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PubMed2004

Single letter coloring and spatial cuing eliminates a semantic contribution to the Stroop effect.

Previous work has shown that the Stroop effect is reduced in size when a single letter is colored and spatially precued. The present experiment addresses a number of criticisms of this work by (1) providing a direct measure of semantic processing, (2) using a vocal response instead of a manual one, and (3) using a more appropriate baseline. A semantically based Stroop effect (slower color naming for color-associated words than for color-neutral words) is observed when all letters in the display are precued and appear in a homogeneous color. This Stroop effect is statistically eliminated when a single letter is precued and is the "odd man out" in terms of its color. Two explanations are considered. In one, single-letter coloring and cuing serve to curtail semantic processing. In the other, single-letter coloring and cuing help to keep the informational sources (i.e, color, word) separate and hence reduce interference, but semantic analysis is not curtailed. The latter account provides a more complete account of existing data.

Color Perception↗

PubMed1997

The organization of multidimensional selection on the basis of color and shape: an event-related brain potential study.

In this paper, we examine whether color and shape, tied to a single object in space, (1) are identified and selected in series or in parallel, (2) are identified and selected in a dependent, self-terminating manner or in an independent and exhaustive manner, and (3) are conjoined by a feature integration process before or only after an initial stage of separate attribute analyses has finished. We measured response time and the selection negativity (SN) derived from event-related brain potentials when participants responded to a unique conjunction of color and shape in a go/no-go target detection task. The discriminability of the color and the shape of the conjunction was manipulated in three conditions. When color and shape were easy to discriminate, the SNs to color and shape started at the same time. When one attribute was less discriminable the SN to that attribute started later, but not the SN to the complementary attribute. This suggests that color and shape are identified and selected in parallel. In all three discriminability conditions, the SNs to color and shape were initially independent but later interacted. This suggests that color and shape are initially selected independently and exhaustively, after which their conjunction is analyzed. The SN to local shape features started later than that to the conjunction of color and global shape features, which suggests that feature integration can start before the analyses of the separate attributes have finished.

Adult↗

PubMed1995

The perception of color from motion.

We introduce and explore a color phenomenon which requires the prior perception of motion to produce a spread of color over a region defined by motion. We call this motion-induced spread of color dynamic color spreading. The perception of dynamic color spreading is yoked to the perception of apparent motion: As the ratings of perceived motion increase, the ratings of color spreading increase. The effect is most pronounced if the region defined by motion is near 1 degree of visual angle. As the luminance contrast between the region defined by motion and the surround changes, perceived saturation of color spreading changes while perceived hue remains roughly constant. Dynamic color spreading is sometimes, but not always, bounded by a subjective contour. We discuss these findings in terms of interactions between color and motion pathways.

Color Perception↗

PubMed1999

Can one pay attention to a particular color?

In an array of elements whose colors vary can we selectively choose to process all the items of a particular color preferentially in relation to those of another color? We addressed this question by presenting subjects with arrays containing many elements, and recording reaction times to a luminance change of one of the elements. Half the elements had one color and the other half another color--the spatial distribution being random. In two tasks--a simple detection of this change or a choice reaction time to the polarity of the change--we found that reaction times were independent of the number of items in the array. Cuing the subjects as to the color of the target item had no significant influence on the detection task, but subjects were faster if cued for the discrimination task. A further experiment replicated these findings and examined possible costs and benefits. Our final experiment separated the roles of attentional guidance and postattentional processes by having subjects judge the orientation of the target element and varying the magnitude of the target flash that defined which element was the target. We found that this judgment was also affected by color cuing, and that the size of the effect interacted with the flash strength, suggesting that color cuing has its influence at the stage of attentional guidance. We conclude that subjects can selectively attend to items on the basis of color given the appropriate task and stimulus dynamics.

Attention↗

PubMed2000

Nonlinearity in color space measured by apparent motion.

We used an apparent motion technique to examine the intensity coding along the three cardinal axes of color space: achromatic (L + M + S), L-M cone, and S cone axes. Two horizontal bars of different colors were alternated to produce a vertical displacement. The color of the background was a mixture varied between the colors of the two bars. When the background color was close to either of the test colors, only the bar that was more salient appeared to jump. Observers adjusted the color of the background until they saw either the two bars moved equally frequently or both bars moved at once. If the color difference in a linear cone excitation space controls this apparent motion, the setting should be midway between the two colors. All of the three cardinal axes showed some deviation from linear behavior. The nonlinearity was less extreme than a logarithmic function for both the achromatic and S cone axes and could be attributed to a small compressive nonlinearity, possibly at the level of cone responses. However, the L-M stimuli showed a more extreme departure from linearity, which suggested a nonlinearity at an opponent site. A test of perceived contrast judgments did not show this nonlinearity for L-M axis, suggesting that it is specific to the L-M contribution to apparent motion.

Color Perception↗

PubMed2003

Color vision in the comb frequency domain.

In 1982, Horace Barlow considered the question of human trichromacy in the context of information theory: according to the Sampling Theorem, three types of receptors covering the visible spectrum (400-700 nm) might be sufficient to reconstruct the color signal. Although Barlow was led to reject the direct application of the Sampling Theorem to explain color dimensionality, the theoretical framework offers a fresh point of view for analyzing the color system in conjunction with the physical characteristics of natural color signals. This review aims to illustrate that if the strict mathematical reconstruction (as implied by the Sampling Theorem) is replaced by a pragmatic approximation of color signals, then trichromacy, with its subsequent opponent-color process, could be regarded as an optimization of color constancy abilities in the spectral environment of primates. Higher dimension systems (tetrachromacy) found in other species can also serve the purpose of color constancy optimization in environments where color signals exhibit a finer spectral structure.

Color Perception↗

PubMed1998

[Experimental and clinical studies of color changes of island flaps].

Skin color of free flaps can represent their vascular conditions after reconstructive surgery. Thus far, however, surgeons have subjectively inspected flap color changes. More precise and objective measurement is necessary for early detection of vascular insufficiency. In order to evaluate color changes of flaps we used a portable non-contact type colorimeter with a L*a*b* color space (L* is brightness and a*, b* are chromaticness) recommended by the CIE (Commission Internationale d'Eclairage). Initially, we successfully performed objective evaluation of flap color changes in rats with or without a tied femoral artery or vein. Vein failure showed a decrease in a* and b* soon after surgery, while the artery failure appeared as b* and L* after 12 and 24 hours, respectively. Then, the color differences between sites of clinical free flaps were examined and considered to be relatively negligible against the time-dependent changes using delta a*, delta b*, delta L*, which represents the difference in color of an objective point from a control point. Next, we demonstrated that the color of abdominal skin did not significantly differ from that of forearm skin using delta a*, delta b*, delta L*. The clinical free flaps were measured with these parameters pre- and post-operatively and their normal course of color changes was revealed. The findings showed that a* changed with characteristic ups and downs before and after elevation due to congestion.

Adult↗

PubMed1995

"Fluid color" sign: a useful indicator for discrimination between pleural thickening and pleural effusion.

Color Doppler imaging has been applied traditionally in the evaluation of cardiovascular diseases. Recently it was observed that color signal may appear within the fluid collection in the pleural space during respiratory and cardiac cycles ("fluid color sign"). We performed this applicability of fluid color sign to the detection of pleural fluid capable of being removed to assess needle aspiration. From July 1992 to February 1994, we prospectively analyzed 76 patients who were suspected of having minimal pleural effusion on the basis of their chest radiographs. All patients were examined by color Doppler ultrasonography for the presence of fluid color sign, which was followed by needle aspiration to verify the presence of pleural effusion. Among the 65 patients with aspiratable fluid, 58 demonstrated positive fluid color sign (sensitivity 89.2%). None of the patients with solid pleural thickening showed fluid color sign (specificity 100%). With its relatively high sensitivity and specificity, the fluid color sign may be a useful diagnostic aid to real-time, gray scale ultrasonography for minimal or loculated effusion.

Adolescent↗

PubMed1998

Comparison of transcranial power Doppler and contrast-enhanced color-coded sonography in the identification of intracranial arteries.

Power-based transcranial color-coded sonography and contrast-enhanced transcranial color-coded sonography are ultrasonographic techniques that allow improved visualization of vascular structures. The present study was designed to investigate and compare the diagnostic capacity and applicability of both methods in the assessment of intracranial vessels of the circle of Willis (33 patients) and the vertebrobasilar system (21 patients). Compared to conventional transcranial color-coded sonography, both power-based and contrast-enhanced transcranial color-coded sonography improved the diagnostic sensitivity in identifying peripheral segments and small vessels of the circle of Willis. Contrast-enhanced transcranial color-coded sonography was significantly superior to power-based transcranial color-coded ultrasonography in the depiction of the second segment of the middle cerebral artery (66 of 66 versus 60 of 66, P < 0.005), both segments of the anterior cerebral artery (66 of 66 versus 56 of 66 for the A1 segment, P < 0.005; 61 of 66 versus 44 of 66 for the A2 segment, P < 0.005), the first segment of the posterior cerebral artery (66 of 66 versus 55 of 66, P < 0.005), and the basilar artery using the transtemporal approach (21 of 21 versus 15 of 21, P < 0.05). Using the transforaminal approach contrast-enhanced transcranial color-coded real-time sonography did not increase fine resolution of the vertebrobasilar system compared to power Doppler sonography. In conclusion, contrast-enhanced transcranial color-coded real-time sonography further improves the diagnostic potential of power Doppler sonography in the identification of vascular structures of the circle of Willis. Contrast-enhanced transcranial color-coded sonography and power Doppler sonography are equally effective in visualizing the vertebrobasilar system with branches.

Adult↗

PubMed1999

Color Doppler ultrasonographic evaluation of osteomyelitis in children.

We investigated the capability of color Doppler sonography in evaluating acute osteomyelitis in children. Twelve children suspected of having osteomyelitis were evaluated with color Doppler ultrasonography at admission and at regular intervals to observe the inflammatory process of osteomyelitis, determine the response of antibiotic therapy, and predict the need of surgery in these patients. At admission, color Doppler flow within or around the infected periosteum was found in patients with symptoms for 4 days or longer, whereas those with symptoms for less than 4 days showed no color Doppler flow within and around the periosteum. During sonographic follow-up, six cases were found to have increased color Doppler vascular flow within and around the affected periosteum, and two of them had periosteal abscess. They eventually required surgical treatment. Persistent or increased color Doppler flow during follow-up examination correlated with elevated serum levels of C-reactive protein as well. Our study indicated that color Doppler vascular flow within or around the infected periosteum correlated with advanced acute osteomyelitis, and surgery usually was required in these patients. Those with early stage acute osteomyelitis usually showed no vascular flow within or around the infected periosteum. Thus, color Doppler sonography allowed detection of advanced osteomyelitis and revealed the progression of inflammation during antibiotic therapy. Color Doppler ultrasonography might be valuable in determining the efficacy of antibiotic therapy and justifying the need for operation.

Acute Disease↗

PubMed2002

Hepatocellular carcinoma: therapeutic experience with percutaneous ethanol injection under real-time contrast-enhanced color Doppler sonography with the contrast agent Levovist.

OBJECTIVE: To describe our experience with percutaneous ethanol injection under real-time contrast-enhanced color Doppler sonography with Levovist (SH U 508A; Nihon Schering, Osaka, Japan) for hepatocellular carcinoma after transcatheter arterial infusion. METHODS: Twenty patients (17 men and 3 women; mean age, 58.4 years) with 23 hepatocellular carcinoma nodules (mean +/- SD, 2.7 +/- 1.5 cm) underwent percutaneous ethanol injection under real-time contrast-enhanced color Doppler sonography 1 week after transcatheter arterial infusion. Therapeutic effects were assessed by contrast-enhanced computed tomography and posttreatment fine-needle biopsy. This study was performed on a prospective basis. RESULTS: After the transcatheter arterial infusion, contrast-enhanced color Doppler sonography showed intense intratumoral color signals in all 23 hepatocellular carcinomas. After the percutaneous ethanol injection, contrast-enhanced color Doppler sonography, fine-needle biopsy, and contrast-enhanced computed tomography showed no color signals, no viable tumor tissues, and no enhancement in any of the 23 hepatocellular carcinomas. Three to 5 (mean, 3.3) percutaneous ethanol injection sessions with a 5.2- to 15.6-mL (mean, 12.8-mL) total volume of ethanol per tumor were required for complete disappearance of color signals on contrast-enhanced color Doppler sonography. CONCLUSIONS: Percutaneous ethanol injection under real-time contrast-enhanced color Doppler sonography has considerable efficacy in treating hepatocellular carcinoma.

Aged↗

PubMed2003

Color Doppler sonohysterography of endometrial polyps and submucosal fibroids.

OBJECTIVE: To describe the typical sonographic findings and clinical applications of color Doppler sono-hysterography and to correlate the vascularity of lesions seen on color Doppler sonohysterography to microvessel density and the presence of vessels greater than 0.5 mm. METHODS: Color Doppler sonohysterography was performed on 25 women with abnormal uterine bleeding. The vascularity (number of vessels > 0.5 mm) and their configuration seen on color Doppler sonohysterography were compared with those obtained on the excised specimen. Microvessel density and histologic features were correlated to the visualization of vessels greater than 0.5 mm and their arrangement on color Doppler sonography. RESULTS: The color Doppler sonographic findings in 18 polyps, 3 submucosal fibroids, and 1 clot showed distinct vascularity patterns. Polyps typically contained a single feeding vessel, whereas fibroids had several vessels, which arose from the inner myometrium. Lesions with higher microvessel density tended to have more vessels greater than 0.5 mm as depicted on color Doppler sonography. CONCLUSIONS: Color Doppler sonohysterography may be useful in distinguishing polyps from submucosal fibroids based on the vascularity of the lesions. The number of vessels seen on color Doppler sonography approximates microvessel density within the lesions.

Adult↗

PubMed1999

Color vision deficits and laser eyewear protection for soft tissue laser applications.

PURPOSE: Laser safety considerations require urologists to wear laser eye protection. Laser eye protection devices block transmittance of specific light wavelengths and may distort color perception. We tested whether urologists risk color confusion when wearing laser eye protection devices for laser soft tissue applications. MATERIALS AND METHODS: Subjects were tested with the Farnsworth-Munsell 100-Hue Test without (controls) and with laser eye protection devices for carbon dioxide, potassium titanyl phosphate (KTP), neodymium (Nd):YAG and holmium:YAG lasers. Color deficits were characterized by error scores, polar graphs, confusion angles, confusion index, scatter index and color axes. Laser eye protection device spectral transmittance was tested with spectrophotometry. RESULTS: Mean total error scores plus or minus standard deviation were 13+/-5 for controls, and 44+/-31 for carbon dioxide, 273+/-26 for KTP, 22+/-6 for Nd:YAG and 14+/-8 for holmium:YAG devices (p <0.001). The KTP laser eye protection polar graphs, and confusion and scatter indexes revealed moderate blue-yellow and red-green color confusion. Color axes indicated no significant deficits for controls, or carbon dioxide, Nd:YAG or holmium:YAG laser eye protection in any subject compared to blue-yellow color vision deficits in 8 of 8 tested with KTP laser eye protection (p <0.001). Spectrophotometry demonstrated that light was blocked with laser eye protection devices for carbon dioxide less than 380, holmium:YAG greater than 850, Nd:YAG less than 350 and greater than 950, and KTP less than 550 and greater than 750 nm. CONCLUSIONS: The laser eye protection device for KTP causes significant blue-yellow and red-green color confusion. Laser eye protection devices for carbon dioxide, holmium:YAG and Nd:YAG cause no significant color confusion compared to controls. The differences are explained by laser eye protection spectrophotometry characteristics and visual physiology.

Adult↗

PubMedDate not supplied

[The reconstruction of the perceptual spaces of brightness and color on the basis of visual evoked potentials and their comparison with the data from behavioral trials].

The visual evoked potentials to a change in color stimuli were studied. The amplitude of the N85 component was correlated with color discrimination. In cases when the brightness of one color was fixed and that of the other one changed, the amplitude dynamics of N85 was V-shaped with the minimum corresponding to the point of equal brightness of both colors. The N85 amplitude in this point serves as a measure of discrimination between stimuli chromaticity. The perceptual color space in rabbit (possessing two cone pigments) was constructed in accordance with the amplitudes of N85 to color change. This space represented a hypersphere in the four-dimensional Euclidean space. The perceptual spaces for brightness and color reconstructed on the basis of conditioning probabilities and N85 amplitudes evoked by replacement of colored and achromatic stimuli were shown to coincide. This suggests the common mechanism of the vector color coding.

Animals↗

PubMed1997

[The study of color stability of ceramic stains subjected to glazing temperature].

Ceramic stains are used to modify the final colors of ceramic dental restorations. They are not color stable when subjected to glazing temperature. In order to understand the color change characteristics, the study tested the color stability of the five Vita VMK68 stains. The international color standard CIE1976LAB color system and CS-5 Spectrocolorimeter are used. The results indicate: significant color changes are noted for five stains; the color change characteristics among them are different; yellow-brown stain shows the most color unstability after firing.

Color↗

PubMedDate not supplied

Differences in color between fired porcelain and shade guides.

The inaccuracy of premixed porcelain shades may cause errors when color matching porcelain crowns. Most brands of porcelain are labeled to match shades of the Vita shade guide, but produce slightly different colors from this guide upon firing. The purpose of this study was to quantify in CIE delta E* units the color differences between the Vita shade guide colors and four commercial porcelains for metal ceramic crowns. Two operators prepared shade-guide teeth from six shades of four brands of porcelain. Opaque, body, and incisal layers were fired in the form of shade-guide teeth on Vita ceramic carriers used for making custom shade-guide teeth. The colors of these teeth were measured with a Beckman spectrophotometer with an integrating sphere. The average delta E* values for the differences between the colors of the Vita shade guide and the fired porcelains for each of the brands were 3.1, 2.9, 4.1, and 2.0, respectively, for the first operator and 4.1, 2.6, 2.8, and 1.6, respectively, for the second operator. The color difference between the custom shade-guide teeth and the Vita master shade guide were significantly affected by both brands and shades. The overall average error resulting from the differences in colors between the Vita shade guide and fired porcelains was 3.0 for the first operator and 2.8 for the second operator. The mean delta E* between the teeth prepared by the two operators was 3.6. The color difference between the teeth made by the two operators was not significantly affected by brands or shades.

Analysis of Variance↗

PubMed1992

[Color-Doppler instruments: their design principles and modes of use].

The use of color-Doppler US equipment allows the clinician to evaluate, at the same time and within the same image, both shape and structure of the examined organs and the flow patterns in the vessels within them. Such information as direction and velocity of blood flow are displayed with a variety of intravascular colors, according to a conventional code. Moreover, this diagnostic method can provide physiological and anatomical pieces of information in the same image and is therefore widely used in medical imaging. However, the images obtained by means of color-Doppler units are not always easy to understand and diagnostic misinterpretations may occur. In this paper we will summarize the physical and technological principles on which such units are based. In the first half of paper, the problems relative to acquisition and construction of the images are presented, together with the different technical approaches used to obtain flow velocity information. Moreover, the relationships between the "black-and-white" and the "color" parts of the images are described. The principles according to which color is assigned to vessels are reported, together with the patterns exhibited by a vessel according to the type of transducer used to examine it. The non-linear correlation between the color scale and flow velocities is also discussed. The second half of the paper deals with technical parameters of color-Doppler scanning, discussing the criteria of choice of transducers, the determination of Doppler angle, the setting of both wall filters and scanning depth. The problem of pulse repetition frequency (PRF) setting is also addressed; this parameter is especially critical in color-Doppler studies. The authors believe that careful setting of all examination parameters and the good knowledge of the physical and technological factors underlying color-Doppler images are the basis for a correct and useful approach to this fascinating technique.

Blood Vessels↗

PubMed1992

[Color-Doppler echography of the testis. Study technique and vascular anatomy].

Color-Doppler sonography has recently made it possible to image scrotal vascularity non-invasively. This study was undertaken to determine the normal color-Doppler appearance and distribution of scrotal vessels and to define the technical principles of the examination. Color-Doppler imaging was effective in detecting both funicolar and testicular vessels. Among these, capsular (25/25), trans-testicular (10/25), centripetal and recurrent (25/25) arteries were easily identified. Waveforms analysis allowed to differentiate veins from arteries within testis and to distinguish (8/10) supratesticular (high impedance pattern with absent diastolic flow) from intratesticular arteries (low impedance pattern with high levels of diastolic flow). The optimal color depiction of scrotal vascularity needed the appropriate selection of several imaging parameters to increase detection of low-velocity, low-volume flows within the small testicular vessels. Such parameters included: PRF (ranging 1500 to 600 Hz), wall filters (ranging 25 to 50 Hz), color gain (maximized for optimal sensitivity while avoiding excessive color noise), color vs. echo priority (ranging 70 to 90%) and color persistence (adjusted to high values). In conclusion, color-Doppler imaging is capable of reliably showing the normal anatomy of testicular vessels. It could make a reliable substitute for scintigraphy and continuous wave Doppler in diagnosing scrotal conditions that alter blood flow.

Adult↗