Temporal integration of the pi 1/pi 3 pathway in normal and dichromatic vision

Stiles' pi 1 and pi 3 mechanisms are thought to reflect adaptation events at two sites in a single pathway, the first site controlled by the short-wavelength cones alone, the second site controlled by opposing signals from these cones vs the other cone classes. We examined this pathway's temporal integration under conditions that yield the full gamut of possible adaptation states at the two sites. Critical duration of the pi 1/pi 3 pathway was always about 200 msec. In addition, we examined the pi 1 and pi 3 mechanisms of dichromatic vision. Our results suggest that protanopic and deuteranopic vision are characterized by a pi 1/pi 3 pathway similar to that in normal color vision.