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1.
BMC Ophthalmol ; 21(1): 238, 2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34049514

RESUMO

PURPOSE: To compare quantitative visual tests, such as visual acuity, contrast sensitivity, and color vision tests in patients with primary open-angle glaucoma (POAG) patients according to three different light systems with different color-rendering index (CRI). METHODS: This was a cross-sectional study of 36 eyes in 36 patients with POAG. Three different light systems consisting of a 3-band fluorescent lamp (CRI 80), a white LED (CRI 75), and a quantum dot LED (CRI > 95) were used. All lights had the same illuminance of 230 lx to exclude illuminance effects. The visual testing included best-corrected visual acuity (BCVA) using an ETDRS chart, a CSV-1000E contrast test, and a color test performed by the Farnsworth Munsell 100-hue test. RESULTS: There was no significant difference in BCVA (p = 0.86). There were no significant differences in the detail contrast tests according to the three light systems (p = 0.95, p = 0.94, p = 0.94, respectively, p = 0.64). There was significant difference between the three light systems in color test (p = 0.042). The color test scores with a quantum dot LED were significantly lower than those of the white LED and 3-band fluorescent lamp (p = 0.03 and 0.047, respectively). CONCLUSIONS: POAG patients did not show significant differences in visual acuity scores and contrast test scores, expressed as black and white symbols, according to the different light systems. However, POAG patients tested under a quantum dot LED (CRI > 95) could distinguish color differences better than in the other light systems.


Assuntos
Glaucoma de Ângulo Aberto , Percepção de Cores , Sensibilidades de Contraste , Estudos Transversais , Glaucoma de Ângulo Aberto/diagnóstico , Humanos , Testes Visuais
2.
Acta Psychol (Amst) ; 216: 103306, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33866276

RESUMO

Previous research by Hazan-Liran & Miller (2017) developed a new Stroop-like task to examine how ink colours as task-irrelevant information affects paired-associate learning (see also Miller, Hazan-Liran, & Cohen, 2018). The task was to learn word-number pairs (e.g. blue-5) whilst only numbers were coloured in either congruent ink colours (e.g. number 5 printed in blue ink), incongruent ink colours (e.g. 5 printed in brown ink) or neutral ink colours (e.g. 5 printed in black ink). The present paper refers to this task as the Associative Memory Stroop Task (AMST). Hazan-Liran & Miller (2017) found that incongruent ink colours interfere and congruent ink colour facilitate the speed of learning word-number pairs. The present experiments employed the AMST to examine the effects of irrelevant ink colours (with colour names) on memory accuracy in cued recall and associative recognition. Memory impairment was found with incongruent ink colours on both memory tests whilst improved memory accuracy with congruent ink colours was not reliable. We discuss possible explanations for these findings.


Assuntos
Percepção de Cores , Tinta , Atenção , Cor , Humanos , Tempo de Reação , Teste de Stroop
3.
Nat Commun ; 12(1): 2315, 2021 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-33875667

RESUMO

The clustering of neurons with similar response properties is a conspicuous feature of neocortex. In primary visual cortex (V1), maps of several properties like orientation preference are well described, but the functional architecture of color, central to visual perception in trichromatic primates, is not. Here we used two-photon calcium imaging in macaques to examine the fine structure of chromatic representation and found that neurons responsive to spatially uniform, chromatic stimuli form unambiguous clusters that coincide with blobs. Further, these responsive groups have marked substructure, segregating into smaller ensembles or micromaps with distinct chromatic signatures that appear columnar in upper layer 2/3. Spatially structured chromatic stimuli revealed maps built on the same micromap framework but with larger subdomains that go well beyond blobs. We conclude that V1 has an architecture for color representation that switches between blobs and a combined blob/interblob system based on the spatial content of the visual scene.


Assuntos
Percepção de Cores/fisiologia , Macaca mulatta/fisiologia , Neurônios/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Cor , Feminino , Masculino , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Estimulação Luminosa/métodos , Córtex Visual/citologia
4.
Sensors (Basel) ; 21(8)2021 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-33924510

RESUMO

In this paper, a novel method to modify color images for the protanopia and deuteranopia color vision deficiencies is proposed. The method admits certain criteria, such as preserving image naturalness and color contrast enhancement. Four modules are employed in the process. First, fuzzy clustering-based color segmentation extracts key colors (which are the cluster centers) of the input image. Second, the key colors are mapped onto the CIE 1931 chromaticity diagram. Then, using the concept of confusion line (i.e., loci of colors confused by the color-blind), a sophisticated mechanism translates (i.e., removes) key colors lying on the same confusion line to different confusion lines so that they can be discriminated by the color-blind. In the third module, the key colors are further adapted by optimizing a regularized objective function that combines the aforementioned criteria. Fourth, the recolored image is obtained by color transfer that involves the adapted key colors and the associated fuzzy clusters. Three related methods are compared with the proposed one, using two performance indices, and evaluated by several experiments over 195 natural images and six digitized art paintings. The main outcomes of the comparative analysis are as follows. (a) Quantitative evaluation based on nonparametric statistical analysis is conducted by comparing the proposed method to each one of the other three methods for protanopia and deuteranopia, and for each index. In most of the comparisons, the Bonferroni adjusted p-values are <0.015, favoring the superiority of the proposed method. (b) Qualitative evaluation verifies the aesthetic appearance of the recolored images.


Assuntos
Defeitos da Visão Cromática , Análise por Conglomerados , Cor , Percepção de Cores , Humanos
5.
Atten Percept Psychophys ; 83(4): 1699-1712, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33686589

RESUMO

Recent studies have revealed an action effect, in which a simple action towards a prime stimulus biases attention in a subsequent visual search in favor of objects that match the prime. However, to date the majority of research on the phenomenon has studied search elements that are exact matches to the prime, and that vary only on the dimension of color, making it unclear how general the phenomenon is. Here, across a series of experiments, we show that action can also prioritize objects that match the shape of the prime. Additionally, action can prioritize attention to objects that match only one of either the color or the shape of the prime, suggesting that action enhances individual visual features present in the acted-on objects. The pattern of results suggests that the effect may be stronger for color matches - prioritization for shape only occurred when attention was not drawn to the color of the prime, whereas prioritization for color occurred regardless. Taken together, the results reveal that a prior action can exert a strong influence on subsequent attention towards features of the acted-on object.


Assuntos
Percepção de Cores , Cor , Humanos
6.
Nutrients ; 13(3)2021 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-33652759

RESUMO

Although most people are aware of the health benefits of consuming sufficient amounts of fruit and vegetables, many do not adhere to current dietary recommendations. Recent studies have suggested meal colour variety as an intuitive cue for healthy and enjoyable lunch meal choices. The present study extends this research by testing the "colourful = healthy" association across meal types. Using smartphone-based Ecological Momentary Assessment, 110 participants recorded 2818 eating occasions over a period of eight days. For each eating occasion, a picture, a short written description of the meal, the meal type (breakfast, lunch, afternoon tea, dinner, snack) and the perceived meal colour variety were recorded. Foods were classified into seven food groups based on the pictures and descriptions. Data were analysed using multilevel modelling. For all meal types except afternoon tea which did not include vegetables, perceived that meal colour variety was positively related to vegetable consumption (bs ≥ 0.001, ts ≥ 3.27, ps ≤ 0.002, quasi-R2s ≥ 0.06). Moreover, perceived meal colour variety was negatively associated with sweets consumption for breakfast, dinner and snacks (bs ≤ -0.001, ts ≤ -2.82, ps ≤ 0.006, quasi-R2s ≥ 0.01). The "colourful = healthy" association can be generalized across meal types and thus may be a promising strategy to promote a healthier diet.


Assuntos
Percepção de Cores , Dieta Saudável/psicologia , Ingestão de Alimentos/psicologia , Comportamento Alimentar/psicologia , Refeições/psicologia , Adulto , Avaliação Momentânea Ecológica , Feminino , Frutas , Humanos , Masculino , Smartphone , Verduras , Adulto Jovem
7.
Quintessence Int ; 52(7): 608-617, 2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-33688711

RESUMO

OBJECTIVE: To determine the reliability of a newly developed software application (Shadent) in natural tooth shade selection. METHOD AND MATERIALS: A smartphone device with the self-developed Shadent software (patent no. 201841046815, Intellectual Property of India) recorded tooth shades of the maxillary right central incisor and canine for 250 volunteers. A prospective, clinical, double-blind trial was conducted. The shade match obtained under the standardized condition from Shadent software was compared with the visual method and spectrophotometer. The digital recordings were captured by two master's candidates, while the visual shade match was evaluated by four master's candidates and one faculty member from the Department of Prosthodontics. Crosstab analysis assessed the relationship between the visual method of shade selection, a spectrophotometer, and the Shadent software. Cohen kappa was used to measure the agreement between the methods. RESULTS: A kappa coefficient of 0.59 was observed between the visual assessment and the Shadent software, with an agreement percentage of 64.6%. A kappa coefficient of 0.65 was observed between the spectrophotometer and the Shadent software with an agreement of 69.3%. The software also had a better Cohen kappa agreement with the maxillary central incisor than the maxillary canine. CONCLUSIONS: Shadent's reliability was comparable with the visual and spectrophotometric methods and offered repeatability with standardized light intensity.


Assuntos
Pigmentação em Prótese , Dente , Cor , Percepção de Cores , Humanos , Estudos Prospectivos , Reprodutibilidade dos Testes , Smartphone , Software , Espectrofotometria
8.
J Prosthet Dent ; 125(5): 815.e1-815.e9, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33678442

RESUMO

STATEMENT OF PROBLEM: The predoctoral dental curriculum includes didactic lectures, demonstrations, and training on shade-matching techniques and protocols. However, a significant percentage of esthetic failures are still observed clinically. An assessment is required to determine whether reevaluation and modification of this training protocol would help future dental practitioners better perceive and communicate the dental shade. PURPOSE: The purpose of this study was to evaluate dental students' knowledge of and skill in shade selection and effective prescription writing before and after educational training with 3 different shade guides. MATERIAL AND METHODS: Thirty predoctoral dental students (interns) who had completed their academic program and were undergoing clinical training were selected. After excluding color vision deficiency, the study participants were first asked to evaluate the shade of the right maxillary central incisor of 5 patient participants by using 3 different shade guides (Vitapan Classical, Vitapan 3D-MASTER, Chromascop) under standardized conditions. They were then asked to write an esthetic prescription, communicating the shade to a dental laboratory technician. A dental faculty member evaluated the baseline control shade for each participant, and a standardized prescription format was written. This was used as a reference by a dental laboratory technician to score the intern's prescription as clear, unclear, poor, or illegible. After the assessment, focused small group learning with lectures, clinical demonstrations, and case-based discussion was provided to the interns on shade assessment over 10 to 15 days. All the interns were reassessed for their visual shade perception and prescription writing after a month's interval. The mean percentage agreement, mean percentage shade match, and mean color difference between the shade selected and the control shade for each of the 5 participants, with all 3 shade guides, were evaluated along with the prescription scoring before and after the educational training. Statistical comparison of before and after values were made by using the paired-sample z-test for percentage agreement versus disagreement among the interns for the shade selected, paired t test for mean percentage agreement, mean percentage shade match, and mean color difference. The repeated measure ANOVA test was used for the prescription scorings (α=.05). RESULTS: A significant difference in prescription scoring (P<.001) was observed. A significant difference in the percentage shade match (P<.01) for all 3 shade guides and mean percentage agreement for Chromascop and Vita 3D-MASTER (P<.05) were observed. A nonsignificant mean color difference between the shade selected by the intern and the baseline shade was observed. CONCLUSIONS: A significant difference in prescription scoring was observed after training, along with a higher percentage shade match and percentage agreement. This indicated a need to reconsider the educational training provided for dental shade assessment and communication and to implement better protocols in the dental curriculum.


Assuntos
Odontólogos , Estudantes de Odontologia , Cor , Percepção de Cores , Planejamento de Prótese Dentária , Estética Dentária , Humanos , Papel Profissional , Pigmentação em Prótese
9.
Atten Percept Psychophys ; 83(4): 1613-1628, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33686590

RESUMO

It has been established that objects sharing color in a visual display can boost working memory. The capacity to encode singletons particularly benefits from the repetition of colors encoded as perceptual groups. We manipulated the algorithmic complexity of visual displays to test whether compressibility of information could account for the color-sharing bonus. This study used a free recall working memory task in which the participants were shown displays of 2 to 8 color items. We examined the influence of set size, complexity, number of same-color clusters and amount of color redundancy. The results showed that the probability of correct recall of the pattern and the proportion of similarity between the pattern and the response decreased with an increase of each manipulated variable, except for color redundancy in terms of probability of correct recall. The model performance of complexity did not differ from that of clusters, but complexity was found more accurate than either set size or color redundancy. The results also showed that similar items were more often recalled adjacently, and complexity correlated strongly with the number of extra color repetitions in the response, suggesting that more complex patterns encouraged the use of information compression. Moreover, color repetitions were more often recalled first and the probability of correct recall for singletons and sub-patterns could be predicted by the compressibility measure. We discuss the potential advantage of using compressibility measures to capture the effects of regularities in visual patterns, in particular to refine analysis of the color-sharing bonus.


Assuntos
Memória de Curto Prazo , Rememoração Mental , Cor , Percepção de Cores , Humanos , Estimulação Luminosa
11.
J Dent ; 108: 103640, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33757865

RESUMO

OBJECTIVE: To evaluate the influence of neutral color backgrounds on the perception of color differences in dentistry. METHODS: A software was developed for this study that calculated the perceptibility (PT) and acceptability (AT) thresholds of color differences between a pair of computer-simulated incisor samples (n = 60 pairs) over three neutral color (white, gray and black) backgrounds. CIELAB and CIEDE2000 color difference formulas were used. Five groups of volunteer observers (N = 100) participated in the psychophysical experiment (n = 20): Dentists; Dental students; Dental auxiliaries; Dental technicians; and Laypersons. The psychophysical experiment was performed in a dark environment on a calibrated high-resolution screen. To determine PT and AT values, the 60 pairs of samples were randomly presented to each observer over the different backgrounds. The data were adjusted (TSK Fuzzy) and analyzed statistically using Student t-test and ANOVA (α = 0.05). RESULTS: Regardless of the metric and the background used, the PT values showed no difference among different observers (p > 0.05). Dentists showed the lowest PT values. Dental technicians showed the lowest AT (p ≤ 0.05) and similar values for the three backgrounds (p > 0.05), regardless of the metric used. The other groups of observers showed the lowest and the highest AT values when using black and white backgrounds, respectively (p ≤ 0.05). CONCLUSIONS: The lowest AT values using a black background indicates that the use of this background allows for the evaluation of slight color differences, and should be used for challenging color differences in esthetic dentistry. This study showed the influence of the observer experience on color evaluation in dentistry. CLINICAL SIGNIFICANCE: There was no influence of the background color on the perceptibility threshold. However, dentists and dental technicians showed greater ability to perceive slight color differences compared to other groups of observers.


Assuntos
Percepção de Cores , Estética Dentária , Cor , Humanos , Incisivo
12.
Toxicol Appl Pharmacol ; 415: 115429, 2021 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-33524447

RESUMO

The zebrafish is extensively used as a model organism for studying several disorders of the central nervous system (CNS), including epilepsy. Some antiseizure drugs (ASDs) have been shown to produce discrepant results in larvae and adults zebrafish, therefore, their anticonvulsant efficacy in subsequent stages of the pentylenetetrazole (PTZ)-induced seizures should be more precisely characterized. The purpose of this study was to investigate behavioral effects of five classic ASDs: valproate (VPA), phenytoin (PHT), carbamazepine (CBZ), diazepam (DZP), and phenobarbital (PB) administered intraperitoneally (i.p.) in the PTZ-induced seizure test in adult zebrafish. We determined the time of maximal effect and the dose-response relationship of the studied ASDs. Furthermore, we assessed changes in the locomotor activity and the anxiety-like behavior in the color preference test. Moreover, drug concentrations in zebrafish homogenates were examined. VPA, DZP, and PB significantly increased the seizure latency at three subsequent stages of seizures (SI-SIII). PHT produced the anticonvulsant-like effect at SI and SII, while CBZ was effective at SII and SIII. Only DZP decreased zebrafish locomotor activity. A strong anxiolytic-like effect was observed after administration of PHT and PB. A weak anxiolytic-like effect occurred after treatment with VPA and DZP. The HPLC analysis showed the average concentrations of the studied ASDs in the fish body during the maximum anticonvulsant activity of each drug. Our results confirm the advantages of using zebrafish with the mature CNS over larval models and its utility to investigate some neuropharmacological properties of the tested drugs.


Assuntos
Ansiolíticos/farmacologia , Anticonvulsivantes/farmacologia , Ansiedade/prevenção & controle , Comportamento Animal/efeitos dos fármacos , Sistema Nervoso Central/efeitos dos fármacos , Convulsões/prevenção & controle , Fatores Etários , Animais , Ansiolíticos/metabolismo , Anticonvulsivantes/metabolismo , Ansiedade/fisiopatologia , Ansiedade/psicologia , Sistema Nervoso Central/metabolismo , Sistema Nervoso Central/fisiopatologia , Percepção de Cores/efeitos dos fármacos , Visão de Cores/efeitos dos fármacos , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Feminino , Locomoção/efeitos dos fármacos , Masculino , Pentilenotetrazol , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Fatores de Tempo , Peixe-Zebra/metabolismo
13.
J Vis ; 21(2): 7, 2021 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-33576764

RESUMO

We examined whether perception of color saturation and lightness depends on the three-dimensional (3D) shape and surface gloss of surfaces rendered to have different hues. In Experiment 1, we parametrically varied specular roughness of predominantly planar surfaces with different mesoscopic relief heights. The orientation of surfaces was varied relative to the light source and observer. Observers matched perceived lightness and chroma (effectively saturation) using spherical objects rendered using CIE LCH color space. We observed strong interactions between perceived saturation and lightness with changes in surface orientation and surface properties (specular roughness and 3D relief height). Declines in saturation and increases in lightness were observed with increasing specular roughness. Changes in relief height had greater effects on perceived saturation and lightness for blue hues compared with reddish and greenish hues. Experiment 2 found inverse correlations between perceived gloss and specular roughness across conditions. Experiment 3 estimated perceived specular coverage and found that a weighted combination of perceived gloss and specular coverage could account for perceived color saturation and lightness, with different coefficients accounting for the perceptual experience for each of the three hue conditions. These findings suggest that perceived color saturation and lightness depend on the separation of specular highlights from diffuse shading informative of chromatic surface reflectance.


Assuntos
Percepção de Cores/fisiologia , Propriedades de Superfície , Humanos , Imageamento Tridimensional , Luz , Orientação Espacial/fisiologia
14.
J Med Syst ; 45(4): 46, 2021 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-33638131

RESUMO

The veracity of claims made by researchers and clinicians when reporting the impact of lighting on vision and other biological mechanisms is, in part, reliant on accurate and valid measurement devices. We aim to quantify the intra- and inter-watch variability of a commercially available light sensor device which has been widely used in vision and other photobiological research. Intra- and inter-watch differences were investigated between four Actiwatch Spectrum Pro devices. The devices were used to obtain measurements on two separate occasions, under three different controlled light conditions; the Gretag Macbeth Judge II lightbox was used to produce Simulated Daylight (D65), Illuminant A (A) and Cool White Fluorescent (CWF) lighting. Significant inter-watch differences were noted when considering tricolour (red, green, blue) and the white sensor outputs under each of the three illuminants (p < 0.01). A significant interaction was also found between tricolour sensor and watch used (p < 0.01). Intra-watch differences were noted for the tricolour and for the white sensor outputs under the three illuminants (≤0.05), for all but one watch which showed no significant intra-watch difference for the white 'sensor output' under the D65 illuminant. Use of spectral sensitivity devices is an evolving field. Before drawing causal relationships between light and other biological processes, researchers should acknowledge the limitations of the instruments used, their validation, and the resultant data. The outcomes of the study indicate caution must be exercised in longitudinal data collection and the mixing of watches amongst study participants should be avoided.


Assuntos
Percepção de Cores/fisiologia , Cor , Iluminação , Algoritmos , Humanos , Processamento de Imagem Assistida por Computador/métodos
15.
Acta Psychol (Amst) ; 214: 103265, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33601162

RESUMO

Attribute amnesia (AA) describes a phenomenon whereby observers fail a surprise memory test which asks them to report an attribute they had just attended and used to fulfil a task goal. This finding has cast doubt on the prominent theory that attention results in encoding into working memory (WM), to which two competing explanations have been proposed: (1) task demands dictate whether attended information is encoded into WM, and (2) attended information is encoded in a weak state that does not survive the demands of the surprise memory test. To address this debate our study circumvented the limitations of a surprise memory test by embedding a second search task within a typical color-based AA search task. The search task was modified so that the attended attribute would reappear in the second search as either the target, a distractor, or not at all. Critically, our results support encoding of the attended attribute in WM though to a weaker extent than the attribute that is required for report. A second experiment confirmed that WM encoding only occurs for the attended attribute, though distractor attributes produce a bias consistent with negative priming. Our data provide novel support for a theory of memory consolidation that links the strength of a memory's representation with expectations for how it will be used in a task. Implications for the utility of this procedure in future investigations previously limited by single trial data (i.e., surprise question methodology) are discussed.


Assuntos
Memória de Curto Prazo , Rememoração Mental , Amnésia , Atenção , Percepção de Cores , Humanos
16.
Atten Percept Psychophys ; 83(4): 1797-1803, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33409899

RESUMO

It is widely agreed that the color vision process moves quickly from cone receptors to opponent color cells in the retina and lateral geniculate nucleus. Many workers have proposed the transformation or coding of long, medium, short (LMS) cone responses to r - g, y - b opponent color chromatic responses (unique hues) on the following basis: That L, M, S cones represent Red, Green, and Blue hues, with Yellow represented by (L + M), while r - g and y - b represent the opponent pairs of unique hues. The traditional coding from cones to opponent colors is that L - M gives r - g, while (L + M) - S gives y - b. This convention is open to several criticisms, and a new coding is required. A literature search produced 16 studies of cone responses LMS and 15 studies of spectral (i.e., ygb) opponent color chromatic responses, in terms of response wavelength peaks. Comparative analysis of the two sets of studies shows the means are almost identical (within 3 nm; i.e., L = y, M = g, S = b). Further, the response curves of LMS are very similar shapes to ygb. In sum, each set can directly transform to the other on this proposed coding: (S + L) - M gives r - g, while L - S gives y - b. This coding activates neural operations in the cardinal directions r - g and y - b.


Assuntos
Percepção de Cores , Visão de Cores , Cor , Humanos , Estimulação Luminosa , Retina , Células Fotorreceptoras Retinianas Cones
17.
Atten Percept Psychophys ; 83(4): 1652-1672, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33462770

RESUMO

Humans use regularities in the environment to facilitate learning, often without awareness or intent. How might such regularities distort long-term memory? Here, participants studied and reported the colors of objects in a long-term memory paradigm, uninformed that certain colors were sampled more frequently overall. When participants misreported an object's color, these errors were often centered around the average studied color (i.e., "Rich" color), demonstrating swap errors in long-term memory due to imposed statistical regularities. We observed such swap errors regardless of memory load, explicit knowledge, or the distance in color space between the correct color of the tested object and the Rich color. An explicit guessing strategy where participants intentionally made swap errors when uncertain could not fully account for our results. We discuss other potential sources of observed swap errors such as false memory and implicit biased guessing. Although less robust than swap errors, evidence was also observed for subtle shift errors towards or away from the Rich color dependent on the color distance between the correct color and the Rich color. Together, these findings of swap and shift errors provide converging evidence for memory distortion mechanisms induced by a reference point, bridging a gap in the literature between how attention to regularities similarly influences visual working memory and visual long-term memory.


Assuntos
Rememoração Mental , Percepção Visual , Percepção de Cores , Humanos , Memória de Longo Prazo , Memória de Curto Prazo
18.
J Dent ; 105: 103560, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33352224

RESUMO

OBJECTIVE: To determine in-vivo chromatic and whiteness changes produced by short-term dental dehydration. METHODS: Spectral reflectance of 452 upper incisors (226 centrals and 226 laterals) of 113 participants were measured using a spectroradiometer at baseline and after short-term dehydration (minutes 2, 4, 6, 8 and 10). CIE L*a*b* color coordinates (L*, a*, b*, C*ab and hab) and whiteness index for dentistry (WID) were calculated. Color differences (ΔE00, ΔEab*) and whiteness differences (ΔWID) were computed and interpreted based on their respective 50:50% perceptibility (PT) and acceptability thresholds (AT). Statistical analysis was performed using the related samples Wilcoxon signed-rank test. RESULTS: L* showed an increasing trend with dehydration, while a*, b*, C*ab and hab have a decreasing tendency. All chromatic coordinates showed statistically significant differences (p < 0.003) at each interval of dehydration compared with baseline, except a* for all teeth. For ΔE00 and ΔEab* values were higher than PT after 2 min of teeth dehydration and higher than AT after 6 and 8 min, respectively. The percentage of teeth exceeding corresponding PT was higher than 50% after 2 min. WID index increased with dehydration time, while whiteness differences were clinically perceptible after 4 min. Statistically significant differences were found for WID between all dehydration intervals (except 8-10 min). The percentage of teeth exceeding whiteness PT was higher than 50% after 6 min of teeth dehydration. CONCLUSIONS: Short-term dental dehydration produces clinically unacceptable changes in tooth color and clinically perceptible increase in tooth whiteness level. CLINICAL SIGNIFICANCE: Clinical shade matching must be done within the first two minutes of any clinical procedure that requires precise chromatic determination but implies a risk of tooth dehydration.


Assuntos
Desidratação , Incisivo , Cor , Percepção de Cores , Humanos , Incisivo/diagnóstico por imagem
19.
J Vis ; 20(13): 18, 2020 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-33372985

RESUMO

Temporal changes in illumination are ubiquitous; natural light, for example, varies in color temperature and irradiance throughout the day. Yet little is known about human sensitivity to temporal changes in illumination spectra. Here, we aimed to determine the minimum detectable velocity of chromaticity change of daylight metamers in an immersive environment. The main stimulus was a continuous, monotonic change in global illumination chromaticity along the daylight locus in warmer (toward lower correlated color temperatures [CCTs]) or cooler directions, away from an adapting base light (CCT: 13,000 K, 6500 K, 4160 K, or 2000 K). All lights were generated by spectrally tunable overhead lamps as smoothest-possible metamers of the desired chromaticities. Mean detection thresholds (for 22 participants) for a fixed duration of 10 seconds ranged from 15 to 2 CIELUV ΔE units, depending significantly on base light CCT and with a significant interaction between CCT and direction of change. Cool changes become less noticeable for progressively warmer base lights and vice versa. For the two extreme base lights, sensitivity to changes toward neutral is significantly lower than for the opposite direction. The results suggest a "neutral bias" in illumination change discriminability, and that typical temporal changes in daylight chromaticity are likely to be below threshold detectability, at least where there are no concomitant overall illuminance changes. These factors may contribute to perceptual stability of natural scenes and color constancy.


Assuntos
Percepção de Cores/fisiologia , Visão de Cores/fisiologia , Luz , Limiar Sensorial/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
20.
PLoS One ; 15(12): e0243237, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33332389

RESUMO

It has recently been demonstrated through invasive electrophysiology that visual stimulation with extended patches of uniform colour generates pronounced gamma oscillations in the visual cortex of both macaques and humans. In this study we sought to discover if this oscillatory response to colour can be measured non-invasively in humans using magnetoencephalography. We were able to demonstrate increased gamma (40-70 Hz) power in response to full-screen stimulation with four different colour hues and found that the gamma response is particularly strong for long wavelength (i.e. red) stimulation, as was found in previous studies. However, we also found that gamma power in response to colour was generally weaker than the response to an identically sized luminance-defined grating. We also observed two additional responses in the gamma frequency: a lower frequency response around 25-35 Hz that showed fewer clear differences between conditions than the gamma response, and a higher frequency response around 70-100 Hz that was present for red stimulation but not for other colours. In a second experiment we sought to test whether differences in the gamma response between colour hues could be explained by their chromatic separation from the preceding display. We presented stimuli that alternated between each of the three pairings of the three primary colours (red, green, blue) at two levels of chromatic separation defined in the CIELUV colour space. We observed that the gamma response was significantly greater to high relative to low chromatic separation, but that at each level of separation the response was greater for both red-blue and red-green than for blue-green stimulation. Our findings suggest that the stronger gamma response to red stimulation cannot be wholly explained by the chromatic separation of the stimuli.


Assuntos
Percepção de Cores , Estimulação Luminosa , Córtex Visual/fisiologia , Adulto , Cor , Feminino , Humanos , Magnetoencefalografia , Masculino , Adulto Jovem
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