I'm kinda with pensieve on this, with the current state of research.
The neurological investigations are pretty crude, and we don't even really know what white matter does, and it all seems like phrenology.
I think the descriptions by aspies & auties show patterns that neurologists won't be able to identify in actual brain tests for another decade or more, and eventually the spectrum will broaden into multiple dimensions with lots of sub-sets. But there seems to be a strong genetic factor. The environment can have a lot to do with whether a characteristic becomes an impairment or not.
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"Yeah, I've always been myself, even when I was ill.
Only now I seem myself. And that's the important thing.
I have remembered how to seem."
-The Madness of King George