Brainwaves: Are you in there?

This is the second episode in 'Brainwaves: Mysteries of the human brain.'

Consciousness is how we are able to feel, dream and imagine. And yet — scientists haven't figured out how consciousness definitively works. What we know, what we don’t and what that tells us about our brains.

Christof Koch, neuroscientist and leading expert on consciousness. He is a “meritorious investigator’ at The Allen Institute, where he’s investigating at the cellular level how cortex and related brain-structures give rise to behavior and consciousness. Author of several books, including “Then I am myself the world: What consciousness is and how to expand it."

Martin Pistorius, after a brain illness, spent 13 years in a state of covert consciousness where he was unable to move or communicate.

Anil Seth, a professor of neuroscience at the University of Sussex in England.

The version of our broadcast available at the top of this page and via podcast apps is a condensed version of the full show. You can listen to the full, unedited broadcast here:

Part I

MARTIN PISTORIUS: A vibrant mind hidden in plain sight. On the outside, I looked empty. Yet on the inside, I was very much alive.

CHAKRABARTI: I am Meghna Chakrabarti, and this is episode two of our special series Brainwaves.

PISTORIUS: I thought a lot about life, about death, about love, about the future. And I felt deeply.

CHAKRABARTI: But nobody else knew it. Nobody at all knew that Martin Pistorius was experiencing those surging waves of human emotions.

Absolutely no one at all. Because for 13 years, everyone around Martin saw only an unconscious body on a bed, first, a boy, then a man cut off from all human experience. Showing no signs of motion or awareness or consciousness whatsoever.

Just stillness.

PISTORIUS: That disconnect between who I was inside and how I was seen outside was devastating.

CHAKRABARTI: Martin is from South Africa. He speaks through a text to speech machine now. It's the only way he could tell us the story of what befall him back when he was just 12 years old.

PISTORIUS: I had a typical childhood for a boy growing up in the 1980s, riding our bikes with my friends around the neighborhood, building things.

Whether that was spaceships out of Lego, forts or simple electrical circuits. Life was good. It had always been this way. How was I to know that would be the day my life would never be the same again?

At first, it seemed like nothing serious, just the flu. But over the days and weeks that followed, things got worse. I became weaker. I started sleeping more and more. Walking became painful, then difficult, then eventually impossible. I lost my ability to speak. I lost control of my movements. And little by little, I slipped away.

At first, the doctors did not really know what was wrong with me. They ran many tests, they tried different treatments. There were a lot of theories, but very few answers. I was treated for things like tuberculosis of the brain and cryptococcal meningitis. But nothing ever fully explained what was happening to me, and nothing stopped the decline.

And eventually they were told that there was nothing more that could be done. My parents were advised to take me home and let the illness run its course. In other words, they were being told to prepare for my death.

CHAKRABARTI: Martin was in a coma, the shell of a boy's body with no consciousness inside.

PISTORIUS: For the first few years, I do not remember anything at all. There are no memories from that time.

No awareness, no sense of what was happening around me.

CHAKRABARTI: That nothingness would last for four years.

PISTORIUS: Then gradually my mind started to knit itself back together, slowly in a fragmented way, almost like fog lifting. There were small flickers of awareness. Then more and more, I was about 16 years old then. I often describe it like an image coming into focus.

At first, everything was gray and blurry. Then little by little the details and colors returned. I started becoming aware of sounds, then voices. Over time, I became aware that I had thoughts again, memories, a sense of myself.

Once I became conscious again, I experienced the world as a silent, invisible observer. I often describe it as feeling like a ghost. I could see and hear what was happening around me, but I could not interact with it in any meaningful way. I could not respond. I could not ask questions. I could not let anyone know that I was there.

I could see and hear what was happening around me, but I could not interact with it in any meaningful way. ... I could not let anyone know that I was there.

Martin Pistorius

I was present, but unreachable.

CHAKRABARTI: To those on the outside, Martin was still in a coma, but inside his mind things began to bloom.

PISTORIUS: My inner world became very important to me and a way to cope with my reality. I spent a lot of time in my own head thinking, remembering, imagining. I created stories. I replayed conversations. I imagined myself doing ordinary things or simply choosing where I wanted to go and who I wanted to be with.

In many ways, my imagination became my freedom.

I was in this state for many years, more than a decade. Life then was all about coping with a situation that often felt unbearable. At one point, my mother turned to me and through tears said, you must die. She did not know that I could understand her. For her, it was as if her son had died when I was 12.

She had been watching her child disappear for years. I could sense how broken she was. I could feel the pain within her. Even though I was suffering, I did not hate her. I loved her. I felt compassion because I understood she was not wishing me harm. She was wishing an end to unbearable pain, both mine and hers.

That compassion came naturally. It was not a decision I made. It was simply there. Even in the darkest times when I was really having a tough time, something inside me would make me want to carry on, to keep fighting. And I guess even though I couldn't really see how this would ever end or change, there was a sense of hope.

It was small, but it was there. Also, small acts, things that perhaps people didn't even realize, like a random stranger smiling at me would spark something inside of me to keep going.

CHAKRABARTI: Martin was able to move his eyes a little. But eye movement in coma patients is often involuntary and not necessarily indicative of consciousness.

So Martin kept going, long enough for someone to actually see him.

PISTORIUS: A caregiver named Verna noticed me. She paid attention to small things, the way I looked at people. The way I reacted to certain words or situations. Over time, she began to realize that I did understand what was being said around me. Verna spoke to my parents about having me assessed. In July 2001, I was taken for an assessment to the specialist communication center.

During that assessment, therapists could see that my eyes consistently moved to the correct pictures when they asked me to identify objects. That was the first clear evidence that I understood. It is difficult to put into words. I felt an enormous sense of relief. After so many years of being unseen, I was finally being recognized.

It felt like someone had opened a small window in a room I had been locked inside for years. Once people realized I was conscious, the focus shifted from there is nothing we can do, to how can we help him communicate? That shift changed everything. Over time, my hand control and upper body strength have also improved.

I can do much more now than I could back then, and I am deeply grateful for what I have regained. It is not always easy, but even with those challenges, I am deeply grateful for the life I now live.

Based on what I have experienced, I would say that consciousness cannot be reliably judged from the outside. A person who appears unresponsive may still be fully aware, because you never know what is going on inside them.

CHAKRABARTI: Martin Pistorius just turned 50 years old in December. Something he says he'd never thought would happen. He's now an author, an accessibility specialist, and a web developer. He's also married and is a father of a 7-year-old son. Christof Koch joins us now. He's a neuroscientist and leading expert on consciousness.

Christof Koch, welcome to On Point.

CHRISTOF KOCH: Thank you, Meghna.

CHAKRABARTI: Now, what do you hear in Martin's story that particularly stands out to you?

KOCH: Amazing story of human resilience, right? Just imagine yourself being this, in this situation for many years, where you are locked in like a stranded astronaut in space and nobody knows that there's anyone home.

And of course, this situation may also well, and we know does occur in thousands of patients today that are in a vegetative state. But we now know that a quarter of these people in a vegetative state that from the outside look behaviorally unresponsive, are actually conscious, feel like something, and maybe they're like Martin.

Some of them, many of them will not have memories of these episodes. Some of them will do, but we, it's very difficult right now. Given our limited technology to reach them, to enable them to communicate with us and even to tell us that they're there.

CHAKRABARTI: Wow. The way Martin described consciousness as a slow flickering back of his awareness was so beautiful to me, but also made me wonder, is there a definitive line in which we can say on one side of it, a person is conscious, on the other side, they are not.

KOCH: So consciousness by itself is all or none. Either you're conscious of something or you're not. However, it may also be very dim. Remember when you fly halfway around the world you have trouble sleeping. Finally, you fall asleep and you wake up in the middle. You, at that point, you may not even know who you are.

You may not even know where you are, but there's already some flickering of awareness. In that sense, it's all or none. But then of course there's also higher arousal and lower arousal, so it's a complicated matter.

Part II

CHAKRABARTI: What is consciousness in human beings?

KOCH: Any experience seeing, dreaming, dreading, imagining, fearing, seeing, all of that, boredom, with all different conscious experience, when it feels like something, and sometimes you're conscious of yourself, but not always. You could just have an agonizing toothache, and your entire content of consciousness is filled with that God-awful pain.

That's consciousness.

CHAKRABARTI: So it's anything that we experience and knowing and we know we're experiencing it.

KOCH: No, that's self-consciousness. That's in you and I. Little baby doesn't know, it doesn't have a sense of self, it doesn't know it's me experiencing hunger, right? It just has hunger.

Same thing in animals. My dog, much as I love dog, I don't think dogs know that they're dogs. They're just pain and pleasure and fear and anger and all of those things that we also have.

CHAKRABARTI: So they don't have to know. Okay. In that case, would plants be conscious?

KOCH: That's an ongoing question. Most people think, certainly, most neurobiologists think no, because we think you need a brain, but we don't know.

CHAKRABARTI: Yeah, because I'm thinking, if, like in the dog example, if a dog is just, it's experiencing things right? Fear, hunger, pain, et cetera. I don't know if plants experience fear, but they do respond. For example --

KOCH: They do respond. But as in the case of Martin Pistorius shows, you can have patients that respond, in a reflex like manner, a spinal cord reflex, although they are not conscious.

So one has to decouple, when you're sleeping, you wake up inside your sleeping brain and you have experiences, we call those dreams. You don't respond. When you are sitting on the meditation cushion. You're immobile. You have conscious experience. When you're tripping on a high dose of psychedelic, you can lie supine on the ground and you can visit heaven and hell.

So there are many cases when you people don't respond yet they're still conscious. And there are many cases where people do respond, but they're not conscious or not conscious yet.

CHAKRABARTI: I still find this so baffling.

KOCH: It is. It is, Meghna.

CHAKRABARTI: And forgive me, because you can be aware of something and you're conscious, but you don't have to be cognitively thinking of it.

But if you are experiencing something that makes you conscious, if you are asleep, let's talk about sleep for a moment, because it makes intuitive sense to me. If when you're dreaming, you may be conscious, but what about in the non-dream states of sleep? Are you conscious then?

KOCH: It's a very good question.

So most people think no, but if you do wake up people, so let's say you put EEG electrodes on them. You wake 'em up when they're in a period of deep sleep, non-REM sleep. Sometimes they have, and you ask them, did anything go through your mind just before you wake up? You wake up, many times, they say nothing, but sometimes they say, yeah, I had a feeling of pain, or I saw a face of my daughter.

So it's not known. And the other things you can dissociate memory from, and again, this is highly relevant to Martin's case. You can dissociate memory from consciousness. Have you ever, if you've ever been extremely drunk, okay, your friends will, you go to a party, you get drunk, you dance, and you do all sorts of stuff.

You, at that moment, you're clearly conscious, you can talk, et cetera, but the next day you have no memories of it. If you get your colonoscopy operation, they inject you with propofol, they give you propofol. You're not typically unconscious, you just don't remember. Depending on the dose, you can be at a state where you can still respond to commands that the doctor tells you, move over or move your cheek, et cetera.

But you may not have memory. So again, consciousness is different from behavior, is different from memory, although they all closely associated.

CHAKRABARTI: It sounds like it's almost multifaceted or can quickly metamorphose into different forms of consciousness.

KOCH: Of course. And then in addition, we humans, adult humans, we have this thing we call self-consciousness.

Which is the high point of consciousness. I can, you and I, we know who we are. We know what we had for breakfast. We know we're going to die one day. And on all of those things, that is a late-stage evolutionary elaboration that only, as I said, some people have.

Patients may not have it. A late stage dementia patient may not know anything at all about themselves anymore. Babies don't have it and most animals probably don't have this highly developed sense of self.

CHAKRABARTI: Okay. Can we go back to infants then? Because you said, I just want to clarify. Infants you say are conscious, even though they do not have that sense of self.

KOCH: Correct.

CHAKRABARTI: They're conscious in the way that other animals may be.

KOCH: Correct.

CHAKRABARTI: Okay. So that's interesting. It doesn't require that. When then, would you say, or is there a collectively agreed upon moment in the community of scientists that study this where consciousness first emerges in a human being.

KOCH: It's not clear. So people have asked this question, for example, a second stage trimester fetus, it's only at that point when you have the axons that when particular brain structures develop, like the thalamus and the cortex, that you even have, if you want, the hardware to be conscious.

So it's a first term trimester fetus probably doesn't feel like anything. Or if it feels like something, it's very difficult to ascertain, and it's a gradual thing. Some people argue that the massive surge of noradrenaline that you get as the fetus exits through the birth canal of her mom, and cries, because the fetus has to breathe for the first time, is now a baby.

That may be the moment when they first begin to be conscious and then it develops, even the sense of self develops. Maybe, it coincides, age three, four, or five when children start having a sense of self and then they develop what we call a theory of mind, where they realize other people, also ourselves, and other people also have intentions and desires, et cetera.

And so it develops, and even, if you're 18-year-old, you're not fully developed yet to truly understand, to truly take someone else's point of view. To have to develop empathy. All those things develop slowly as a brain develops.

CHAKRABARTI: Okay, so I'm only smiling right now because I'm thinking how challenging must it be to be a scientist in this field.

When there isn't even any agreed upon baseline for what consciousness is or when it first is established in human beings, don't you need some kind of baseline from which to advance your research?

KOCH: So I think most people would agree. Consciousness is the feeling of when you're in love, right?

Or when you see, or that voice, this is how I first about it. Where does that voice inside my head? I have a voice inside my head. Where does that voice come from? Not everyone has it, but most people have it. Where does that voice come from? And it's not clear. It's not clear how physics, ultimately, our brain is a piece of furniture of the universe.

Our brain is a piece of furniture of the universe.

Christof Koch

Like any other piece of furniture, quarks and like viruses and like trees. It's all the same sort of physical matter, although the brain is the most complex piece of highly active matter. And where is that point where this piece of active matter can hear a voice or can love or can hate?

That's unclear. But where we have made a lot of progress since 40 years is trying to locate which bits and pieces of the brain are involved. And also contrary to what Martin said at the end of his beautiful comments, we are now in a position where we can begin to detect in these patients that are otherwise impossible to reach, whether or not they're conscious.

So that's a big advance.

CHAKRABARTI: Okay. You can detect it by obviously examining brain activity.

KOCH: By detecting. So this is a technique that's been pioneered by a team in Milan and Professor Marcello Massimini and an American-Italian scientist, Giulio Tononi in Madison, where you essentially, you probe the brain, you essentially knock the brain, in this case, using magnetic pulses.

And then you're listening to the echo using EEG. And this technique where you perturb the brain and listen, you knock the brain and listen. This can very reliable tell whether the patient, in normal, for instance, in normal people, are they in a deep sleep or are they awake? Are they in a REM sleep or are they, let's say, under ketamine or under some other psychedelic where they are not responsive but they're conscious.

And also in many of these patients, it can reliable detect the difference between being conscious, being there, but that's really all we're trying to detect. Is the patient there, is there someone in home? So that can now begun, happens. There's another technique developed by a neurologist here at Columbia, Jan Claassen, where you ask the patient, although they lie there, they don't respond.

They may have their eyes open, but they don't respond. You ask them, imagine squeezing your fist very hard and then letting go and then squeezing your fist very hard and letting go. And now if you put them in a brain scan or EEG, you can sometimes see the rise and fall of their brain activity.

So in other words, although they can speak, they can move, they can't move the eyes, they can reliably, voluntarily on command change their brain state. So that tells us, yes, there's someone home.

CHAKRABARTI: Oh wow. Okay. Take me back a little bit. Christof, when we say there's reliable brain activity, does that mean that there are specific areas of the brain that are, for lack of a better term, in charge of consciousness, or does it --

KOCH: Yes.

CHAKRABARTI: Oh yeah. Go ahead. Go ahead, please.

KOCH: Yeah, so the brain is a, as I said, it's the most complex, active matter anywhere we found so far. It's very complicated. It's highly differentiated. We know now it consists, this is stuff we've done at the Allen Institute.

There are 5,000 different types of, so there roughly 2 billion cells in the brain of probably 5,000 different types. So it's amazingly stunningly complex, and not every part contributes equally. We know this, certain parts of your cortex, the outermost layer that's more highly developed in us, in humans.

There's some parts that are involved in vision. There are other parts that if you lose them, you can't speak anymore. There are other parts where you feel where you have where you don't have a sense of self anymore. Or conversely, if you have seizures in that part of the brain you have weird distortion of the sense of cells.

So we know that specific regions, neighborhoods of, in particular the cerebral cortex, seem to underlie specific visual, let's say, visual behaviors or auditory behaviors. But not only behaviors, also the experience of it. So yes, it seems to be that cortex is the one that mediates most of our consciousness in the sense of seeing, hearing, touching, wanting, the feeling of volition, the feeling of wanting the sense of self.

Those all appear to be, arise or are strongly correlated with the cerebral cortex.

CHAKRABARTI: Okay, so the cerebral cortex, which is why, I was reading a paper that you had in Nature, the journal Nature or an essay essentially. And you talked about defining neural correlates of consciousness, right?

... And so is that what you're talking about now with these parts, the cerebral cortex, for example?

KOCH: Yeah. So this is a program that Francis Crick, the molecular biologist.

CHAKRABARTI: Yes. And Nobel Prize winner.

KOCH: Yeah. In the late '80s, early '90s that now many people are engaged in where independent of your philosophical attitude to consciousness.

Okay. Independent whether you're materialist or dualist or panpsychist, we can all agree it's the brain, not the heart. As most people thought for most of human history, it's the heart. Because that's visible, palpable, moving. The brain is just this passive goo, right? But we now know it's a brain.

We know it's not the spinal cord. We know it's incidentally, it's not even your cerebellum. So most of your neurons Meghna, are in this little brain at the back of the brain called the cerebellum. You can remove if you lose that due to stroke or gunshot or tumor, when the surgeon removes it. You may became a toxic, you look like you're drunk.

You have difficulty speaking, but you do not lose consciousness. So we know that certain parts of the brain are much more critically involved in others. And yeah, this is  trying to chase down these correlates of consciousness. Think of them as a footprint of consciousness in the brain.

CHAKRABARTI: What's interesting with the spinal cord and cerebellum examples is that you can lose function, say in the spinal cord, right? That's the source of paralysis for many millions of people. But it has no impact on their consciousness. And similarly for other parts of the human brain, right?

You can lose those functions, but you remain conscious. So that, I guess that means that consciousness really has specific locations in the brain. But does that conversely mean that, let's talk about the eyes for a moment. People can actually have functioning eyes and maybe functioning optic nerve that is delivering information to the brain, but still not be conscious, right?

KOCH: That's correct.

CHAKRABARTI: I'm asking that because it's like that means that these two, the two things aren't always connected in terms of processing input and experiencing it.

KOCH: Exactly. As I said, it's very complicated and you can dissociate some of these cases. We know this from animal experiments, and we know this in patient. Now, it's different if you ask a patient, can you move? You ask patient right now, please move your eyes to the left, to the right. Up, down, and they can follow that as in a typical locked in patient. Then we take that as evidence, even though the patient can speak that they are fully conscious.

In fact, there's a famous book, The Diving Bell and the Butterfly, where a French person who had this tiny stroke in his brainstem, he became locked in, dictated an entire book, just using his eyes. Which is pretty amazing. And he was fully conscious, conscious enough that he could, he wrote this beautiful, evocative memoir from inside, this locked in brain.

CHAKRABARTI: Wow. Okay. So I'm looking at this paper again, and it says that so far as, as long, as much as you can tell, or science can tell, almost all conscious experiences are originating in the posterior cortex or the back of the head, brain, right? Not in the prefrontal cortex.

KOCH: Yes. Now that's my position.

In fact, you may recall, you had me on with the philosophy of Chalmers two years ago, in summer of '23. So that's still being debated. Is it only the back of the brain, or is it the back of the brain and the front of the brain? Most people, of course, argue, think rightfully so, that the front of the brain that's maximally expanded in us compared to great apes and monkeys is the seed of human intelligence, right?

But once again, intelligence is different from consciousness. There's nothing particularly intelligence, Meghna, if you have a god-awful toothache, that fills your entire consciousness with just pain, right? There's nothing particularly intelligent about it. If you open your eyes and you see it's a conscious sensation, but again, that doesn't have to be intelligence.

Although intelligence and consciousness are related, they're still distinct phenomena. Which is particularly relevant as we come to speak about artificial intelligence versus artificial consciousness.

Part III

CHAKRABARTI: You had talked about the question of consciousness and AI.

We actually did want to hit on that very specifically. Because there are already, some of those models already are so advanced that we've known or heard of people falling in love with them, wanting to marry their AI chatbots. They're that sort of socially convincing that they seem to be conscious, but are they?

ANIL SETH: They are clearly intelligent, so it's very natural for us to imbue these systems with consciousness too, especially when they start talking about consciousness. And many language models do, because they're trained on a lot of data in which people talk about consciousness. So it's no surprise that they talk about it.

CHAKRABARTI: Anil Seth is a professor of neuroscience at the University of Sussex in England, and Christof said earlier, Professor Seth also says that people should not confuse AI intelligence with consciousness.

SETH: Intelligence is about doing things. It's not really surprising that artificial systems like computers can be intelligent because computers are very good at doing things.

That's what an algorithm is. It's a mathematical recipe for doing stuff, consciousness, on the other hand, is different. It's fundamentally about being, it's about feeling, it's having an experience of redness or of pain, taste of ice cream or the sound of children's laughter.

But just because you can do stuff doesn't mean that you feel anything.

CHAKRABARTI: Professor Seth says that really what we're seeing now with AI is a computational simulacrum of human consciousness.

SETH: When we simulate a brain, we are just generating a very useful computational model of the brain, which is helpful for us in understanding the kind of thing it is.

Just as a computational simulation of the weather is very helpful in understanding the weather. When we simulate a rainstorm, it doesn't get wet and windy inside the simulation of a rainstorm. We know it's just a simulation, but a simulation will only give rise to consciousness if consciousness just is a matter of computation.

If it isn't, then all we'll have is a model of it, a simulation of it, and not the thing itself.

CHAKRABARTI: Not only does Professor Seth think that AI is not conscious now, he argues that it's unlikely to gain conscious ever in the future for as long as the physical hardware that AI relies on is nothing like the organic matter that makes up the human brain.

SETH: Built into the foundations of computers as we have them, these silicon digital computers, is this sharp separation between hardware and software, between what the computer is and what it does. This is why they're useful. They can run many different programs and you run the same program on different computers, it does the same thing, but in a brain, there is no sharp separation between what we might call the mindware.

And the wetware, it's very difficult. It's probably impossible in real brains to separate what they do from what they are. And because of this way that brains are all mixed up and they don't allow this clean separation of mindware and wetware, that makes the idea that all our biology is just there to implement an algorithm, that makes this very unlikely.

CHAKRABARTI: So when you're talking about the brain, Professor Seth says, you also cannot ignore the fact that the brain is a living organism.

SETH: They take in energy and they reproduce their own components. Now, every cell reproduces itself over time from energy through metabolism. Computers don't do that, and they don't produce themselves.

They take in everything from an external world, like a factory and produce some output. And that self-producing aspect of biology, I think there's some pretty strong reasons to connect processes like this to consciousness. Computation is just not the only option for what might breathe fire into the equations of experience.

CHAKRABARTI: Bottom line, since experts do not definitively know how consciousness works, but what Professor Seth does say is that even if AI were to experience consciousness, it would never be the same as human consciousness because AI just isn't human.

SETH: The idea of the brain as a computer is a very powerful metaphor.

In fact, it's what's driven a lot of the AI that we have. We talk about AI as neural networks often, and these metaphorical abstractions of the real biology of the brain. But we usually get into trouble when we confuse a metaphor with the thing itself when we mistake the map for the territory.

CHAKRABARTI: That's Anil Seth, professor of Neuroscience at the University of Sussex. Christof, I have to say that the wetware and hardware or mindware analogy that the professor used there to me is the most convincing explanation so far about why AI is not conscious right now, because we can ask that same NVIDIA chip to do something else entirely, whereas we can't really do that with the human brain.

What do you think about that?

KOCH: I totally agree with them that the LLMs are not conscious. They imitate our intelligence, but that has nothing to do with our consciousness, with our conscious mind.

CHAKRABARTI: It's interesting though because this also makes me want to argue.

I want to be the devil's advocate here because you know very well the figure of Thomas Nagel, right? Who basically said that for a conscious organism to be conscious is to just simply be, to be, have the experience of being that organism. Yes? I wonder, the idea is what is it to be a bat?

Only bats know. We humans can't actually know, can't we apply the same thing to AI though? Like we don't actually know what it is to be an AI system. So how do we know for sure it's not consciousness in a way, all unique to AI.

KOCH: We don't know for sure. It's an inference. It's an inference based on our best understanding of what consciousness is.

Look, we have something we call the, in the perception box, which describes my sense of reality, which is created by my brain, which is my conscious experience of the world. Okay? And I don't even know exactly your perception box. You have different genes; you have a different up upbringing and so you might experience things differently.

You might misinterpret me or you might misinterpret other people. So we each live in our own reality. We assume it's a very powerful assumption that all of us are conscious and using similar mechanism. We assume we infer that other creatures like dogs and cats and all the other creatures that populate our homes are also conscious, but it's in the final analysis. It's always an inference to the best explanation. And so we infer that today, although I'm not a hundred percent sure, that computers are not conscious.

CHAKRABARTI: You're not a hundred percent sure --

KOCH: They don't feel anything. They do not feel well.

But you have to realize as a scientist or as a philosopher, you are not a hundred percent sure of almost anything. The only thing, Meghna, that you are really sure of is that you are conscious. This is the Cartesian insight. The only thing I know for absolutely sure, I feel like something right now.

Not when I'm deeply asleep, not when I'm anesthetized.

CHAKRABARTI: Okay. I'm gonna mention the movie The Matrix, but in all seriousness. Because that is a phenomenal movie that raises so many questions about consciousness. What if we were in a matrix and our experiences of being are actually the source of like artificial inputs to my brain that I'm not in control of it.

KOCH:  Logically. Yeah, logically it's plausible, but in both cases, Neo always knows that he exists. He might be, and René Descartes has explicitly pointed out this. He said there might be an evil deceiver. That deceive me about the way the world appears, about his perception box.

But the fact is that you experience something, that cannot be denied. That is a central insight from which any research about consciousness has to start. That you are, I'm right now conscious, and this has to be explained, why a piece of matter can have consciousness. Because it's not in the foundational equation of quantum mechanics of relativity.

It's not in the theory of evolution. Why is it that that matter can love and hate? That's really the fundamental question.

Why is it that that matter can love and hate? That's really the fundamental question.

Christof Koch

CHAKRABARTI: I think this is what's so exciting about where the work that you and others are doing right now is, right, because you talked about new ways in which we've been able, you've been able to measure certain activities, say in the posterior cortex.

I was reading about new technologies that are allowing for different ways to do that sort of selective excitation of the brain. And finding out what the responses are. So we could make a lot of progress in understanding.

KOCH: We will.

CHAKRABARTI: Okay. We will make a lot of progress in understanding consciousness, but let me ask you this, you are one of the most eloquent proponents of the theory that we can basically embed the experience of consciousness in the biological and mechanical operations of the brain.

What do you say to people who just fundamentally disagree with that premise to begin with, that they say, Christof, you're just chasing rainbows because consciousness cannot be so reduced down to physical matter.

KOCH: Look, that's a metaphysical question, right? Is it not reducible at all?

Maybe, some people have a certain ... history that fundamentally the everything physical, including the brain is a manifestation of something, the mind is a manifestation of the mental, call it the cosmic mind. Call it mind at large. Those are metaphysical questions, right?

But the empirical question is, it's, once again, we can go back to Martin and you come into the ICU because you had a bad car accident or a stroke or cardiac arrest. Now the question is, are you conscious or not? And can we test that? And now we are at a stage where 40 years ago we weren't, and that we can now say, yes, this patient is conscious and no, that patient is not conscious, that is progress.

Will we ultimately understand the secret of the universe and how it relates to consciousness. That, I don't know. But we are making progress. We're understanding which bits and pieces of the brain are involved, when do they first start, what happens in late-stage dementia, which other creatures are conscious.

Those are all questions that we have partial answers, and we will have full answers.

CHAKRABARTI: But I certainly, I don't hear you dismissing the metaphysical aspect of this, right? Because I think some of the most exciting aspects of this research is it's right there on the border between the metaphysical and matter, right?

KOCH: Entirely. In fact, I'm also the chief scientist of this Tiny Blue Dot Foundation. We are organizing now a workshop with scholars, philosophers, neuroscientists, people who do psychedelics around the question of mystical experience. So many people throughout history have had what people, in hindsight, called mystical experience at different names, transformative experience, non-dual experience. This includes near death experiences.

This also includes psychedelic experiences where the person who has this experience feels at one, they lose their sense of self. They become one with the universe. That's how it feels, and some of them, it can profoundly change the life, the attitude, the habits of this person who has this.

And many people argue that what happens during this experience, that they access an ultimate reality, that it's all mental, that it's all phenomenal. And so yes, I think the border is ... between doing neuroscience and we, with the question of consciousness, we have to, we are confronted with these metaphysical existential question, what is real?

What is the fundamental nature of reality?

CHAKRABARTI: Yeah. Oh, and that question couldn't be more important than it is these days. But Christof, let me ask you, we talked about some of the places in the brain that might be critical to our experience of consciousness, but is there yet a sort of dominant theory of how consciousness works?

KOCH: No, I would say there are at least two strong contenders. One is this integrated theory of consciousness of Julie Chen. The other one is global workspace theory. ... And there are also other theories. So in terms of theoretical understanding, we, at least, again, we've made progress.

We are now in a position where we have scientific theory, not just philosophical schools of thought, like materialism, idealism. But where we have precise theories that try to account what consciousness is. So there's again, there's a lot of progress. We don't have final answers. That's why I lost my bet against the philosopher David Chalmers because we don't know yet, 25 years after we started this bet.

But we are making progress. We are making a lot of progress, and it's very exciting times.

CHAKRABARTI: We have just a few seconds left here. You've been doing this for several decades now, Christof. I wonder how it's changed your understanding of your own sense of consciousness.

KOCH: It has, particular since I've also had one of these experiences that transformed me, that have transformed me and fundamentally changed my attitude to the metaphysics of what is reality?

CHAKRABARTI: What was that experience?

KOCH: Yeah, I prefer not to talk about it. It was one of these transformative experience where everything afterwards has changed. Where you are at your fundamentally attitude to what is real and what is reality and what is constituted by reality changes. And this has lots of other side effects.

For example, you lose your sense of your fear of death and other psychological benefits.

The first draft of this transcript was created by Descript, an AI transcription tool. An On Point producer then thoroughly reviewed, corrected, and reformatted the transcript before publication. The use of this AI tool creates the capacity to provide these transcripts.