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October 16, 2000
Every month, the Harvard Graduate School of Education invites educators, researchers, community activists, and policymakers from across the country to talk about key issues in schools and school reform. We are pleased to be able to provide you with an edited transcript of some of these forums. Below is an edited transcript of a talk that took place at the Harvard Graduate School of Education on October 16, 2000.
For easier reading, we have divided the transcript into the following sections:
Introduction by Kurt Fischer, Director of Mind, Brain, and Education Program, HGSE
Remarks by Marion Diamond, Professor at UC-Berkeley
Questions and remarks from the graduate student panel
Questions and remarks from the audience
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INTRODUCTION BY KURT FISCHER
I'm Kurt Fischer, director of the Mind, Brain, and Education program here at the Harvard Graduate School of Education. It's a special pleasure for us to have Marion Diamond here. Marion is one of the great leaders in research and development in the field of neuroscience, especially plasticity, or the effects of the environment on the development and growth of the brain. Marion has anticipated where we are going now in the field and where we've come over the last 30 or 40 years. Plasticity is the rage today in developmental neuroscience, but she may tell you that when she started out, it wasn't. I'm not going to say much about Dr. Diamond's accomplishments. There are many of them, not only in biology but also in science education. She was director of the Lawrence Hall of Science, among other things, at the University of California at Berkeley. Dr. Diamond is going to talk to us, as I said, about her work with the ever-changing brain, then we're going to have a discussion, led primarily by three of our doctoral students in Mind, Brain and Education. So I present to you Professor Marion Diamond.
REMARKS BY MARION DIAMOND
Well, it's a great pleasure and an honor to be here. Thank you very much for inviting me and allowing me to get to know the young students here so we can work together this evening. I love being with the students. I consider them our young, precious colleagues.
I have two introductions. I wasn't quite sure whether I had the courage to use the first one, but I decided I would because science should be fun. So first, I'd like to thank all of our brains for inviting me for this rare occasion for brains to be studying themselves. [laughter] Because that's really what we're doing isn't it? Cells studying themselves? How many of you think about your brains? I mean, seriously, what controls that behind your eyes? Do you ever think about it? Can you picture a brain in there or do you picture something back here? Do we have the sensory mechanism to imagine our own brains within our own skulls? You can picture your heart, right? You know where it is. You know where your bones and muscles are, but how about your brain? Do we have the sensory mechanisms for our brain, really for sense and smell? Something to think about.
If you transplant the brain, you transplant the person. He can get a new heart and Kurt will still be Kurt; if he gets new kidneys, he'll still be Kurt. But transplant the brain and you transplant the person. You are your brain. So you can see why it fascinates all of us.
When I was a little girl, I'd look at people and say, "What's going on behind your eyes?" But we didn't have MRIs; we didn't have CAT scans; I didn't know what was going on in there. Of course, we've been studying brains for a long time. Before 1960, scientists considered the brain to be immutable and subject only to genetic control, but investigators had speculated that environmental influences might alter brain structure. This was pure speculation, though. However, during the early 1960s two research laboratories, one at Berkeley and one at Harvard--isn't that appropriate for this evening?--proved that the brain could be experientially altered. Since this time, brain plasticity, meaning structural and chemical adaptability due to environmental input, has become a common theme amongst neuroscientists, educators, and others. All of us are beginning to be interested in brains. We've seen Mars, we've seen the depths of our ocean, but how much do we really know about what is going on within our heads? It's sort of the last frontier.
We had the fun of finding that the brain's anatomical modifications, due to enriched or impoverished conditions, can be demonstrated at any age. That was extremely encouraging for all of us.
How many of you know about the cerebral cortex? The cerebral cortex is a few millimeters of neural tissue that covers your large cerebral hemispheres. Your cerebral hemispheres account for 85 percent of your brain and are covered with a thin mantle of cells that have the capacity to send man to the moon. I sometimes tell my students that they have the capacity to build the Golden Gate Bridge. When you stand on that bridge and think that little protoplasmic masses designed it, you give the brain the credit it deserves. It truly is phenomenal. So we will see that it is an ever-changing entity, powerfully shaped by our experiences before birth.
Let me offer a few slides. I'm only going to show five slides because we want to hear from the students. These slides will demonstrate how statements about how the brain can change have come about. So we'll start with what we call our enriched and impoverished environments, which we designed at Berkeley way back in the early 1960s, to show that we could put rats in different kinds of living conditions and change the structure of the brain. We have twelve rats living in a large cage, roughly a yard square. In the cage we have objects with which they can interact; we simply call them toys. What is important is to change these objects. Rats, like people, become tired of the same input. If we put in some toys at the beginning of the experiment and leave the same ones in, we'll see the brain goes up with enrichment to begin with, but then comes right back down again. So it's essential to keep the toys new and challenging. In the upper right, one rat lives by himself. We call that an impoverished condition: no friends, no toys, equal food, equal access to food. So the question we ask is this: With impoverishment, does the brain shrink, compared to a standard, and with enrichment does it increase?
Now, you may be saying, "What in the world do I have in common with a rat?" But the basic structures are very similar. The rat has a medulla, a cerebellum, and cerebral hemispheres, just like you have. But when we take a cross section through the cerebral hemispheres, we have the cerebral cortex. In the rat's case, it's the outer millimeter of brain tissue. In your case, the frontal cortex is 4.5 millimeters, and the visual cortex is about one millimeter. The rat brain has not yet begun to fold. Yours is highly folded; if yours weren't folded, it would be 2.5 feet square, but folding is essential for it to fit into this skull.
The beauty of the rat brain, for our purposes, with a basic cerebral cortex made up of two kinds of cells, is that we can measure it so easily. All we have to do is take slices through the brain, and we blow them up large so we can take measurements directly on the thickness of the cortex. Later we count the cells in the cortex: we count their branches, we count their synapses, we find out what kinds of changes have occurred due to experience. The first thing we do is just measure the thickness--very simple. If we don't find a thickness change, we don't go in and do all the microscopic measurements. But we did find that with enrichment it grew, and with impoverishment, it shrank. So then we go in and measure the blood vessels, the capillaries. The small blood vessels increased their diameter with enrichment, bringing more blood to the brain. With impoverishment, they shrank.
[Describing slide] This is a nerve cell in the cerebral cortex. It's increased its surface area by forming branches. It starts like this: As it gets stimulated, it grows branches and the cell body increases, the liquid increases and, equally as important, the support cells. The second set of cells in the brain are glial cells. (Glia in Latin means glue. Early anatomists thought that the glial cells glued the nerve cells together; that's why they were called glial cells.) But we now know that they are very dynamic support cells, both metabolic and structural support cells. So with enrichment, you get more glial cells. With impoverishment, you lose them. This is why we studied Einstein's brain, because we predicted he would have more glial cells per neuron in the most highly developed part, his cerebral cortex. We found he had significantly more glial cells in his interior left parietal cortex. And we had predicted that these would be areas where it might occur. So what am I saying? We get more glial cells with enrichment; we lose glial cells with impoverishment. So it's that basic principle: use it or lose it, very simply.
Surely we'd shown that the young brain can change very readily. Everybody could anticipate that. Then we tried the middle-aged brain, with 600-day-old rats, the equivalent to 60-year-old people. We put half the rats in enrichment and half in non-enrichment. Still, at 600 days, we were showing that with enrichment we had bigger dendrites and longer dendrites. With impoverishment, nothing changed.
I was invited once to the German Academy of Sciences and I remember a German professor at the back of the audience saying, "Those 600-day-old animals aren't old animals! Our German rats live to be 800 days!" When we came back to Berkeley, however, we couldn't get our rats to live beyond 600 days. But talking to older people out in retirement homes I noticed one thing was missing: basic, simple TLC. People had sort of sent older people to their impoverished retirement homes and left them there. So we decided to give our rats TLC to get them to live beyond 600 days. We got those rats up to 776 days of age. At 904 days of age we took them out and measured their brains. Even at 900 days of age, we still could show changes from enrichment.
[Indicating new slide:] This is what we used to have in our medical texts. This was our fate with aging. We start with our healthy nerve cells and slowly, down, down, down until we lose all of our processes. This is what a terminal Alzheimer nerve cell looks like. It has lost its receptor services, which are those branches. But we now look at 60-year-old brains from healthy people and we find a full set of branches.
So I wanted to give you this introduction to show you what we've been looking at with our enriched experience and counteract the negativity that has surrounded earlier investigations about the potential of the brain. I find five key words that are meaningful at the present time to maintain a productive, useful brain. One, a healthy diet; two, exercise; three, challenge; four, newness; five, love. And with that, let's proceed to learn as much as possible from our students and find out what they have to share with us.
QUESTIONS AND REMARKS FROM THE GRADUATE STUDENT PANEL
KURT FISCHER: I'm going to introduce each of the students and then have them say a little bit about themselves. Before I do, though, I want to mention that Dr. Diamond has written this fabulous book called Magic Trees of the Mind, which describes a lot of this work in comprehensible terms and is related to issues of education and parenting.
MARION DIAMOND: Thank you very much.
KURT FISCHER: We'll start with Mary Helen Immordino-Yang.
MARY HELEN IMMORDINO-YANG: Hi, I'm Mary Helen Immordino-Yang. I'm a third-year doctoral student in human development and psychology. My interests are in the ways that neuroscience can be applied to education, specifically looking at the co-evolution of language and symbolic thinking in the brain, and the ways that can inform the kinds of thinking that we do as a species now. What can the evolution of the brain tell us about the constraints and the possibilities of the ways that we think now?
MIKE CONNELL: I'm Mike Connell. I'm entering my fourth year as a doctoral student in the human development and psychology program. My research interests are in computational models of the brain and mind. Whereas Dr. Diamond does experiments on rats and can actually do controlled experiments, we obviously can't do those on people where we cut their brains open and measure the mantle of their cortex. So we try to do through simulation what we can't actually do through biology. And I'm interested in understanding how we acquire knowledge, how it's represented in our brains, and then how it gets used. That's my sort of educational bench.
KIM SHERIDAN: I'm Kim Sheridan. I'm a third-year doctoral student in human development and psychology as well, and I'm interested in the development of aesthetic taste. I'm also interested in how I can look at neurological correlates, using functional neural imaging to look at some of the changes in the brain.
KURT FISCHER: So which of you would like to lead off?
MARY HELEN IMMORDINO-YANG: First, you can imagine that students are very impressed and in awe of the kinds of results that you get and very interested in what these can mean for people. Toward the end of the discussion, we'd like to work back around to education and, at the most practical level, what we can say about kids, the environments that we put them in, the ways that we love them, and things like that. But first, I guess, you showed us what an impoverished and an enriched environment looks like for a rat, and we're wondering if you might be able to say something about what such an environment might look like for a person. Briefly, what kinds of general characteristics it would have?
MARION DIAMOND: One has to begin by saying that no two human brains are identical, and that's one of the best lessons in self-respect we can teach children. We can get anybody to know that his or her brain is unique. So what's an enriched environment for one obviously isn't necessarily the same for another. We see just this bringing students to college. We have all the fields for them to go into, but there are two important things for an enriched environment. One is challenge: not just staying in the same environment that you've been staying in for a long time but increasing the intensity or the activity of that. If you're doing crossword puzzles, take harder crossword puzzles, not ones that you can just do in 20 minutes or five minutes or whatever. Challenge is important to the nervous system. We have a core of nerve cells going through the whole brain stem and spinal cord called the reticular formation: it samples what's coming in and gets bored with the same things. It likes newness, so newness and challenge are two important things for an enriched environment for humans.
KIM SHERIDAN: To follow up a little bit on what you're saying, it's sort of an intuitive idea that challenge is good for people. Education is based on that idea. But you're talking about an impoverished rat environment and an enriched rat environment, which, in actuality, is a lot less enriched than a wild rat's environment. How do we know that it's not just the brain coming up to a norm, rather than really a product of enrichment?
MARION DIAMOND: It's a very good question. The beauty of the experiments is that we can design our level of enrichment, so this is compared to a standard and an impoverished level. So whatever it means, it's more than you get with impoverishment. But I can say that we did try one winter in Berkeley to get more of an enriched environment by putting the rats in the local Berkeley hills. We built a fence around them and put it down so that they couldn't dig out, but they could dig into the ground. They were living essentially like feral rats. Well, unfortunately, designing the first experiment, we had our first really cold winter and they all froze. It's something you can't do here in Cambridge, but we thought we could there. Repeating that experiment, however, a little later in the spring, the rats did live and, sure enough, we found that their cortexes grew more than our laboratory encaged, enriched rats. So it's true, it is deprivation to some extent, but an experimental design gives us a clue that we can change that brain from a standard.
MIKE CONNELL: Staying on the same line, the notion of critical periods has been very important in a lot of areas of research, whether it's applying ridge order, vision, those sorts of things. What did this research do to that line of thinking or that paradigm?
MARION DIAMOND: Yes, we have critical periods for auditory mechanisms, for visual mechanisms, for language, meaning that, if you don't stimulate by a certain period, it may be too late to get the optimum conditions. We showed that if we put the rats in enriched environments before the eyes were open, we could change all sorts of parts of the brain, but not the visual cortex. So we needed that receptor, namely the eye, to be sensitive enough to send the stimulus back to the visual cortex for it to respond. We were told, after this, that doctors were beginning to check eyes before children left the hospital, after they were born, to be sure the receptor is in optimum condition to take the information back to the visual cortex. So I think here's one case in which you would need to be certain that what's receiving the information is well enough established to carry it to the cerebral cortex, to give the information to it.
MARY HELEN IMMORDINO-YANG: When I was reading about the experiments of the rats being put in the different conditions, I sort of thought that the outcome depended on the condition that the rat was put in. But then I started to wonder, how do you see the role of the rat in that process? What's its interaction with the environment that's changing its brain? Is there a lot of individual variability in the ways different rats interact with these environments, and how do you see the rat's action on the environment as affecting its brain?
MARION DIAMOND: Let's take the rat solving a maze. First, we put him in the box and there's food in this corner. He's in this corner and he just runs right across, there are no barriers. Then you put one barrier in. He's got to learn to go around that barrier. Then you put another one in the next day. Pretty soon you have 19 different barriers. It's essentially a simple visual/spatial process. What do we find when we look at his brain? We slice it from front to back and we find back in the visual cortex, just one area responds. We get a six percent increase in the cortex in that one area. It's bilateral. It's very clear. It's a beautiful response. Whereas, if we put them in the enriched environment, where there's the sociability with 12 rats, there are new objects coming in. Every day they're getting something that's a little different type of stimulus. Then we change the whole mantle, we change the frontal cortex, we change the parietal cortex and the occipital cortex. So I always think, when raising children, it's terribly important to have a multiple-sensory environment to develop the whole cortex. I worry when we hear that children are sitting in front of a computer for eight hours a day. Here you have one kind of input coming in. It's like it was with the first challenge, changing the visual, spatial cortex, with a little bit of frontal. But if the child has a richer environment, we've changed the whole mantle rather than just one area with one type of task.
MARY HELEN IMMORDINO-YANG: So it seems like the brain changes are very task-specific, which could be interesting for education.
MARION DIAMOND: Yes.
MIKE CONNELL: This is related to that. Mary Helen was telling me about a school in California that I can only assume was inspired by your work. They decided they would provide an enriched educational environment and put in a lot of high-tech computers and things for the students. I guess they found no increases in their performance educationally. So can we go from this finding with the rats to kinds of knowledge that are uniquely human?
MARION DIAMOND: One possibility is that when we teach in school and we increase those dendrites, we send the children home and nobody continues to support them. I think parental involvement is key. It reminds me of these cases that I've heard of that are going on in New York state and in Texas where these young, vibrant people are coming in to teach the children. They teach them, but they involve the parents as well, so it's a continual stimulation. If they stay with the same toys, if they go home and there's no stimulation, then they all come back down again. They found this with Head Start, to my knowledge. They had this wonderful program where they enriched the children from age three to five, but then they went into urban-area elementary schools and the affects of the enrichment group diminished.
On the other hand, Berry Brazelton, who was our pediatrician when we were at Harvard 40 years ago, said later, while we were doing this work, "Marion, why don't you see what happens if you over-stimulate? What is the potential of this brain?" Well, normally we'd change the toys maybe once a day at most, in the daytime for our convenience. But then we decided, since rats are nocturnal animals, to change the toys at night when they're active. So the students came in and changed them at 7:00 at night, 8:00 at night, and 9:00 at night, for four nights for four weeks. We were really excited about this experiment. What was the potential? Were we going to have great big brains in there? We did not find significant changes when we bombarded them as we do our children today with so much input. When I teach my classes, I purposely don't use PowerPoint, I purposely write, give them time to think. By the time they leave the lecture hall, they should know the material, not go home and cram. Don't give them handouts; make them write it. It's the old-fashioned way, but it's for a learning purpose. I teach the medical students, so I just know that they're so overwhelmed and they don't remember it. They wait until they get through their first two years of being subjected to all this information, and then they get on to the clinics, and then they have time to associate with their learning and work with the material.
MARY HELEN IMMORDINO-YANG: Well, building on the idea of too much stimulation, one question we had planned to ask was about the wrong kind of stimulation. There's evidence that kids in certain kinds of abusive, especially physically abusive, environments can show supernormal precocious development--like very precocious language development. They can learn to speak faster than normal children and develop sort of fast reflexes to jump out of the way when someone who hits them comes toward them. And you might think that if you could look at these kids' brains, they actually would show more dendritic growth, more cell growth than normal children because of this sort of stressful environment that they're put in. I'm wondering how you might comment on that?
MARION DIAMOND: The beauty of rats is that we can design experiments for stress that we can't do with humans, and stress does decrease the cortex. If one gives the cortical steroids from the adrenal cortex, the cortex is stressed. So when I speak in classrooms, I tell teachers, "You've got to reduce the stress as much as possible, so you don't dampen and counteract your effect." But all of us need a little bit of stress to really think well. When the adrenaline is high, that's fine, the adrenaline's coming from the adrenal medulla, the cortical steroids are coming from the adrenal cortex--it's the same organ, but with different embryonic derived tissue, giving different hormones and having different effects. In fact, I was reviewing an article for the New England Journal of Medicine recently by somebody who was writing on stress and talking about the effects of stress on the brain. At no time did they address the issue of how much stress is good versus how much stress is bad. And that's what we need with all of this. How much enrichment is beneficial and how much is detrimental? That's where we need our common sense. As I always tell the students, the two most important sensory mechanisms in the brain are common sense and a sense of humor. And we don't know where either of them is.
MIKE CONNELL: Howard Gardner talks about crystallizing experiments. We have that "Aha!" Mihaly Csikszentmihalyi talks about, the flow state. Are there concomitant changes in the neurotransmitters to the brain that we could monitor and maybe even use to shape the way that we do what we do?
MARION DIAMOND: I think we could expand on the early work that we've done, just looking at the known transmitters. When we started working on this 40 years ago, there were only about five known neurotransmitters in the brain. Well, today I'm told there are some 70 neurotransmitters and neuromodulators. Imagine trying to monitor those for all of these conditions and all of these states. Phenomenal, but technology's getting there, so maybe we will do that. I just think it's amazing that any of us can think alike at any one moment when you consider the amount of neurochemical balance that goes on within our skulls. And I think if we taught racial tolerance from that point of view, if we taught sexual tolerance from that point of view, we'd all be more accepting. A forum like this will be held again 50 years from now, and you'll be up here and telling everybody what we've done and what we thought we could do back now.
KIM SHERIDAN: One of the things that really struck me about your work was that you had all these years of incredibly rich research exploring all the variables with rats and then, at the same time, we have even more variables to deal with when we're talking about the education of a child. And to think about taking your findings and applying them to educational research is such a daunting task, thinking of this incredible complexity. One of the theories that we are interested in is John Brewer's idea that cognitive psychology is a way of providing a bridge between neuroscience research, the kind that you're doing, and educational application. What do you think about that, or can you think of other ways that we can sort of bridge the findings to eventually apply it to education?
MARION DIAMOND: We hit tremendous barriers when we first showed that the brain could change. But you can use this in education. You can use the fact that no two human brains are alike in education. So you look at each individual and his learning or her learning capacity. Use some of the data that we have to date, and obviously more will be coming.
KIM SHERIDAN: It is a daunting task, though, and it seems to me there does need to be some sort of middle ground to interpret these results. I could easily interpret that more stimulation is better or I could just take whatever I generally think to be true about education and say, well, brain growth supports that.
KURT FISCHER: There's a lot of that in education; people sort of saying, this is brain-based education.
MARION DIAMOND: Every kind of education is brain-based. I can't understand their terminology. Somebody at UCLA is writing her thesis on this and she asked me about brain-based education. I said, "I don't know of any other kind." That's their terminology because they haven't studied brains.
KURT FISCHER: That's right.
MARION DIAMOND: That's the real problem that we face. There are too many people getting into this that have no knowledge about brains at all.
KURT FISCHER: That's why we have a new program in Mind, Brain, and Education. Now, we'd like some questions from the audience.
QUESTIONS AND REMARKS FROM THE AUDIENCE
AUDIENCE MEMBER: When I speak with lay people about your research, I allude to the studies of Einstein, and they say, "Well, how do you know he just didn't have more glial cells to begin with?" And I say, "We don't."
MARION DIAMOND: We don't, that's for sure. Well, we didn't have a baseline to start with, but we had only one Einstein brain. And fortunately, the way that it's preserved, about the only thing that one can do to quantify it under the microscope is the kind of thing we did.
AUDIENCE MEMBER: Thank you for the work with the older folks because people think that you get gray hair and this brain inside shrivels. They treat people past 60, 70, 80 as if they're feeble-minded. I asked one 89-year-old lady what was the worst part of being 89 and she said being treated like she was 89. She was still doing everything, that brain was lively. But we have a lot of education to do. It's the attitudes that we need to work with, so congratulations on what you're doing. It's wonderful.
AUDIENCE MEMBER: You were saying before that the cerebral cortex is the part that can change forever, as compared to the other parts of the brain; they're more hard-wired. Can you talk about, then, which activities are subject to this growth throughout the lifetime and which activities really aren't?
MARION DIAMOND: That's a very difficult question, because we don't know the answers to that; that's for the next generation to work out. It's too complex to give that an intelligent answer. The brain stem, for example, doesn't change as much. But they're now finding that the cerebellum does. I think the hind brain is more primitive than the forebrain, which is our cerebral hemisphere. So perhaps that is hard-wired because of its more basic functions--cardiovascular regulation, respiration, and so on--rather than the more esoteric functions that take place in the cerebral cortex. It's not a simple answer.
AUDIENCE MEMBER: Do you know anything about language?
MARION DIAMOND: Let's leave other people for language, I'm not a language specialist. Who wants to talk about language?
AUDIENCE MEMBER: Is language something that's modifiable throughout the lifetime?
KURT FISCHER: Much more modifiable than the myths in the world would suggest. Marion talked about myth. There's a myth of language to the effect that adults can't learn a new language. The evidence is basically that that's hogwash.
MARION DIAMOND: It's hogwash. It takes longer, but some people could do it very easily. Just like in childhood, some of us had trouble learning a second language, others did not. You watch these people coming in from Asia now who don't speak English at all and these young students are learning their language within six months. They're speaking English fluently at the university, and it's amazing. If their parents had the same challenge, how long would it take for them to do the same thing? Do they have the same motivation?
AUDIENCE MEMBER: I have a question with regard to the plasticity that you studied, the changes in the cerebral cortex with stimulation. When you stimulate that area of the brain or if you stimulate an individual, can you increase their intelligence?
MARION DIAMOND: I certainly think so, since intelligence comes from nerve cells, and nerve cells grow with use. But again, one has to define intelligence. We turn this over to Howard Gardner. When we were teaching in Africa, one of the medical students said, "We were told that you're more intelligent if you're north of the equator than south of the equator. Is that true?" And my answer was, "What's your definition of intelligence?" I'm sure there are things that you can do that I can't do, and there are things that I can do that you can't do.
AUDIENCE MEMBER: I was very interested in your comments on the relationship between immune function and cognitive stimulation. I work with a mostly autistic population. If you look at preschool and elementary school populations now, you'll see that one out of 500 students is autistic. Obviously if you look at the general population, it's not as frequent, but it does seem to be going up. Now, you're talking about environmental factors that impinge on intelligence. One of the hypotheses on why autism is increasing is toxicity, that there are really more toxins in the environment. Some of the factors seem to be the ingredients in vaccines or the giving of multiple vaccines, which seem to overwhelm the immune system, as well as the mercury that's in vaccines. Pharmaceutical companies are now considering decreasing the amount of mercury, which exceeds FDA levels if you give more than one vaccine at a time. And a lot of parents report that they see autistic symptoms in their children or that their children lose language or seem to develop or not develop after being given vaccines. That's not to say don't vaccinate, but some modifications seem to have to be made. I'm just wondering where the research is behind this.
MARION DIAMOND: I don't know. This is the first time I've heard this. This is very interesting to know, because I have heard that autism is increasing.
KURT FISCHER: In general, there's a lot of research you might know of on lead and cadmium poisoning and other heavy metals and that any level of those metals in the body is damaging to the brain. Is there one more question?
AUDIENCE MEMBER: I'd like to focus on the other end of the age spectrum. You hear a lot about prenatal stimulation with chords and music. What are your views on this?
MARION DIAMOND: Van de Carrr's work shows that, with prenatal stimulation, children are more advanced in certain areas such as music. To my knowledge, it's been quantified that they can hear at five months in utero, so I don't know if beginning things earlier than that extenuates the ability to hear early or not. We tried this with rats by enriching our pregnant rats, and we showed that we could change the cortex of those pups. But we should definitely worry about over-stimulation. Some people who don't have any brain training jump into this and are out teaching about using the brain, or producing musical belts for women to wear. Can you imagine? There's no place for that infant to grow. It just has to hear it all day long. Van de Carr, who promotes this, says no more than 10 minutes of music a day. It should be something reasonable for this little one, because it's getting all these sounds anyhow.
KURT FISCHER: Thank you.
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