After consolidation, a memory is stable — until it is retrieved. Retrieval briefly re-opens the molecular machinery that originally encoded it. During this labile window, the memory can incorporate changes. Then it re-stabilizes, in whatever form it currently holds.
The most-accessed memories are the most frequently modified memories. The access history is not stored in the memory itself.
Elements struck through have drifted from the original. Each recall that reaches re-stabilization locks the current form in place.