Personally, I always thought that this head sensitivity is a psychological factor, meaning that your mind reacts very anxious to any movement of the brain. But after I got rid of this anxiety, i still experience that I can feel some faster movements, without worrying about it. So I would expect that there is indeed a physical influence as well on the nerves in the brain, that causes this feelings. Unless no one is able to look inside, one cannot really tell where this comes from.