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Search Results: 1 - 10 of 74839 matches for " Natanael Antonio dos;Oliveira "
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The effects of age on visual perception of sine-wave gratings at low luminance / Os efeitos da idade na percep o visual de grades senoidais em luminancia baixa
Natanael Antonio dos Santos,Adriana Bastos Oliveira,Renata Maria Toscano Barreto Lyra Nogueira,éllen Dias Nicácio da Cruz
Psicologia: Reflex?o e Crítica , 2006,
Abstract: The aim of this work was to investigate the contrast sensitivity function for sine-wave gratings in the range between 0.25-2 cpd in young and older adults (20-23, 30-39, 40-49, 50-59, 60-69 years old) using low luminance. All subjects were free from identifiable ocular disease and had normal acuity. We measured the contrast thresholds for 30 participants (six volunteers in each age) using the psychophysical forced-choice staircase method. In this method the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., a sine-wave grating), or another neutral stimulus at mean luminance (0.7 cd/m2). The results showed significant changes of CSF for sine-wave gratings at 1 and 2 cpd for the adults 50-59 and 60-69 years old compared to the adults of 20-23 years old. These results suggest age-related changes in the CSF for sine-wave grating at low luminance levels.
Os efeitos da idade na percep??o visual de grades senoidais em luminancia baixa
Santos, Natanael Antonio dos;Oliveira, Adriana Bastos;Nogueira, Renata Maria Toscano Barreto Lyra;Cruz, éllen Dias Nicácio da;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2006, DOI: 10.1590/S0102-79722006000300010
Abstract: the aim of this work was to investigate the contrast sensitivity function for sine-wave gratings in the range between 0.25-2 cpd in young and older adults (20-23, 30-39, 40-49, 50-59, 60-69 years old) using low luminance. all subjects were free from identifiable ocular disease and had normal acuity. we measured the contrast thresholds for 30 participants (six volunteers in each age) using the psychophysical forced-choice staircase method. in this method the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., a sine-wave grating), or another neutral stimulus at mean luminance (0.7 cd/m2). the results showed significant changes of csf for sine-wave gratings at 1 and 2 cpd for the adults 50-59 and 60-69 years old compared to the adults of 20-23 years old. these results suggest age-related changes in the csf for sine-wave grating at low luminance levels.
Detec??o de estímulos radiais e espaciais em adultos e idosos
Santos, Natanael Antonio dos;Oliveira, Adriana Bastos;Nogueira, Renata Maria Toscano Barreto Lyra;Cavalcanti, Melyssa Kellyane;Simas, Maria Lúcia de Bustamante;
Psicologia: Teoria e Pesquisa , 2007, DOI: 10.1590/S0102-37722007000300011
Abstract: the aim of this work was to compare contrast sensitivity curves for radial (rcsf) and sine-wave gratings (csf) stimuli of 0.25, 0.5, 1 and 2 cpd in young and older adults. we measured the contrast thresholds for six young and six older adults using the psychophysical forced-choice staircase method. all were free of ocular diseases and had normal visual acuity. the older adults presented a loss in rcsf and fsc if compared to the young adults. the contrast sensitivity for young and older adults was higher for spatial frequencies (csf) than radial frequencies (rcsf). these results suggest that these stimuli can be processed by distinct visual areas.
Altera??es na sensibilidade ao contraste relacionadas à ingest?o de álcool
Cavalcanti, Melyssa Kellyane;Santos, Natanael Antonio dos;
Psicologia: Teoria e Pesquisa , 2008, DOI: 10.1590/S0102-37722008000400015
Abstract: the purpose of this paper was to characterize the contrast sensitivity function (csf) for spatial frequencies equal to 0.25, 1.0 and 4.0 cpd (cycles per degree) in the absence (control group-cg) and after moderate alcohol ingestion (experimental group-eg). for such, the forced choice psychophysical method was used. the participants were four 21 to 30 year-old-women with normal or corrected visual acuity. the results showed a significant difference between groups at the spatial frequency of 4.0 cpd (p= 0.039), such that the eg was more sensitive to contrast than the cg. these results suggest alcohol-related alterations in the csf.
Sensibilidade ao contraste mesópica de crian as surdas para estímulos radicais e grades senoidais
Santos, Natanael Antonio dos et. al.
Psico , 2009,
Abstract: O objetivo deste estudo foi medir e comparar as curvas de sensibilidade ao contraste mesópicas para estimulos radicais (FSCr) e grades senoidais (FSC) de 0,25; 0,5; 1 e 2 cpg em crian as surdas de 7 a 12 anos. Mensuramos limiares de contraste para 10 crian as, utilizando o método psicofisico da escolha for ada e luminancia média de 0,7 cd/m2. Todos os participantes estavam livres de doen as oculares e apresentavam acuidade visual normal. Os resultados mostraram que a sensibilidade das crian as surdas foi maior para grades senoidais (FSC) do que para estimulos radicais (FSCr). Estes resultados sugerem que os dois estímulos podem ser processados por áreas visuais corticais distintas.
Pacientes com depress?o maior têm menor sensibilidade a contraste visual que indivíduos saudáveis
Nogueira, Renata Maria Toscano Barreto Lyra;Santos, Natanael Antonio dos;
Estudos de Psicologia (Natal) , 2012, DOI: 10.1590/S1413-294X2012000100014
Abstract: the aim of this study was to measure visual contrast sensitivity, cs, for concentric circular sine-wave gratings with spatial frequencies of 0.25, 4 and 8 cpd, cycles per degree of visual angle, in adults without and with major depression disorder. we measured the visual cs for 20 participants, ten without and ten with major depression disorder medicated, using a temporal two-alternative forced-choice psychophysical method with mean luminance of 0.7 cd/m2. all volunteers were free from identifiable ocular disease and had normal acuity. the results showed maximum contrast sensitivity to spatial frequency occurred in the range of 0.25 cpd for both groups. the results also showed that the visual cs for major depression was lower than those of adults without depression (p < 0.05). these results showed alterations in the visual perception related the major depression.
Percep??o e processamento visual da forma em humanos: filtros de freqüências radiais de 1 e 4 cpg
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2002, DOI: 10.1590/S0102-79722002000200015
Abstract: the aim of this work was to measure narrow-band frequency response curves for two radial frequency filters, spatial stimuli modulated by cylindrical bessel profiles, j0, whose test frequencies were 1 and 4 cpd. five humans observers with normal or corrected visual acuity measured 15 curves for each filter with a supra-threshold response summation psychophysics method allied within a forced-choice paradigm. the results showed maximum summation effects at test frequency for filters 1 and 4 cpd surrounded on both sides by strong inhibition. these results are consistent with the existence of narrow-band radial frequency filters operating in human visual system either through summation or inhibition of specific frequency ranges.
Processamento visual da forma: análise de sistema linear e alguns paradigmas psicofísicos
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2002, DOI: 10.1590/S0102-79722002000300007
Abstract: the goal of this work is to discuss some basic aspects of fourier analysis as a tool to be used in the approach of multiple channels of spatial frequencies on the study of visual processing of form. some of the psychophysical paradigms more frequently used to characterize response of the human visual system to spatial frequency filter of narrow-band. the linear system analysis and some psychophysical paradigms have contributed to theoretical development of perception and of the visual processing of form.
Percep??o e processamento visual da forma: discutindo modelos teóricos atuais
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2001, DOI: 10.1590/S0102-79722001000100013
Abstract: this work discusses some aspects about feature detectors and spatial frequency analysis models in five sections. the first section describes briefly historical aspects and the basic rationale idea of each model. the second section shows the neurophysiological and psychophysical evidences about spatial frequency selectivity. the third, the fourth and the fifth sections show controversial aspects about these models: spatial frequency versus feature detectors, global versus local filtering and nonlinear versus linear spatial processing, respectively. one of the goals of this paper is to discuss important aspects about perception and visual processing of form.
O fen?meno de muitas-faces: investiga??es preliminares
Simas, Maria Lúcia de Bustamante;Santos, Natanael Antonio dos;
Psicologia: Reflex?o e Crítica , 2005, DOI: 10.1590/S0102-79722005000100014
Abstract: the multiple-faces effect was first investigated at the blind spot using familiar faces. we analyzed the effect into 4 categories: 1) disappearance/darkening/whitening of face parts; 2) variation in size of face parts; 3) perception of movement /change in facial expression; 4) perception of other faces. categories 1 and 2 reflect initial impressions. only reports falling into categories 3 and/or 4 show the multiple-faces effect. results analyzed data from 37 subjects (using mother and/or father and/or other relatives' photographs). analysis across subjects yielded 87% and 68% in categories 3 and 4, respectively. in category 3, changes in facial expression were 90% and 82% for mother and father faces, respectively. in category 4, other faces were more frequently observed with the mother's face (73%) than the father's (41%) face. we discuss these results in terms of peripheral processing of form considering a possible tuning for faces resulting from frequency of viewing the same face during early visual development.
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