Saturation Discrimination Research Articles

Assessment of potential macular function using a color saturation discrimination test in eyes with cataract

Purpose: To study the efficacy of a color saturation discrimination test (CSDT) in assessing potential macular function in eyes with cataract. Setting: Yamanashi Medical University and Nirasaki City Hospital, Yamanashi, Japan. Methods: In this prospective study of 200 consecutive eyes with cataract, thethresholds of color saturation discrimination on 6 hues were measured with the CSDT The CSDT program was run on a personal computer and cathode-ray tube color monitor. The preoperative CSDT scores and postoperative visual acuities were compared. In addition, preoperative laser interferometry (LI) and postoperative CSDT were performed on selected patients and the results compared with their preoperative CSDT results. Results: Patients who had a CSDT score of 11 or more had a significantly lower postoperative visual acuity ( P < .0001). The prevalence of neuroretinal abnormality postoperatively increased with the preoperative CSDT score. The CSDT score was not correlated with preoperative visual acuity ( P = .1409). Cataract severity had little influence on the CSDT score. The preoperative results of the CSDT and LI were correlated with the postoperative acuity, with the correlation coefficient being stronger with the CSDT ( r = 0.338 and 0.276 for CSDT and LI, respectively). Conclusion: The CSDT was effective in evaluating neuroretinal pathology andpredicting postoperative acuity. Drs. Fumihiko Mabuchi and Teruhiko Gotou, Yamanashi MedicalUniversity assisted with this paper.

Human Newborn Color Vision: Measurement with Chromatic Stimuli Varying in Excitation Purity

Groups of newborn human infants (N= 180) were habituated to large 16° achromatic (“white”) lights of varying luminance (0.35 to 1.16 log cd/m2) and then tested for recovery of habituation to 16° green (dominant λ = 545 nm), yellow (dominant λ = 585 nm) or red (dominant λ = 650 nm) lights which varied in the level of excitation purity (range = 32 to 83%). Results showed that newborns discriminated the chromatic stimuli from white only when excitation purity values exceeded at least 41% for 545-nm green, 47% for 650-nm red, and 65% for 585-nm yellow, limits much higher than those for adults (<1%). Taken together with the results from previous experiments, these saturation discrimination data (with the exception of the yellow data), provide some support for an expanded MacAdam ellipse model of early color discrimination (Brown, 1993; Teller & Lindsey, 1993). This helps reinforce the current view that neonates’ vision is based on general rather than selective immaturities or inefficiencies within the requisite optical, photoreceptoral and neural mechanisms.

P-1-52 - Aneurysm occlusion using multiple clips, with special reference to the configurations of the cerebral aneurysm and parent vessel

To study the efficacy of a color saturation discrimination test (CSDT) in assessing potential macular function in eyes with cataract.Yamanashi Medical University and Nirasaki City Hospital, Yamanashi, Japan.In this prospective study of 200 consecutive eyes with cataract, thethresholds of color saturation discrimination on 6 hues were measured with the CSDT The CSDT program was run on a personal computer and cathode-ray tube color monitor. The preoperative CSDT scores and postoperative visual acuities were compared. In addition, preoperative laser interferometry (LI) and postoperative CSDT were performed on selected patients and the results compared with their preoperative CSDT results.Patients who had a CSDT score of 11 or more had a significantly lower postoperative visual acuity (P < .0001). The prevalence of neuroretinal abnormality postoperatively increased with the preoperative CSDT score. The CSDT score was not correlated with preoperative visual acuity (P = .1409). Cataract severity had little influence on the CSDT score. The preoperative results of the CSDT and LI were correlated with the postoperative acuity, with the correlation coefficient being stronger with the CSDT (r = 0.338 and 0.276 for CSDT and LI, respectively).The CSDT was effective in evaluating neuroretinal pathology andpredicting postoperative acuity.Drs. Fumihiko Mabuchi and Teruhiko Gotou, Yamanashi MedicalUniversity assisted with this paper.

Normal Saturation Processing Provides a Model for Understanding the Effects of Disease on Color Perception

Saturation discrimination has been reported to be affected early in the course of a disease. Our empirical data show a compressive curvi-linear relationship between opponent/nonopponent channel activity and saturation thresholds in normal trichromatic observers. This relationship can be explained by a model based on the Hurvich and Jameson saturation coefficient (1957), Psychology Reviews, 64, 384–404. The model considers effects of both selective and nonselective channel losses on saturation processing based on the assumption that disease produces elevated thresholds while maintaining normal psychometric response functions. Both the model and data support clinical observations of saturation losses occurring early in disease. However, the results also indicate that saturation may not be the best modality for monitoring long-term progression of such conditions. We suggest that the different processing characteristics for blue-yellow thresholds may yield added information for saturation testing under some circumstances and that saturation processing occurs at a higher cortical level. Copyright © 1996 Published by Elsevier Science Ltd.

The opponent colour functions and their relations with the colour discriminability

The paper deals with the problem of a construction of opponent functions, which stem from the linear summation of three receptor (R, G, B) signals. It is considered two stages model: stage of the receptors and stage of the opponent cells. Each stage has the own intrinsic independent generators of noise. The colour is determined by the point in three-dimensional space with coordinates {xi}, (i=l, 2, 3), where xi is value of the output signals of the opponent cells. Let V be the volume of “colour body” and be the volume of sphere, where an end of a colour vector is located with a given probability P0. Then a ratio V/s characterizes a colour discriminability: the greater ratio V/s the greater discriminability of the system. It is looking for such transformation of receptor signals into opponent those (i.e. searching a linear operator A), that the ratio V/s would be maximal. The properties of the proposed model were investigated. They fit well to the properties obtained in traditional psychophysical experiments: opponent colour functions, hue coefficients, wavelength and saturation discrimination, achromatic channel sensitivity, non-additivity of brightness. This led to conclusion that the possible role of the colour opponency is ensuring optimal colour discriminability in human vision.

The effects of V4 lesions on the visual abilities of macaques: hue discrimination and colour constancy

Monkeys with lesions of cortical visual area V4 were compared with unoperated monkeys in three experiments. In Expt. 1 they were tested for the reacquisition of a pre-operatively learned hue discrimination task. In Expt. 2, as a test of colour constancy, the monkeys were required to perform previously overlearned colour discrimination tasks when the amounts of red, green and blue light in the illuminant were changed. In Expt. 3 the animals were compared on the post-operative acquisition of hue, greyness and saturation discrimination tasks. The results of Expt. 1 showed that monkeys with V4 lesions can regain their pre-operative levels of performance on hue discrimination tasks. Expt. 2 showed that monkeys with V4 lesions have a colour constancy deficit. Expt. 3 reinforced the finding that the animals with V4 lesions could learn to perform fine hue discriminations but that their final, asymptotic performance was not as reliable as that of normal animals. The wavelength discrimination data are discussed within the context of recent electrophysiological findings that V4 is involved in selective attention to visual stimuli and the constancy data are interpreted as evidence that V4 is important for defining colour constancy thresholds but not for constructing the perceptual categories underlying constant colour perception.

Colour Discrimination of Two Passerine Bird Species in the Munsell System

Two male Yellow Wagtails Motacilla f. flava and one male Bluethroat Luscinia s. svecica were successively trained to ten colour papers, each representing one of the ten colour families in the Munsell 40 hue system. Discrimination was tested between the training hue and four neighbouring hues under standardized illumination. Yellow Wagtail hue discrimination was best in the red, orange and yellow families and less good towards shorter wavelengths and for red-purple hues. The Bluethroat discriminated best in the orange, purple-blue and purple families. Both species could memorize and make statistically significant discriminations between c. 20 hues. Their best discrimination occurred in spectral regions corresponding to their own sexually dimorphic plumage. Brightness (value) and saturation (chroma) discrimination was studied by training the same birds to the middle value/chroma of seven Munsell hues. The birds' value discrimination was poor: they learned to reject the darkest value(s) but not the brighter ones. Both species could discriminate between the less saturated chromas but they chose more saturated colours almost as frequently as the correct ones. Between the species there were differences particularly in chroma discrimination similar to those in hue discrimination. The Bluethroat's better hue discrimination in the short wavelength end of the spectrum (violet and blue) may tentatively be connected with the fact that this species has a larger proportion of cones sensitive to shorter wavelengths (about 75% of cones with colourless or pale greenish droplets), while in the Yellow Wagtail about 50% of the cones have red or yellow-orange oil droplets transmitting light efficiently only in the long wavelength part of the spectrum.

The Use of the Lanthony New Color Test in Determining the Effects of Aging on Color Vision

The primary purpose of this study was to collect data on the loss of color vision as a function of age. The Lanthony New Color Test (NCT), which measures acquired losses of color vision in the dimensions of hue, saturation, and brightness, was used to compile data on 68 subjects. The minimum number of subjects were 10 per decade from age 30 to 90 years. An age gradient of selective loss of discrimination of saturation beginning at age 50 was demonstrated, with rapid change noted after age 60. Similar findings were seen for hue but were not evident for brightness. By age 70, a neutral zone emerged at blue/purple, Munsell chroma level 2. The instrument was shown to be reliable and valid in comparison to the Farnsworth Dichotomous Panel D.15. It is seen that this information will provide a basis for planning safer, more functional environments for elderly people.

Effects of luminance level on the saturation function: Sensitivities based on saturation discrimination

AbstractThe saturation of a monochromatic light λ is defined as the reciprocal of the just noticeable colorimetric purity ΔP(λ) from a white, which is a conventional definition having been used previously often. The present study measures saturation functions of monochromatic lights at various luminance levels ranging from 10 to 1000 Td. The main result of this article is that the saturation function systematically changes in shape with the luminance level; as the luminance increases, the values of 1/ΔP(λ) relatively increase for shorter wavelengths. The chromatic sensitivity function C(λ) is defined by the reciprocal of the radiance of a monochromatic light λ added to the white field in order to detect a difference in chromaticity from the equal‐luminance reference white. The C(λ) functions at various luminance levels are shown to have three peaks at the short‐, middle‐, and long‐wavelength regions. These peaks are similar to those of the increment threshold functions, and the saturation function can be approximated by the ratio of the increment threshold spectral sensitivity to the relative luminous efficiency, except for the 570 nm data.

Model of saturation and brightness: Relations with luminance

AbstractThe model is simple: For flicker luminance stimuli and maximum purity, the hue cycle's relative luminance (computed from CIE data) is reciprocal to relative saturation. Brightness/luminance ratio B/L is proportional to relative saturation S, i.e., B/L = 1.5 S1/4. S times B/L ratio gives relative saturation for brightness stimuli; just as relative luminance times B/L ratio gives brightness. Predictions for any purity agree with data on saturation discrimination, color appearance in CIE space, B/L, and CIE brightness Vb. Predictions support Hunt's concept of “colorfulness” and indicate its causal role in proporitionality of S and B/L.

Illusory contours induced by isoluminant chromatic patterns

An illusory-contour was induced by abutting colored gratings embedded in the white field under isoluminance condition. The present study specified the stimulus conditions that invoked the justperceptible illusory contours for the isoluminant chromatic patterns. The results showed that the purity difference between the colored lines and the white field required for the illusory-contour perception gave a function closely resembling in shape the function obtained for saturation discrimination. Increasing the width of lines reduced threshold for the perception of illusory contours, while the line spacing had no significant effect. The dependence of the illusory-contour perception upon saturation could be accounted for by considering the extraction of the edge and colour information by means of the opponent-color processes observed for the cells in the retina and LGN. On the other hand, the effects of the spatial parameters met the response properties observed for the cells in the visual cortex. It is suggested that the perception of illusory contour may result from hierarchical organization from the retina to cortex in the visual system.

Clinical measurement of saturation discrimination

In this paper, we describe how a circular reflective neutral-density wedge can be used to construct an apparatus which provides a relatively rapid procedure for the clinical measurement of saturation discrimination. Subsequent to an initial measurement of the patient's relative luminosity function, the patient need only turn a single control which varies the colorimetric purity of a test field which remains luminance matched to a white light reference field.

Accuracy of memory for brightness of colored lights measured with successive comparison method.

Successive and simultaneous brightness comparisons between test colors and a comparison white were performed to study how accurately the brightness of colored lights was maintained in memory. The test colors were monochromatic lights chosen from 410 to 670 nm and a white light. The stimulus duration was 1 sec, and test-comparison stimulus-onset asynchronies in successive comparisons were more than 11 sec depending on the experiments. The results show that the variability of successive brightness comparisons was 1.5-2.0 times greater than that of simultaneous brightness comparison. This degree of deterioration of brightness discrimination is reasonably consistent with those of hue and saturation discrimination previously reported. Brightness shifts in the darker direction were found for most colors.

Blue Saturation Discrimination by Honeybees and its Potential Influence on Cross Pollination1

Blue saturation discrimination of honeybees (Apis mellifera L.) was investigated using artificial flowers constructed of Munsell standard colored matte paper with blue 7.5 PB 5/10 (Bmax), 7.5 PB 5/6 (Bmed), and 7.5 PB 5/2 (Bmin). Bees trained to Bmax, could distinguish Bmax from Bmin, though discrimination of Bmax from Bmed was not demonstrated. In a test of the reciprocal of the former test, bees trained to Bmin could not discriminate it from Bmax. This and tests with three saturation levels of green suggest that honeybee blue saturation discrimination is inferior to their color discrimination. However, these results indicate that honeybees may not forage randomly among plant genotypes having flowers of the same color with differences in saturation levels beyond Bmax and Bmin, especially when a greater reward is provided by the one with greatest color saturation.

Latencies for chromatic and achromatic visual mechanisms

Relative visual onset latency and offset latency (visual persistence) were measured (using perceived simultaneity methodsl for pulsed chromatic stimuli presented under two conditions: as luminance increments of 0.2 or 0.3 log unit above a prevailing achromatic background field, or in hue substitution, matched in luminance to the achromatic field so as to eliminate spatio-temporal luminance transients. In the first experiment, for the hue substitution condition, both onset and offset latencies were found to be slow relative to latencies for the increment condition, and varied with wavelength according to a function resembling trichromatic saturation discrimination (slowest latency at 570 nm). Latencies to increment pulses of equal luminance did not vary with wavelength. In a second experiment, offset latency was measured as a function of pulse duration and pulse luminance level. The observed decrease in offset latency with pulse duration was markedly steeper at short pulse durations for chromatic increments than for hue substitution stimuli. Offset latency decreased with increasing pulse luminance for incremental stimuli but not for hue substitution stimuli. These results are interpreted as reflecting the temporal response properties of chromatic neural mechanisms (the hue substitution data) and the achromatic mechanism (the increment data).

Optimum probabilistic processing in colour perception. I. Colour discrimination.

A comprehensive account of wavelength discrimination and colour saturation discrimination is given in terms of optimum probabilistic signal detection. The theory is a logical deduction from statistical estimation theory of the visual estimate of the spectral parameters of the stimulus. In place of geometrical concepts associated with colour-space geometry, stimulus discriminability is determined by optimum decision rules given by likelihood ratio tests on statistics that are postulated for the trichromatic responses. The classical line element theory and its formulations are deduced to be discriminability measures between signals. The different mathematical forms of classical theory are shown to correspond to different statistical constraints.

Das Farbensehen bei Schielamblyopie

Colour vision in squint amblyopia depends on the fixation modus. In eyes with foveolar or unsteady foveolar from fixation the 3 primary colour vision mechanisms (CVMs) gave normal foveolar CVM patterns. The absolute spectral retinal sensitivity was somewhat, but not significantly lowered. The spectral sensitivity for hue discrimination was either normal, or slightly reduced in the short wavelength side, or slightly reduced over the whole visible spectrum. The spectral sensitivity for saturation discrimination showed normal curves. -- In amblyopic eyes with parafoveal to perifoveal fixation mode the absolute spectral retinal sensitivity is lowered for about 0.45--0.60 log units in comparison to an approximately corresponding excentric retinal area in a normal eye. In eyes with parafoveolar to perifoveal fixation mode measurements of CVMs and of hue discrimination gave better results than could be expected with regard to the position of the fixating area as determined by visuscope. The values correspond to those obtained in retinal areas at least as close to the foveola as the amblyopic fixation point, but usually of an even more central position. The sensitivity for saturation discrimination showed no significant disturbance.

Structure and function of the pigeon visual system

This comprehensive, up-to-date account of vision in the pigeon begins with a description of the eye, its dimensions, and optical properties. The retina is discussed in considerable detail, with particular attention given to: the distribution of the various cell types within and across the retina, the number and the nature of the oil drops in the cones, the highly developed inner plexiform layer, the response characteristics of the ganglion cells, and the damage to cones caused by exposure to light. Lastly, the three major visual pathways are examined neuroanatomically and electrophysiologically. In the second section, several important issues have been emphasized: the putative differences between frontal and lateral vision, visual sensitivity to both discrete and periodic stimuli at various adaptation levels, polarotaxis in the pigeon, the bipartite spectral sensitivity of its retina, hue and saturation discrimination, sensitivity to ultraviolet light, panoramic acuity, and the detection of movement.

Hemispheric dominance and normal color memory

Hemispheric asymmetry in memory for color was investigated using the tachistoscopic laterality paradigm with 120 normal familial righthanded males. Experiment I employed hue and saturation discrimination tasks. A significant RVF superiority was found for both tasks with retention intervals of 1·6 and 10 sec. Experiment II used a finer saturation discrimination task and again a significant RVF superiority was produced. In both experiments the availability of color names which could have been used to mediate the retention intervals was demonstrated. For Experiments III and IV more complex color discrimination tasks designed in an effort to preclude verbal mediation resulted in an elimination of visual field differences.

Chromatic two-pulse resolution with and without luminance transients*

Two-pulse discrimination thresholds determined for homochromatic pulses presented as luminance increments or decrements are invariant with wavelength. Wavelength does affect two-pulse temporal resolution if chromatic pulses are presented in hue substitution, matched in luminance (with flicker photometry) to an achromatic background field. For relatively long pulses, the wavelength effect resembles trichromatic saturation discrimination, with poorest temporal resolution at 570 nm. For shorter pulses, temporal resolution for hue substitution stimuli appears related to saturation discrimination under conditions of artificial tritanopia. Under conditions of hue substitution, short-wavelength pulses yield good temporal resolution.