ADDED: In the comments, Galvanized says:
How cool -- so the human brain defragments itself. Cognition is so interesting! I think that this is why a prof once told me that actually making lists and actually marking off obsolete items is important, as a visual boost to jog the brain to drop old items from memory. I believe that it works, too, since list-makers seem to be more together than the rest of us.
This reminds me of one of my favorite vids of animated poetry by poet Billy Collins: