Which statement about retinal neurons is most accurate?

Which statement about retinal neurons is most accurate?

• A. Ganglion cells greatly outnumber photoreceptors
• B. Each photoreceptor forms a one-to-one connection with a ganglion cell
• C. Many photoreceptors converge onto fewer ganglion cells
• D. The retina contains no interneurons

Answer: (C)

Pooling of signals in the retina is the key idea here. Many photoreceptors feed into fewer ganglion cells through intermediate neurons, so many inputs are combined before generating a signal that reaches the brain. In humans, there are about 120 million photoreceptors but only around 1–2 million ganglion cells, so a high degree of convergence is the norm. This arrangement boosts sensitivity to light because a single ganglion cell can respond when many photoreceptors are stimulated, though it comes at the cost of spatial detail. In the central retina (the fovea), convergence is reduced, allowing nearly one-to-one wiring to support high acuity. The other statements don’t fit this arrangement: photoreceptors do not typically form one-to-one connections with ganglion cells, ganglion cells do not outnumber photoreceptors, and the retina does contain interneurons such as bipolar, horizontal, and amacrine cells.

Pooling of signals in the retina is the key idea here. Many photoreceptors feed into fewer ganglion cells through intermediate neurons, so many inputs are combined before generating a signal that reaches the brain. In humans, there are about 120 million photoreceptors but only around 1–2 million ganglion cells, so a high degree of convergence is the norm. This arrangement boosts sensitivity to light because a single ganglion cell can respond when many photoreceptors are stimulated, though it comes at the cost of spatial detail. In the central retina (the fovea), convergence is reduced, allowing nearly one-to-one wiring to support high acuity.

The other statements don’t fit this arrangement: photoreceptors do not typically form one-to-one connections with ganglion cells, ganglion cells do not outnumber photoreceptors, and the retina does contain interneurons such as bipolar, horizontal, and amacrine cells.