I think it's got more to do with maintenance, not temperature. From my own experience, lack of sleep leads quickly to "spinning my wheels" as my thought proces

I think it's got more to do with maintenance, not temperature. From my own experience, lack of sleep leads quickly to "spinning my wheels" as my thought process becomes bogged down to the point of not being able to "finish a thought". At some point the brain needs to clean out molecular by-products, replenish stores of needed neurotransmitters, I'm sure at some level there's some garbage collection going on, maybe mark and sweep everything out of short term memory that's been moved to long term. Maybe dreaming actively helps us to connect disparate thoughts and concepts into some kind of of aggregate. Some of my best thinking comes easily after a great nights sleep...