M: Your work implies that the brain and nervous system is physically molding (adapting) itself to the environment moment to moment. What does that mean?
D: One can say that the brain is responding to the external environment and to the internal environment at all times. The nerve cells are designed to receive stimuli, store information and transmit information. Every cell receives input from both the internal and the external environment at all times. And we've shown that we can (physically) change the brain by changing the internal and external environments at any age. Admittedly the brain is growing most rapidly right after birth. This explosive development of fibers receives stimuli and grows branches. And this is what is happening in those first years after birth, the development of the branches which are the main receptive portion of the cell, and forming connections with other cells.
M: The number of potential connections are vast.
D: There are a hundred billion nerve cells in a brain and many of those nerve cell can make connections with thousands of others. A single nerve cell can receive as much input from about 20,000 other cells, so you think of the computation that goes on in a single cell before it fires. The interaction of the environment with this system is extremely dynamic and important.
M: What is the relationship between the development of these connections and what we call learning?
D: Learning is essentially the formation of these new connections. We know that protein synthesis takes place during learning and nerve cells are made of protein. So we are growing these branches while we're learning. We've been able to show this in the laboratory with rats learning to solve mazes. We measure the cells afterwards and find more branches on those cells that have been challenged and are learning, versus those cells that are inactive.
M: One of the things that seemed rather startling about your work is the implication that changing environmental conditions associated with childhood can and do alter the physical development of the brain. This was a major emphasis of the Book Endangered Minds, by Jane Healy.
D: She's expressing some of our concerns with the modern day child who sits in front of a television for hours. Even though we know some learning is taking place, it's the passivity for most children that is so detrimental. In the laboratory it's been shown that only the rats that are playing show changes in the brain that we can measure. The rats that are sitting and watching the others play, their brains don't change. We think it's a total activity of the body, both physical and mental, that bring about these changes.
M: Most of us think that we are born with a brain and that its capacities are, more or less hard wired and fixed.
D: When we first presented our work way back in 1964, I remember one man stood up and said, "I'm sorry, but the brain cannot change." And I said, "I'm sorry but we've been able to show that it does." Now, in the scientific world, most people say yes, the brains like a muscle. When you use it, it develops larger nerve cells and that includes the cell body and all of its branches and connections.
M: What are the implications of your research when we look at the unprecedented changes that are occurring in childhood today?
D: We live in a multi-sensory environment and the brain is designed to receive many types of sensations. When it is developing so fast, we should be giving it the opportunity to utilize this kind of input, rather than single tract. I think it's very important, as we watch modern technology coming in, that might focus children in single channels, that we develop whole factions. We have taste, we have sight, hearing, multi-sensory, and we need this whole cortex to grow and develop so that it's ready to handle the problems of this complex world, rather than give them narrow focused learning.