Abstract
Recently, we described the temporal characteristics of color-sensitive (blue-ON) cells in the lateral geniculate nucleus (LGN) of anaesthetized cats. Since anatomically, this pathway is heavily underrepresented compared to the achromatic channel (low S-cone and blue-ON cell density in the retina and LGN, respectively), we were wondering (1) if this system plays a role in color vision on the perceptual level and (2) if the sluggish behavior of thalamic blue-ON cells is reflected in reaction times to S-cone isolating stimuli. We trained two male cats to perform a simple contrast discrimination task where they had to respond to the appearance of a spot by pressing a glass plate located in front of the stimulus monitor. We rewarded responses given within a limited time window by liquified food. A trial was deemed incorrect when the animal pressed the response key outside the valid time window. The target spot had 50% positive or negative cone-contrast for the ML-, S- or both cones (achromatic) against the grey background and trials without a target were used as control. We measured simple reaction times and percentage of correct trials. Reaction times were not significantly different for the three color conditions (S: 908.54±214.35 ms; ML: 906.01±198.45 ms; ach: 874.63±211.18 ms (mean±SD) , p=0.46, ANOVA), although they were slightly longer for the S- and ML-cone isolating stimuli. However, percentage of correct trials was significantly lower for the S-cone isolating condition than for the achromatic one (56.06±18.26% and 74.38±19.07%, respectively, p=0.015, ANOVA). Performance for the ML-cone isolating stimuli was between that of the other two conditions but did not differ significantly (64.76±13.92%; ML vs S: p=0.17; ML vs Ach: p=0.14). Based upon our results we can conclude that the S-cone-driven pathway plays an important role in the cat color perception but S-cone isolating colors are harder to see.