Thanks so much! Appreciate the kind words and the feedback.
There is a "core" memory for each section that relies on you unlocking some smaller memories. If you go over the core memory before you've unlocked it you would see a tiny lock with two of those diamond "coins". Good to know that it's not super intuitive of what they do if you haven't seen the lock first, thanks for the feedback!
As you continue through the story... check the resemblance of your character to one of the other characters in the memories ;)