ESTIMATION OF LINEAR DETECTION MECHANISMS FOR STIMULI OF MEDIUM SPATIAL-FREQUENCY

Detection thresholds were obtained for a circularly-symmetric Gabor pr ofile and Craik-Cornsweet profiles presented on a large white adapting field. These stimuli possessed peak spatial power between 1 and 6 c/d eg. Their contrast was represented in an L, M and S cone contrast spac e. Detection thresholds were obtained for many vectors close to specif ic but theoretically important planes within this space. These data we re fitted with a model comprising independent mechanisms, each a weigh ted sum of cone contrasts. The fit revealed a chromatic mechanism driv en by Delta L/L - Delta M/M with no S cone input. Within cone contrast space, this mechanism was more sensitive than both a luminance mechan ism with little S cone input but considerable variation in relative L to M cone input, and a blue-yellow chromatic mechanism.