Since it has not been recorded in any way as of yet, I will record it.

Moon has different dialogue for greetings etc when she has less neurons, but strangely enough she can describe pearls perfectly well! It was a myth for some time that you needed at least 7 to get any lore pearl dialogue, but as it would turn out you only need 1 neuron total. That's it. Moon says exactly the same things as if she had 5 or more.

If you eat all 5 neurons however, you're out of luck. Regular neurons will not revive moon, and she obviously can't read any pearls after they're all gone. Strangely enough though, she still moves her arm to pet you after death. ¯\_(ツ)_/¯