Christof Koch Interview: Conversations with History; Institute of International Studies, UC Berkeley

Consciousness and the Biology of the Brain: conversation with Christof Koch, Lois and Victor Troendle Professor of Cognitive and Behavioral Biology at Caltech, March 24, 2006, by Harry Kreisler

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Visual Consciousness

You, as a matter of your strategy, are focusing not on all the different senses but really perception. Tell us about that choice.

Yes, we focus on vision, visual consciousness. It's a little bit like the drunkard who lost his keys and then looks for his lost key where the lamp is. These are all very, very difficult problems, we haven't made that much progress over the last 2000 years, so when you ask people [about] consciousness, they say, "Oh, you mean soft consciousness." Yes, soft consciousness, one aspect of consciousness, but it's very difficult to study, that fact that I know I'm Christof, I know I'm a son, I know I have children, etc. That's very difficult to study empirically because it's it's unclear [whether] animals have consciousness. Some probably do, like the great apes, but it's very difficult to study that.

So, let's study a much simpler consciousness, namely [seeing] red or blue or seeing motion or seeing a face. We can manipulate that very well. We can do what magicians have done for hundreds of years. If you go to a magic show you look at the magician. The magician will make things disappear in front of your eyes. He does that partly by using attention distraction. There's a beautiful bikini-clad assistant next to him and you'll be distracted. Although you're looking at him, you're actually paying attention to her. We can do something similar -- less sexy, but we can do something similar in the lab. We can show you things that you routinely don't see. They're in front of your eyes: sometimes you see them, sometimes you don't.

We can use this technique to ask -- well, in both cases there's an image present on your eyes, but in one case you were actually conscious of the image, in the other case you were not conscious of the image. Where's the difference in your brain? The Area X, the consciousness area that lights up, that's one I posited. I said, "Whenever this area lights up, you're conscious of it. Where is that area? Is it a series of stages? It's not going to be one area, we know that, it's going to be a series of areas, probably distributed, that have different properties."

So, we can do this in a magnet, we can put you in a magnet and we can show you these images that you see sometimes and sometimes you don't, and we can study that. And you can also do this in a monkey, you can do it in a mouse. So, vision has the advantage, visual perception, and we can manipulate your visual perception very precisely in space and time. We can do that as well as for pain, [but] it's very difficult to recruit people to do pain experiments. It's very easy to recruit them to look at a monitor, and we pay them twenty bucks to do that. And so, it's a tactical reason why we focus on visual perception.

Some of these experiments play with [the idea that], for example, these coalitions are often in competition. Is that [right]?

Yes. Again, that's where the election or democratic analogy or metaphor is very appropriate. You have all these neurons in your head and they constantly compete. They excite and inhibit each other and they constantly compete. At any given point in time there's only one dominant coalition. That reflects the character of your consciousness. By and large, you're only conscious of one or two things at any given point in time. You can shift rapidly within a fraction of a second, but at any given point in time you're usually only conscious of, let's say, one or two things. And so, when you're conscious of one thing, something else is suppressed. You can see that, for example in the phenomenon of "tip of the tongue," when you say, "Oh, what's that name? What's that name?" Then you do something else and twenty minutes later it pops into your mind. That's exactly a case where the coalition of neurons that represent the name of this acquaintance you're trying to recall is suppressed by something else.

So, you want to track this, and again, we have experiments in the lab where we can do this very well. We have two different images, and for example, we put one image in one eye and a different image in the other eye and they compete. You only see one image at any given point in time, although they're both present. Let's say you put a picture of George Bush here and you put a picture of John Kerry here. You will only see one of them at a time. It's called binocular rivalry. For ten seconds you may see Bush, and then there's a transition, you see Kerry for a couple of seconds, then again it changes to Bush. So, you have the two images and the underlying neurons that represent them compete for attention. So, you can use this paradigm to, again, study the footprints of consciousness in the brain, in a human brain or in a monkey brain.

Next page: More Thoughts on Consciousness

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