The influence of contrast adaptation on color appearance

Abstract

Most models of color vision assume that signals from the three classes of cone receptor are recoded into only three independent post-receptoral channels: one that encodes luminance and two that encode color. Stimuli that are equated for their effects on two of the channels should be discriminable only to the remaining channel, and are thus assumed to isolate the responses of single channels. We used an asymmetric matching task to examine whether such models can account for changes in color appearance following adaptation to contrast-to temporal variations in luminance and chromaticity around a fixed mean luminance and chromaticity. The experiments extend to suprathreshold color appearance the threshold adaptation paradigm of Krauskopf, Williams and Heeley ((1982) Vision Research, 32, 112>1131]. Adaptation changes the perceived color of chromatic test stimuli both by reducing their saturation (contrast) and by changing their hue (direction within the equiluminant plane). The saturation losses are largest for test stimuli that lie along the chromatic axis defining the adapting modulation, while the hue changes are rotations away from the adapting direction and toward an orthogonal direction within the S and L-M plane. Similar selective changes in both perceived color and perceived lightness occur following adaptation to stimuli that covary in luminance and chromatic@. The selectivity of the aftereffects for multiple directions within color-luminance space is inconsistent with sensitivity changes in only three independent channels. These aftereffects suggest instead that color appearance depends on channels that can be selectively tuned to any color-luminance direction, and that there are no directions that invariably isolate responses in only a single channel. We use the perceived color changes to examine the spectral sensitivities of the chromatic channels and to estimate the distribution of channels. We also examine how adaptation alters the contrast-response function, how it affects reaction times for luminance and chromatic contrast, the extent to which the aftereffects exhibit interocular transfer, and the way in which the perceived color changes differ from those induced by conventional light adaptation. Color appearance Luminance and chromatic channels Contrast adaptation Cardinal color directions Color-luminance interactions INTRODUCTIONMost models of color vision assume only three independent post-receptoral channels-one that encodes luminance and two that encode color (Lennie & D'Zmura, 1988). The luminance channel depends on inputs of the same sign from different cone classes, while the chromatic channels draw inputs of opposite sign. However, the number and nature of the post-receptoral transformations of the cone signals remain ill established. The phenomenal appearance of chromatic stimuli suggested two "second-stage" chromatic channels whose responses correspond to sensations of red-green or blue-yellow (Hurvich & Jameson, 1957 Grand, 1949; Krauskopf, Williams & Heeley, 1982). Stimuli that isolate...

Habituation Reveals Fundamental Chromatic Mechanisms in Striate Cortex of Macaque

“…The chromatic preferences of neurons there are broadly distributed throughout the isoluminant plane (Lennie et al, 1990;Wachtler et al, 2003;Johnson et al, 2004;Solomon and Lennie, 2005;Conway and Livingstone, 2006;Horwitz et al, 2007), reminiscent of the higher order color mechanisms inferred psychophysically (Krauskopf et al, 1986;Webster and Mollon, 1994). This suggests that the fundamental mechanisms characterized psychophysically might be established early in V1, at or near the interface with LGN inputs, and that their signals are combined with variable weights before being expressed in the broadly distributed chromatic signatures of most V1 neurons.…”

“…Chromatic preferences are broadly distributed among cortical neurons, so over the population as a whole response adaptation will cause the greatest loss of sensitivity in neurons tuned to the direction of the habituating modulation. This is of considerable interest in the context of psychophysical observations (Krauskopf et al, 1982(Krauskopf et al, , 1986Webster and Mollon, 1994) that reveal, in addition to the cardinal mechanisms, innumerable less prominent mechanisms tuned along different directions in color space. These characteristics of what have been called "higher order" mechanisms (Krauskopf et al, 1986) are consistent with their arising in response adaptation in neurons that receive input from the fundamental mechanisms.…”

Is discrimination enhanced at the boundaries of perceptual categories? A negative case

“…If the eye is adapted to daylight, then a line running obliquely in the diagram (from approx. 475 to 575 nm) divides chromaticities into reddish and greenish hues; and a second, superposed division into yellowish and bluish hues is made by a line that runs from approximately 520 nm to the white point and then nearly horizontally [4][5][6][7][8]. Chromaticities lying along the first of these boundaries comprise 'unique blues', 'unique yellows' and white (i.e.…”

Adaptation from invisible flicker

“…The attenuation of human flicker sensitivity, consequent to adaptation, is evident in both behavioral (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and neural (9,23,24) response measures, but its frequency dependence has never been assessed systematically. Here we measure the reduction in flicker sensitivity after prolonged exposure, or adaptation, to both luminance and chromatic flicker across a wide range of frequencies.…”

“…Here we pursue these questions through an experimental design that exploits, as a functional landmark, the known process of flicker adaptation, by which flicker sensitivity of an observer is attenuated after prolonged exposure to flickering lights (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). The attenuation of human flicker sensitivity, consequent to adaptation, is evident in both behavioral (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and neural (9,23,24) response measures, but its frequency dependence has never been assessed systematically.…”