A long while back I had read a book by Chris Dolley called Resonance. It is, in retrospect, one of the best introductions to exactly how crazy-making gaslighting can be. Sadly, his next book was one I couldn't finish. No, that's not what was going on, but the utter sense of unreality the main character had was so well done that several people I know who'd dealt with Narc's and other cluster-B types literally could not get through the first chapter.
I'd also recently rewatched Ghost in the Shell, the original movie, which of course dealt with the question of how much of us is our personality, and how much is our memories?
So on a related note, I know someone with Alzheimers. It is utterly surreal. If you sit and think about it, it's crazy making for everybody.
The person has no idea why reality isn't matching up to their memories, or why much older strangers claim to be their kids. And it's no easier for those talking to them. Nothing is remembered, conversations repeating several times every few minutes. There are several specific time frames I'd seen her lock into repeatedly.
Which floored me when recently she flashed back to a point in time where she'd remembered getting the call her mother had died.
Keep in mind - she doesn't remember her mother has long passed on.
And if she flashes back to that time frame, she'll be remembering it, again, as if it is a brand new event.
And again. And again.
It's like being stuck in the movie Groundhog Day without knowing what day you would be in at any given moment, or any memory that you'd been there before. Sometimes reliving happy times, but also reliving grief, over and over, and many other events become startling, or dismaying because the people aren't who they're supposed to be.