As such, they have a high capacity to act differentially in accordance with a given set of circumstances. The incoming light image is actually focused on the innermost layer of cells, where it is differentiated primarily according to its color or lack thereof. This outer nuclear layer, as it is called, is where the rod cells and cone cells reside. The cones react to color, whereas the rods generally do not. The electrochemical signals sent from the outer layer back toward the front of the retina to what is called the inner nuclear layer carry a great deal of information about color, contrast, brightness, position, and movement.
Further processing is done in the inner layer.
Some cells are excited by the presence of color whereas others are inhibited. Still other cells have different regions which react differently depending on a combination of connections made to them. In brief, a great deal of computing power has been applied to incoming light signals before they ever get to the visual cortex, which is located at the top and rear of the human brain. Following processing by the retina, visual information is sent along the optic nerve toward the visual cortex. However, this is not a straight path.