Does the scotopic system have more or less spatial summation?

Does the scotopic system have more or less spatial summation?

• A. Less
• B. About the same
• C. More
• D. None

Answer: (C)

In dim lighting, vision relies on rods, which converge heavily onto the same downstream neurons. Spatial summation is the process of pooling signals from neighboring photoreceptors over space. Because many rods feed into a single neuron, signals from a wide area are integrated before a response is produced, creating larger receptive fields. This greater pooling means more spatial summation, which increases sensitivity to light but reduces the ability to resolve fine detail. So, the scotopic system has more spatial summation than the photopic (cone) system, which is why night vision is more sensitive yet blurrier.

In dim lighting, vision relies on rods, which converge heavily onto the same downstream neurons. Spatial summation is the process of pooling signals from neighboring photoreceptors over space. Because many rods feed into a single neuron, signals from a wide area are integrated before a response is produced, creating larger receptive fields. This greater pooling means more spatial summation, which increases sensitivity to light but reduces the ability to resolve fine detail. So, the scotopic system has more spatial summation than the photopic (cone) system, which is why night vision is more sensitive yet blurrier.