The methods that affect the brain are none other than those few: personal emotional factors, external stimuli, chemical agents, and some form of energy affecting the brain.
Personal emotional factors can be ruled out, as although Li Xiu is trapped here, his emotions are very stable, and very few things can cause significant emotional fluctuations for him.
External stimuli have also not been discovered as anything that could stimulate him; the room is empty, and there won't be a donkey kicking him in the head. It's purely environmental factors, which basically can't affect Li Xiu.
Regarding chemical agents, Li Xiu is not too sure. There are many gases that are difficult for the human eye to discern, and he might not even see them. Currently, he has no sense of touch or smell, making it probably difficult to discover.
