I am just going to ramble incoherently a bit now, I have some rich, if vague nostalgic memories from childhood and I can even remember alot of my dreams from then, but the interesting thing is that I can bend these memories with my imagination, imagine other alternate reality memories and these have an equal footing with the actual memories I experience. So I can look back and "feel" nostalgic for a past I never firsthand experienced. Is this some kind of Si Ne thing where (Si) is having these rich memories to go by and then I use my imagination(Ne) to create other possibilities/alternative realties for my past?
For the notion I get from Ni, it seems to want to look beyond the surface to what is really going on behind the scences, like reality is not exactly what it appears to be just going by your intial impression/5 senses, where as Se just accepts the present experience for what it is, a rose is a rose, a crackhead banging on your door at four in the morning is a crackhead banging on your door at 4 in the morning*. I think in this way it is kind of similar to Ti as Ti wants to look at the structural blueprint(and it helps if it can be simple and universal too) behind the surface phenomena and this "blueprint" probably won't be clearly obvious to the uninformed.
For instance Einstien's quest to find a simple, elegant theory of everything that can explain the behaviour of the smallest particle to the motions of the largest galaxies, "simple, beautiful concise equation". I think where Ti and Ni might differ is that Ti is working closely with one(or a few) predefined meanings/principles/whatever and branching off from there and Ni just constantly switches its meanings and having a clearly defined meaning and sticking to that might hinder Ni from shifting the user's perspective to other meanings. Ne could branch off with numerous possibilities and implications from the concise Ti starting point/idea, could the Ti+Ne combo mimic Ni in certain situations? Sometimes I have those "aha" moments too, especially if I'm walking somewhere(I have came up with entire storylines and plots unexpectly/random while walking to the store), could Ne have aha moments like Ni?
*Oh, this has never happened to me if you are getting that idea, I ain't in no ghettoooooo