Discrimination of cone contrast changes as evidence for colour constancy in cerebral achromatopsia

@article{Hurlbert1998DiscriminationOC,
  title={Discrimination of cone contrast changes as evidence for colour constancy in cerebral achromatopsia},
  author={Anya C. Hurlbert and D. I. Bramwell and Charles A. Heywood and Alan Cowey},
  journal={Experimental Brain Research},
  year={1998},
  volume={123},
  pages={136-144}
}
Abstract One proposed mechanism for underpinning colour constancy is computation of the relative activity of cones within one class – cone ratios, or cone contrasts – between surfaces in a fixed scene undergoing a change in illuminant. Although there is evidence that cone ratios do determine colour appearance under many conditions, the site or sites of their computation is unknown. Here, we report that a cerebrally achromatopsic observer, MS, displayed evidence of colour constancy in asymmetric… 

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References

SHOWING 1-10 OF 27 REFERENCES

Relational colour constancy from invariant cone-excitation ratios

Cone-excitation ratios offer a possible basis for perceptual colour constancy in so far as it concerns colour relations and are statistically almost invariant under changes in illumination by light from the sun and sky or from a planckian radiator.

Quantifying color constancy: Evidence for nonlinear processing of cone-specific contrast

Color constancy in variegated scenes: role of low-level mechanisms in discounting illumination changes.

It is found that photoreceptor and opponent-color signals from a large sample of natural and man-made objects under one kind of natural daylight were almost perfectly correlated with the signals from those objects under every other spectrally different phase of daylight.

Chromatic Discrimination in a Cortically Colour Blind Observer

Photopic spectral sensitivity showed evidence both for activity of three cone channels and for chromatic opponent processing, indicating that postreceptoral chromatic processing is occurring despite the absence of any conscious awareness of colour.

Color constancy in the nearly natural image. I. Asymmetric matches.

Measurements made under more natural viewing conditions provide a link between human performance and computational models of color constancy.

Colour constancy influenced by contrast adaptation

It is shown here that changes in an illuminant can also alter colour contrasts in images (how colours are distributed around the mean) enough to alter the state of contrast adaptation, so perceived colour under different illuminants may also be noticeably influenced by contrast adaptation.

Colour is what the eye sees best

The high sensitivity to colour detected in this study is consistent with the prevalence and high colour contrast-gain of retinal P cells, and may compensate for the low chromatic contrasts typically found in natural scenes.

A Vector Model of Colour Contrast in a Cone-Excitation Colour Space

A vector model of colour contrast is examined in a colour space that is a logarithmic transformation of the MacLeod – Boynton cone-excitation diagram, which describes observers' matches to the hues induced in a neutral square for a range of inducing surround colours, arange of right-eye (match) surround colours and four different luminance contrasts.

On the role of parvocellular (P) and magnocellular (M) pathways in cerebral achromatopsia.

The patient was singularly proficient at detecting coloured forms in static or dynamic displays even when the saturation of the colours of which the form was composed were such that they were rendered invisible when concealed as a single square in a checkerboard, implying that signals about chroma are still available in extracting shape.