Before they have surgery, participants will either sit or lie down, with their head in a helmet covering the entire head, with openings for the eyes and ears. Brain magnetic fields will be recorded with a 275-channel OMEGA system. Throughout the session, visual and two-way audio communication will be maintained with the patient. Acquiring data from the participant will be conducted during several sessions, each lasting from 10 to 60 minutes, not exceeding a total of 120 minutes. If the first recording is not of sufficient quality, the patient may have it repeated once or twice.