The taste of mango is the brain's interpretation of the neural signals from the taste buds, very usually together with input from the olfactory sensors. The response has evolved so as to reward eating useful food and deter eating harmful food (but it evolved before there were supermarkets). In a near analogy, the color red is the brain's interpretation of those neural signals from the optic nerve which are generated by light in about the 740-620 nm range.
Perhaps it's that healthy sleep is deepest when all the components are working in best harmony?
There's quite a bit of biochemical literature on depression. One noted example is the role of serotonin reuptake inhibitors, which increase the available serotonin in the synapse by slowing down the reuptake part of the cycle. The increased serotonin reduces depression and anxiety, though of course, like all psych medicines, they work extremely well for some people and not so well for others. All these researches are steps on our path to understanding.
That consciousness is non-sleep seems an odd and unhelpful definition to me. And not all unconsciousness is sleep ─ there's also trauma, anesthesia, catatonia caused by infection &c. (My sister-in-law, with a PhD in Biochemistry, once commended Damasio to me, and despite a few interesting ideas I found him hard reading.)
Hmm ─ that's not bad. It might be setting the bar a bit higher than I would, but the central notion is attractive.
If that's true then it should be verifiable by our brain researches, no? Has that been done?
I don't understand the significance of knowing that we've been asleep.