What concept explains why a single ganglion cell can respond to inputs from multiple photoreceptors?

• A. Temporal summation
• B. Spatial summation
• C. Lateral inhibition
• D. Center-surround antagonism

Answer: (B)

Spatial summation explains how a ganglion cell can be driven by signals from many photoreceptors spread across its receptive field. In the retina, inputs from multiple photoreceptors converge onto a single ganglion cell via intermediate neurons, so the combined activity within that spatial area can push the ganglion cell to fire. This integration across space is what allows a single ganglion cell to respond to light patterns that cover more than one photoreceptor, not just to signals from a single receptor alone. Temporal summation would involve integrating input over time from one receptor, while lateral inhibition and center-surround antagonism describe contrast enhancement and the receptive field organization, respectively.