Your brain works the same way any physical muscle does. If you want to make a certain muscle do something different, you want two things to happen: muscle fibers to increase in size and, muscle to use energy better. You need increased blood flow to the muscle and you need changes in the structure of the muscle cells – so it will use energy better. If you want to do this with your bicep you lift something heavy until you reach a point that feels difficult for you…it is new, beyond your comfort zone. Then you rest and the muscle says something like, “I had to do something today that was a little beyond my comfort zone. So, I’m going to remodel myself to make it easier. I’m going to predict that i’m going to have to do this again.” Then changes begin: the muscle cells get bigger and the muscle changes in a way that allows it to get more blood flow.