Letter: Impaired colour vision in diagnosis of digitalis intoxication.
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Child↗
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Colour association and "colour amnesia" in aphasia.
"Colour association" performance of 50 aphasic patients was investigated by means of a test in which they identified the characteristic colours of objects shown in line drawings. All aphasics with defects in colour association were impaired in reading comprehension. However, some (33%) retained normal aural comprehension. Approximately half the aphasics with receptive language impairment performed normally in colour association. The findings suggest that "colour amnesia" may be the result of a specific cognitive disturbance which is also responsible for a subtype of aphasic alexia.
Adult↗
Color-discrimination tests on fibers in ground squirrel optic nerve.
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Animals↗
Changes in colour discrimination during the menstrual cycle.
A group of normal women of reproductive age were recruited to investigate colour discrimination during the various phases of the menstrual cycle. Colour vision was tested with the Farnsworth-Munsell 100-hue arrangement test, and the test was administered at 3 time points: the beginning of the cycle, ovulation, and the end of the cycle. We found that colour discrimination was better at ovulation than at the other 2 time points. It is possible that psychological as well as hormonal factors could contribute to improved colour vision performance at ovulation.
Adult↗
Color vision in the ring-tailed lemur (Lemur catta).
Behavioral discrimination tests were used to examine spectral sensitivity and color vision in a pair of ring-tailed lemurs (Lemur catta). Sensitivity tests revealed the presence of a Purkinje shift and a photopic visual system. As measured at increment-threshold, the photopic spectral sensitivity function for the lemur has multiple peaks (at ca. 440-460, 540, and 620 nm). In color vision tests lemurs behave trichromatically in that (a) they show no evidence for a neutral point in the spectral range of 470-510 nm, and (b) they set a unique Rayleigh match (540 nm + 645 nm = 570 nm). Tests of wavelength and colorimetric purity discrimination reveal that although this prosimian has color vision, it is not an acute capacity--thresholds for these color discriminations were consistently much higher for lemurs than for normal human trichromats tested in the same situation.
Animals↗
Wavelength discrimination in the leopard frog: a reexamination.
A reexamination of wavelength discrimination using a 2-choice paradigm and both chromatic-chromatic and chromatic-achromatic stimulus pairs has reaffirmed the positive tendency of Rana pipiens to approach short wavelengths. In addition, a strong avoidance of long wavelengths was observed and an interaction of these two opposite response tendencies was demonstrated. Thus, the percent choice frequency for a short-wavelength stimulus depends upon the stimulus with which it is paired. A positive phototaxis appears to influence response to some short-wavelength stimuli when they differ in brightness from an achromatic stimulus, but not with wavelengths above 471 nm.
Animals↗
Color vision in the tree shrew (Tupaia glis).
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Animals↗
Color vision in the spider monkey (Ateles).
Spectral sensitivity and color vision were investigated in 2 spider monkeys (Ateles) using a forced-choice discrimination paradigm. The increment-threshold spectral sensitivity functions of both animals were very similar to those of normal human trichromats; all had three regions of peak sensitivity located at 440-460, 520-540, and 670-620 nm. However, color vision tests (neutral point, anomaloscope, and wavelength discrimination) indicated that at least two qualitatively different types of color vision exist among spider monkeys. The female tested had essentially normal trichromatic color vision (although her anomaloscope match was shifted slightly in the deutan direction) with acute wavelength discrimination. The male, however, was clearly a protanomalous trichromat. He required much more red light in a red/green mixture to match a standard yellow than did normal trichromats. This variation in color vision is discussed in the context of an analogous variation known to exist among other South American monkeys.
Animals↗
Farnsworth 100-hue test in diagnosis of ethambutol-induced damage to optic nerve.
In patients treated with EMB, disturbances in colour vision may be the first and only symptoms of the onset of toxic damage to the optic nerves. Owing to its sensitivity, the Farnsworth 100-Hue test is of great value in the ophthalmic control examinations. Moreover, it permits observation of the dynamics of the toxic process. The three reported cases of damage to the optic nerves confirm the great importance of colour vision examinations, as regards the detection of the complications of EMB treatment.
Adult↗
Pupil increment thresholds are influenced by color opponent mechanisms.
Pupillomotor and sensory spectral sensitivity curves of light-adapted eyes were compared. Experimental conditions were designed to favor (despite the threshold criterion) opponent processing of signals: long (500-ms) stimuli of large diameter (60 degrees) were presented centrally on an intense (16 cd/m2) white background. Narrow spacing of monochromatic stimuli permitted the recording of peaks and troughs in the increment spectral sensitivity curve which neither coincided with the characteristics of receptor pigment absorption spectra nor with the V-lambda curve. They are considered as showing influences of opponency mechanisms. Pupillomotor spectral sensitivity paralleled the sensory one, exhibiting the influence of opponency mechanisms on the pupil. Using more physiological conditions, human photopic spectral sensitivity was revealed as a three-peaked function, in sensory as well as in pupillomotor terms.
Adaptation, Ocular↗
Blue-yellow colour vision changes as early symptoms of ethambutol oculotoxicity.
To find out the most sensitive parameter of early toxic ocular changes, a group of patients was extensively examined at regular intervals during therapy with ethambutol. Colour vision abnormalities could be detected using the desaturated panel of Lanthony in the presence of normal visual acuity, normal visual fields, normal visual-evoked potentials and a normal panel D-15 test. Major blue-yellow errors were found in treated patients without visual complaints as well as in a group of healthy volunteers, but there was a significant difference between both groups. In a later stage of intoxication, blue defects, red-green defects or tritanomalous defects can be observed, together with other symptoms of ocular intoxication.
Adult↗
Effect of repeated therapeutic doses of digoxin on relative red and green sensitivity detected by Nagel's anomaloscope in healthy trichromats.
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Adult↗
Composition of human thrombus assessed by quantitative colorimetric angioscopic analysis.
BACKGROUND: Angioscopy surpasses other diagnostic tools, such as angiography and intravascular ultrasound, in detecting arterial thrombus. This capability arises in part from the unique ability of angioscopy to assess true color during imaging. In practice, hardware-induced chromatic distortions and the subjectivity of human color perception substantially limit the theoretic potential of angioscopic color. We used a novel application of tristimulus colorimetry to quantify thrombus color to both aid in its detection and assess its composition. METHODS AND RESULTS: A series of human thrombus models were constructed in vitro. Spatial homogeneity was ensured by light and electron microscopy. Quantitative colorimetric angioscopic analysis demonstrated excellent measurement reproducibility (mean difference, 0.07% to 0.17%), unaffected by illuminating light intensity (coefficient of variation, 0.21% to 3.67%). Colorimetric parameters C1 and C2 were strongly correlated (r=.99, P<.0001) with thrombus erythrocyte concentration. Principal components analysis transformed these parameters into a single value, the thrombus erythrocyte index, with little (0.06%) loss of content. Measured and predicted concentrations were similar (mean difference, 0.16 erythrocytes per 1 ng). Randomly ordered images were also subjected to visual analysis by three experienced angioscopists, with suboptimal levels of both intraobserver (mean kappa=0.63) and interobserver (mean kappa=0.48) agreement. In addition, visual ranking resulted in a Kendall rank coefficient of 0.72 to 0.76 versus a perfect 1.00 from quantitative measurement. CONCLUSIONS: Quantitative colorimetric angioscopic analysis provides a new, objective, and reproducible analytic tool for assessing angioscopic images of human thrombus. Even under ideal circumstances, experienced angioscopists do a poor job of assessing color (and therefore composition) of human thrombi. This technique can, for the first time, provide quantitative information of thrombus composition during routine diagnostic imaging.
Angioscopy↗
Texture segregation in chromatic element-arrangement patterns.
An element-arrangement pattern is composed of two types of elements arranged differently in different regions of a pattern. Rapid texture segregation depends on spontaneously discriminating the difference in the arrangement of the elements. Five experiments investigated the perceived segregation of patterns composed of two types of squares arranged in vertical stripes in the top and bottom regions and in a checkerboard arrangement in the middle region. The squares were either equal in luminance and different in hue or equal in hue and different in luminance. The rated similarities of the two hues in a pattern failed to predict perceived segregation. For a given background luminance, the perceived segregation was predicted by the square-root of the sum of the squares of the differences in the outputs of the L - M + S and L + M - S opponent channels, where L, M, and S were the cone contrasts of the long-, medium-, and short-wavelength receptors. The perceived similarity of the two hues in a pattern was not affected by the background luminance but was a function of cone excitations instead. For patterns differing in hue and equal in luminance, perceived segregation was an inverse function of the background luminance. A white background decreased the perceived segregation, but a black background did not. The effect of background luminance was not on the discrimination of the individual hues. The two hues making up a texture pattern were clearly distinguishable on a white background. A white background interfered with the discrimination of the vertical and diagonal columns of squares that distinguished the texture regions. For patterns differing in luminance and equal in hue, black and white backgrounds decreased the perceived segregation. The results indicate that adapting to an achromatic luminance distant from the luminance of the squares increased the Weber threshold for discriminating luminance differences, but did not increase the Weber threshold for discriminating hue differences. The experiments also revealed that luminance was the primary factor affecting perceived segregation and that perceived brightness is secondary. The results are consistent with the hypothesis that perceived segregation in element-arrangement patterns is primarily a function of the differences in the outputs of relatively early filtering mechanisms that encode pattern differences prior to the specification of the element shapes and their properties.
Color Perception↗
Development, maturation, and aging of chromatic visual pathways: VEP results.
It has been argued that the development and aging of the different achromatic and chromatic visual pathways may proceed independently. We review here the evidence for such independent changes with particular emphasis on electrophysiological results. Changes in chromatic and achromatic visual processing throughout the life span were studied using visual evoked potentials (VEPs). VEPs were recorded in response to the presentation of patterns designed to preferentially stimulate achromatic and S-(L+M) and (L-M) chromatic mechanisms. Recordings were made in subjects aged 1 week to 90+ years. Longitudinal measurements were obtained from several infants and cross-sectional measurements were obtained from infants and older subjects. Responses to achromatic reversing patterns at low spatial frequencies appeared early and changed rapidly. Latencies of the achromatic reversal response decreased to mature values within the first 12-15 weeks of life. Responses to chromatic pattern onsets, however, appeared later (L-M: 4 weeks; S: 6-8 weeks) and changed continuously throughout the first year of life. Chromatic waveforms from 1 year to puberty appeared inverted relative to the adult waveform. The waveforms did not appear adultlike until about 12-14 years of age. The latencies of the major negative component of the adult response reached a minimum around 17-18 years of age. Throughout the remainder of the life span, VEP latencies steadily increased and amplitudes slightly decreased. Latencies of responses to chromatic pattern onsets increased more rapidly than latencies to moderate contrast achromatic pattern reversals.
Adolescent↗
Accuracy of color scission for spectral transparencies.
When surfaces are overlaid by a transparent filter, color scission refers to the perceptual separation of the colors of the image into the colors of the underlying surface and the color of the overlaying layer. We used filter matching to measure the accuracy of color scission for simulated physical filters and materials. Standard filters were placed on various sets of chromatic materials and match filters on achromatic materials. In the majority of cases, filter matching was close to veridical. The spectral effects of filters are complex, but with respect to the visual system, they can be closely approximated by 3-D affine transformations of cone absorptions or chromaticities. Veridical filter matches can be predicted by neural strategies that match ratios of mean cone absorptions or match mean chromatic contrasts between filtered and exposed regions. However, when the shape of a filter transmittance differed significantly from the shapes of background reflectances, the overlaid region had lower saturation than the surround, and filter matches had broader transmittance spectra than veridical.
Color Perception↗
Adult brightness vs. luminance as models of infant photometry: variability, biasability, and spectral characteristics for the two age groups favor the luminance model.
When infants fail to make chromatic discriminations, do the characteristics of their performance minima coincide more closely with the properties of adult luminance matches or heterochromatic brightness matches? In addition to their spectral properties, adult luminance matches are typically characterized by relatively small individual differences, whereas brightness matches are believed to be both more variable and more biasable. Two complementary experiments were carried out on adults and 8-week-old infant subjects. Both groups were tested with small (1.5 degrees to 4 degrees ) red and blue test fields of varying luminances, embedded in a white surround. In adults, heterochromatic brightness matches were measured. Individual differences spanned about 0.5 log units, and brightness matches could be biased by as much as 0.8 log units by varying the range of test field luminances. In infants, the locations of performance minima were measured. Individual differences spanned less than 0.1 log units, the mean performance minima coincided with predictions based on V10(lambda), and the location of the performance minimum was nearly unaffected by the range of test field luminances used. Thus by all three criteria, these data suggest that infants' performance minima are mediated by luminance rather than by brightness signals. To date there remains no evidence that the infant visual system computes a brightness signal.
Adult↗
Discrete color filling beyond luminance gaps along perceptual surfaces.
Perceived color at a point in space is not determined simply by the color directly stimulating the corresponding retinal position. Surface color is informed by flanking edge signals, which also serve to inhibit the intrusion of signals from neighboring surfaces. Spatially continuous local interactions among color and luminance signals have been implicated in a propagation process often referred to as filling-in. Here, we report a phenomenon of discrete color filling whereby color jumps over luminance gaps filling into disconnected regions of the stimulus. This color filling is found to be blocked at boundaries defined by texture. The color filling is also highly specific to the elements belonging to a common perceptual surface, even when multiple surfaces are transparently overlaid. Our results indicate that color filling can be governed by a host of visual cues outside the realm of first-order color and brightness, via their impact on perceptual surface segmentation and segregation.
Color Perception↗