Search Results
Results 551 - 600 of 1224
< 7 8 9 10 11 12 13 14 15 16 17 >
Gunther Karen L - - 2003
Many previous studies employing paradigms such as adaptation, masking and summation-near-threshold have demonstrated the existence of separate mechanisms underlying the detection of the three cardinal axes of color space: L+M, L-M and S-(L+M). In addition, some studies have demonstrated the existence of higher-order mechanisms tuned to non-cardinal axes (which are ...
Johns E E - - 2003
We report two experiments using Sternberg's (1969) multitrial recognition-memory paradigm. We used colored shapes as stimuli and manipulated the frequency of the shapes (but not of the colors) across trials. For lures containing an extralist shape (i.e., a shape not studied in the current study list), responses were faster if ...
Carsten David L - - 2003
Dental practitioners can avoid expensive and embarrassing shade matching errors by learning about the structure and function of the eye and how to control the external and internal factors that affect human vision. The color of objects is identified by the visible light that they reflect; objects can reflect only ...
Doi Eizaburo - - 2003
Neurons in the early stages of processing in the primate visual system efficiently encode natural scenes. In previous studies of the chromatic properties of natural images, the inputs were sampled on a regular array, with complete color information at every location. However, in the retina cone photoreceptors with different spectral ...
Lucia S - - 2003
Behavioral responses of Halobacterium salinarum appear as changes in the frequency of motion reversals. Turning on orange light decreases the reversal frequency, whereas blue light induces reversals. Light pulses normally induce the same response as step-up stimuli. However, anomalous behavioral reactions, including inverse responses, are seen when stimuli are applied ...
Westland Stephen - - 2003
When we observe the light reflected from surfaces in a scene or look directly at light emitted by light sources, we experience the sensation of color. Color is just one attribute of a complex and not fully understood set of properties that define the appearance of our surroundings. To measure ...
Niggemann Birgit - - 2003
Latanoprost, the phenyl-substituted prostaglandin F2alpha, has been found to be an effective agent for glaucoma therapy. This prostaglandin derivative exerts ocular hypotensive activity but is also associated with an untoward side effect, namely iris color changes. Latanoprost provoked iris color changes in cynomolgus monkeys and in multicenter clinical trials. Until ...
Gerth Christina C Department of Ophthalmology and Section of Neurobiology, Physiology and Behavior, University of California Davis, CA, USA. - - 2003
The chromatic pattern-onset VEP has been used successfully as a sensitive and objective technique to determine congenital and acquired color vision deficiency. It also has been applied to characterize development, maturation and aging of the chromatic visual pathways. Here we determine the topographic components of the full-field VEP using the ...
Gegenfurtner Karl R - - 2003
Color vision starts with the absorption of light in the retinal cone photoreceptors, which transduce electromagnetic energy into electrical voltages. These voltages are transformed into action potentials by a complicated network of cells in the retina. The information is sent to the visual cortex via the lateral geniculate nucleus (LGN) ...
Schulz Melissa F - - 2003
Does perceptual grouping operate early or late in visual processing? One position is that the elements in perceptual layouts are grouped early in vision, by properties of the retinal image, before perceptual constancies have been determined. A second position is that perceptual grouping operates on a postconstancy representation, one that ...
Cardinal Kristen S - - 2003
The detection of many chromatic stimuli is mediated by mechanisms that sum their inputs linearly. As a result, these mechanisms have a broad range of selectivity in color space, as do the majority of cells in the early stages of visual processing. In extrastriate cortex, there are cells with a ...
Yang Joong Nam - - 2003
This study investigates color perception in a scene with two different illuminants. The two illuminants, in opposite corners, simultaneously shine on a (simulated) scene with an opaque dividing wall, which controls how much of the scene is illuminated by each source. In the first experiment, the height of the dividing ...
Atchison David A - - 2003
We investigated the effect of color-vision deficiency on reaction times and accuracy of identification of traffic light signals. Participants were 20 color-normal and 49 color-deficient males, the latter divided into subgroups of different severity and type. Participants performed a tracking task. At random intervals, stimuli simulating standard traffic light signals ...
Balldin U I - - 2003
INTRODUCTION: Only sporadic information exists concerning perceived color shifts at increased G-loads. The purpose of this study was to investigate whether or not color vision is affected by rapid onset high G7-loads up to +9 Gz, and specifically whether perception of hue changes. METHODS: There were 10 male subjects, 9 ...
Clifford Colin W G - - 2003
At the early stages of visual processing in humans and other primates, chromatic signals are carried to primary visual cortex (V1) via two chromatic channels and a third achromatic (luminance) channel. The sensitivities of the channels define the three cardinal axes of color space. A long-standing though controversial hypothesis is ...
Lotto R Beau - - 2002
Rationalizing the perceptual effects of spectral stimuli has been a major challenge in vision science for at least the last 200 years. Here we review evidence that this otherwise puzzling body of phenomenology is generated by an empirical strategy of perception in which the color an observer sees is entirely ...
Lau Daniel L - - 2002
In color halftoning, moiré is the low-frequency spatial artifact generated by the interference of superimposed primary color dot screens that adds an unwanted artificial texture to the printed image. When these overlapping dot screens are irregular, as in the case of stochastic dot screens, this interference pattern follows a random ...
Lardelli-Claret Pablo - - 2002
BACKGROUND: Bright- or light-colored vehicles are sometimes regarded as safer because they are presumably more visible. We examined the effect of vehicle color on the risk of being passively involved in a collision. METHODS: This paired case-control study used data from the Spanish database of traffic crashes. We selected those ...
Lindsey Delwin T - - 2002
Many languages have no basic color term for "blue." Instead, they call short-wavelength stimuli "green" or "dark". We show that this cultural, linguistic phenomenon could result from accelerated aging of the eye because of high, chronic exposure to ultraviolet-B (UV-B) in sunlight (e.g., phototoxic lens brunescence). Reviewing 203 world languages, ...
Dow Bruce M - - 2002
The literature on orientation and color columns in monkey visual cortex is reviewed. The orientation column model most consistent with existing data is one containing 'stripes' of alternating positive and negative orientation 'singularities' (cytochrome oxidase blobs) which run along the centers of ocular dominance (OD) columns, with horizontal and vertical ...
Sugimoto Masazumi - - 2002
Pigment cells enable fish to change their coloration. It has been recognized that fish color changes can be divided into two categories; one is a physiological color change, which is attributed to rapid motile responses of chromatophores, and the other is a morphological color change, which results from changes in ...
Ekroll Vebjørn - - 2002
Although current theories of color vision differ in many respects, they all assume the existence of a uniquely defined neutral point in chromaticity space. It generally is assumed that this point satisfies several criteria simultaneously. One of these criteria is that it is perceived as achromatic. A further criterion shared ...
Montarou Carole C - - 2002
A colorimetry-based retardation measurement (CBRM) method is presented. The specimen, between crossed polarizers, is illuminated with a white-light source. The retardation that is due to the birefringence of the specimen produces a white-light interference color. The x, y chromaticity coordinates of the color produced are measured with a spectrophotometer. The ...
Vladusich Tony - - 2002
A central problem in visual perception concerns how humans perceive stable and uniform object colors despite variable lighting conditions (i.e. color constancy). One solution is to 'discount' variations in lighting across object surfaces by encoding color contrasts, and utilize this information to 'fill in' properties of the entire object surface. ...
Neitz Jay - - 2002
An intensely debated issue concerning visual-experience-dependent neural plasticity is whether experience is required only to maintain function or whether information from experience is used actively, relieving the necessity to hard-wire all connections and allowing adaptive adjustments. Here, an active role for experience is demonstrated in circuits for color vision. Chromatic ...
Winnacker Albrecht - - 2002
The two-color photorefractive response of near stoichiometric lithium niobate (SLN) doped with Mg above a critical threshold has been investigated. Striking differences as compared with non Mg-doped material were observed: The intermediate level in the two-color writing process has approximately a two orders of magnitude longer lifetime in SLN:Mg than ...
Romney A Kimball - - 2002
In this paper we present the results of an analysis of the physically measured surface reflectance spectra of 360 matte Munsell chromatic color chips plus 10 flat achromatic vectors corresponding to Munsell value levels 10 (white) to 1 (near black) for a total sample size of 370. Each of the ...
Chen Vincent J - - 2002
We report that color and depth, as well as form, are recovered in tandem with seeing motion. The stimulus, consisting of multiple frames, was designed to keep all aspects, except color, of the binocular images identical. In still view, rivalry occurs due to the unmatched color of some corresponding image ...
Stamps Arthur E AE - - 2002
The author reports relationships between subjective impressions of visual diversity or pleasure with statistical entropies of stimuli. The stimuli were 34 rows of houses that varied in color, scale, and shape, or in shape and articulation. Entropies ranged from 0.0 to 5.6 bits. Fifty-seven participants rated the stimuli on scales ...
Hardy Joseph - - 2002
Alternating adaptation to red and green luminance-varying gratings of different spatial frequencies simultaneously induces opposing color-selective size aftereffects (Blakemore & Sutton, 1969) in the same retinal locus. With single-color adaptation, the aftereffect is larger and affects test patterns of both colors, though not equally. The color-insensitive portion of the effect ...
Bäuml Karl-Heinz - - 2002
In a number of recent adaptational studies evidence for a different processing of incremental and decremental cone signals has been reported. The present study examined whether such asymmetries occur in spatial pattern as well. Subjects set color matches between a uniform, 2 degrees matching box and bars within squarewave patterns. ...
Rowe Michael H - - 2002
Trichromatic color vision is rare among mammals, occurring only in some primates. Recent work has elucidated the adaptive behavioral significance of trichromacy as well as its underlying genetic and neurophysiological mechanisms. These studies reveal a complex neural system whose design and operation apparently does not conform to rigid deterministic principles.
Wee Alvin G - - 2002
The total quantifiable color difference between shade matching and shade duplication has not been investigated formally. The purpose of this in vitro study was to evaluate and compare the color difference of the total color replication process and the direction of the individual color parameters for 3 dental porcelain shade-matching ...
Arnold E N - - 2002
Differences in surface structure (ober-hautchen) of body scales of lacertid lizards involve cell size, shape and surface profile, presence or absence of fine pitting, form of cell margins, and the occurrence of longitudinal ridges and pustular projections. Phylogenetic information indicates that the primitive pattern involved narrow strap-shaped cells, with low ...
Marchant John A - - 2002
We develop a method for calculating invariant spectra of light reflected from surfaces under changing daylight illumination conditions. A necessary part of the method is representing the illuminant in a suitable form. We represent daylight by a function E(lambda, T) = h(lambda)exp[u(lambda)f(T)], where lambda is the wavelength, T is the ...
Moutoussis K - - 2002
We have recorded from wavelength-selective cells in macaque monkey visual area V2, interposed between areas V1 and V4 of the color-specialized pathway, to learn whether their responses correlate with perceived colors or are determined by the wavelength composition of light reflected from their receptive fields. All the cells we recorded ...
Branchini Bruce R - - 2002
Beetle luciferases (including those of the firefly) use the same luciferin substrate to naturally display light ranging in color from green (lambda(max) similar 530 nm) to red (lambda(max) similar 635 nm). The original mechanism of bioluminescence color determination advanced by White and co-workers was based on the concept that the ...
Vimal Ram Lakhan Pandey - - 2002
In this study, we have compared foveal SF discriminations for luminance and color-defined stimuli using two different tasks (criteria): in criterion-A, the discrimination is based on spatial (size of the stimuli) and/or spatial frequency; in criterion-B, it is based on apparent motion (contraction/expansion). We used high contrast (75%) spatially localized ...
Rutherford M D - - 2002
Many models of color constancy assume that the visual system estimates the scene illuminant and uses this estimate to determine an object's color appearance. A version of this illumination-estimation hypothesis, in which the illuminant estimate is associated with the explicitly perceived illuminant, was tested. Observers made appearance matches between two ...
Johnsen Sönke - - 2002
Despite the importance of cryptic and conspicuous coloration in pelagic ecosystems, few researchers have investigated the optimal reflectance spectra for either trait. In this study, the underwater radiance distribution in tropical oceanic water was modelled using measured inherent optical properties and radiative transfer calculations. The modelled light field was then ...
Qiao M - - 2002
Three replicate trials were conducted to determine the effect of raw broiler breast meat color on marinated and cooked meat quality. In each trial, 90 fillets were collected from a commercial processing plant based on lightness (L*) values of breast meat as follows: light, L* > 53; normal, 48 < ...
Lotto R Beau - - 2002
The colors perceived by humans in response to light stimuli are generally described in terms of four color categories (reds, greens, blues and yellows), the members of which are systematically arrayed around gray. This broadly accepted description of color sensation differs fundamentally from the light that induces it, which is ...
Vimal RamLakhan Pandey - - 2002
The sustained spatial-frequency-tuned (SF-tuned) mechanisms of nonoriented units were examined by means of orthogonal masking for the Red-Green (R-G) color channel, and those of oriented units by oblique masking for the achromatic channel but not for the color channels. An oblique-masking technique minimizes the artifacts that are due to spatial ...
Manuel Cristina - - 2002
We imagine shining light on a lump of cold dense quark matter, in the color-flavor locked phase and therefore a transparent insulator. We calculate the angles of reflection and refraction, and the intensity of the reflected and refracted light. Although the only potentially observable context for this phenomenon (reflection of ...
Khang Byung-Geun - - 2002
The identification of objects, illuminants, and transparencies are probably the most important perceptual functions of color. This paper examines the effects of perceptual scission, image junctions, color adaptation, and color correlations on identification. Simulations of natural illuminants, materials, and filters were used in a forced-choice procedure to simultaneously measure thresholds ...
Chen Vincent J - - 2002
In an effect we call color from motion (CFM), apparent motion is accompanied by subjective color spread seen in physically achromatic regions. Here we report that physical lights can cancel the subjective color seen in CFM. As measured by cancellation, the saturation of the subjective color spread increases as the ...
Dobkins Karen R - - 2002
One hallmark of vision in adults is the dichotomy between color and motion processing. Specifically, areas of the brain that encode an object's direction of motion are thought to receive little information about object color We investigated the development of this dichotomy by conducting psychophysical experiments with human subjects (2-, ...
Jiménez J R - - 2002
We determined visual reaction times to monocular and binocular changes in the luminance of isochromatic stimuli and to monocular and binocular changes in the color of isoluminant stimuli. Two isoluminant color changes were tested: chromatic variations along the red-green axis of Boynton's (1986) two-stage color vision model and chromatic variations ...
Wollschläger Daniel - - 2002
We analyze the properties of a dynamic color-spreading display created by adding narrow colored flanks to rigidly moving black lines where these lines fall in the interior of a stationary virtual disk. This recently introduced display (Wollschläger et al, 2001 Perception 30 1423-1426) induces the perception of a colored transparent ...
Intskirveli I E - - 2002
We investigated the ability to recognize the color of surfaces in fish (Poecilia reticulata), bred from birth in conditions of artificial light with constant spectral content. The capacity for color constancy significantly deteriorated when compared that to the control group. Further alteration of lighting conditions and transfer into natural daylight ...
< 7 8 9 10 11 12 13 14 15 16 17 >