What is the approximate critical duration for the scotopic system during temporal summation?

The critical duration for the scotopic system during temporal summation is approximately 100 milliseconds. This temporal summation refers to the ability of the visual system to integrate light stimuli over a specific time period, which is particularly relevant in low-light conditions where the scotopic system, primarily driven by rod photoreceptors, is active.

At this duration, the scotopic system can effectively combine multiple flashes of light, enabling the perception of brightness even with brief presentations of stimuli. Beyond this duration, the system reaches its limit in terms of how much information it can integrate and starts to experience saturation. This property is essential for vision in dim lighting conditions, allowing us to perceive a continuous relationship in visual stimuli by integrating light over time despite the poor spatial resolution and lower sensitivity of the rod system compared to the cone system in brighter conditions.

In summary, the choice of approximately 100 milliseconds aligns with established findings regarding the temporal response characteristics of the scotopic visual system, highlighting its role in low-light environments and the importance of temporal summation for visual perception under these conditions.