They do hurt the brain after awhile, especially when you're trying make it all look like something.  You've probably seen those ones I do where the top half looks like a face, and the bottom half looks like a different face, yet when flipped it's the exact same image.  Those ones hurt the brain. 

Dirtbikes don't hurt the brain unless I forget to tighten the strap for my helmet.  I will enjoy it!