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PubMed2001

Asynchronous processing in vision: color leads motion.

It has been demonstrated that subjects do not report changes in color and direction of motion as being co-incidental when they occur synchronously. Instead, for the changes to be reported as being synchronous, changes in direction of motion must precede changes in color. To explain this observation, some researchers have suggested that the neural processing of color and motion is asynchronous. This interpretation has been criticized on the basis that processing time may not correlate directly and invariantly with perceived time of occurrence. Here we examine this possibility by making use of the color-contingent motion aftereffect. By correlating color states disproportionately with two directions of motion, we produced and measured color-contingent motion aftereffects as a function of the range of physical correlations. The aftereffects observed are consistent with the perceptual correlation between color and motion being different from the physical correlation. These findings demonstrate asynchronous processing for different stimulus attributes, with color being processed more quickly than motion. This suggests that the time course of perceptual experience correlates directly with that of neural activity.

Color Perception↗

PubMed1999

Evaluation of coronary bypass flow with color-Doppler and magnetic resonance imaging techniques: comparison with intraoperative flow measurements.

OBJECTIVES: After coronary artery bypass surgery, patency and flow assessment is based on invasive methods such as angiography and intravascular ultrasound or flow wire techniques. The aim of the study was to compare intraoperative transit time flow measurements of coronary bypass grafts with early postoperative color-Doppler and MR-imaging assessment. METHODS: In 22 patients (62+/-8.5 years) undergoing elective coronary bypass surgery the flow was measured in all internal mammary artery grafts (IMA) and saphenous vein grafts using the transit time flow technique. Postoperatively (days 5-7) all patients had a color-Doppler IMA graft assessment followed by a MR-angiography and flow measurement (navigator echo phase contrast technique with and without contrast bolus application) to determine patency and graft flow. RESULTS: Data are expressed as the mean +/- SD). (1) In all patients the left IMA graft to the left anterior descending coronary artery (LAD) could be identified and flow could be assessed with both color-Doppler and MRI. Venous grafts could only be visualized by MRI. The use of an intravenous contrast bolus enhanced the visualization of coronary artery bypass grafts. (2) The mean IMA to LAD flow was 33+/-17 ml/min intraoperatively by transit time and postoperatively 36+/-25 ml/min by MR respectively 66+/-54 ml/min by color-Doppler technique. (3) The systolic/diastolic flow ratio was 0.44+/-0.12 intraoperatively and 0.43+/-0.17 postoperatively by MR respectively 0.67+/-1.0 by color-Doppler. (4) A statistically significant correlation could be demonstrated between intraoperative transit time and postoperative MR flow measurements (r = 0.57; P < 0.04), whereas the correlations to color-Doppler flow were poor. Postoperatively MR and color-Doppler showed a good correlation of systolic/diastolic flow ratio (r = 0.88; P < 0.008). CONCLUSIONS: The color-Doppler method during echocardiography and MR-imaging are useful non-invasive techniques to visualize postoperative IMA grafts for patency assessment. The quantification of IMA flow is still difficult with either technique, but MR flow measurements showed the best correlation to the intraoperatively measured transit time flow. The MR technique is the most promising non-invasive method for postoperative evaluation of coronary bypass grafts, since it allows visualization and reliable flow quantification.

Blood Flow Velocity↗

PubMedDate not supplied

Minimum-variance cone-excitation ratios and the limits of relational color constancy.

Relational color constancy refers to the constancy of the perceived relations between the colors of surfaces of a scene under changes in the spectral composition of the illuminant. Spatial ratios of cone excitations provide a natural physical basis for this constancy, as, on average, they are almost invariant under illuminant changes for large collections of natural surfaces and illuminants. The aim of the present work was to determine, computationally, for specific surfaces and illuminants, the constancy limits obtained by the application of a minimum-variance principle to cone-excitation ratios and to investigate its validity in predicting observers' surface-color judgments. Cone excitations and their changes due to variations in the color of the illuminant were estimated for colored surfaces in simulated two-dimensional scenes of colored papers and real three-dimensional scenes of solid colored objects. For various test surfaces, scenes, and illuminants, the estimated levels of relational color constancy mediated by cone-excitation ratios varied significantly with the test surface and only with certain desaturated surfaces corresponded to ideal matches. Observers' experimental matches were compared with predictions expressed in CIE 1976 (u',v') space and were found to be generally consistent with minimum-variance predictions.

Color Perception↗

PubMed1993

Color improves object recognition in normal and low vision.

Does color improve object recognition? If so, is the improvement greater for images with low spatial resolution in which there is less shape information? Do people with low visual acuity benefit more from color? Three experiments measured reaction time (RT) and accuracy for naming food objects displayed in 4 types of images: gray scale or color, and high or low spatial resolution (produced by blur). Normally sighted Ss had faster RTs with color, but the improvement was not significantly greater for images with low spatial resolution. Low vision subjects were also faster with color, but the difference did not depend significantly on acuity. In 2 additional experiments, it was found that the faster RTs for color stimuli were related to objects' prototypicality but not to their color diagnosticity. It was concluded that color does improve object recognition, and the mechanism is probably sensory rather than cognitive in origin.

Adult↗

PubMed2001

Attentional capture by irrelevant color singletons.

Four experiments investigated attentional capture by a color singleton in visual search for a nonsingleton target. B. S. Gibson and E. M. Kelsey (1998) found that a color singleton in a precuing array facilitated target discrimination at that location if the same color also signaled the target array onset. The authors found similar cuing effects regardless of whether the singleton color matched the target array and regardless of whether subjects could anticipate the singleton or target-array color. In Experiment 4, a color singleton captured attention when it appeared in the precuing array but not when it appeared in the target array. The results indicate that attentional control settings for displaywide attributes are imprecise: Although subjects may anticipate a specific color, they cannot avoid attentional capture by other irrelevant colors. In addition, the effect of irrelevant singletons depends on whether a target is simultaneously present in the array.

Attention↗

PubMed1985

Some effects of color on naming and recognition of objects.

In this article, we investigated the role of color in the recognition and naming of everyday objects. In the first experiment we found that color pictures were named faster than black-and-white and that shape information did not facilitate color naming. Experiment 2 was carried out to determine at which stage of object processing the color facilitation occurred. We found that color had no effect on object recognition but did facilitate object naming, even when color was redundant for discrimination. This did not apply to naming abstract shapes. Experiment 3 replicated the findings of Experiment 2 using different objects and colors. The results showed that color could facilitate but not inhibit object naming and did not affect object recognition.

Adolescent↗

PubMed1997

Attenuating verbal overshadowing through color retrieval cues.

Five experiments showed that interference resulting from verbalizing visual stimuli (verbal overshadowing) can be reduced by reintroducing visual cues present at encoding. Object color and background color were used as cues. Participants learned either easy- or hard-to-name figures and then performed an image rotation task. Before performing the imagery task, participants were re-presented with the color patch associated with each figure. Color re-presentation attenuated the impairment associated with easy-to-name stimuli (Experiment 1) as well as labeled hard-to-name stimuli (Experiment 2). However, background color cues had no effect on imagery performance (Experiment 3). Experiment 4 showed that naming the object colors at encoding makes color retrieval cues ineffective. Finally, Experiment 5 showed that object color cues can help participants to overcome previously exhibited impairment resulting from covert verbalization.

Color Perception↗

PubMed2006

Stroop dilution depends on the nature of the color carrier but not on its location.

Stroop dilution is the reduction of the Stroop effect in the presence of a neutral word. It has been attributed to competition for attention between the color word and neutral word, to competition between all stimuli in the visual field, and to perceptual interference. Five experiments tested these accounts. The critical manipulation was whether the color to be named was carried by the color word or the neutral word. Neutral words diluted the Stroop effect when they were the color carrier, but not when the color word was the color carrier. We argue that Stroop dilution is due to attentional competition between the color word and neutral word, with priority given to the color carrier.

Attention↗

PubMed2000

Assessment of left ventricular regional wall motion by color kinesis technique: comparison with angiographic findings.

The analysis of segmental wall motion using two-dimensional (2-D) echocardiography is subjective with high interobserver variability. Color kinesis is a new technique providing a color-encoded map of endocardial motion. We evaluated the accuracy of color kinesis and 2-D for assessment of regional asynergy compared with left ventricular angiography as a reference method. Fifteen patients admitted for myocardial infarction were studied by echocardiography the day before left ventricular angiography. The left ventricle was divided into seven segments. Each segment was classified by two independent observers as normal or abnormal in 2-D and color kinesis. Accuracy of color kinesis and 2-D was evaluated and compared to left ventricular angiography. Color kinesis is significantly superior to 2-D for all seven segments (mean 0.80/0.68, P = 0.05), except for the septum (0.67/0.60, P = NS). Interobserver variability studied by chi-square statistic is lower with color kinesis (0.70) than with 2-D (0.57). We conclude that these data suggest that color kinesis is a useful method for assessing systolic wall motion in all segments, except the septum and for improving the accuracy of segmental ventricular function and interobserver variability.

Adult↗

PubMed2003

Dynamic three-dimensional color flow Doppler: an improved technique for the assessment of mitral regurgitation.

BACKGROUND: Prior studies have reconstructed mitral regurgitant flow in three dimensions displaying gray scale renditions of the jets, which were difficult to differentiate from surrounding cardiac structures. Recently, a color-coded display of three-dimensional (3D) regurgitant flow has been developed. However, this display was unable to integrate cardiac anatomy, thereby losing spatial information, which made it difficult to determine the jet origin and its spatial trajectory. To overcome this limitation, an improved method of 3D color reconstruction of regurgitant jets obtained from color flow Doppler using a transesophageal approach was developed to allow the combined display of both color flow and gray scale information. OBJECTIVES: To demonstrate the feasibility of 3D reconstruction of regurgitant mitral flow jets using an improved method of color encoding digital data acquired by transesophageal echocardiography (TEE). METHODS: We studied 46 patients undergoing a clinically indicated TEE study. All subjects had mitral regurgitation detected on a previous transthoracic study. Atrial fibrillation or poor image quality were not used as exclusion criteria. The 3D study was performed using a commercial ultrasound imaging system with a TEE probe (Sonos 5500, Agilent Technologies). A rotational mode of acquisition was used to collect two-dimensional (2D) color flow images at 3-degree intervals over 180 degrees. Images were processed off line using the Echo-View Software (TomTec Imaging Systems). Volume-rendered 3D color flow jets were displayed along with gray scale information of the adjacent cardiac structures. RESULTS: Mitral regurgitant flow, displayed in left atrial and two longitudinal orientations, was successfully reconstructed in all patients. The time for acquisition, post-processing, and rendering ranged between 10 and 15 minutes. There were 28 centrally directed jets and 15 eccentric lesions. Eight patients in the study had periprosthetic mitral regurgitant flow. CONCLUSIONS: Three-dimensional imaging of mitral regurgitant jets is feasible in the majority of patients. This improved technique provides additional information to that obtained from the 2D examination. Particularly, in patients with paravalvular leaks 3D color flow Doppler provides information on the origin and the extent of the dehiscence, as well as insight into the jet direction. In addition, in patients with eccentric mitral regurgitation, this new modality overcomes the inherent limitations of 2D echo Doppler by depicting the full extent of the jet trajectory.

Echocardiography, Doppler, Color↗

PubMed1995

[Echo contrast agents for the color Doppler sonographic diagnosis of deep femoral venous thrombosis].

PURPOSE: Evaluation of an echo contrast medium (Echovist) for color-coded duplex sonography of deep venous thrombosis of the thigh. MATERIAL AND METHODS: In 19 patients with deep vein thrombosis of the thigh, diagnosed by contrast phlebography, 22 color-coded duplex sonography studies were performed for flow analysis at the top of the thrombus. During the studies 8.5 ml echo contrast medium were injected in an ipsilateral vein at the back of the foot. The flow signals of the non-enhanced color coded duplex sonography were compared with those of the echo enhanced study for differentiation between floating thrombi from those adherent to the vein wall. RESULTS: The echo-enhanced color-coded duplex sonography showed a significant increase in detection of perfusion at the top of the thrombus in comparison with non-enhanced color-coded duplex sonography (p < 0.01). 9 thrombi were regarded as wall adherent after the native study, 7 of these could be identified as floating thrombi by echo-enhanced color-coded duplex sonography. CONCLUSION: Echo-enhanced color-coded duplex sonography yields a significant increase of diagnostic information in certain findings of the non-enhanced color-coded duplex sonography differentiating between floating thrombi and wall adherent thrombi in the deep venous system of the thigh.

Adult↗

PubMed1985

Effect of color on judgments of food aroma and flavour intensity in young and elderly adults.

The hypothesis was tested that subjects' judgments of food aroma and flavour strength will be increasingly influenced by food color as the chemosensory differences between foods become less apparent. Elderly (n = 24) and young (n = 22) adults were presented with pairs of food samples and instructed to indicate which sample had the more intense aroma or flavor. The chemosensory discriminations varied in difficulty, and the color of the food pairs was also manipulated so that either they were similarly colored, or the color strength differed so that it was either positively or inversely correlated with flavour strength. Overall, the results failed to support the hypothesis that color alters the perceived intensity of the food aroma or flavor. There was a weak trend toward a greater number of errors among sample pairs that varied in color, especially when color strength was inversely related to flavor strength. Elderly and young adult groups did not differ in chemosensory ability or in their responses to food color differences, although the elderly adults were significantly more certain of the accuracy of their chemosensory judgments.

Adult↗

PubMed1999

Color filling-in under steady fixation: behavioral demonstration in monkeys and humans.

Color filling-in is a phenomenon in which the color of an object appears to be filled-in by the color of the surrounding field. We have studied the question of whether monkeys perceive color filling-in with near-foveal stimuli under steady fixation. Two monkeys were trained to fixate steadily and to attend to a disk, surrounded by an annulus of the complementary color, in parafoveal vision. Using displays in which the color of the disk was gradually changed to that of the annulus, we trained the animals to signal when they perceived a uniform color field. During the experiment, we introduced a small percentage of trials in which the disk color remained constant, and looked for 'filling-in' responses in these trials. Three human subjects were also tested for comparison. All subjects produced 'filling-in' responses with frequencies that were significantly higher for static disks with blurred borders than for moving disks or disks with sharp borders. This indicates that the monkeys' responses reflected perceptual filling-in, rather than random behavior. The time course of filling-in was similar in monkeys and humans. For the blurred static disks, responses occurred first after 3-4 s of fixation, reaching a probability of 0.2-0.8 by the end of 6 s, depending on the subject.

Adult↗

PubMed2001

The evolution of coloration and toxicity in the poison frog family (Dendrobatidae).

The poison frogs (family Dendrobatidae) are terrestrial anuran amphibians displaying a wide range of coloration and toxicity. These frogs generally have been considered to be aposematic, but relatively little research has been carried out to test the predictions of this hypothesis. Here we use a comparative approach to test one prediction of the hypothesis of aposematism: that coloration will evolve in tandem with toxicity. Recently, we developed a phylogenetic hypothesis of the evolutionary relationships among representative species of poison frogs, using sequences from three regions of mitochondrial DNA. In our analysis, we use that DNA-based phylogeny and comparative analysis of independent contrasts to investigate the correlation between coloration and toxicity in the poison frog family (Dendrobatidae). Information on the toxicity of different species was obtained from the literature. Two different measures of the brightness and extent of coloration were used. (i) Twenty-four human observers were asked to rank different photos of each different species in the analysis in terms of contrast to a leaf-littered background. (ii) Color photos of each species were scanned into a computer and a computer program was used to obtain a measure of the contrast of the colors of each species relative to a leaf-littered background. Comparative analyses of the results were carried out with two different models of character evolution: gradual change, with branch lengths proportional to the amount of genetic change, and punctuational change, with all change being associated with speciation events. Comparative analysis using either method or model indicated a significant correlation between the evolution of toxicity and coloration across this family. These results are consistent with the hypothesis that coloration in this group is aposematic.

Amphibian Venoms↗

PubMedDate not supplied

Dose-related color vision impairment in toluene-exposed workers.

Occupational exposure to various neurotoxic chemicals can impair color vision. We evaluated this possibility in toluene-exposed workers. Thirty-three rubber workers and 16 referents were studied. We estimated toluene exposure by measuring urinary excretion of the unmodified form of the solvent (i.e., TolU). Color vision was tested with the Lanthony D-15 desaturated panel, and the outcomes were expressed quantitatively with the Color Confusion Index and the Total Confusion Index. Toluene-exposed workers had a subclinical reduction in color vision, compared with referents. We related this effect to solvent cumulative exposure--estimated as the product of urinary excretion of unmodified toluene by previous toluene exposure duration. This approach supports the hypothesis that impairment progresses as exposure continues. In the examined group of workers, toluene exposure was within the occupational limit proposed by the American Conference of Governmental Industrial Hygienists. The observed loss in color vision raises doubts on the real protection afforded by this limit--at least for effects of the solvent on the eyes. Finally, the Total Confusion Index was a more sensitive index than the Color Confusion Index in the evaluation of toluene-related color-vision impairment, suggesting that this index should be adopted in future studies of the effects of chemicals on color perception.

Adult↗

PubMed1995

Colors and emotions: preferences and combinations.

Within three age groups (7-year-old children, 11-year-old children, and adults), preferences for colors and emotions were established by means of two distinct paired-comparison tasks. In a subsequent task, participants were asked to link colors to emotions by selecting an appropriate color. It was hypothesized that the number of times that each color was tied to a specific emotion would be predictable from the separate preferences for colors and emotions. Within age groups, participants had consistent preferences for colors and emotions, but preferences differed from one age group to another. Especially in the youngest group, the pattern of combinations between colors and emotions appeared to be meaningfully related to the preference order for colors and emotions.

Adult↗

PubMed1990

Stroop Color-Word Test performance in patients with Alzheimer's disease.

Patients with Alzheimer's disease (AD) (n = 36) and normal older adults (n = 36) were individually administered the Stroop Color-Word Test. Eight of 36 (22%) AD patients exhibited confusion between the colors blue and green, while no control subject had difficulty distinguishing among the colors. In a second experiment, a subset of the original sample (15 AD patients and 8 control subjects) was retested using the Stroop. Only 2 AD patients showed color confusion on both test occasions, while 7 AD patients exhibited color confusion on one occasion. No control subject exhibited confusion between colors the second time. These results indicate that color confusion in AD patients is inconsistent. Due to the high incidence of color confusion in AD patients, the Stroop should be used with caution in patient populations.

Aged↗

PubMed2003

Comparison of the amniotic fluid index with gray-scale and color Doppler ultrasound.

OBJECTIVES: This study was undertaken to compare the amniotic fluid index (AFI) obtained with gray-scale ultrasound and color Doppler. STUDY DESIGN: We examined 77 patients ranging from 22 to 41 weeks' gestation with two of five sonographers obtaining two measures of the AFI utilizing gray-scale and color Doppler. RESULTS: Of the measurements of AFI, 96% showed the gray scale measurement to be greater than the color measurement (p < 0.0001; mean 9.3 +/- 3.3 cm vs. 8.5 +/- 3.0 cm). At gray-scale AFI < 5 cm, color AFI was essentially the same, but at gray-scale AFI 5-10 cm, color AFI was < 5 cm, 15.2% and 7.8% of the time. At gray-scale AFI > 10 cm, no color AFI was < 5 cm. Individual (n = 5) interobserver reliability was r = 0.79 (p < 0.0001) and intraobserver reliability was r = 0.94 (p < 0.0001). CONCLUSIONS: AFI by color Doppler was always less than with gray scale. At an AFI of 5-10 cm, color demonstrated an AFI of < 5 cm in up to 16% of patients, and increased the diagnosis of oligohydramnios.

Amniotic Fluid↗