Brain tissue may be fuel for marathon runners

No probably not, except inasmuch as hallucinations are a known side effect of exhaustion.

Children for example are known to not have much/any (people who actually know shit step in and select right answer) but aren't constantly tripping balls.

My understanding of how stuff like hallucinations normally happen is the brain can be though to be a series of networks doing their own thing and relaying information between each other. Some networks try to pattern match: "I just heard something, my name is often a heard thing shaped approximately like this. This is my name!" and others filter the results of these matches for truthiness by synthesis with a bunch of crap: "we're in the middle of a highway. who the fuck is going to be calling out our name? you misheard the radio".

those other networks for reasons I don't know are vulnerable to disruption. Like when we're tired, or taking psychedelics, or have a brain tumour or whatever.