Rod-cone interaction in human scotopic vision-I. Temporal analysis

Document Type

Journal Article

Publication Date



Vision Research








A series of experiments studied temporal interactions between spatially superimposed stimuli in the dark adapted human observer: rods or cones were selectively stimulated by utilizing either 420 or 680 nm light. In Experiment 1, the threshold of a test flash was determined at various time intervals from onset of a supraliminal conditioning flash. Conditioning flash presentation increased test threshold above control level for heterochromatic and homochromatic stimulus pairs, thus indicating rod-cone interaction. The time course of threshold changes suggested that rod signals have a longer latency the cone signals. By having the observer adjust the onset of the 420 or 680 nm conditioning flash to appear simultaneous in onset with respect to either an auditory (Experiment 2) or second visual (Experiment 3) stimulus, it was estimated that the 420 nm flash produced a response with a 30-75 msec longer latency than the 680 nm flash. In Experiment 4, test flash threshold was measured at various delays from the onset of a subliminal conditioning flash. The magnitude of summation for heterochromatic and homochromatic stimulus pairs was similar, again indicating rod-cone interaction. Furthermore, the time course of threshold changes again indicated rod signals to have a longer latency than cone signals. The data were discussed in terms of underlying retinal mechanisms, and contrasted with prior behavioral studies which suggested rod-cone independence. © 1973.

This document is currently not available here.