I was fortunate enough be able to take an altitude chamber course a number of years ago.
I wish these were more available for civilians.
They showed us the following video as part of that course...
What stands out to me is the "Sir, you are going to die, put on your mask!!" (paraphrased I am sure), and his response is "4 of spades"
I think this brain going into a loop is a fairly common exterior symptom of hypoxia, the dangerous part is the victim (??) doesn't even realize they are doing it.
I am aware of another accident last year where an experienced pilot encountered a hypoxia event (mechanical issue) and continued on a course a line (fortunately he was in a slow descent) until he was at a location that he had no other option but to ditch the aircraft.
Afterwards he remembered doing it, but was at a total loss to explain why he did it, it wasn't until a couple months after the accident the likely issue with the O2 system was discovered.
Brian
CFIIG