There's a pretty convincing theory that says that while we sleep, brain is processing signals from our internal organs instead of processing the sensory input.

There's a pretty convincing theory that says that while we sleep, brain is processing signals from our internal organs instead of processing the sensory input. Experimentors were triggering impulses in monkey stomach and seeing them activate some areas of the brain that are normally used in the cognitive process. That way brain inspects the organism and balances it's functions. One of the side effects of this theory is that our dreams are just an interpretation of these signals. Like your liver signals trigger some areas of the brain and that produces the weird imaginery we call dreams. Can't find the link to that paper right away.