We’ve said it before and we will say it again: The brains of teenagers are fundamentally different from adult brains.
One of the biggest differences is in the development of myelin.
As you might remember from our last article, myelin is a fat coating that develops along nerve cells and speeds up the signals the nerve transmits. A fully myelinated nerve cell transmits its signal 100 times faster. Obviously, that brings a huge advantage, but how does myelin develop?
The simple answer is through use. There are literally billions of connections between nerve cells in our brain, and these connections form circuits that allow different parts of the brain to communicate with each other. Each time one of those circuits is used, it develops a little more myelin around itself, just like muscles develop in response to exercise. The more you use a particular nerve circuit, the faster it becomes.
It takes a lot of time for myelin to fully develop, as we can see from this image. The lighter colours represent areas of lower myelin while the darker colours show more complete development of myelin along the nerves. If we could see a cross-section of the brain, we would see that even at age 20, there are large portions of the brain that are not fully developed.