Quote Originally Posted by Thor View Post
Here you are assuming that any hallucinatory proprioceptive experience will necessarily lead to body movement, but that's an invalid assumption. For example, just as you could be hallucinate a pink elephant hovering in the air in front of you, you could hallucinate raising your arm, but that doesn't mean your arm has to actually move (or it wouldn't be a hallucination, would it?). The same holds true for hallucinatory experiences in sleep, also known as dreams. So it shouldn't be a mystery that you can have "inhabited" NREM dreams without acting them out.

So why then is atonia necessary to keep you from acting out your dreams in REM sleep? Well, bear in mind that the brain in REM sleep works in a very different way than in NREM sleep. It's probably safe to say that the difference between REM and NREM is as big as the difference between NREM and wakefulness. Just because atonia is necessary in REM sleep, there is nothing that implies that it's necessary in NREM sleep; the brain just works in a different way.

That seems a bit woolly to me thor. That theory would apply only if NREM and REM dreams were similar.

For what I've read they are not. NREM dreams have clearly been described, by scientists, as thoughtlike or daydreaming.
Which in my mind is a more credible reason for not needing SP during NREM sleep.