Postreceptoral chromatic-adaptation mechanisms in the red-green and blue-yellow systems using simple reaction times

Abstract

(Doc. ID 62073) Simple visual-reaction times (VRT) were measured for a variety of stimuli selected along red-green (L − M axis) and blue-yellow [S − ͑L+M͒ axis] directions in the isoluminant plane under different adaptation stimuli. Data were plotted in terms of the RMS cone contrast in contrast-threshold units. For each opponent system, a modified Piéron function was fitted in each experimental configuration and on all adaptation stimuli. A single function did not account for all the data, confirming the existence of separate postreceptoral adaptation mechanisms in each opponent system under suprathreshold conditions. The analysis of the VRT-hazard functions suggested that both color-opponent mechanisms present a well-defined, transient-sustained structure at marked suprathreshold conditions. The influence of signal polarity and chromatic adaptation on each color axis proves the existence of asymmetries in the integrated hazard functions, suggesting separate detection mechanisms for each pole (red, green, blue, and yellow detectors).

Effect of rod–cone interactions on mesopic visual performance mediated by chromatic and luminance pathways

“…We do not make direct comparisons between the RTs for stimuli mediated via different pathways because they are measured using different stimulus contrast ranges, there are differential sensitivities to the photoreceptor excitation types, and the irreducible minimums were not determined due to the available instrument contrast gamut. These issues have been considered elsewhere [21–24,53,54]. …”

1/f noise in human color vision: the role of S-cone signals

“…Although the dependence of RT to chromatic contrast and spatial summation has been widely studied [56][57][58][59][60][61][62][63][64], previous RT studies have taken the average mean response from a few static experimental conditions. This has ignored the presence of correlations or memory effects.…”

“…One common way to study the stochastic latency mechanisms that generate RT variability deals with the analysis of the hazard functions ht [23,26,27,63,71]. The hazard function is defined as the quotient between the probability density function (pdf) f t, and the reciprocal of the cumulative distribution function Ft, i.e., ht f t∕1 − Ft (measured in units of events per millisecond).…”

“…However, the analysis of the hazard functions offers distinctive information in the right tails of the RT distributions, and it can discriminate between experimental pdfs that have very similar shapes [23]. The hazard functions are more useful than the simplified method of taking mean values to examine the structure of RT distributions at different stimulus strength [23,27,63,71,73], to distinguish models of RTs [23,71], and to model the capacity or the total completion stage in binocular color processing [74,75].…”

“…On the contrary, at near-threshold level conditions, the peak is absent or attenuated and the visual system will show evidence of quasisustained or power-law dominant dynamics [23,26]. In previous works, the hazard functions were estimated for chromatic-opponent responses at isoluminance [27,63]. Comparisons between red-green hazard functions at different chromatic-contrast increments and stimulus size were compatible with the existence of power-law dominant activity at low chromatic-contrasts [27,63], and low stimulus size [27].…”