My wife does these surgeries. I'm not going to ask her for journal citations on Christmas, but paraphrased answers: 1. You use electrodes to interfere with eac

My wife does these surgeries. I'm not going to ask her for journal citations on Christmas, but paraphrased answers: 1. You use electrodes to interfere with each piece they are are going to resect, and see if it interferes with the task they are having the patient perform. This is a mostly non-destructive way to test before doing something that damages the brain. It is not completely perfect for a bunch of complex reasons, but it works pretty well. 2. It's somewhat more complex than that (especially "the part of the brain that's responsible for that muscle memory"), but the goal is to identify the regions you want to avoid removing before you damage them. 3. "Becoming Hendrix" doesn't happen, but it's common for people to be able to perform the task in question better post-surgery than before. The reason for this is simple: you do these surgeries because the tumor is very close to the region whose function you want to preserve, and it tends to be interfering with the normal operation of that region already due to that proximity (if it wasn't interfering, you would try to delay surgery until it was). Removing the tumor removes that interference.