The medium in which memories are stored isn't exactly digital or isolated from stimulus. If something disturbs the memory, or the memory gets taken over by some other shit you learn, then I imagine the memory will take on another shape. So in essence, you are recalling a current snapshot of the memory. But the more often you recall it, the more recent and solidified/consolidated the memory will be. Just like muscle memory. The brain will make strong connections for things it uses often, because it is implied that those things are important for survival.

I'm no expert(!) but I imagine this is how it works.