. One of the most basic
questions you can ask is, do we consciously see
what we expect to see? Or do we see what violates our
expectations of what we expect? And a recent study from our
group, led by Yair Pinto, used a method called
continuous flash suppression to address this question. It’s illustrated here. You see different images
in the different eyes. In one eye you see this rapidly
changing Mondrian pattern of squares. And in the other eye, you
either see a face or a house. And they change
contrast like this. So initially, the person would
just see this random pattern, and then they’ll see
either a house or a face. And simply, you just
ask them to expect to see– you just tell
them a face is more likely or a house is more likely. And what we find over
a number of studies is that we see faces
more quickly when that’s what we’re expecting to see. It may seem obvious, but it
could be the other way around. At least in these studies,
we see what we expect to see, not what violates
our expectations. That’s the data. And the same goes for houses. These kinds of studies
support the idea that it’s the top-down
predictions that are really important
for determining what we’re conscious of. There’s another experiment
which I will just mention. We did pretty much
the same thing. This is called motion
induced blindness. If you are in a lab rather
than in a lecture theatre, and you stare at this
central point here, then this red dot might
disappear from time to time. And what we did was
after it disappeared, we changed its colour and we
led people to expect the colour change to be one
thing or another. And again, it reappeared more
quickly if it changed colour in the way you were expecting. Again, I am confirming that
once your expectations were validated, then that accelerated
your conscious awareness of something in the world. Now that’s just
behavioural evidence. That’s just asking people what
they see and when they see it. We’ve also been interested
in the brain mechanisms that underlie and shape how
our expectations change, what we consciously see. And we’ve been particularly
interested in something called the alpha rhythm. Now the alpha rhythm
is an oscillation of about 10 hertz or
10 cycles per second. That’s especially prominent
in the visual cortex, across the back of the brain. In one study, led by in
this case a PhD student, Maxine Sherman, with
Ryota Kanai, in Sussex. What we did here, we manipulated
people’s expectations of what they we’re
likely to see. And it’s a very boring
experiment, this was. The only thing they could see
was what we call Gabor patches. They’re just very dim
patches of lines that are blurry around the edges. But the visual system loves
these kinds of things. They activate early visual
cortex very, very well. And people were expecting
either that a patch was there, or that it wasn’t
there, in different conditions. And while doing this we
measured brain activity. And to cut a long story
short, what we found was that there were certain
phases, certain parts of the cycle, this
10 Hertz cycle, at which your expectation
had a greater effect on what you said that you saw. So there was part of this
cycle, as the alpha rhythm, there was part of it where
your expectations dominated your perception. And there was another
part of it which was the opposite, where
your sensory signals were more important in determining
what you saw at that point. So this suggests
that this oscillation in the back of the
brain is orchestrating this exchange of predictions
and prediction errors. And that’s the
sort of cycle that might be the neural mechanism
for conscious vision. And other theories about what
the alpha rhythm is doing, there are many. One is that it’s doing
nothing, it’s just the brain idling away, and I think this is
at least a more interesting way to think about it. Another experiment we’ve
done with another PhD student Asa-Chang, we showed
people these very fast changing luminance sequences. And it turns out
that your brains will learn to predict
the specific changes in these sequences that
change you very quickly. And the signature
of this learning, again, happens to be
in the alpha rhythm, and suggests that this
oscillation has something important to do with how
the brain learns and updates predictions about
sensory signals. But we do not go around the
world looking at Gabor patches or rapidly changing
things like this. We go around the world
looking at people and objects. And that’s what our visual
world is composed of. So can any of these
ideas say anything about our everyday
visual experience? And I think that’s a
very important challenge in neuroscience to cross. Get out of the lab and think
about real world experiences. So we’ve been using virtual
reality over the last few years to try to get at
some of these ideas. This is an Oculus Rift, which is
now available to buy, I think. And we’ve been using
these to address some of these real world
aspects of visual perception. And one of these
real world aspects is called perceptual presence. And this is the
observation that, in normal perception, objects
really seem to be there, as opposed to being
images of objects. And this is, of
course, what Magritte plays with in his
famous painting, The Treachery of Images. For instance, this is an object. I think it’s there,
and in some sense I can perceive the back
of it, even though I can’t see the back of it,
even though the back of it’s not giving me any sensory
data, I perceive it as an object with a back. How does one explain that? Well one idea you can come up
with within this Bayesian brain framework is that,
the brain is not only predicting the possible causes
of the sensory signals getting right here, right now. But it’s also predicting
how sensory signals would change were I to
make particular actions. Were I to pick this object
up and move it around, or just move my eyes from
one place to another. There’s a long paper. I wrote about that which I– please don’t read it. [LAUGHTER] – But that’s the basic idea. And how do you test
an idea like that? So we’ve been using some
innovative virtual reality methods, or augmented
reality methods, with my post-doc,
Keisuke Suzuki. And what we do is, we
have virtual objects, and these virtual objects,
they either behave as a normal object would. They’re all weird,
unfamiliar objects. But they can either behave as
a normal object would behave, so you can learn to
predict what would happen. This one is weird. It always shows
you the same face, a little bit like having
the moon on a plate in front of you. And then there are
other conditions where objects respond
to your movements, but they do so in
unreliable and strange ways. So the question is,
what does the brain learn about these objects,
and how do we experience them? Do we experience them as
objects in different ways when they behave differently? And we’re still doing
those experiments. Another way we can use
VR, is to investigate what happens in visual
hallucinations of the kind experienced in psychosis,
and in certain other more pharmacologically
induced conditions. What we’re doing here
is, we’re coupling immersive virtual
reality, imagine you’ve got a headset
strapped to your head again, with clever image
processing that models the effects of overactive
priors on visual perception to generate a highly
immersive experience. This is Sussex campus,
actually, but now it seems quite different than
it did at lunchtime today. I’ll tell you that. What we’ve done, we’ve
recorded this panoramic video which we can feedback
through VR headset. And we’ve processed
this video through one of these Google deep dream
algorithms you might have seen, that can generate
sort of bowls of pasta that looks like animals. And this might seem
like a lot of fun. It is fun, but there is
a serious purpose here, because it allows us to
model the effects, model very unusual forms of
perception and how they might play out in different
ways in the visual hierarchy. And understanding how visual
hallucinations might happen, and how the wider effects they
have on the mind, I think, is a very important part of
studying visual perception. So that brings us to the
second take-home message, which is that what
we consciously see is the brain’s best guess of
the causes of its sensory input. Normal perception is a fantasy
that is constrained by reality. Now before I move on
to the last section, I want to pay tribute to an
unlikely character in a talk about neuroscience,
which is Ernst Gombrich. Ernst Gombrich was one of
the foremost historians of art of the 20th century. And it turns out that Gombrich’s
approach to understanding art had a lot in common with
ideas and the Bayesian brain. And more specifically,
with the idea that perception
is largely an act of imagination, or construction,
on the part of the perceiver. And this is most apparent in
his concept of the beholder’s share, which emphasises
that the viewer brings an awful lot to the table in the
act of experiencing an artwork. So he had this to say in his
1960 book, Art and Illusion, “the artist gives the beholder
‘more to do’, he draws them into the magic circle of
creation and allows him to experience something of the
thrill of making which had once been the privilege
of the artist.” I think for me this
is very powerful when looking at, especially,
things like Impressionist art. And here, one way
to think about this is, that the artist
has reverse engineered the whole perceptual
process, so that what’s there are not the objects,
the end points of perception, but rather the raw materials;
the patterns of light that engage our perceptual
machinery in doing its work. And for me this might be
why paintings like this are particularly powerful. Now the final dimension
of consciousness I want to talk about
is conscious self. The fundamental experience
of being someone. Being someone like you. There are many aspects
to our experience of being a conscious self. There is the bodily
self, the experience of being and identifying
with a particular body. A bit of the world goes
around with you in the world all the time. There’s the perspectival
self, the experience of seeing the world, or
experiencing the world, from a particular first
person perspective, usually somewhere in the
body, but not always. There is the volitional
self, the experience of intending to do things,
and of making things happen in the world of agency. And these ideas are, of
course, often associated with concepts of will. Then there’s the narrative self. This is where–
only until now, we don’t have to worry
about the concept of I, but when we get to the narrative
self, there is now and I. There is a continuity of self
experience from hour to hour, from day to day,
from month to month, and from year to year, that
you associate a name with, and a particular set of
autobiographical memories. And finally, there’s
a social self. The way I experience
being me is partly dependent on the way I
perceive you as perceiving me. I’m just going to talk,
in the minutes remain, about the bodily self. This is something we’re working
on quite a lot in Sussex. The experience of
identifying with, and owning, a particular body. And the basic idea I want to
convey, is again, very simple. It’s just that we should think
of our experience of body ownership in the
same way that we think about our experience
of other things, as well. That is, it’s the brain’s
best guess of the causes of body-related signals. And the brain is always
making this inference. It’s making its inference
about what in the world is part of the body, and
what is not part of the body. But it has access, in
this case, to other sorts of sensory signals, not
just visual signals, or tactile signals, but
also proprioceptive signals. The orange arrows here. These inform the brain about
the body’s configuration and position in space. And then also, and
often overlooked, are interoceptive signals. These are signals that originate
from within the body, that tell the brain about
the physiological state or condition of the inside
of the internal physiological milieu. And you can think the idea
is that our experience of embodied self-hood
is the brain’s best guess of the causes of all
the signals put together. Yeah, that’s just to
emphasise interoception. An important part
of this idea is that interoception, the sense
of the body from within, should work along the same
principles, the same Bayesian principles that we’ve
been thinking about, vision and audition, previously. That is, our experience of
the inside of our bodies is the brain’s best guess of the
causes of the signals that come from the inside of our bodies. So we can think of, again,
top-down predictions carrying predictions about
what the bodily state is like, and bottom-M up
prediction errors that report the differences
between what’s going on and what the brain expects. So what is our experience
of the inside of our bodies? Well, way back at the
beginning of psychology, William James and
Carl Langer proposed that emotions,
emotional experience, was really about the brain’s
perception of changes in its physiological state,
rather than perception of the outside world. So, in this classic
example, seeing a bear does not in itself generate
the experience of fear. Rather seeing the
bear sets in train, a load of physiological changes
preparing for fight and flight responses. And it’s the perception
of those bodily changes in the context with the
bear being around that leads to our experience of fear. So the Bayesian perspective
just generalises that idea, and says that
emotional experience is the brain’s best
guess of the causes of interoceptive signals. And this fits very nicely
with a lot of evidence. And this is just one study
done by a Finnish group. And all they did here was,
they had people report where on their bodies they felt
various emotions to take place. And so you feel anxiety
in one part of your body. You feel fear in
another, and so on. So our experience
of emotion does seem to be
intrinsically embodied. Now another part of our
experience of being a body is the body as a physical
object in the world. And this might seem quite
easy to take for granted, since our physical body
is just always there. It goes around with us,
it changes over the years, in unfortunate ways. But it’s always there. But it would be a mistake to
take our experience of body ownership for granted. And there are some
classic experiments that demonstrate how malleable
our experience of body ownership is. This is the famous
rubber hand experiment. Probably some of
you have seen this. What happens here is that a
volunteer has their hand hidden under a table, and the fake
hand is put on top of the table, and then both hands
are simultaneously stroked with a paintbrush. And it turns out that just
seeing a hand-like object where a hand might be, feeling
touch, and then seeing the object being touched,
is enough evidence that the brain’s best guess
becomes that fake hand is, in fact, part of my body. Sort of part of my body. This is what it looks
like in practise. Here you can see the fake
hands, focusing on it. There’s the real
hands, not focusing on it, simultaneous
stroking– and there are various ways you can test it. [AUDIENCE LAUGHTER] – I found in doing this, it
works even better on children, by the way, if you do that. So that’s interesting,
because that’s using visual and tactile
signals to convince the brain that this object
is part of its body. In my lab, we’ve been
interested in whether these signals that come from inside
the body also play a role. So we set up a virtual reality
version of this rubber hand illusion, where people
wear these goggles, and they see a
virtual fake hand. And we also record
their heartbeats. And now what we can do is,
we can make the virtual hand flash either in time or out
of time with their heart beat. And we asked the
question, do people experience this
virtual hand as more belonging to them
when it’s flashing in time, rather than out of
time, with their heartbeat? And the answer is that it does. And this is just some
data, basically that, bigger than that, which means
that, indeed, they experience the hand as more their own. The way we measure
that actually, is that first we can ask them. That’s the easiest way. Then we can also
ask them to point to where they think
their hand really is, and we can see
how far they drift from where their hand really is
to where the virtual hand is. And that provides a
more objective way of measuring the
strength of the effect. Here’s what it looks
like in practise. Again if you can see this,
that’s the real hand. That’s somebody’s virtual hand. Again, imagine you’re
wearing a headset so you’ll see this
in 3-D. And you can just about see it pulsing
to read and back, I hope. And you can also do
some other things with these virtual
reality rubber hands that you couldn’t do
with real rubber hands. For instance, you can map
movements of the real hand to the virtual hand, so you
can start to ask questions about the extent to which
the virtual hand moves as I predict it to move. How much does that affect
the extent to which I feel it to be part of my body? You can make it change colour. So you can have somebody embody
a skin colour associated with a cultural out-group, and see
if they become less racist as a result. And then my favourite is where
you can change, actually, the size of the body. And that’s coming up here. So here what we do is, we
can have the hand telescope up and down in size. And again, this might seem
like fun, and it is fun, but there is a serious purpose. There are various conditions. There’s in fact,
a condition called Alice in Wonderland
Syndrome, where people report that all parts of their body
are, indeed, telescoping up and down in size. And in a more subtle way, there
are lots of body dysmorphias, of subtle misperceptions
of body shape, which might be associated
with eating disorders. And so these sorts of
techniques allow us to approach, in a very fine grained
way, how people might mis-perceive their own bodies. That brings me to the third
take-home message about self. And with apologies to
Descartes, the take home message is that, I predict
myself, therefore I am. In the last nine minutes,
before the bell rings, I want to go full circle and
return to this Cartesian idea of the beast machine. To try to convince you that
our experience of being a conscious self is intimately
tied up with our beast machine nature. And to do this, I need to
mention one final aspects of perceptual inference,
which has a lot to do with Karl Friston,
who’s done a lot of work in the Bayesian brain
UCL here in London. And if we think of the brain
as being in the business of minimising prediction
errors, this can be done either by updating our
perceptual predictions, which is what I’ve been
talking about so far. And this what Helmholtz said. Or we can minimise prediction
errors by making actions. We can change what
we predict, or we can make an action so that
our predictions come true. You can change
with sensory input, or you can change
what you believe about your sensory input. One point of doing this is,
that you can make actions, then, to find out more about
the world that surrounds you. And this is what
Helmholtz has in mind when he says that
each movement we make, by which we alter the
appearance of objects, should be thought of as
an experiment designed to test whether we’ve
understood correctly the invariant relations of
the phenomena before us. Which Gregory, much later,
said something similar when he talked about perception
as hypothesis testing. The point of this
is, that we make eye movements, and other
kinds of movements, to understand what
the world is like. That, in fact, there was is
tomato there, for instance. But there’s another way to
think about active inference, which is that, when we
minimise prediction error, what we’re actually doing is
controlling a sensory variable. We’re preventing
it from changing, because we’re making our
prediction about what it is come true. And this is the use
of active inference, to control or
regulate something, rather than to understand what
the causes of that something are. And this brings a very
different tradition to mind, which is 20th
century cybernetics. And this is Ross Ashby,
who was a pioneer of this way of thinking. And he, with Roger Conan
right at the end of his life, wrote a paper. The title of the paper,
was “Every good regulator of a system must be a
model of that system”. The idea here is, if you want
to regulate something very precisely, then you
need a good model of what effects that system. Now you could apply this idea
to the external world, as well. When you try to
catch a cricket ball, you are actually trying
to control the level of the angle above the horizon. But it applies more
naturally, I think, to the internal
state of our body. So really, what matters about
my internal physiological condition, I don’t
really need to know exactly what it’s like inside
my body, and care about it. But I need to control it, and
my brain needs to regulate it. So this way of thinking
about active inference applies more naturally
to interoception. Think about it this way that. Having good predictive
models are always useful, but we can have a pendulum
that swings, on the one hand, towards control. We can use these predictive
models for control, and that’s more applied to the
state of our internal body. Or we can swing the other way,
and think about perception, understanding. You could think of the
instrumental, epistemic ways of thinking about the role
of action and perception. And this brings to mind– I mentioned Karl Friston. He’s come up with this
thing called the free energy principle. And I can only nod
to the vast body of work he’s done here on this. With the slogan, which is that
organisms, over the long run, maintain themselves in states
in which they expect to be in, in virtue of having
good predictive models about their own
internal condition. So this takes us right
back to Descartes, but in a very different way. As I said right at the beginning
of this lecture, for Descartes our physiological
reality was rather irrelevant to our minds, our
rationality, our consciousness. This is a quote from a 1968
paper on his beast machine argument, “without minds to
direct their bodily movements, animals must be regarded as
unthinking, unfeeling machines that move like clockwork.” Now I think if you
try to think how this idea of our
predictive models controlling our internal
physiological states, and the resulting experiences
that perceptual content that might give rise to, you
can make the opposite case. And the opposite case would
be that conscious self-hood emerges because of, and
not in spite of, the fact that we are beast machines. And I think this is a deeply
embodied view of consciousness and self, and it speaks to this
fundamental link in continuity between what it is to be alive,
what it is to have a mind, and what it is to
be a conscious self. So I repeat, the third
take-home message should make even more sense now. That I predict myself,
therefore I am. And I am a conscious
self because I’m a bag of self-fulfilling
predictions about my own physiological
persistence over time. Now why does any of this matter? It’s a lot of interesting
ideas, but why should we be interested in
studying consciousness? Well it’s a very
interesting thing, I hope I’ve convinced you. But there are lots
of practical reasons to be interested as well. There are between 20 and
60,000 patients in the UK alone, who are in
disorders of consciousness. You are in the vegetative
state, or in coma, or in some other
severely abnormal state of consciousness. Having better measures
of conscious level, as I described at
the beginning, is going to really
change again, and how we treat people like this. And of course, in psychiatry. Psychiatric disorders are
increasing that prevalence across all modern
societies, and it’s estimated one in six
of us, at any one time, are suffering from a
psychiatric condition. And understanding the mechanisms
that underlie conscious content and conscious
self, because a lot of psychiatric disorders
include disturbances of the way we
experience our body, even though that might not
be the most obvious symptom, can help us understand
the mechanisms involved in
psychiatric disorders, not just the symptoms. There are also some
more general reasons for studying consciousness,
which bring up some ethical questions. When does consciousness
emerge in development on newborn babies conscious? Or does consciousness
start even in the womb? Maybe different dimensions
of consciousness emerge at different times. Are other animals conscious? Well I think it can make a
very good case for mammals and primates, but what
about the octopus? The octopus has more
neurons in its arms than in its central brain. They’re very smart creatures. Here, you have to ask the
question not only, what is it like to be an
octopus, but what is it like to be an octopus arm? And finally, with the rise
of artificial intelligence, we should begin to ask
questions about what would it take for a machine to have some
kind of subjective experience. I don’t think we’re
anywhere near that yet, but we should consider
what science can tell us about its possibility, because
that would raise some very, very tricky ethical questions. But, fundamentally,
consciousness remains fascinating for
me for the same reason that it’s motivated people
throughout the ages. I mean, Hippocrates, the
founder of modern medicine, put it one way. He said, from the brain and
from the brain alone arise our sorrows, our joys. And he also had his
first view of psychiatry that madness comes
from its moistness. And then Francis Crick,
in the 1990s, who I mentioned in the beginning. He gave birth, if you like,
to the modern neuroscience of consciousness. He said much the same thing
in his astonishing hypothesis. But there is this
mystery and wonder still, about how the biological
machinery inside our heads gives rise to the rich
inner universe that makes life worth living. And despite this mystery, modern
science is making progress. I hope I’ve given you a flavour,
even though we don’t understand how consciousness happens, we
can begin to understand its mechanisms. So we should not be afraid of
naturalising consciousness. It’s not a bad thing
to understand its basis in the material world. As so often in science,
with greater understanding comes a larger sense of wonder,
and a greater realisation that we are part of, and not
apart from, the rest of nature. [AUDIENCE APPLAUSE]

100 thoughts on “The Neuroscience of Consciousness – with Anil Seth

  1. Thanks to a very kind Spanish speaker, we now have Spanish language subtitles for this incredible video. Thank you so much. Gracias!

  2. Descartes didn't create the body/mind dichotomy. He tried to look at it in a philosophical, not theological way.

  3. ALWAYS sooo sad! Very clever people just start in the middle of their belief system and westeners mostly ignore a vast ralm of centuries old experiences from the East. Assumably the scientific approach can only be from a materialistic brain??? Sad that it misses a lot and unfortunate that it easily might mislead the majority with certenty into a much too regit but also uncertain thinking model :-(.

  4. "hallucinations mimic perception" as Oliver Sacks said in a Ted talk .. in my view Anil Seth sets off in a sincere manner but is caught up in a scientific paradigm that is de-humanizing, Making something full of wonder like our existence into measureable stuff, instead of having the courage to stand baffled and admitting that he do not know (I am not blaming him and he does well under the circumstances .. in fact very well ) . We need to link concepts such as biomimicry, mirror-neurons , hallucinations vs perception, psychedelic trips vs "true reality" , We are getting there! Truly exciting times

  5. This guy is really smart but he's got it backwards. The predictability aspect is the subconscious. It exists because we need it to survive when born, it's based off of a combination our parents subconscious minds. The awareness and the consciousness aspect, it comes from an entanglement and superposition of our cells. The subconscious is all about measurement, prediction and knowing things for purposes of survival. We live in a dialectal universe, everything, literally everything is a dialectal. The whole thing with quantum physics is it's based on uncertainty. Physics in general is. The more we try to understand and know, the less we will understand and know, as new thing will always be found. The answer to the theory of everything is to do the opposite of what we are doing. To be learn to be okay with uncertainty, and with not knowing. In a sense this like having unconditional love, for everything and everyone. That shuts off the measurement aspect of the brain, that allows for better access to the conciousness mind. Which is entangled to our minds, and our cells. I believe it's stored in black holes, maybe one black hole for the collective conscious of each species. These blackholes are all entangled to each other all the way back to the big bang black hole. It's even fucking cool how our brains are designed, we have astrocytes that work together to heal, power and build neurons. Astrocytes is a greek term meaning "star" "cavaties". It's cool because blackholes, where our conscious mind exists, is powered by stars. The conscious mind actually has the power to heal the subconscious mind. We can actually live a lot longer than we are, if we can understand this. Which is the key to knowing everything. Basically for that to happen we have to all be okay with not knowing. That's the secret. Hope that helps somebody, we are all one, so anything I share, it comes from us all, not just from me. Much love.

  6. I am surprised there are people who will double down on close-mindedness and state, as if it were a fact, that ghosts do not exist. But then give zero reasoning for their statement.

  7. You should study the fringe science regarding consciousness to understand the hard problem, there are answers out there which appear to give the information you are seeking, research Stewart Hameroff's ground breaking work regarding cellular micro tubules. In essence, I believe the consciousness operates both upon and through the brain, it having many functions, but not solely created there, instead the brain is a partner in the process, not source.

  8. I am an expert in visual Hallucinations. I love the brains ability to create pictures. And I am a musician, so I perceive that I can read another musicians mind during a performance. In fact, I can read every mind on stage. And it acts like a living entity. It breaths, and has a heart beat, it perceives on a higher level than the individual members of the group. And the audience is a part of the bigger organism. The lights and the sound, and the artistic expression of the musicians, spontaneously create a sea of emotions that flood the room with a grand ellusion, that this song is about you. And every one in the audience, has the perception, that the song is about them, but each individual, has its own memories that flood the brain, each person has their own moment in time that the music takes them to. Every person is flooded with the emotions of their past, present, and future of possibilities, and we all hear and feel the emotions and perceive different imiges in our minds. And the song is about us. We have made the song about us, in a way that the artists have made the song about them, and about others. It is the magic of conciousness, illusion, of what is real, and what is possible, and what we wish could be. I believe that in some ways, our minds connect, and information is shared, and in some cases, what is ours, belongs to us and to us alone. There is a way to control mind over matter. But there is a limit. Science that looks only at our human brain for its conciousness, misses the bigger picture, of billions of tiny organisms that communicate with our brains, and exist within our bodies. Is our conciousness the collective of all the living organisms, in ,on and around us, that are sending signals back and forth between our neurons, and the living cells. If bacteria in our guts, send a signal to our brains, that we have had enough acidity, and we don't need any more vitamin c , then is it conciouslly telling us that we have created an optimal environment for the existence of this bacteria? And our brains are being manipulated to create these conditions, because both the bacteria, and the human, have evolved to depend on each other to exist?
    Then it is possible, that it is the communication between all of the cells and the brain, that is our conciousness. The electricity itself, that is tied to the universe, that is our conciousness. And like particles of light that travel through billions of years of space time, so does the electricity of our conciousness flow out into what surrounds us.

  9. @39.41: does that chap have a bird on his shoulder?
    It looks like some sort of big paroquet/parakeet (whichever you prefer)?

  10. SACKLERS. I suppose some people do benefit from their oxys, legitimately so that is. Their marketing is what pushed docs to prescribe in excess.. what should have been a routine root canal for me in 2006 turned out to be weeks of doc scrips for their pills then out of nowhere it stopped, cold turkey from oxy is hell, Sacklers knew it, I didn't. It was my choice to have the root canal (well sort of), but not the weeks of withdrawls and months of p.a.w.s., and years of opiate cravings.. Would have rather had the tooth pulled the medieval way if I had known, or just advil. This is a very interesting discussion, but it would be much better if not brought to you by the SACKLER family, blood on their "philanthropy". This is brought to you by all who died from opiate addiction which began with Perdue.

  11. You are giving a talk on the human brain.
    Explaining what you have been taught and mainly read
    And experienced I guess.
    Contact me please .
    I have my own insight into the human brain and psyche.
    Can u control ur dreams or stear them ? So to speak .

  12. Tms
    Banging on the brain.
    Disect a dolphin
    We are not ,as a species not even scratching or shocking the service.
    In a vegetive state you still have activity.
    Regardless how small
    Language was developed the mask vibration.
    Without this we could be so much more now as a species
    Would be so much more if used by knowing that the person
    Is being used as .
    What is phenoloology?

  13. We could also propose that consciousness does not originate in the brain however it creates the brain in order to settle in reality which sounds logical if you think about it… ironically….

  14. "If there is an external set of objects at all. I'm not sure about that." That sums up everything. He still hasn't a clue what consciousness is. Is it part of the brain or not? Nobody has a clue.

  15. This kind of points to consciousness being a always in relation to a form of belief (or simplification of prelearned information) in the model of the self. What I liked is that this might vary throughout the day, I wonder if anyone has ever tested that. Also I would like to postulate that a sufficiently large amount of neurons will actually produce this effect. So a sufficiently complex neural net will produce consciousness and will be utterly useless, because it will be slower at ´believing´ than a brain.

  16. In the self (40:00>) I missed the self that is observing the self. Observing the inner processes. Who is watching the movie of your memories? Who is talking to yourself adressing? Who can judge if a perception is a hallucination? The meta-thoughts like thoughts about thoughts? That kind of thing.

  17. Plants have a form of conciousness too… Water has memory. Dmt is a good way to experience losing your sense of self. Its quite amazing.

  18. Studies in consciousness, at The Sackler Centre, funded by the Sackler family.
    A family of Jews, currently under investigation for promoting the opioid crisis in the US, making people unconscious.

  19. 17:00 is an very important minute of information. Excellent talk about the function of mind. But we all (as consciousness experts 😉 feel that that is not the base don't we? Being conscious like awake and aware of our a-a-roundings is not the consciousness we want address, right? I have without any scientific claim the impression that science is putting a TV in peaces and analyzes them in detail to understand the broadcast … like I as a child destroyed once a radio to find the speakers inside 😉 But that being said, understanding the TV set well is surely not a bad start! And it can help heal and prevent many health problems.

  20. Consciousness is just a word.a human construct.we are the universe.there is no "I".we are simply the lastest effect of the universe.we didn't come from outside the universe nor are we apart from the environment

  21. Perhaps a simpler explanation of the brain: A tool of our higher source of knowledge—intuition. The brain filters down our intuition for more practical tasks.

  22. Our consciousness created the brain to experience this dimension/time/physical reality, not the other way around.

  23. I am not really satisfied with the argument presented here. It is similar to the "consciousness is an illusion" theory. To start with, I find this line of reasoning unconvincing because consciousness, referring to the 'experiencer,' is not expressly required for the mind and body to function. Because the experiencer merely experiences, it does not affect outcomes in reality. And if there is some sort of influence the experiencer has, then there must be some theory, at he very least, to posit how. This is important because, if we are discussing consciousness in the context of the physical, then we must discuss it in the context of evolution, as the apparent success of such a trait in our species makes the question of "why," pressing. As an aside, I wish there were some discussion of variation of consciousness between human beings (and not just impairments from brain damage). There must be some sort of measurable variation, if consciousness is a trait that is subject to natural selection.
    Secondly, if consciousness (again, used to refer to the 'experiencer'), is the result of the predictive function of the brain's perceptual system, then how does that happen? These talks pretty much all stop right before this point, and then try to bridge that gap (more like an ocean-wide chasm) with philosophical jargon. If I think (or predict, in this case) therefore I am, then through what process does the thought become me, the receiver of experiences? How is continuity of 'me' established through the major changes in my life, from infant to death? Certainly my brain structure, my thoughts, body, and even the physical matter of which my brain is composed, are different from when I was a child. How is the "me" from my childhood still here when everything else is different.
    Lastly, if the 'me' I speak of is simply an illusion, then what is it that is experiencing the illusion of 'me?' Is the illusion simply witnessing itself? The speaker tries to stick to hard facts, yet cannot escape the underlying philosophical questions. I am not pushing for a metaphysical explanation – I just want something more than what we tend receive from these talks. Even a thorough acknowledgement of the unknowns would be nice.

  24. It's not about biological, it's about reaching understanding that all made from same cause. BE like The one.

  25. The greatest missing piece of the puzzle is the denial of importance and the very fundamental role of our emotions, which we generally misunderstand as "just feelings". This talk briefly touches on them but falls for the same distorted false assumption and even calls emotions a product of the brain. While we do empirically know that brains and the mind developed very late in evolution of all living beings. The very primary interface and a earliest tool to understand reality with all living beings have were our physical sensations, which evolved into feelings, which evolved into what we call emotions. They are not just stuff that we feel – but instead we actually feel the reality and understand and comprehend it through this – with this primordial earliest fundamental capability of all living beings.
    It was this very primary capability that fueled and pushed and influenced the specific evolution of minds and the brains themselves as we know them today, because all these things work in feedback loops. They affect each-other. Evolution affects our biology and our minds and emotions, but they in turn also affect the very evolution – because they change the environment in specific ways, which then affects us back, both in the natural selection range and in epigenetic changes every individual creates and experiences in his own lifetime. We literally have two distinct hemispheres of the brain – precisely because of this fundamental, earliest interface with reality, this ability to FEEL the world and other living beings. (Iain McGilchrist gives a great overview and explanations of this biological fact)
    Yet when we discuss this phenomena, we only think about the mind and reductionist approach.
    It is this very false dichotomy that prevents us to understand these fundamental abilities fully, because we limit ourselves to one single approach, one single tool. Instead of using both the reductionism of our "rational minds" and the ability to FEEL the whole as a whole, with our emotions. Yet we still use both in every part of our lives, including science – only we dont admit it – because it makes us feel bad. In a nutshell.

    Explained in more detail but as short and to the point as possible at:

  26. 32:26 MAJOR problem with this study. The EYE connects to the OPPOSITE side of the corresponding cranial LOBE. Each SIDE of the brain has been shown to have it's OWN properties. One side is more CREATIVE and the other more RATIONAL. YOU DIDN'T INCLUDE IF THE STUDY HAD PARTICIPANTS LOOK AT THE PATTERNS IN BOTH OF THEIR EYES, OR IF THE PARTICIPANTS HAD LAZY EYE, OR A DOMINANT EYE, AND WHICH SIDE THE BRAIN WOULD HAVE BEEN.


    Not YOUR fault, but it is YOUR FAULT to not think about this. AND THERE'S NOTHING WRONG W/ THAT.


    PLEASE address this problem; it is FASCINATING (the idea of perception of things being changed from creative to rational based on the eye that is perceiving)


  27. Tldr: we don't understand consciousness yet, but we've contrived some interesting ways of trying to measure it. Also, do LSD, it lights your brain up.

  28. Thank you Anil Seth and The Royal Institution. I find you very effective "Information Sharers". AND, because of your Brilliance and Generosity, I have become more "informed" about this fascinating and seldom discussed/understood subject. I prefer to "learn better" than to "know better".
    Thank You for Advancing My Learning!,
    Ted Furlo

  29. You are either lying or refuse to believe facts such as the fact that our chances of evolving in 16 billion years are greater than all the electrons in the universe so because you push this darwinism fantasy you have one less viewer.

  30. Not quite through looking at this one yet, but while the speaker is clearly well-informed he doesn't bridge the gap very well from academic knowledge to the more general audience. He uses quite a few unexplained bits of jargon and doesn't seem to see some fairly obvious analogies that would help a non-academic person understand him.

    For example, the section on Bayesian predictive perceptive thinking (my rough attempt to express it the way he did) seems pretty easily expressed by analogy to our common experience of empiricism: We take in some information, we make guesses at what it means, we either act on the guess or take in more information in a passive way, and our guess is either confirmed or refuted – its the "little scientist" we all carry with us.

    Another spot is where he shows the checkerboard illusion, where one square is in shadow, and so looks lighter than the one not in shadow (but the colors are identical). Why not simply say that we have evolved to model the world in our thoughts as it most probably is rather than as it actually is (which he demonstrated) because when catching food (or avoiding becoming lunch) we don't normally have the luxury of fiddling with such details – we have survived by being good guessers and improving our guesses.

    I don't think he was being superior; he seems too mature for that and was quite humble for a person so obviously in command of his subject. Perhaps he's not used to speaking to the general public. All the more reason for respecting him for making the effort on such an interesting topic.

  31. Where is consciousness?

  32. God,, a higher power, whatever you want to call it imo is an all encompassing consciousness. Always been, always will. The moment of light, or the start of the universe, was just God observing. And so on and so on. Which eventually made its way to our planet on a smaller, yet important, level. Once our bodies, which are receivers, connected to each one's individual consciousness, we observed. And created outward. And the more our brains evolved, the better the stronger the signal (consciousness). How far outward does the consciousness effect change? Idk. But everything we "see" is a product of observation.

    Animals before us might have even had a lower level type of consciousness. And because of that, many things were more elementary, and they only created necessities for the species. And in a more local manner. Not above and beyond. Maybe the more advanced the brain, the better the receiver, and the higher connection and deeper level of consciousness. Maybe all living beings have it? Maybe. With the connection to their consciousness relying on the size of their brain. Like a cheap radio compared to the best radio you've seen with an massive antenna and everything inbetween.

  33. We've learned that we have neurons in the gut. Well, some people more than others. Some people keep all of them there.

  34. Excellent talk, but……………
    As far as science can go with consciousness, Scientists will never be able to "see what is seeing, hear what is hearing, taste what is tasting, smelling what is smelling, or touch what is touching."

    Science about consciousness is like studying the sky by examining its reflection in a bucket of water.

    The brain, and consciousness arise together. They are correlative. The brain doesn't cause consciousness any more than consciousness causes the brain.

    He said it himself, as Crick did: "Neuro-CORRELATES"

  35. He can speak of levels, types, qualities, durations, correlations with the brain, etc. But he cannot tell you what consciousness IS.

    IE: Defining a "conscious level" is not defining consciousness itself. This is mostly why the study of consciousness has been put off for so long.

    The same with time:

    “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.”
    – Saint Augustine

  36. The perception of light is only a neural simulation. Light and colors do not actually exist outside our brain. Vision, is in fact, just a figment of our imagination. In other words, light is a hallucination.

    Many people believe that light travels along the optic nerves into the brain, and that we see light inside our brain like a projection, but that is not what is happening. What we call light is actually invisible electromagnetic energy. Invisible electromagnetic energy hits photochemical cells in the back of our eyes (retina,) which then stimulates invisible electrochemical impulses to the brain. Billions of neurons then generate the illusion of vision.

    Light works just like heat does. Put a flame under your finger and it burns, but the flame and heat does not travel up your arm into your brain, only electrochemical impulses travel through nerve pathways to your brain. Neurons in your brain create the sensation of pain, not the flame itself. Electrochemical impulses do not transport light or heat either. The stimulus of light and heat just stimulate sensory cells; from that point on, it is electrochemical impulses that travel along a nerve pathway to the brain, not heat or light.

    Vision projects the sense that we are seeing outside ourselves, when in fact, we are only seeing within our imagination. A pointblank example is a dream; the dream seems as if we see outside ourselves, when obviously, it is our imagination that is creating the illusion of seeing. We take vision for granted as a real thing because we can obviously see objects around us. What we do not realize is that those objects do not emit light or colors; they only emit invisible electromagnetic energy, no different from a radio wave. Our brain invents the sensations of light and colors to differentiate between trillions of minute differences in electromagnetic radiation.

  37. The really hard problem of consciousness is: Near death experiences and astral projection. Which completely disprove the absurd theory that the brain somehow and for some reason creates consciousness.

  38. The deal is that if consciousness is a physical aspect, then we should be able to explain it in physics and maths, but as far as im concerned theres only one theory that involves that: Integrated Information Theory by Koch (same guy he mentioned at the beginning of the speech) and Tononi. This theory is starting to gain support from Chalmers himself and mathematicians like Tegmark. Basically, there is a possibility for panpsychism to actually be a thing. Of course its not perfect but it is a work in progress that could eventually be true.

  39. Thank you for your work on higher levels of consciousness and it´s mathematical measurement, the "Neural Signal Diversity"!

  40. "Humans had more moral virtue than animals."
    (look at random history book)

  41. The truth is…. the World..??, neither round nor FlaT…. but exists only as a conduit for human activity, it is both and neither at the same time

  42. The more I learn about consciousness the more capable I feel of influencing it for the betterment of my life. Thank you for the talk.

  43. Anil shows excellent progress we made in understanding ourselves and the universe we are part of.
    Some time ago I wrote this article on my blog being intrigued about the notion of "nothing" and tried a hypothesis that "nothing is everything". I think that idea can be extended to understand what consciousness is. I'd try to advance another hypothesis that the conscious "self" it is just a space-time focused (or concentrated) wave of the universe's self consciousness. Or in a word we are all (including non human living things) small parts of a universal consciousness.

    My article on "Nothing is everything":

  44. Detailed comment on the validity of this conference here:

  45. Everyone assumes the brain "houses" our consciousness. When you point to yourself do you point to your brain? No, you point to your heart. Not that the heart is the center of consciousness, obviously I don't know. And what about animals that don't have brains? If you are sane, you have to agree that they are conscious too.

  46. Why don't you just look in to Vedas and Upanishads which has a detailed explanations on what is consciousness and how it works. Why struggle so much? Your explanations and questions are too naive. The whole universe is alive with different units of consciousness. Understand sleep and you understand death. Where does consciousness go when you sleep? How do you come back from deep sleep? What happens when someone dies? Where does the consciousness goes? There are people who die for not health problem.

  47. This guy has no idea how consciousness works – we still don;t even know where consciousness resides (ie in the brain, or is the brain just a receiver of sorts)

  48. We still don't know if consciousness creates reality or if consciousness was merely created by chance as part of evolution – I'd be putting my money on the former

  49. Imagine taking apart a TV trying to find where the program you enjoy watching comes from – that's what neuroscientists have been doing for decades

  50. One addition to the concept of self: researchers have recently discoverd one (1) cell in cenorabdis elegans that signals SELF. It’s important to the tiny flatworm to know when its head touches its tail.

  51. Bit frustrating as a lot of content glossed over leaving a lack of continuity due to a lack of explanation, hey it's a talk not a text book!

  52. Excellent Film. Thanks To Seth & The Royal Institution.
    I have had 'Grand Mal Epilepsy' for 26 years. – Not far short of half of my life. With me, I seem to suffer a complete 'Ego Death', in that after I sense the smell of Tom Cat Urine, I quickly black out. My vision is the first thing to return, yet for a couple of minutes, I have no idea of what I am/who I am or absolutely no idea of what I can see around me. – I am less conscious than a newborn baby, because I have no notion and no instinct to feed. – 'Familiarity' seeps back slowly, and family/friends start to become things I feel safe (with) – even though I don't know who or what they are… Interestingly, if I can see outside into the sun, through a large window, this helps me back to consciousness at a speedier rate.. – I am not yet frightened, but that comes later on, and I believe it has to do with my sense of dignity, rather than any 'perceived threat'…. After I get 'me' back, I retain a dreamlike state where 'things just do not seem like they should be! – Then I get frightened. I believe that each time I Fit, I get 'ego/personality death, and on many occasions it has been 'Cathartic', leading to joy. – In many ways, I identify with folks who have suffered 'near death experiences', except for me not experiencing 'Angels', or White light. I hope that this will help some folks. Best Regards To All. Eddie Hoare.

  53. The mind is separate from the brain , but depending on the development of the brain the amount of mind/ consciousness thats allowed inhabit that brain will result in particular personality traits & habits that are limited commensurate with its development. but should that brain be damaged or injured in any way effects in personality & traits will manifest themselves because the brain can no longer interpret properly the commands of the mind/ consciousness & it will appear to be no longer in control of the entity, due to the damaged brains misinterpretation of the subjects mind/ consciousness, will, or instruction. In some cases brain damage whilst reducing cognitive ability in some areas, can greatly greatly enhance abilities in other areas, creating geniuses. or savants in these areas.


  55. The brain is answering questions before they were asked! To be able to move correctly or drive a car, or just simply speak, your brain tells the future (the most probable outcome of some actions, and the reactions for those…) and your brain reacts to the future event! So you can avoid collisions, you can drink your drink and eat your food! You can catch a falling object or step aside when something vants to hit you… If things work correctly 😀 "we all"(???) bend space-time in our heads 😀

  56. Today I was surprised to find out this guy is a professor in my college. I was shocked when I saw his name as the course instructor for our undergraduate project.

  57. Solo la mitad tiene subtítulos en español….qué lástima porque está muy interesante!

  58. In the plains of Africa, where we presumably competed with ferocious animals in order to survive, we relied mainly on fast reflex actions to save time to evade being eaten alive. We still retain those reflexes with us today. Being social animal and relatively successful species, we slowly decreased our dependence on those fast reflexes. Conscious actions are slow but effective in securing food by hunting smart, foraging and later on planting for food. We now became sedentary with lots of time in our hands to contemplate on useless (in terms of surviving) things.

  59. this is fascinating I admit at the time of this comment I didn't have time to watch it all but ill be coming back to it later today to finish it…. but I have always pondered what consciousness is and why it exists and some time ago I thought what if the reason consciousness exists is because of entropy… it instantly changes the thought to think about change and change is entropy and change happens over time but the only way we see that change is because our brain also has become more complex and able to store information through the creation of memories, and I think the mere fact we can form memories and remember a past where entropy was less is what makes us conscious.

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