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How are Developments in Neurobiology Changing our View of Children? 6 MRI Reveals the Brain's Mechanisms

Dialogue between Noboru Kobayashi and Toshiyuki Sawaguchi

6 MRI Reveals the Brain's Mechanisms

Kobayashi: Many books on neurobiology were published starting in the 1980s. They included books on the brain, genetics, and primates. Was this a major trend or turning point?

Sawaguchi: In the field of evolutionary biology, the study of human evolution has made remarkable progress in the last decade. In neurobiology, we have long had a map of brain functions, and this has become more precise and detailed over time. This is due to technological progress, particularly to PET (Positron Emission Tomography) and MRI (Magnetic Resonance Imaging). Before that, we had to look at the brain of a monkey to study how the brain develops, and that was not exactly accurate. Thanks to MRI, we are now able to directly image the brain of a child.

By looking at the brains of children, we have learned that the brain changes more dynamically that we had ever supposed. Before we could only confirm brain function distribution statically when a part of the brain was damaged. It was not possible to follow the brain development dynamically. But we have now learned from MRI that the age of six is most critical. According to an article in the U.S. journal, "Science," the prefrontal association cortex shows rapid growth when children are about six. Experts can't keep up with the enormous amount of research and all the discoveries that are taking place around the world.

As the structure of the human brain and the process of human evolution gradually become clear, methods of child rearing should also change. I believe that we will be seeing more theories of child-rearing backed by biology as advocated by you, Dr. Kobayashi.

However, the individual differences in the brain are much greater than we had thought, and this is one problem we face. We want to attain some sort of universality, but there are individual differences, and we want to understand the principle behind these individual differences at this point.

Kobayashi: What do you mean by wanting to understand the principle behind individual differences?

Sawaguchi: We want to know how these individual differences come to exist.

Kobayashi: You mean why such individual differences are necessary?

Sawaguchi: Individual differences probably arose because creating variation benefits evolution. I think that genes also show this range of variation. Since the brain is also a kind of organ and genetically formed, it is possible to imagine that there would be variation. However, we don't know the process by which these variations arise.

Kobayashi: I see.

Sawaguchi: At present, we are approaching this by looking at the physical matter that transmits information in the nervous system. We know there is considerable genetic variation in the physical matter that makes up the nervous system.

For example, there is variation in the number of repetitive sequences in genes related to serotinin, and this leads to differences in emotional stability. These differences are also apparent in groups. Compared to Europeans and Americans, Japanese people are said to be lacking in stability. We can tell if a person is prone to depression or emotional stability by examining these repetitive sequences.

There is also variation in the dopamine D-4 receptor. It has been found that a person with a large number of D-4 receptors is drawn to new things. In other words, they are sensation-seeking or novelty-seeking. This means that variation at the genetic level leads to variation in personality. Attention-deficit hyperactivity disorder may also be a genetic irregularity involving noradrenaline, serotinin, or dopamine or a slight variation.

Apart from the question whether it will be good or bad, it may be possible in the future to decide how to educate a child by looking at his or her genes and the physical matter that transmits information in the nervous system. However, when we talk of systems, they don't correspond to genes on a one-to-one basis so there are many aspects that are still unclear.

Kobayashi: Even if the brain's basic genetic framework is the same and it is genetically controlled in the same way, it is still greatly affected by the environment.

Sawaguchi: Yes, it is not easy to tell what kind of environment will result in a certain kind of nervous system in the end.

Kobayashi: But at least we know for a fact that rather than the current education system that educates all children in a uniform way, one that gives them more freedom to grow would be better. That doesn't require considering genetic makeup.

Sawaguchi: Yes, creating a wide variation is part of the nature of evolution and living beings.


Pediatrician and Director, CRN
Born in Tokyo in 1927. Doctor of Medicine, Faculty of Medicine, The University of Tokyo, 1954. Books include Human Science, Kodomo wa mirai de aru (Children are Our Future), Kodomogaku, Sodatsu sodateru fureai no kosodate (Reciprocal Development Through Child-raising).

Toshiyuki SAWAGUCHI, Ph.D.
Professor of Neurobiology, Hokkaido University School of Medicine
Born in Tokyo in 1959. Majored in biology, Faculty of Science, Hokkaido University. Doctor of Science, Kyoto University. Specializes in cognitive neuroscience and primatology. Research interests include mechanisms within the brain related to thought and self and evolution of the brain and cognitive function. Publications include Wagamama na no (The Selfish Brain), Watakushi wa no no doko ni iru no ka? (Where is the Self in the Brain?), and Yoji kyoiku to no (Early Childhood Education and the Brain).
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