There is a place in our brain which maintains our sense of BEFORE and AFTER while all of us ever live in is NOW.
This means Before is a fiction to some degree and so is After because of imperfect perception and imperfect memory.
Deja Vu is a hiccup in that time-tracking.
(Did you ever see the movie MEMENTO?)
Hypnosis could be a brain/mind hack to the authentication safeguard in our head distinguishing REAL from UNreal. This alternate version of events is uncanny because it is a distortion image rather than a direct imprint.
All this is untrained speculation on my part.