ESTIMATION OF THE L-CONE, M-CONE, AND S-CONE WEIGHTS OF THE POSTRECEPTORAL DETECTION MECHANISMS

We have obtained two- and three-dimensional detection threshold contou rs in cone contrast space for sinusoidal gratings for three subjects a t three spatiotemporal conditions (1 cycle/degree (c/deg), 0 Hz; 0.125 c/deg, 0 Hz; 1 c/deg, 24 Hz). These conditions were chosen to favor t he response of each of the three postreceptoral mechanisms in turn. Co ntours were obtained from measurements in as many as 60 axes in (L, M, S) cone contrast space and were fitted by superellipses. Our techniqu e permitted us to improve on earlier estimates of the cone weightings to the mechanisms. We found that the red-green mechanism has an input cone weighting of L-M with a 2% S-cone input; the luminance mechanism has a weighting of kL + M, where k varies between 3 and 5 at the high- temporal condition, with a 5% S-cone input in opposition to L- and M-c ones; and the blue-yellow mechanism consists of S inputs in closely ba lanced opposition to L and M inputs. These cone weights were found to be consistent among our three subjects. (C) 1996 Optical Society of Am erica