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PubMed1992

Color perception within a chromatic context: changes in red/green equilibria caused by noncontiguous light.

We measured changes in the color appearance of one light caused by another light presented in a well-separated region. Observers viewed a 1 degrees test field superimposed on a 3 degrees, 540 or 660 nm adapting field (32 or 320 td). The change in appearance due to noncontiguous light was determined by surrounding the 3 degrees adapting field with a continguous 3 degrees i.d., 5 degrees o.d. ring of either 32 or 320 td. The ring was 540, 660 nm or achromatic (tungsten-halogen "white"). The test was an admixture of 549 and 660 nm light, and varied from 6 to 1000 td. The observer adjusted the ratio of 549 to 660 nm test light so the test appeared neither reddish nor greenish. A 540 or 660 nm ring had a chromatic inducing effect on the small test that mimicked a simple surround contiguous with the test. Results with an achromatic ring were more complex: an isolated achromatic ring (no adapting field present) had virtually no effect on the color appearance of the test, but the same achromatic ring surrounding a chromatic adapting field shifted the test toward the color appearance of the adapting light (e.g. introducing a "white" ring surrounding a "green" adapting field shifted the test toward greenness). A thin pencil-width band of "white" light superimposed on a larger 5 degrees adapting field had an effect similar to a "white" 3-5 degrees ring. These results demonstrate (1) strong effects of the remote noncontiguous lights and (2) that the change in color appearance they cause is not a simple function of only the light in the noncontinguous region. The change depends on other lights in view. The visual processes revealed in these experiments are considered in terms of inferred illumination and surface reflectances of objects in natural scenes.

Adaptation, Ocular↗
PubMed2005

Unconscious operant conditioning in the paradigm of brain-computer interface based on color perception.

This study investigate the mutual fine-tuning of ongoing EEG rhythmic features with RGB values controlling color shades of computer screen during neuro-feedback training. Fifteen participants had not been informed about the existence of neurofeedback loop (NF), but were guided only to look at the computer screen. It was found that during such unconscious NF training, a variety of color shades on the screen gradually changed from rather various types to the main one within the framework of color palette specified for each individual. This phenomenon was not observed in control experiments with simulated neuro-feedback. Individual color patterns induced on the screen during NF did not depend on the schema of connection between of EEG rhythms and RGB controller. It is suggested that the basic neurophysiological mechanism of described NF training consists of the directed selection of EEG patterns reinforced by comfortable color shades without conscious control.

Adult↗
PubMed1988

Color perception under chromatic adaptation: red/green equilibria with adapted short-wavelength-sensitive cones.

Chromatic adaptation can dramatically alter the color appearance of a light. The specific effect of adapting short-wavelength-sensitive (SWS) cones is examined by using two adapting wavelengths that lie on a tritanopic confusion line. The change in color appearance caused by signals from adapted SWS cones is isolated by restricting the wavelengths of the test light to 550 nm or longer. Thus the test negligibly stimulates SWS cones, so their sensitivity does not affect the test's appearance. The results show that adapted SWS cones contribute redness to the appearance of a superimposed test light, while not affecting sensitivity of MWS and LWS cones. Quantitatively, the redness from SWS cones illuminated by a large adapting field approaches physical admixture of test and adapting lights. This is very different from an adapting field that stimulates only MWS and LWS cones which, due to a postreceptoral process, contributes much less redness to a small superimposed test than expected from admixture. The difference between the adapted SWS-cone and the adapted MWS/LWS-cone contributions to the color of a small test explains a surprising result: a bluish-green (491 nm) adapting field contributes redness to a superimposed test light.

Adaptation, Ocular↗
PubMed1999

[Modification of color perception during the course if glaucoma].

Direct heterochromic comparisons were made in 334 examinations of 148 patients with glaucoma. This test evidenced the classical breaches of blue and also alterations in the red spectrum which were observed mainly in cases with an unfavorable course or during the most severe stages of the disease. This examination technique is easy to repeat and gives an accurate assessment of disease course. It is useful for guiding treatment.

Color Perception Tests↗
PubMed2006

Crepuscular and nocturnal illumination and its effects on color perception by the nocturnal hawkmoth Deilephila elpenor.

Recent studies have shown that certain nocturnal insect and vertebrate species have true color vision under nocturnal illumination. Thus, their vision is potentially affected by changes in the spectral quality of twilight and nocturnal illumination, due to the presence or absence of the moon, artificial light pollution and other factors. We investigated this in the following manner. First we measured the spectral irradiance (from 300 to 700 nm) during the day, sunset, twilight, full moon, new moon, and in the presence of high levels of light pollution. The spectra were then converted to both human-based chromaticities and to relative quantum catches for the nocturnal hawkmoth Deilephila elpenor, which has color vision. The reflectance spectra of various flowers and leaves and the red hindwings of D. elpenor were also converted to chromaticities and relative quantum catches. Finally, the achromatic and chromatic contrasts (with and without von Kries color constancy) of the flowers and hindwings against a leaf background were determined under the various lighting environments. The twilight and nocturnal illuminants were substantially different from each other, resulting in significantly different contrasts. The addition of von Kries color constancy significantly reduced the effect of changing illuminants on chromatic contrast, suggesting that, even in this light-limited environment, the ability of color vision to provide reliable signals under changing illuminants may offset the concurrent threefold decrease in sensitivity and spatial resolution. Given this, color vision may be more common in crepuscular and nocturnal species than previously considered.

Animals↗
PubMed1995

[Disorders of color perception and increase glare sensitivity in phenytoin and carbamazepine therapy. Ocular side effects of anticonvulsants].

Advanced psychophysical tests, performed in 42 epileptic patients, show that the antiepileptic drugs phenytoin and carbamazepine can specifically affect the retinal function, while Valproic Acid and the epileptic seizures do not. The Farnsworth-Munsell 100-Hue and Panel D-15 désaturé tests revealed an accumulation of errors along the tritan/tetartan axis (blue colour vision deficiencies) and a high total error score. The same defect was shown by measurement of the spectral sensitivity functions. The results obtained for mesopic vision and especially glare sensitivity measured by nyktometry were markedly affected in these patients compared to a normal population. The enhanced sensitivity to glare is mainly the only one symptom complained by the patient. We propose a screening method for early detection of phenytoin- and carbamazepine-induced neurotoxicity. The literature of ocular side effects of anticonvulsant drugs is carefully reviewed.

Adolescent↗
PubMed1990

[Early diagnosis of congenital disorders of color vision with the Velhagen "Pflügerhaken Color Charts for evaluating color perception" in 3,375 preschool children].

In three series of examinations, 3375 male preschool-age children and 93 adult normal trichromates were tested using the Velhagen Pflügerhaken charts. The authors recommend modifying the evaluation of the results slightly by introducing a "doubteful" category for children who make one mistake or who show hesitation and lack of assurance in interpreting the charts. Using this modified form of assessment, diagnoses of "probably achromatopic" and "doubtful" were made in 7.16% and 2.13% respectively of 1689 preschool-age boys. The failure rate during the test and the duration of the examination were age-dependent, and declined with increasing age from 4.15% to 0.45% and from 1.18 min to 0.59 min, respectively. Most mistakes were made with charts nos. 9, 3, and 5. The results of tests with Pflügerhaken charts are fully comparable with those of other internationally used tests for adults. They can be recommended for screening preschool-age children.

Adult↗
PubMed1994

[The history of research in color perception as a key to understanding various forms of congenital defects in red-green perception].

It is accurate to date the first scientific report about colour-deficiencies on 1777. Earlier descriptions may be followed up to the end of the 17th century. But usually it is only mentioned, that mistakes had happened. Huddart 1777, however, reported for the first time, that more than one person was involved in a family and that demonstrations of coloured ribbons helped to find out which colours became confounded. The famous self-observation of Dalton contains the assortment of individually combined silk-threads, which is an anticipation of subsequent arrangement-tests. Goethe developed a systematic arrangement-test of self-made small coloured targets with colours out of his own colour-wheel. A. Seebeck was the first who--using the spectrum for examination--found out that a special group of subjects showed a shortening of the spectrum at the red end. From this result Helmholtz concluded the existence of two types of red-green blindness. This new argument for the trichromatic organisation of our colourvision was the basis for the statement of the three types: protanopia, deuteranopia and tritanopia (v. Kries, A. König). Rayleigh later on succeeded in finding out anomalous trichromats following preparatory examinations of Maxwell. Nagel has the merit to have analysed protanomaly and deuteranomaly using the anomaloscope constructed by himself. Side by side with the spectral colour-tests pseudoisochromatic plates were developed for diagnostic purposes, at first thought out and introduced by Stilling and in the meantime used in many variations.

Color Perception Tests↗
PubMed2006

Variant and invariant color perception in the near peripheral retina.

Perceived shifts in hue that occur with increasing retinal eccentricity were measured by using an asymmetric color matching paradigm for a range of chromatic stimuli. Across nine observers a consistent pattern of hue shift was found; certain hues underwent large perceived shifts in appearance with increasing eccentricity, while for others little or no perceived shift was measured. In separate color naming experiments, red, blue, and yellow unique hues were found to be correlated with those hues that exhibited little or no perceptual shift with retinal eccentricity. Unique green, however, did not exhibit such a strong correlation. Hues that exhibited the largest perceptual shifts in the peripheral retina were found to correlate with intermediate hues that were equally likely to be identified by adjacent color naming mechanisms. However, once again the correlation was found to be weakest for the green mechanism. These data raise the possibility that perceptually unique hues are linked to color signals that represent the most reliable (minimally variant) chromatic information coming from the retina.

Adult↗
PubMed1988

[The effect of combined iodine treatment in Bad Hall on the color perception of patients].

After taking a cure with iodine treatments in Bad Hall (Upper Austria), patients with eye diseases repeatedly report improvements in their color vision. They state that colors are once again "more saturated, richer, and more distinct." These statements were checked using the Farnsworth Panel D-15 dicotomous test and the Lanthony desaturated 15 Hue test. The analysis of the results showed that there is indeed a statistically significant improvement in color vision after the cure. The spontaneous observations of the patients were therefore confirmed by the study.

Adult↗