Which example illustrates spatial summation?

Which example illustrates spatial summation?

• A. Signals from a single photoreceptor feeding into one ganglion cell
• B. Signals from multiple photoreceptors feeding into one ganglion cell
• C. Temporal summation within a bipolar cell
• D. Lateral inhibition from horizontal cells

Answer: (B)

Spatial summation is the process of combining signals from many photoreceptors across different locations within a ganglion cell’s receptive field to produce a single, unified response. When several photoreceptors feed into one ganglion cell, their signals overlap and sum as they reach the ganglion cell, increasing the chance that the cell fires in response to the overall light pattern across that area. This is different from temporal summation, which is about accumulating input from the same pathway over time rather than across space, and from lateral inhibition, which modulates neighboring inputs to sharpen edges rather than summing multiple inputs into one output. So, signals from multiple photoreceptors feeding into one ganglion cell best illustrate spatial summation.

Spatial summation is the process of combining signals from many photoreceptors across different locations within a ganglion cell’s receptive field to produce a single, unified response. When several photoreceptors feed into one ganglion cell, their signals overlap and sum as they reach the ganglion cell, increasing the chance that the cell fires in response to the overall light pattern across that area. This is different from temporal summation, which is about accumulating input from the same pathway over time rather than across space, and from lateral inhibition, which modulates neighboring inputs to sharpen edges rather than summing multiple inputs into one output. So, signals from multiple photoreceptors feeding into one ganglion cell best illustrate spatial summation.