The bottom pictures was the start of our brain discussion in 2nd grade. We read "My Fantastic Elastic Brain" and discussed brain highways. Using tofu, students got to "carve" their own brain highways into their model brains. We discussed how some things are deep, long highways because we do them often and it is repeated. Some things are the opposite, and we may not do them or practice them as often. For this, we have smaller brain highways.
I use "brain highways" as a term to teach students that you have to train your brain properly in order to get the response or reaction they desire. For example, if we continuously do a routine incorrectly because we think it's comical, it will start to carve a brain highway that teaches our brain to do something we don't want it to. In other words, students understand that they are in charge of creating their own brain highways, and how they can change past reactions and responses, aka Growth Mindset.