The actions we take can literally expand or contract different regions of the brain, firing up circuits or tamping them down. The more you ask your brain to do, the more cortical space it sets up to handle the new tasks. It responds by forging stronger connections in circuits that underlie the desired behavior or thought and weakening the connections in others. Thus, what you do and what you think, see, or feel is mirrored in the size of your respective brain regions and the connections your brain forms to accommodate your needs.