The Quest for Consciousness
Professor Christof Koch
Professor of Biology, California Institute of Technology
Author, The Quest for Consciousness: A Neurobiological Approach
Consciousness is an aspect of human life that many of us take for granted. The world passes seamlessly before our eyes unified as holistic perceptions. But, much of this conscious experience may be an illusion created by the operations of an imperfect brain. Indeed, it is even unclear why there should be such experiences at all. Scientific inquiry into the nature of consciousness is just beginning and starting to reveal some surprising facts about how the brain gives rise to conscious experience. Well, joining us today to discuss these issues of consciousness is Prof. Christof Koch. Prof. Koch is the Lois and Victor Troendle Professor of Cognitive and Behavioral Biology and Executive Officer for the Computation and Neural Systems Program at the California Institute of Technology. He is the author of several hundred scientific papers and journal articles, and he studies the biophysics of computation and the neural basis of visual perception, attention and consciousness. He is the author of the new book, “The Quest for Consciousness: A Neurobiological Approach”, and he joins us to discuss these issues of consciousness.
Christof Koch (CK) joins Charles Lee (CL) to discuss a neurobiological approach to studying consciousness.
CL: You’ve certainly written a very fascinating book, “The Quest for Consciousness”. Consciousness is certainly a very tricky issue. How do you actually go about scientifically defining the problem of consciousness?
CK: First of all, different people mean different things by “consciousness”. At one level consciousness is about whether I am awake, or unconscious, or a patient in persistent vegetative syndrome. So, the consciousness that we mean, and most philosophers and scientists who study it mean, is that assuming I’m a normal subject, I’m well awake, then I can see something or I can feel something. These subjective states, when I can see the blue sky or feel a toothache, those subjective states, philosophers call them “qualia”. Those are the elements of consciousness. How do they arise? How can a physical system, like the brain undoubtedly is, how can it give rise to these subjective states? When my computer, for example, I and most computer scientists believe, does not have such subjective states.
CL: You talk about your approach as trying to find the Neuronal Correlates of Consciousness.
CK: So, for the past 2500 years, since people really began to systematically think about what consciousness. How do you define it? How do you get at the heart of the Mind-Body Problem? Which I just mentioned is how can a physical system have subjective states. We’ve not made a lot of progress there. So, the approach that Francis Crick and I have advocated is let’s leave that aside for the moment and focus on the correlates of consciousness in the brain. What are the minimal neural mechanisms necessary for any specific percept like seeing blue, having pain, hearing a tone, smelling mom’s apple pie? What are the minimal neuronal conditions in my brain, your brain, or the brain of a dog, or maybe even of a mouse or fly that are sufficient for this particular percept. This is something that can now be addressed in the lab using empirical research.
CL: So, how do you actually go about this?
CK: Well, one of the best ways to study this is visual perception. Now, the advantages of studying visual perception over studying self consciousness or pain consciousness is that it’s very easy to manipulate, I can very easily take an image and put it on a monitor and show it to you and manipulate it, but in particular I can make things disappear. Magicians have done this for several hundred years, but psychologists over the last few decades have also learned to systematically manipulate the relationship between what’s out there in the world and what you see. So, in other words I can show you things, you’re directly looking at them with your eyes, but you may not see them. There are all sorts of visual illusions for example that you can see at my web site: http://klab.caltech.edu. When there’s an illusion, you may only see it transiently or you may not see it at all, yet it’s still physically present. So, now I can take such illusions and I can study them in humans, or I can put people in a magnetic resonance scanner, or I can train animals to do this. I can now look for the footprints of consciousness in your brain. Where are the neurons, the nerve cells, the part of the brain that responds to the stimulus when it’s just physically present in the world, but you don’t perceive it or consciously see it. And, where are the neurons that are only active when you actually see something, or hear something, or smell something consciously.
CL: So, you can actually look at the parts of the brain when you’ve changed these conditions of what people are seeing, and see which parts are active and not active.
CK: Exactly. That’s really the most direct way to track the footprints of consciousness in the brain.
CL: You talk about the architecture of the visual pathways as consisting of two different pathways, a conscious and unconscious pathway.
CK: It’s probably a general story not only for vision, again vision we know best. We know more about visual modalities then about the other ones. But, it’s probably a general phenomena that we call a zombie system. These are quite sophisticated, but still unconscious sensory-motor system that help me get around my day, when I get up in the morning, tie my shoes, brush my teeth, drive a car, bike, run, climb a mountain. These are all sophisticated activities. We know they’re sophisticated, because people try to build robots to do them and it’s very difficult. Yet, I can do these things without being aware of them. Or if I am aware of them, I’m usually only aware of them after I’ve initiated them. It’s like the batter who sees the ball coming and he has to decide to hit the ball way before he’s actually consciously aware that he’s hitting it. Now, these are all stereotyped systems. Like driving. Very often you find yourself lost in thought and you suddenly arrive at home, but you don’t have any recollection of consciously driving, yet you had to make lots of very complicated decisions on the way from your work back home. Now this compares with the things we are actually conscious of, like right now you may be conscious of my voice. So, the question you have to ask is where’s the difference in your brain. If it’s true that many things you can do unconsciously with these highly trained stereotypical sensory motor agents, why do you need consciousness at all? And, where’s the difference in the brain? How can my brain do things that do not give rise to consciousness, and how is that different from the parts of the brain that are involved when I am actually conscious of things? Are they different parts of the brain, or do the neurons fire in a different mode, or where’s the difference?
CK: Yes. The claim is that much of what you actually do in your daily life is totally unconscious. For example, when you talk, you have sort of a vague idea of the idea that is in your head that you now want to transmit. But, it’s not that I, Christof, am sitting inside of my head as it were saying, “Okay. This is the noun. This is the subject. This is the adjective. Now I conjugate it and then send it out to my larynx.” I just have a vague idea and the next thing I hear these words come tumbling out of my mouth. It’s a very complicated thing. Yet, I don’t have any conscious access to it. You know there are myriad of examples like that. For instance, most people don’t know that down in their stomach, in their guts, they have a nervous system called the enteric nervous system, sometimes called the second brain. It’s quite sophisticated. There are neurons, synapses, and neurotransmitters. Yet, for the most part, and happily, you are oblivious of all of that activity down there, that regulates your digestion and all of that. Well, there are probably as many neurons in your enteric nervous system as are in your dog. Most people are perfectly happy with the idea that a dog is conscious, so why is my enteric nervous system conscious? It’s a good question. Right now, we don’t have the answer. Why are there no feelings generated there, with very few exceptions.
CL: You bring up the issue, if we are able to go about activities without being conscious of them, why indeed have consciousness at all?
CK: So, this is the eternal question of the function of consciousness. Many people have speculated on it. If you go back to all the things that your unconscious zombie can do, those things are all stereotypical. Now if suddenly something happens that hasn’t happened before. Let’s say I’m in southern California and an earthquake begins to shake. I quickly have to see where’s the danger? Where’s the door? How do I quickly get out of the house? For those untoward and unplanned things that happens all the time, because the world is so complicated, and I can not plan for every possible contingency, that’s exactly when I would need consciousness. I need a concise summary of what’s going on right now in the world, of things that are happening to me right now in this second. That’s what I’m conscious of.
CL: So, it helps deal with an ever changing and novel environment.
CK: Exactly. So, the claim is that if you live in a total stereotypical world where nothing changes, then for the most part you could be totally unconscious, because you wouldn’t need consciousness. Your body could perfectly do all of those routine things.
CL: I see. You talk a little bit in your book about whether other animals might have some degree of consciousness. Is there some minimal architecture that’s necessary for consciousness.
CK: It’s unclear. So, most biologists would assume that certainly mammals are conscious. Their behavior is very similar, with the exception of language, which is certainly pretty much unique to ourselves. But, certain aspects of self-consciousness, knowing that I’m Christof, knowing I’m an American citizen, knowing that I’m going to die. Even monkeys or apes are probably not nearly as self-conscious to the extent that we are. But, there’s no doubt that if you look at the behavior of whether they see, hear, or smell things, they behave very much similar to us. If I gave you a little piece of monkey brain, a little piece of human brain, and a little piece of mouse brain, only very few experts on the planet could tell the difference. The structure and evolutionary history is very similar. So, most of us assume that at least mammals are conscious, which would imply that you may need a neocortex. But, at this point, we simply do not know to what extent a “simpler” organism, such as a bee, which after all is very complicated and has roughly one million neurons, how do we know that it doesn’t feel like something to be a bee? That the bee can’t experience the world by feeling. Right now, we just assume obviously it’s not, but that assumption is totally unwarranted. There’s really no evidence either way to back it up. Right now, it’s a question that’s difficult to answer empirically in any sort of satisfactory way. That’s why again the research strategy is to focus on things where most of us can agree are conscious, humans certainly, and similar creatures such as monkeys or maybe mice.
CL: Is there a difference between the sort of perceptual consciousness or the self-consciousness that most of think about when we say “consciousness”.
CK: Well, we don’t know. The assumption that we make is that consciousness is something that was evolved by natural selection a long time ago and then was adapted. Probably the earliest form of consciousness was for pain, way back in evolutionary history, then for pleasure, then for simple forms of smelling and then maybe seeing. And then as we evolved, it became more elaborated and we developed not only a picture of the outside world but also a model of ourselves. We began to manipulate that, and we call that self-consciousness. So, our claims is that it shares a lot of commonalities among all of these different forms of consciousness. Ones that are all about sensation, feeling, experience, subjective states. And then of course there’s specialization, like for us having to do with language, but the assumption is that at rock bottom they all share a great deal of similarity.
CL: So, what really needs to be done to get at the heart of this issue?
CK: Well, the brain for it’s size is by far the most complicated system in the known universe, and what we really need to understand is at the detailed level of the components, which are neurons. Unfortunately, you don’t really see neurons if you do a brain scan, what you’re looking at is a comparatively very large fraction of the brain that includes probably a few million neurons. We really need to understand the working of the brain at the detailed level. Just like molecular biology we now know we need to understand individual molecules, proteins, enzymes and how they interact. Likewise with the brain. This, by and large, can not be done in humans, but requires appropriate experiments in monkeys or mice or other model organisms.
CL: Do you think the two approaches will converge at some level where the global activity patterns will meet with the neuronal activity patterns.
CK: Yes. We can begin to see that very faintly the outline where people may record in brains from individual neurons. And then at the same time they are studying global patterns to try and relate the two. Ultimately that’s what needs to happen, but right now we’ve got reasonable tools to study global patterns like EEG or imaging devices. We’ve got pretty good devices called microelectrodes and arrays of them where you can study individual neurons. What’s missing is trying to bridge that giant intermediate scale. We really need to be able to understand and record from a hundred thousand or a million neurons, identify them, and try to understand how do these neurons interact with each other. And, that’s really what’s lacking right now.
CL: As a final note, I’m curious how did you become interested in this whole question of consciousness?
CK: Well, I think it’s a problem that most intelligent people at some point in there lives ask themselves. Where do we come from? And, in particular, why is it that we can have feelings? It’s not really apparent why it should feel like anything. I first thought about this a long time ago when I had a toothache, and I was lying in bed, and I asked why did my tooth hurt. I mean, I could see why evolutionarily it makes sense for it to hurt. But, I couldn’t understand and still don’t why is it that the electrical activity of neurons in my brain gives rise to this feeling? I could take my computer and connect a thermometer to it, and if the temperature goes about 100 degrees, the computer will say “hot”. But, nobody will actually believe that it actually feels like anything. People will just say, “Well, that’s just electrons flowing onto the gate of a transistor. That’s not really about feeling hot.” In my case, and your case, and the case of my dog, when we have pain, we actually have these bad feelings. So, how is that they arise in brains that’s what we are trying to understand.
CL: Maybe as a hypothetical note, how long do you think it will be before we have a clear understanding?
CK: It’s very difficult to say. I mean, the answer may be around the corner, within the next few years there might be significant breakthroughs. Or, it may take us another 50 to 100 years. It’s very difficult to say in problems of this nature, when you’re not really sure exactly what the solution looks like, how long it will take.
CL: Well, we’ll have to wait and find out.
CK: That’s correct.
CL: Prof. Koch, I just want to thank you joining us today for a very fascinating discussion.
CK: It’s been my pleasure.