This topic really interests me. I've tried to catch some of those thoughts as I'm falling asleep, but any time I examine one it falls apart. It's like the train of thought is impossible to reconstruct logically. It's not even as if it's just a chain of unrelated words or symbols; at the time of thinking there definitely seems to be some sort of semantic linkage between the constituent concepts.

I actually agree that sleep deprivation could bring this thought style closer to the waking state. There have been rough mornings after a night of no sleep that this sort of thinking has started to creep into my head. Never as free-flowing or bizarre, though. When I start to notice it, I usually just take it as a sign I should get some sleep- and then do so.