How Do Brains of Children Grow?, Nature

Complexity Digest

How does a complex organ like a brain grow? That is a very difficult question since the growth is certainly not a uniform change in size but also involves many developmental changes. Thompson et al. used state of the art computational tools fro continuum mechanics that allowed them to track in considerable detail the dramatic changes that a human brain undergoes from the age of three to almost grown-up age of fifteen. The basic strategy of the researchers involved "tensor" mapping. A tensor is a mathematical object like a point and a vector. While a point only has a position, a vector additionally has a direction attached to a point. Analogously a tensor attaches each point in the developing brain independent directions of change and growth that will be tracked on a computer.

The researchers obtained their data from repeated magnetic resonance imaging (MRI) that provides a three-dimensional, high-resolution image of the brain during different developmental stages. They found that one of the most striking features is a growth in the structure that connects the two brain hemispheres (corpus callosum). It does not grow uniformly but starts growing in the front and then the center of growth moves more towards the back of the head. Brain areas that are related to association and language slow down in their growth after puberty. During the same time the amount of gray matter deep inside the brain is reduced. At young ages (3-6 years) fastest growth takes place in areas corresponding to planning and decision making.

• Growth Patterns In The Developing Brain Detected By Using Continuum Mechanical Tensor Maps, Paul M. Thompson, Jay N. Giedd, Roger P. Woods, David MacDonald, Alan C. Evans, Arthur W. Toga, Nature 404: 190-193 (2000)