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.
Threshold has changed, the definition is still the same, we're just getting better at reverting the stop of some activities, like breathing or heartbeat. If we someday could revert neuronal depolarization, that would be great, but it seems difficult to achieve.
The other part is not just philosophy, it's the best we can do to define a "self". The philosophical part is only whether we can consider them a continuum, or whether we have to see them as usually similar but separate (there are reasons to support both versions).
