Not all of you read Maggie's Farm, and I wanted to make sure you saw this from Slate Star Codex. My wife and I both have some Asperger-y traits, I along the OCD side of things and she along the social cue side, and this reflects in one of our sons. Whether my sleep movement disorders are related I don't know, but I have always thought so. The odd sustained focus to the exclusion of other input while awake is very similar to the odd sustained focus of dreaming.
Of course, I may be just making up a story in explanation that has no basis in reality.