Stay at school, don't do drugs, check your facts

So they can feel the cold knives and fingers touching their brain...

They usually use a local anesthetic, but because of the complexities of the brain its the only wau to know immediately if something is wrong or if one thing may affe ct another, such as removing pressure causes numbness in extremities or blindness ect

Fun fact: you wouldn't actually feel it if someone touched your brain, as there is no sense of touch on the surface of your brain