S-cone excitation ratios for reaction times to blue-yellow suprathreshold changes at isoluminance.
We examined different contrast metrics to scale visual latencies for suprathreshold stimuli modulated along tritan confusion lines. S-cone increments ('blue') and decrements ('yellow') were isolated along two different tritan confusion lines, each one having a different luminance value. Reaction times (RT) were evaluated as a function of the Weber contrast and the S-cone excitation ratio between the test stimulus and the background. RTs were described using a model that generalizes Piéron's law and incorporates the notion of threshold units and power law scaling. Our results show that RTs for S-cone increments and decrements equate better when using the S-cone excitation ratio. However, a single function did not describe all RT data. S-cone RTs are better described by separate functions. We conclude that S-cone increments and decrements do not scale in the same manner. Both Weber contrast and the S-cone excitation ratio are plausible metrics at isoluminance. The implications for the S-cone pathways are discussed.
Medina
José M
JM
Center for Physics, University of Minho, Braga, Portugal. jmanuel@fisica.uminho.pt
Díaz
José A
JA
D003118:Color Perception / Q000502:physiology; D055253:Color Vision / Q000502:physiology*; D015350:Contrast Sensitivity; D006801:Humans; D008297:Male; D008954:Models, Biological; D008960:Models, Psychological; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology