Side note: Should we lump (d-e) together?
Or more generally, should we lump all of these levels together or not?
On the one hand, I think yes, because I think the same basic mechanism is at work (homeostatic feedback loop).
On the other hand, no, because those loops are wired together in different ways in different parts of the brain to do different things. I draw my model of what the levels are from the theory of dependent origination but other theories are possible, and maybe we can eventually get some thoroughly grounded in empirical neuroscience.