Pain is not an input. It is simply (and complexly?!) a nerve being stimulated, sending an action potential up to the spinal cord and then brain, where the brain interprets those signals.
…and that’s where it get’s sticky… because what is the interpretation of those simple action potentials? It’s nothing but a bunch of action potentials itself (in a coordinated and orchestrated manner). That orchestra of action potentials, read: neurotag if you like, produces that feeling.
So, if you are going to take a snap-shot of the leg’s neural input, afferent fiber, and say that that’s just an action potential, then you can easily break down the biological parts of the brain and say “hey, that’s just an action potential” also.
Where is the actual interpretation coming from…?
Is it just the brain? I suppose that research (currently) has concluded that yes indeed, the interpretation part happens in the intricacies of the brain, even though it’s the same biological mechanism of information transmission (just propagation). The Central Nervous System has a different structure, purpose, and life-cycle than peripheral nervous tissue… but since we are all biology, and this inquiry is a biologically driven endeavor… well, this is clearly an instance of the whole being more than the sum of it’s parts.
The neurobiologists agree (probably) that the mind is created by the physical brain, and therefor so are the interpretations and outputs. Or, as some suggest, it is a theoretical waste to say that the brain produces the feeling/output… the brain just is. There is no separation.
“The easy way to cut through…is to draw lessons from the history of science. Electromagnetic waves don’t cause light; they are light. That’s what light is. Similarly with sound: a sound of middle C isn’t correlated with a compression wave train of 263 Hz. It is a compression wave train with that frequency. And the feeling of warmth from a coffee cup isn’t something that’s correlated with mean molecular kinetic energy; it’s identical with the mean molecular kinetic energy of the molecules in the cup.” –Paul Churchland
My brain made me write this.