If someone stuck a pin in your arm, you would experience pain. Surprisingly enough, though, if someone stuck a pin directly into your exposed cortex, you probably wouldn't consciously experience any discomfort at all. With certain minor exceptions, there simply are no pain receptors in the brain. (There are pain receptors in the membrane covering the brain, however.) Because brain tissue is insensitive to pain, patients undergoing brain surgery are often conscious, so they can help the doctor locate whatever damaged section might need to be treated. During such surgery, the doctor may stimulate various parts of the patient's cortex electrically and ask what the patient feels the moment the current is turned on.