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PubMed1984

Colored neon flanks and line gap enhancement.

When a colored line connects two black (or differently colored) lines across a gap, colored neon flanks are seen on either side of it. These flanks extend over gap sizes of 50 min arc foveally and are not explained by Bezold-type assimilation. They may be elicited by black lines as short as 6 min arc adjoining the colored line at each end. To maximize these flanks, the black and colored lines must appear linearly continuous. Nonaligned junctions weaken the effect and an angular tilt of more than 40 dog destroys it. In this and other respects, (local) neon flanks are similar to van Tuijl's (global) neon color spreading (1975). Both phenomena have analogs in brightness perception. We propose that neon spreading is a lateral extension of neon flanks across the empty space between them, and discuss similarities of these effects with other brightness illusions (Schumann, Prandtl, Ehrenstein). For this group of illusions the term "line gap enhancement" is introduced to imply perceptual enhancement of changes in brightness and/or color along lines. Correspondences between the psychophysical properties and structural prerequisites for line gap enhancement on one hand and neuronal response properties of end-zone inhibited (hypercomplex) cortical cells on the other are discussed.

Color Perception↗

PubMed1984

Spatial mapping of monkey V1 cells with pure color and luminance stimuli.

We recorded the responses of single macaque striate cortical cells to color-varying and luminance-varying patterns. We show that (a) the vast majority of primate striate cells respond to pure color stimuli, in addition to responding to luminance-varying stimuli (b) in general, simple cells are color-selective whereas complex cells respond to multiple color regions, (c) most cortical cells show bandpass spatial frequency tuning to pure color-varying gratings, with various cells tuned to each of a wide range of spatial frequencies and (d) the peak spatial frequency and bandwidth of most striate cells is the same for color as for luminance-varying gratings; when they differ, cells tend to be more broadly tuned and peak at lower spatial frequencies for color (e) complex cells, on the average, respond to higher spatial frequencies than do simple cells.

Animals↗

PubMed1991

Color opponent coding in the visual system of the honeybee.

A model is presented for the color vision system of the honeybee, which takes the nonlinear phototransduction process in the photoreceptors into account and assumes linear computations of the excitations of the photoreceptors. The model parameters are derived by a least squares fit of the scale values determined by multidimensional scaling analysis of the results of color choice experiments to the excitation values of two hypothetical spectral antagonistic coding cells. The psychophysical scale values are interpreted physiologically. Furthermore, a color difference formula is presented which is based on the color opponent coding (COC) model. The model explains quantitatively (1) the sensitivity of spectral antagonistic neurons measured by Kien and Menzel (1977; Journal of Comparative Physiology, 113, 17-34, 35-53), (2) the color discrimination function measured by von Helversen (1972; Journal of Comparative Physiology, 80, 439-472). The following predictions are derived from the model: (1) excitation/log (I) curves of the spectral antagonistic neurons; and from the model in conjunction with the color difference formula: (2) intensity dependent color shifts (Bezold-Brücke effect); (3) the intensity dependence of wavelength discrimination.

Animals↗

PubMed1993

The role of features in preattentive vision: comparison of orientation, motion and color cues.

Arrays of lines or blobs were used to investigate the role of features vs feature contrast in preattentive vision. This study continues earlier work on orientation cues and extends it into the dimensions of motion and color. Tests were performed on patterns displaying continuous feature gradients, i.e. continuous variation, from element to element, in either line orientation, direction of motion, or color. In different series of experiments, the following four aspects of visual perception were investigated: (i) detection of a salient target ("odd man out" paradigm), (ii) segmentation of texture fields, (iii) search strategies for given targets, and (iv) figure-ground discrimination by grouping. Features were, in general, not found to play an important role in these tasks and performance was instead related to feature contrast. Only in the case of color did performance also depend upon hue, i.e. feature properties themselves. Whereas in all dimensions tested pop-out ("saliency") and segmentation were obtained from target or border elements whose local feature contrast was well above the level of variation elsewhere in the pattern, performance in the two latter tasks differed between orientation, motion, and color. In search, orientation targets were detected quickly when sufficiently distinct from their neighbors, but were apparently searched for serially if feature contrast was similar to that of other elements nearby. Color targets, however, were always detected fast in these patterns, independently of local feature contrast. Also, the perceived grouping of orientation or motion defined targets depended only on local feature contrast and not on the similarity of target elements. In fact, figures of dissimilar elements were seen as easily as figures of similar elements, indicating that, in these dimensions, stimulus coherence is not essential for the discrimination of figure and ground. For color, however, figures made up of the same targets were always seen slightly better than figures composed of different colors.

Adolescent↗

PubMed1994

Visual suppression and its effect upon color and luminance sensitivity.

Psychophysical increment thresholds were compared for periods of phenomenological dominance or suppression produced by different stimulation of the two eyes. Three experimental procedures were used; binocular rivalry, permanent suppression and flash suppression. The amount of suppression produced by each procedure was evaluated under conditions intended to accentuate color or luminance system contribution to the detection of a spectral flash. All three procedures resulted in a different pattern of color and luminance suppression. Binocular rivalry suppressed color sensitivity more than luminance and within color, blue (439 nm) sensitivity was more suppressed than red (613 nm). Permanent suppression resulted in a similar pattern of suppression but only blue color sensitivity was reliably more suppressed than luminance sensitivity. Flash suppression produced distinctly different results such that blue color sensitivity was reliably less suppressed than luminance or red color sensitivity, which were not different from each other. Taken together these results provide clues as to where and when the physiological processes mediating visual suppression may be found in the nervous system.

Color Perception↗

PubMed1990

Social preference of female gerbils (Meriones unguiculatus) as influenced by coat color of males.

Female gerbils (Meriones unguiculatus) of three distinct coat colors (agouti, black, and sandy or pink-eyed dilution) were tested in a Y-maze whose arms led to compartments containing unfamiliar male gerbils of varying coat colors. The stimulus animals were separated from the females by a Plexiglas door. The trials lasted for 2 min and each female was exposed to the following four combinations: two males of the same coloring as the female; one male of the same color and another of a different color from the female; both males of different color from the female. The number of crossings to the left and right arms was relayed by photocells to an IBM PC computer. The results indicate that agouti females preferred visiting the arm occupied by agouti males while those of the other coat colors showed no preference for the "wild-type" males. Instead, sandy and black female gerbils preferred to be in proximity with those of non-wild types.

Animals↗

PubMed1994

Retrieval of color and form during suppression of temporal cortex with cold.

Five cryodes were implanted on each side over the dorsal aspect of inferotemporal cortex (TEd) of three monkeys. They were trained on a form discrimination and three color discriminations. Suppression of TEd with cold disrupted retrieval of the color, but not the form discriminations. The animals could find the colors in a background of shifting values of gray, indicating that the suppression did not reduce their color perception to gray. They initially had great difficulty matching red to red and green to green, although that recovered with experience. The animals tended to respond to one or the other of the colors, indicating that they could perceive and discriminate them, but, either lost information about the correct stimulus, or something from past experience was interfering with performance. We suggested that cooling TEd suppresses new and recent learning of color discriminations, but it does not suppress some previous experience that intrudes upon performance of new tasks. TEd might contain episodic information about colors necessary for performance of the immediate task.

Animals↗

PubMed2004

Assessment of plaque vulnerability by angioscopic classification of plaque color.

BACKGROUND: The disruption of yellow plaque and subsequent thrombosis is regarded as the mechanism of acute coronary syndrome. However, there are limited reports on the assessment of plaque vulnerability. Therefore, we tested whether the angioscopically determined yellow color intensity of plaque is associated with the prevalence of thrombosis on the plaque. METHODS: The angioscopic images of 843 patients who underwent catheterization and angioscopic examination from November 1999 to July 2003 for the diagnosis of coronary artery diseases were analyzed. Suspected culprit vessel was observed by angioscopy, and the yellow color intensity (1, light yellow; 2, yellow; 3, intensive yellow) of all yellow plaques (n = 1253) detected in the nonstenotic (diameter stenosis <50%) coronary segments was determined, as well as whether there was thrombosis on the plaques. RESULTS: The number of detected yellow plaques was 345, 721, and 187 for color grade 1, 2, and 3, respectively. The prevalence of thrombosis detected by angioscopy (15%, 26%, and 52% on the plaque of color grade 1, 2, and 3, respectively, P <.0001) was significantly higher on the plaque of higher yellow color grade. CONCLUSIONS: The yellow color intensity of plaque determined by angioscopy was strongly related with the prevalence of thrombosis on the plaque. The yellow color intensity may be a marker of plaque vulnerability.

Aged↗

PubMed2006

Contrast sensitivity and color vision in HIV-infected individuals without infectious retinopathy.

PURPOSE: To investigate the relationship between abnormal contrast sensitivity and abnormal color vision among human immunodeficiency virus (HIV)-infected individuals who have normal visual acuity and to seek host factors that predict these abnormalities. DESIGN: Noninterventional, cross-sectional study. METHODS: We evaluated 71 HIV-infected subjects with visual acuity of 20/25 or better, clear media, and no vision-threatening retinal lesions. Visual function was determined using the Pelli-Robson contrast sensitivity test and the Farnsworth-Munsell 100-Hue color test (FM-100). Results were compared with published values for normal populations and to measures of HIV disease severity. We evaluated two levels of impairment for each visual function. "Mild dysfunction" was defined as > or =1 standard deviation (SD), but <2 SD from normal means. "Abnormal" was defined as > or =2 SD from normal means. RESULTS: The prevalences of abnormal contrast sensitivity and abnormal color vision were 7.0% and 9.9%, respectively. We did not identify relationships between impaired contrast sensitivity and impaired color vision. Impaired color vision was associated with increasing age (r = 0.36, P = .002). We could not identify significant correlations between either contrast sensitivity or color vision values and the following factors: current or nadir (lowest previous) CD4+ T-lymphocyte count, HIV blood level, and Karnofsky score. CONCLUSIONS: Abnormal contrast sensitivity and abnormal color vision can occur independently in HIV-infected individuals and can be present in the absence of severe immunosuppression.

Adult↗

PubMed2005

Color makes a difference: two-dimensional object naming in literate and illiterate subjects.

Previous work has shown that illiterate subjects are better at naming two-dimensional representations of real objects when presented as colored photos as compared to black and white drawings. This raises the question if color or textural details selectively improve object recognition and naming in illiterate compared to literate subjects. In this study, we investigated whether the surface texture and/or color of objects is used to access stored object knowledge in illiterate subjects. A group of illiterate subjects and a matched literate control group were compared on an immediate object naming task with four conditions: color and black and white (i.e., grey-scaled) photos, as well as color and black and white (i.e., grey-scaled) drawings of common everyday objects. The results show that illiterate subjects perform significantly better when the stimuli are colored and this effect is independent of the photographic detail. In addition, there were significant differences between the literacy groups in the black and white condition for both drawings and photos. These results suggest that color object information contributes to object recognition. This effect was particularly prominent in the illiterate group.

Adult↗

PubMed2004

Integration of color and boundary information for improved region of interest identification in electron magnetic resonance images.

A Windows-based, object-oriented application system for segmentation and analysis of electron magnetic resonance (EMR) images is described. The integrated system is developed for better recognition of regions of interest (ROI) in murine EMR images. The system combines the clustering method of color segmentation with boundary detection, for efficient segmentation of regions of interest in EMR images. Initially, the red/green/blue (RGB) color space is converted into spherical coordinates transform (SCT) space. Color quantization is then achieved by center split algorithm applied on the color dimensions of the SCT space. Subsequently, Laplacian boundary detection operator is used to extract the contours of the ROI from the variegated coloring information. The system is implemented in Visual C++ and tested on temporal EMR color images of mouse. The system performs well giving perceptually reasonable segmentation of tumor, kidney and bladder of the mouse image. Experimental results with extensive set of EMR color images demonstrate the efficacy of the system developed.

Animals↗

PubMed2005

Relations in color among maxillary incisors and canines.

OBJECTIVES: To establish the strength of color relation among the maxillary central incisor, lateral incisor and canine teeth by using digital photography. This relation might be useful for the color reconstruction of the missing part of a tooth from the color obtained from neighboring teeth. METHODS: The L*a*b* values of the maxillary incisors and canines were determined in 100 subjects. Paired t-tests, Pearson correlations and linear regression analyses were used to describe the relation of the L*a*b* values between the three teeth for each segment (cervical, middle and incisal). RESULTS: The mean L*a*b* values of the canines differed statistically significantly from the values of the central incisors (p<0.001) except for L* and a* values in the cervical segment between the lateral incisor and canine. The color differences between the incisors were statistically significant in fewer cases. The relation in color was the highest between the cervical segments of the three teeth, with respect to L* (r = 0.45-0.65; p < 0.001), b* (r = 0.49-0.55; p < 0.001), and a* (r = 0.38-0.61; p < 0.001), and no relation was found between the incisal segments of central incisor and canine. SIGNIFICANCE: There is a relation in color between the maxillary incisors and canines, which is stronger between the cervical than between the middle and incisal segments. Therefore, the color prediction is most reliable when the cervical parts of the teeth are used.

Adult↗

PubMed2006

Influence of scattering/absorption characteristics on the color of resin composites.

OBJECTIVES: Optical scattering has been studied because of its important effects on the color and translucency of a material. The objective of this study was to determine the influence of the scattering and absorption characteristics including translucency and opalescence on the CIE color coordinates (L(*), a(*), and b(*)) of resin composites. METHODS: Color and spectral distribution of seven resin composites (14 shades, 1mm thick) were measured in the reflectance and the transmittance modes. Optical constants including scattering coefficient (S), absorption coefficient (K) and light reflectivity (RI) were calculated from the spectral reflectance data using Kubelka's equations. The opalescence parameter (OP) was calculated as the difference in yellow-blue (Deltab(*)) and red-green (Deltaa(*)) coordinates between the reflected and transmitted colors. The translucency parameter (TP) was calculated for the translucency evaluation. Simple correlation among each of CIE L(*), a(*) and b(*) values measured using varied protocols with optical parameters (S, K, RI, OP and TP) was determined, and multiple regression analysis was used to determine the significantly influencing variables on the color coordinates (p<0.05). RESULTS: CIE L(*), a(*), and b(*) values were influenced by S, K, RI, TP and OP values. The CIE L(*) value without backing and that in the transmission mode were highly correlated with S. OP and TP values also influenced CIE L(*) value. The CIE b(*) value was correlated with the OP value when different composites with the same shade designation were compared. SIGNIFICANCE: Since the scattering and absorption characteristics influence the color of resin composites, the size and volume fraction of fillers should be controlled for the best color reproduction, considering the refractive indices of filler and resin matrix.

Absorption↗

PubMed2006

Color encoding of endocardial motion improves the interpretation of contrast-enhanced echocardiographic stress tests by less-experienced readers.

BACKGROUND: We hypothesized that color encoding of endocardial motion could aid less-experienced readers in detection of wall-motion abnormalities at rest and stress in patients with poor acoustic windows. METHODS: Color-encoded images (color kinesis) were obtained at rest and peak dobutamine stress in 4 standard views during intravenous infusion of contrast agent in 117 patients with poorly visualized endocardium. In 101 of 117 patients (86%), in whom contrast enhancement allowed endocardial tracking, images were reviewed by two expert readers without color overlays. Each reader graded regional wall motion as normal, abnormal, or uninterpretable, and their consensus grades served as a gold standard. The same images were then reviewed and graded with and without color overlays by 3 cardiology fellows. The accuracy of the interpretation was calculated against the gold standard separately for the 3 vascular territories (left anterior descending, left circumflex, and right coronary arteries) and averaged for the 3 fellows. RESULTS: With the addition of color encoding: (1) the number of uninterpretable segments decreased by 55% at rest and 61% at peak stress; and (2) all 3 fellows reached higher levels of accuracy in all 3 vascular territories both at rest (6%-82% average) and at stress (73%-80%). CONCLUSION: The addition of color encoding of wall motion to contrast-enhanced images obtained in patients with poor acoustic windows during stress tests improves the interpretation of regional left ventricular function by less-experienced readers.

Dobutamine↗

PubMed2005

Color vision and contrast sensitivity in epilepsy patients treated with initial tiagabine monotherapy.

The purpose of the study was to determine whether the use of a GABAergic antiepileptic drug (AED), tiagabine, affects color vision and contrast sensitivity. Twenty newly diagnosed patients with partial epilepsy (aged 19-72 years), receiving tiagabine as their initial monotherapy for 5-41 months were examined. Color vision was examined with the Standard Pseudoisochromatic Plates 2 (SPP2), with the Farnsworth-Munsell 100 Hue Test (FM100) and with the Color Vision Meter 712 (CVM) anomaloscope. Contrast sensitivity was measured with the Pelli-Robson letter chart. Three patients excluded from the color vision evaluation for congenital red-green color vision defects. Seven out of 17 patients (41%) had acquired color vision deficit examined with the FM100. The CVM anomaloscope revealed minor defects in two patients. Contrast sensitivity function was within normal ranges. The present study suggests that AED therapy with tiagabine, like with other established and newer AEDs may interfere with color perception.

Adult↗

PubMed2005

A large Eustachian valve is a confounder of contrast but not of color Doppler transesophageal echocardiography in detecting a right-to-left shunt across a patent foramen ovale.

BACKGROUND: Transesophageal contrast echocardiography (cTEE) is considered to be the method of choice for diagnosing patent foramen ovale (PFO), but its diagnostic accuracy compared with color Doppler guided TEE in the presence of an Eustachian valve (EV) has not been evaluated. The main aim of this study was to assess the diagnostic accuracy for PFO diagnosis of color Doppler TEE at low pulse repetition frequency. METHODS: We ascertained the presence of PFO and EV using cTEE and transthoracic contrast echocardiography (cTTE) in 292 consecutive patients (age 42+/-12 years) with cryptogenic stroke. A diagnosis of PFO was based on the observation of right-to-left shunting of contrast bubbles or by color Doppler with pulse repetition frequency of 20-30 cm/s. An EV with a diameter of >1.5 cm in the bicaval view was considered large. RESULTS: Overall 204 patients (70%) had evidence of a right-to-left shunt by either contrast echo method. Shunting was demonstrated more frequently by color Doppler than by cTEE, either spontaneously (133 vs. 92; p=0.01) or during provocative maneuvers (166 vs. 184; p=0.01). The sensitivity of color Doppler was significantly higher than that of cTEE (90% vs. 81%; p=0.01). A large EV was found in 37 patients, 31 (84%) of whom had a PFO. The presence of a large EV did not significantly influence the sensitivity of color Doppler for detecting shunting through a PFO, but the sensitivity of cTTE and cTEE was significantly reduced (from 88% to 42%, p<0.001). CONCLUSIONS: Color Doppler TEE is more accurate than traditional cTEE for PFO diagnosis and is not negatively influenced by the presence of an EV, provided that a low pulse repetition frequency is used.

Adult↗

PubMed2005

Two different sensory mechanisms for the control of pupal protective coloration in butterflies.

The butterflies Graphium sarpedon nipponum Fruhstorfer and Papilio xuthus Linné show pupal protective color polymorphism, but the two species appear to have different sensory mechanisms for determining pupal coloration. When light was of sufficient illumination, the larvae of Graphium sarpedon became bright yellowish green pupae on white pupation boards and reddish brown pupae on black pupation boards. The pupal coloration thus strongly depended on the brightness of the pupation site. In addition, larvae became bright yellowish green pupae in complete darkness. From these results, measurement of the illumination suggested that pupal color is determined by the illuminant difference between incidence light from the dorsal direction and ventral light from a paper board; i.e., the sum of the reflected light of the board plus the penetrated light passing through the board. The illuminant difference required for reddish brown coloration was 40 lux or more. The optical signals received through the stemmata during a critical period before formation of the thorax garter (band string) were important for coloration. By contrast, in Papilio xuthus, successive tactile signals from a rough surfaced pupation site during a critical period before and after formation of the garter were important for determining brown pupal coloration.

Animals↗

PubMed2003

Assessing the potential of a "color effect" for hair analysis of 11-nor-9-carboxy-delta(9)-tetrahydrocannabinol: analysis of a large sample of hair specimens.

It has been hypothesized that hair color may play a role in the concentration of various drugs of abuse in hair. Several studies have shown that melanin in hair appears to play a binding role for at least some commonly abused drugs. However, these studies have been limited by a number of factors when assessing the clinical significance of a hypothesized melanin or color effect. This study evaluates the possible effect of hair color on the concentration of 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (c-THC) in human hair. The analysis is based on 3886 positive c-THC hair specimens drawn from a universe of approximately 80000 specimens of scalp hair harvested from the posterior vertex of the head. Analysis of variance of color categorization by c-THC concentration shows that c-THC concentration does not have a significant association with hair color (Hair Color F = 1.148, p =.332) and therefore does not have a demonstrable "color effect".

Dronabinol↗