As for rods being for "peripheral knowledge," though they are certainly the only perceptual cells in the periphery of our vision. Rods are everywhere on the retina with the exception of the fovea centralis, which essentially means "the central point of focus." The fovea is only populated with cones, which are responsible for color vision, and actually transmit far more information per cell, because there is only one cone per nerve, no competition. That's why we can see things so clearly, assuming our lenses focus the outside world properly on the fovea. The reason we can adjust to light down to the level of only a few lumens (light quanta) is because we have so many rods attached to so few nerves that the information can summated and amplified. This would be a better explanation for how PR works, because it is the rods that are gathering the information that is not focussed centrally, therefore all of that similar input can be summated and amplified to give an even more powerful signal to the brain, even though the brain is expecting the information to come through the front door and not the side windows.
If anybody (i.e., Dana, Paul or Pete especially) has more scientific information regarding just how PR works, I would be very interested in seeing it.
Bill
