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.
We have a good definition of "death", it's the irreversible stop of some activity. For a brain, that's neuronal depolarization; for a body organ or cell, it's destruction past its ability to regenerate.
The self, is a snapshot of a brain state at a certain moment, which is technically irreversibly disappearing 30 times a second, but we like to think of it as just "changing" and forming a causal sequence we call "consciousness".
