While reading into visual phototransduction I was surprised to learn that photoreceptor cells are actually depolarized when there is NO excitation (no light, i.e. when you see nothing, black) and hyperpolarized when there is light (I expected the opposite).
This got me thinking...
Let the collection of neurons located within the eye be referred-to as IEN (inside-eye neurons) and, similarly, the collection of neurons directly linked to the eye, yet external to it be referred-to as OEN (outside-eye neurons).
Let the collection of neurons directly getting input from the retina be referred-to as RN (retinal neurons). I'm assuming RN < IEN (subset of - correct me if I'm meaningfully-wrong).
And finally, let the collection of neurons that directly link to OENs but are part of IEN be referred-to as XN (eXporter-neurons, in the sense that they export visual information from the eye to the "listeners" outside of it).
So the path of visual stimulus would then be RN -> [...] -> XN -> OEN.
Now, if my eyes were to be completely popped-out I'm assuming that relative to OENs that would have the same effect as XNs not passing along any excitatory/inhibitory information at all. Also, since what I'd perceive would be pure black, that seems to imply that XNs also don't get activated at all when we actually see black (e.g. close our eyes in a very dark room).
So, when we perceive black => RNs get depolarized => they release glutamate continuously => XNs don't excite/inhibit OENs at all (seems to also imply that RNs don't intersect XNs). It is this inversion that intrigues me - why is it that for XNs to transmit NO information RNs have to continuously be excited? By that sense, this makes me think of the eye as if it was a big NOT gate.