A Highly Predictable Trajectory of Brain Development

The trajectory of brain development through childhood is so predictable that scientists can estimate a child's age within a year, using brain structure revealed in brain scans.

The group performed structural magnetic resonance imaging (MRI) on the young peoples' brains. The images showed features such as the size of each brain region, the level of connectivity between neurons, and how much white matter was insulating the neurons. By putting all these features together in an algorithm, the researchers formed a picture of what the average brain looks like at each year of childhood. Different areas and features of the brain varied between individuals, but the algorithm correctly predicted a child's age to within a year in 92 per cent of cases. Brown says this suggests that brain anatomy is a developmental clock of which we were unaware. _NewScientist

Journal Abstract from Current Biology

Brain development begins early, inside the womb. After birth the brain continues to add neurons and connections rapidly, then begins to prune back and refine neuronal connections in the toddler years.

The pattern of brain myelination -- or the adding of insulation to nerve fibres -- occurs from the back of the brain to the front of the brain, over a period of between 20 and 30 years. Teenagers lack full development and use of the pre-frontal lobes of the brain, for example, which contributes to impulsivity and lack of sound judgment.

As new structures and connections grow and mature, the developing brain passes through "critical developmental periods," which seem to allow especially rapid skills formation for the particular circuits which mature, or come online. In other words, newly functional brain circuits appear to be particularly "plastic" when they first develop and mature.

Understanding this trajectory of brain development should help anyone who deals with children to see that children are not simply "little adults." Depending upon the age, children are quite different creatures altogether than an adult's daily work or recreational companions.

Brain imaging is providing powerful tools to understand the dynamics of brain structure and brain function. We should expect many of our conventional prejudices about the brain to be overturned in the near future.