Mind & Brain

Last November, DISCOVER and the National Science Foundation launched a series of events to explore the biggest questions in science today. In the first event, “Unlocking the Secrets and Powers of the Brain,” four leading psychologists and neuroscientists discussed the hottest issues in brain research, from predicting human behavior to manipulating memory to pinpointing consciousness. Hosted by the Franklin Institute in Philadelphia, the panel was moderated by the award-winning author (and DISCOVER blogger and columnist) Carl Zimmer.

Click here or on the above image to see video of the event and interviews with Zimmer and the four scientists. The transcript of the event is below.

Sam Wang: We might imagine that the visual part of our brain handles information the way a camera does, or perhaps our memory works the way a computer’s hard drive does. But that’s not the case.

When we process a visual scene, we are in the business of extracting salient features. We might be interested in finding a face in the scene or looking for objects. At the same time, we are in the business of throwing away information. Instead of getting all the pixels of a bottle of water I see, I might want to reduce it just to “bottle of water.” I might not be concerned about the fact that a particular bottle of water looks a little bit different from the other bottles. We toss away things that are not salient.

These shortcuts help us survive. They get us through the jungle. They get us to live another day. What they don’t get us is a little gigabyte hard drive of factual information.

Zimmer: Often it seems that we recall musical memories better than visual ones. Does that offer more clues into how the brain stores information?
Daniel Levitin: I think music can tell us a lot about the role that emotion plays in memories, the accuracy of memories, and the way in which knowledge can be encoded into memory.

When a song comes on the radio that you haven’t heard since high school, you’re right there with it. You’re singing along. You remember all the nuances. The big story of memory revealed by music is that you tend to remember those things that you care about or that you have some deep emotional connection with. It can be a positive emotion, it can be negative, but there appear to be neurochemical tags associated with memories that are highly emotional. Those are the ones that get most accurately recorded in your memory and the ones that are easiest to draw out.

Now, accuracy. What we’ve learned from musical memory is that it is astonishingly accurate. People can remember details and nuances of songs they know to such a degree that you can play them a 100-millisecond burst of a piece of music they know and they can name it from that. I’m talking about a tenth of a second—before the melody has a chance to evolve, before there’s any rhythm. If you alter a little bit of a well-known piece of music, people pick it up instantly. And if I were to ask you to sing your favorite pop song, the likelihood is that you would sing it at very near the right tempo and in very near the right key, even if you’re not a professional singer. It’s the nature of memory in general and musical memory in particular that it has this accuracy.

The third thing has to do with knowledge representation. There is something special about music that allows us to encode information. For tens of thousands of years before humans had writing, they still had important information they needed to preserve, to pass on to their children, to share. Anthropology has taught us that most of this information is encapsulated in song. I’m talking about survival information: which plants are poisonous and which aren’t, how you treat a wound so that it won’t become infected, don’t drink from that well over there. Our ancestors discovered that if they set the words to music they were easier to remember. The internal constraints of music—the meter, the accent structure—not to mention poetic elements like alliteration and rhyme, limit the possible words that will fit.

Almost every child learns the alphabet through a song. We learn the body parts. You put your right foot in, you put your right foot out, you shake it all about; you do the Hokey Pokey. That is what it’s all about.

Consciousness is not a thing in the brain that information is poured into. It’s the struggle of different circuits to hold the stage for a second.

Zimmer: We asked DISCOVER readers to submit questions, and we got a great one: “Where is consciousness in the brain?”
Michael Gazzaniga: The brain is a vastly parallel distributed system. There are specializations throughout the brain that carry out particular tasks. The consciousness trick is that any particular mental state you might be in is enabled by neural circuits specific to that state. That sounds fancy, so let me break it down into a clinical example.

For years I’ve studied patients who have had their brain hemispheres divided in an effort to control epilepsy. This results in people who can speak and talk and think out of the left hemisphere but who are now disconnected from the right. The right hemisphere does not speak, as a rule, and has very limited cognitive capacities. The overriding finding from studying these patients is that the left brain doesn’t seem to miss the right.

But after the surgery, if these patients are looking right at you, they can’t see the right half of your face. Yet they never mention it. They never see it as a problem. It never comes into their mind. So you realize that maybe the consciousness about that half of space is actually localized in the hemisphere that is now disconnected. It isn’t even a concept to the other hemisphere, the one that is doing the talking.

All of these circuits that are distributed throughout the brain allow for what we call conscious experience. I like to think of it as being like a pipe organ. When one note is playing, that’s what you’re conscious about. Then the next note starts playing, and that’s what you’re conscious about. These things come on and off constantly, and there’s this appearance of unity to it all, but in fact it’s each of these separate circuit systems being enabled and being expressed in a particular moment in time. Consciousness is not a thing in the brain that information gets poured into and you’re aware of it. It’s the constant struggle of all these circuits to come up to the top and hold the stage for that second.

We feel as if we can see what other people are thinking. In fact, there’s a mechanism ?in the brain generating these inferences and perceptions.

Zimmer: And yet, as central as consciousness is to our sense of being human, we mostly experience it in the context of our other quintessential trait, sociability. We speak to each other with language and then start to have a sense of what other people are thinking. Rebecca, you’re involved in this fast-moving area of research. How are we beginning to explore the social brain?
Rebecca Saxe: Through most of the short history of neuroscience, what we’ve been able to study are the kinds of things that brains in general do—the things that brains of all kinds of animals can do. Studying these functions in nonhuman animals has given us the most detail about how neurons get put together to do complex functions because we can really look, neuron by neuron, at how vision gets put together, how motor control gets put together.

This has led to a focus on those functions that our brains share with other animals. But for any parent watching a child grow up, these are not the most striking functions. Although it’s fabulous when kids start to walk, what’s amazing is to watch a kid start to interact socially.