Some great fictional stories are opening by amnesia (but rather not alzheimer ) , im thinking about those parralles playing Disco Elysium (protagonist start with no memory after self inflicted chemical damage) .
This is tragedy of course in reall life, but in fiction it gives possibility to learn world by reader/player/viewer at same pace as main character.
Examples :
"Nine princess of Amber" - Roger Zelazny's first volume of Amber chronicles.
Harry Angel movie based on novel by William Hjorstberg "Falling Angel"
Planescape Torment
True Detective (Season 3) ...
also question "who I am" is rather fundamental classic one even for healthy person.
Thank ypu for shaing this entry . : ) anyhow , seems like I've needed some excuse to put those examples somewhere.