Does general anaesthesia switch experience off, or only the memory of it?
Last month, a patient I was interpreting for asked before surgery whether she would "be there" during the operation and simply forget it, or whether she would not be there at all. I passed on the reassuring answer she was given. Afterwards I realised I didn't know if it was true.
Some anaesthetic drugs are powerfully amnesic. We know from rare cases of intraoperative awareness that a patient can be conscious and later remember. We also know, from studies where one arm is kept free of muscle relaxant, that some patients under general anaesthesia will respond to a spoken instruction during surgery and later recall nothing. That seems to show responsiveness, and perhaps experience, without memory.
So how would we ever know that experience was absent rather than unremembered? The obvious evidence, the patient's report, is exactly what amnesia removes. The less obvious evidence, brain measures, is calibrated against reports.
I would like several answers here, from philosophers and from clinicians. Is this a scientific question that better instruments will settle, a philosophical one about the limits of third-person evidence, or both? And does it matter morally if the experience is never remembered?