Why do ganglion cells respond strongly to local contrast rather than uniform light?

Ganglion cells in the retina respond strongly to local contrast rather than uniform light due to their specialized centre-surround organization.12

In this arrangement, the receptive field of a ganglion cell is divided into a central zone and a surrounding periphery. These two regions have antagonistic effects: if the centre is excitatory, the periphery is inhibitory, and vice versa. When uniform light covers the entire receptive field, the excitatory and inhibitory signals tend to cancel each other out, resulting in little to no net response from the cell.13

This physiological design serves several critical functions:
* Efficiency: It prevents the brain from being overwhelmed by redundant information from uniform illumination, as the cell only signals when there is a change in the visual environment.13
* Feature Detection: By responding to differences in illumination, the organization effectively highlights contours and boundaries between light and dark areas.1
* Movement Sensitivity: The system is highly sensitive to the movement of light or dark spots across the receptive field, as the transition between the centre and periphery triggers a prominent discharge.1

This contrast-sensitive mechanism is mediated by bipolar cells and amacrine cells, which facilitate the inhibitory interactions necessary for this spatial antagonism.14