Well, I finally got around to listening to this, and it was worth my time.
A good story, told well. Excellent job, Mat.
As for the mother's brain discussion: at the end there it was mentioned that the Nots were thinking about maybe one day reviving a human brain, so maybe it is possible.
I have to say that throughout the entire story I debated whether they were called "Naughts" or "Nots" or "Knots". All of those options made sense at least at one point in the story, and I still prefer Naughts over Nots. There is a subtle difference in meaning, one that I can't really put my finger on, but it seems more apt in my mind.
Also, Eytanz, you mentioned that you didn't understand Dream's decision to return to the mainland (I'm too lazy to find the quote). The way I understood it, there was no actual rationalization involved. As you so succinctly put it, she is a creature of instinct. Instinct and habit rule her world. She completely disregards any information, however interesting, as not important if it was not relevant to her. She is the ultimate pragmatist. She feels strange and out of place actually thinking and planning and having ideas, she says as much to Mercer.
So why did she go back to the mainland? Because she is a creature of instinct and habit. She could never truly be herself on the island. The small area argument was a rationalization, and a weak one. She has to go back to the mainland, otherwise she will die. Her body might live, but not her spirit, not what makes her "her".
On some level, Mercer was exactly the same way. He couldn't change his ways if he wanted to. The only difference is that he was aware of his personality freezing. He denies its affect on him, but he is aware of it.
That raises an interesting question: how mutable is an indestructible brain? Clearly they are capable of forming some new connections, otherwise they couldn't learn anything. But it must be difficult. In our universe it is hard enough for us to change our habits. Imagine how hard it would be if you had spent thousands of years developing those habits, on top of the fact that your brain finds it very difficult to change its wiring, to form new connections.