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PubMed1978

Central representation of colour vision deduced from studies on a subject with a central colour vision defect.

M.W.'s grossly defective responses to red light stimuli are caused by an abnormality of central vision which is highly specific in its action. The abnormal activity does not affect stereoscopic function and only partially modifies the parametric characteristics of the contrast threshold elevation effect. These experimental observations lend support to the concept of parallel processing of different attributes of the visual stimulus, possibly by different cortical areas. We suggest that understanding of central visual processes could be facilitated by further studies on subjects with malfunction of the visual cortex.

Adult↗
PubMed1992

Color chart assisted diagnosis of Raynaud's phenomenon in an unselected hospital employee population.

The prevalence of Raynaud's phenomenon (RP) in 750 subjects was assessed by questionnaire, clinical interview, and use of a chart of color photographs taken of hands during attacks of RP. Eighty-three of 600 women (13.8%) and 7 of 150 men (4.7%) reported cold induced digital color changes on the questionnaire, 76 women (12.7%) and 6 men (4%) were diagnosed as having RP at an independent clinical interview, and 3 women could not be assessed using the color chart because of defective color perception. Fifty-four of the remaining 597 women (9%) and 6 of 150 men (4%) were diagnosed as having RP when a positive response to both chart and questionnaire was required. The color chart should be useful in lessening the frequency of false-positive responses and in standardizing the diagnosis for epidemiological surveys.

Adult↗
PubMed2006

Influence of different post core materials on the color of Empress 2 full ceramic crowns.

BACKGROUND: For esthetic consideration, dentin color post core materials were normally used for all-ceramic crown restorations. However, in some cases, clinicians have to consider combining a full ceramic crown with a metal post core. Therefore, this experiment was conducted to test the esthetical possibility of applying cast metal post core in a full ceramic crown restoration. METHODS: The color of full ceramic crowns on gold and Nickel-Chrome post cores was compared with the color of the same crowns on tooth colored post cores. Different try-in pastes were used to imitate the influence of a composite cementation on the color of different restorative combinations. The majority of patients could not detect any color difference less than DeltaE 1.8 between the two ceramic samples. So, DeltaE 1.8 was taken as the objective evaluative criterion for the evaluation of color matching and patients' satisfaction. RESULTS: When the Empress 2 crown was combined with the gold alloy post core, the color of the resulting material was similar to that of a glass fiber reinforced resin post core (DeltaE = 0.3). The gold alloy post core and the try-in paste did not show a perceptible color change in the full ceramic crowns, which indicated that the color of the crowns might not be susceptible to change between lab and clinic as well as during the process of composite cementation. Without an opaque covering the Ni-Cr post core would cause an unacceptable color effect on the crown (DeltaE = 2.0), but with opaque covering, the color effect became more clinically satisfactory (DeltaE = 1.8). CONCLUSIONS: It may be possible to apply a gold alloy post core in the Empress 2 full ceramic crown restoration when necessary. If a non-extractible Ni-Cr post core exists in the root canal, it might be possible to restore the tooth with an Empress 2 crown after covering the labial surface of the core with one layer of opaque resin cement.

Ceramics↗
PubMed2001

Unconscious priming eliminates automatic binding of colour and alphanumeric form in synaesthesia.

Synaesthesia is an unusual perceptual phenomenon in which events in one sensory modality induce vivid sensations in another. Individuals may 'taste' shapes, 'hear' colours, or 'feel' sounds. Synaesthesia was first described over a century ago, but little is known about its underlying causes or its effects on cognition. Most reports have been anecdotal or have focused on isolated unusual cases. Here we report an investigation of 15 individuals with colour-graphemic synaesthesia, each of whom experiences idiosyncratic but highly consistent colours for letters and digits. Using a colour-form interference paradigm, we show that induced synaesthetic experiences cannot be consciously suppressed even when detrimental to task performance. In contrast, if letters and digits are presented briefly and masked, so that they are processed but unavailable for overt report, the synaesthesia is eliminated. These results show that synaesthetic experiences can be prevented despite substantial processing of the sensory stimuli that otherwise trigger them. We conclude that automatic binding of colour and alphanumeric form in synaesthesia arises after initial processes of letter and digit recognition are complete.

Adult↗
PubMed1994

Quality of life: an interpersonal perspective.

Quality of life is a continuum having a higher to lower range. A person's perceptions of life quality are time-related and situation-dependent and tend to vary according to changing life circumstances. Human relationships, especially during the early years of growth and development, can be constructive or destructive influences which can color perceptions, expectations, and behavior patterns manifested in interpersonal interactions throughout the life span. Relationships define and confirm self-worth, identity, acceptance as a human being, a sense of belonging, and other essential interpersonal needs. Relationships provide social support and tend to reduce stress. The quality of interpersonal relationships has a strong bearing on perceptions of quality of life.

Behavior↗
PubMedDate not supplied

The influence of different thicknesses of dentin porcelain on the color reflected from thin opaque porcelain fused to metal.

Gold and nickel-chromium alloys were used as substrates for one shade of fused porcelain. Chroma characteristics were compared between samples with opaque thicknesses of 0.1, 0.2, and 0.3 mm. Thicknesses of 0.1 to 0.5 mm of dentin porcelain fused on each of the thicknesses of opaque porcelain were measured. Perceptible color differences were found for most of the samples, and all nongold alloy samples showed such changes.

Chromium Alloys↗
PubMed2003

Color stability and hardness in dental composites after accelerated aging.

OBJECTIVES: To investigate the color and microhardness changes of five chemically- and five light-curing composites as a function of accelerated aging from light exposure. MATERIALS AND METHODS: From each material five composite specimens were embedded in epoxy resin prior to determining the Knoop microhardness of the surface. For analyzing the color DeltaE*=f((L*a*b*)) with a spectrophotometer, three discs per composite were prepared. After measuring the baseline for hardness and color the same specimens were exposed to a xenon arc light and water in a Weather-Ometer machine for a total radiant energy of 150 kJ/m2 and 122 h. The microhardness and the color were again determined following the aging treatment. RESULTS: Each material showed a significant increase in hardness after aging treatment (p<0.05). Comparing the hardness changes (in %) of the light-cured materials with the chemically cured materials, no significant difference could be found. Perceptible color differences could be observed for all the materials. Three brands showed small differences with DeltaE*=1.6-2.2, while four composites had DeltaE* ranging from 6.2 to 15.5. A significant correlation between hardness values and color changes could not be established. CLINICAL SIGNIFICANCE: The findings suggest that, since light-curable materials showed significantly more resistance to color changes after accelerated aging by light and water than chemically-cured materials, they may be more esthetically acceptable. Color changes were not correlated with surface hardness changes of the materials after aging.

Analysis of Variance↗
PubMed2003

Wavelength dependence of the optomotor response in zebrafish (Danio rerio).

The action spectrum of motion detection in zebrafish (Danio rerio) was measured using the optomotor response in the light adapted state. The function has a single maximum at 550-600 nm, and is similar to the spectral sensitivity function of the L-cone type in the mid and long wavelength range. At shorter wavelengths the values of three of the five fish tested are lower. As in goldfish [Vis. Res. 36 (1996) 4025], the result indicates a dominance of the L-cone type with an inhibitory influence of M- or S-cones. Experiments with a red/green striped cylinder showed that the optomotor response was at minimum whenever the L-cone type was not modulated by the moving pattern. This demonstrates that motion vision in zebrafish is "color blind", using mainly one of the four cone types probably involved in color vision.

Animals↗
PubMed1984

Measurements of the Pulfrich effect over days of exposure.

Mean depth settings and subjective reports appear to confirm previous subjective reports from users of the X-Chrom prescription lens that Pulfrich Effect depth distortions decrease with continued exposure to light intensity disparity. Depth setting variability across Days of exposure indicates a rapid increase in depth judgment errors which persists without decrement across Days. This increased variability, the apparent depth decrements, and color discrimination improvements shed light on the visual processing underlying the Pulfrich Effect and reveal a potentially dangerous illusion.

Adult↗
PubMed1992

Color-vision deficiency--what does it mean?

Color-vision deficiency is a disorder affecting a significant proportion of the population, yet it remains poorly understood by school personnel as well as the general public. This article examines the many ways abnormal color perception affects peoples' lives. The role of the school nurse in detection of the problem, plus education and counseling of the affected student, parents, and teachers is discussed.

Adult↗
PubMed1992

Effects of colour substitutions upon motion detection in spatially random patterns.

To investigate the effects of colour upon motion detection, the short-range motion displacement limit (Dmax) was determined using two-frame kinematograms in which the two classes of square comprising the pattern differed both in luminance and in colour. In the second motion frame, the squares retained either the same luminance and colour as in the first frame, or they changed their colour while retaining their luminance. The experiment was repeated at three different viewing distances to investigate the effects of element angular size. Two of the four observers had normal trichromatic colour vision; the other two were dichromats (protanopes). For the trichromatic observers, the change of colour between frames made motion displacements harder to detect when the squares were large, but not when they were small. The result accords with an input of colour into motion detection at low but not at high spatial frequencies. For the dichromats, the colour change had little effect at any of the viewing distances, thus ruling out the possibility that the deleterious effects of colour substitution upon motion detection in trichromats was due to chromatic aberration or other artefacts.

Color Perception↗
PubMed1994

Spatial integration in human vision with bichromatically-mixed adaptation field.

The present study showed that the spatial integration area was expanded even if the background energy was increased, provided that the background consisted of the two colors which were opponent to each other (red/green). This expansion was not found for the subjects with dichromatic color vision even though the same condition was utilized. It was suggested that polarization and its release (the change of adaptation level) of the chromatically-opponent red/green system were involved in control of spatial integration area.

Adaptation, Ocular↗
PubMedDate not supplied

Luminance-dependent hue shift in protanopes.

For normal trichromats, the hue of a light can change as its luminance varies. This Bezold-Brücke (B-B) hue shift is commonly attributed to nonlinearity in the blue-yellow opponent system. In the present study, we questioned whether protanopes experience analogous changes. Two protanopes (Ps) viewed spectral lights at six luminance levels across three log steps. Two normal trichromats (NTs) were tested for comparison. A variant of the color-naming method was used, with an additional "white" term. To overcome the difficulty of Ps' idiosyncratic color naming, we converted color-naming functions into individual color spaces, by way of interstimulus similarities and multidimensional scaling (MDS). The color spaces describe each stimulus in terms of spatial coordinates, so that hue shifts are measured geometrically, as displacements along specific dimensions. For the NTs, a B-B shift derived through MDS agreed well with values obtained directly by matching color-naming functions. A change in color appearance was also observed for the Ps, distinct from that in perceived brightness. This change was about twice as large as the B-B shift for NTs and combined what the latter would distinguish as hue and saturation shifts. The protanopic analogue of the B-B shift indicates that the blue-yellow nonlinearity persists in the absence of a red-green signal. In addition, at mesopic levels (< or = 38 td), the Ps' MDS solution was two dimensional at longer wavelengths, suggesting rod input. Conversely, at higher luminance levels (76 td-760 td) the MDS solution was essentially one dimensional, placing a lower limit on S-cone input at longer wavelengths.

Adult↗