Nicholas Humphrey is a psychologist and sometime collaborator with Daniel Dennett who's essays and books on the nature of consciousness are superbly illuminating as showing consciouousness as a plausible eventuation of natural material and biological process.
Significantly he has coined "sentition" as the brain's accessible perception of its own state in controlling specific musculature. The implication is that all sense awareness and memory are extensions of this.
"Ipsundrum" is his coinage for an evolution and extension of "sentitition" such that the brain reacts to sensory nerve events and then records how it itself reacts as a memorialization of that sense event. Internally then (as of this writing this is still speculative, but I've no clue of any other means that comprehensively explains so much) this memory OF ITS OWN ACTION is perpetuated and propogated in time in the brain as the particular sense discrimination to which it was originally the memory of its own reactive response. THe ipsundrum then, is the quite plausible material reality which likely underlie the philosophers' otherwise crypto-mystical quale.
(this idea is the basis for much of my own speculative notions of consciousness)
Humphrey has himself commented on some of his departures as compared to Dennett's writinngs. But as of this juncture I perceive that there is a different emphasis and "carving" of what is expressed but in the substance of what they assert is materially happening they aren't at any disagreement. So far as I see their differences are wholly semantic.
I doubt there is anything he's written I wouldn't recommend, but what I have read and recommend: