Consciousness is often said to disappear in deep, dreamless sleep. We argue that this assumption is oversimplified. Unless dreamless sleep is defined as unconscious from the outset there are good empirical and theoretical reasons for saying that a range of different types of sleep experience, some of which are distinct from dreaming, can occur in all stages of sleep.
Sleep is NOTHING like death. You're still experiencing lots of stuff, you still very much have a sense of self, you're still thinking things, your brain is still processing lots of information.
General anesthesia - now THAT is a real close period to what being dead is.
A human being is a process of computation. Ending the computation is death. Pausing the computation is, well, simply pausing the computation. It has no profound significance.
(This is also my answer to the "teleporter problem." As long as the computation continues, a change in the substrate on which it takes place also has no profound significance.)