Dataset Information

Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection.

ABSTRACT: While contrast normalization is well known to occur in luminance vision between overlaid achromatic contrasts, and in colour vision between overlaid colour contrasts, it is unknown whether it transfers between colour and luminance contrast. Here we investigate whether contrast detection in colour vision can be normalized by achromatic contrast, or whether this is a selective process driven only by colour contrast. We use a method of cross-orientation masking, in which colour detection is masked by cross-oriented achromatic contrast, over a range of spatio-temporal frequencies (0.375-1.5 cpd, 2-8 Hz). We find that there is virtually no cross-masking of colour by achromatic contrast under monocular or binocular conditions for any of the spatio-temporal frequencies tested, although we find significant facilitation at low spatio-temporal conditions (0.375 cpd, 2 Hz). These results indicate that the process of contrast normalization is colour selective and independent of achromatic contrast, and imply segregated chromatic signals in early visual processing. Under dichoptic conditions, however, we find a strikingly different result with significant masking of colour by achromatic contrast. This indicates that the dichoptic site of suppression is unselective, responding similarly to colour and luminance contrast, and suggests that dichoptic suppression has a different origin from monocular or binocular suppression.

SUBMITTER: Mullen KT

PROVIDER: S-EPMC4261179 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection.

Mullen Kathy T KT Kim Yeon Jin YJ Gheiratmand Mina M

Scientific reports 20141210

While contrast normalization is well known to occur in luminance vision between overlaid achromatic contrasts, and in colour vision between overlaid colour contrasts, it is unknown whether it transfers between colour and luminance contrast. Here we investigate whether contrast detection in colour vision can be normalized by achromatic contrast, or whether this is a selective process driven only by colour contrast. We use a method of cross-orientation masking, in which colour detection is masked ...[more]

PMID: 25491564

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Project description:PurposeThe purpose of this study was to design and evaluate an instrument for assessing vision-related quality of life appropriate for the specific visual impairment characteristic for all stages of age-related macular degeneration (AMD), with a focus on the low luminance deficit in early/intermediate stages.MethodsA standardized questionnaire was developed in three steps with participants with early, intermediate, and late AMD: (1) based on in-depth interviews (n = 19) and two focus group discussions (n = 5 each), content was developed followed by 2. (2) The questionnaire development using cognitive debriefing interviews (n = 3) and leading to a preliminary version of the questionnaire. (3) This version was then administered to 127 participants with early, intermediate, and late AMD. Psychometric properties, such as response category functioning (floor and ceiling effects) and targeting of item difficulty to patient ability of the pilot Vision Impairment in Low Luminance (VILL) questionnaire were evaluated using Rasch analysis.ResultsThe preliminary VILL questionnaire consisted of 68 items with a 5-step response scale. Several items were removed based on floor/ceiling effects or misfit and a final pool of 37 items remained. The response scale was collapsed to four categories as one category was underutilized. The targeting of the instrument was good with minimal difference in person and item means (0.52 logits). Precision was also good with a person separation index of 3.55 and reliability of 0.93. There was evidence of multidimensionality (eigenvalue of the first contrast = 5.95) in the scale, which could be resolved by splitting the items into subscales including a reading, mobility, and emotional well-being subscale.ConclusionsIndividuals with AMD report difficulties with vision-related activities and functioning under visually challenging conditions at all stages of the disease. These aspects were considered when developing the 37-item VILL, which demonstrates promising psychometric characteristics. Further assessments of reliability and validity are warranted.Translational relevanceThe VILL questionnaire is a new patient-reported outcome (PRO) measure developed for future use in AMD studies.

Dataset Information

Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection.

Publications

Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection.

Similar Datasets

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