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Search Results: 1 - 10 of 408262 matches for " Maria Lúcia de Bustamante;Nogueira "
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Sistema visual humano: evidência psicofísica para filtros de freqüência angular baixa
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Estudos de Psicologia (Natal) , 2005, DOI: 10.1590/S1413-294X2005000100012
Abstract: the aim of this work was to measure narrow-band frequency response curves for four angular frequency filters whose test frequencies were 1, 2, 3 and 4 cycles/360o. five human observers with normal or corrected visual acuity measured nine curves for each filter with a supra-threshold response summation psychophysical method allied within a forced-choice method. the results showed maximum summation effects at test frequency for filters 1, 2, 3 and 4 cycles/360o surrounded on both sides by strong inhibition. these results are consistent with the existence of narrow-band angular frequency filters operating in human visual system either through summation or inhibition of specific low angular frequency ranges.
Percep??o visual de contraste em humanos: evidência psicofísica para canais de freqüência angular alta
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Psicologia: Reflex?o e Crítica , 2007, DOI: 10.1590/S0102-79722007000100005
Abstract: the aim of this study was to measure narrow-band frequency response curves for four angular frequency filters. the test frequencies were 32, 48, 64 and 96 cycles/360o. six humans observers with normal or corrected visual acuity measured nine curves for each filter, with a supra-threshold response summation psychophysical method allied with a forced-choice method. the results showed maximum summation effects at test frequency for filter frequencies 32, 48, 64 and 96 cycles/360o, as well as a strong inhibition for neighboring frequencies. these results are consistent with the existence of narrow-band angular frequency filters in the human visual system either through summation or the inhibition of specific high angular frequency ranges.
Processamento visual da forma em idosos: curvas de limiar de contraste para freqüências angulares e senoidais
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Psicologia: Reflex?o e Crítica , 2003, DOI: 10.1590/S0102-79722003000200007
Abstract: the aim of this work was to measure contrast sensitivity curves for angular and spatial frequencies in the aged. we measured the contrast thresholds from young adults (20-26 years-old) and aged (60-67 years-old). all the participants had good visual acuity and were free from significant ocular pathology. the angular and spatial frequencies measured with a forced-choice psychophysic method were 2, 4, 8, 16, 24, 32, 48, 64 and 96 cycle/360o and 0.5, 1, 2, 3, 4, 6 and 9 cpd, respectively. the results showed a loss in contrast sensitivity for the aged at high and medium angular and spatial frequencies compared to the younger group. we still found that the contrast sensitivity of the aged group at low angular frequency is better than the younger group. these results are consistent with age-related changes in contrast sensitivity function.
Processamento visual da forma em humanos: curvas de limiar de contraste para padr?es circularmente simétricos
Santos, Natanael Antonio dos;Simas, Maria Lúcia de Bustamante;Nogueira, Renata Maria Toscano Barreto Lyra;
Psicologia: Reflex?o e Crítica , 2004, DOI: 10.1590/S0102-79722004000200016
Abstract: the aim of this work was to measure contrast sensitivity curves to concentrically symmetric patterns in a system of polar coordinates. we measured the contrast thresholds to sine wave gratings, radial frequencies and coupled radial/angular frequencies. six young adults with corrected-to-normal visual acuity participated in the experiments. the frequencies measured with a forced-choice psychophysical method were 0.2, 0.3, 0.5, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 and 9.0 cpd. results showed that coupled radial/angular frequencies caused an increase in the sensitivity of at least 1.6 times in relation to radial contrast sensitivity function. these results were in agreement with the model of multiple channels processing of spatial frequencies of stimuli defined in terms of polar coordinates.
Processamento visual da forma: evidências para canais múltiplos de freqüências angulares em humanos
Santos, Natanael Antonio dos;Nogueira, Renata Maria Toscano Barreto Lyra;Simas, Maria Lúcia de Bustamante;
Psicologia: Reflex?o e Crítica , 2005, DOI: 10.1590/S0102-79722005000100013
Abstract: the aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/360o defined in polar coordinates. we measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. the results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360o) filters surrounded on both sides by strong inhibition. these results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.
Processamento visual da forma em idosos: curvas de limiar de contraste para freqüências angulares e senoidais
Santos Natanael Antonio dos,Simas Maria Lúcia de Bustamante,Nogueira Renata Maria Toscano Barreto Lyra
Psicologia: Reflex?o e Crítica , 2003,
Abstract: O objetivo deste trabalho foi mensurar curvas de sensibilidade ao contraste para freqüências angulares e senoidais em idosos. Foram estimados limiares de contraste para um grupo de jovens com idade entre 20-26 anos e um grupo de idosos com idade entre 60-67 anos. Todos os sujeitos apresentavam acuidade visual normal e se encontravam livres de doen as oculares identificáveis. As freqüências angulares e senoidais estimadas com o método psicofísico da escolha for ada foram: 2, 4, 8, 16, 24, 32, 48, 64 e 96 ciclos/360o e 0.5, 1, 2, 3, 4, 6 e 9 cpg, respectivamente. Os resultados mostraram declínio na sensibilidade ao contraste nos idosos nas freqüências angulares e senoidais médias e altas comparados aos jovens. Encontramos, ainda, que a sensibilidade ao contraste dos idosos nas freqüências angulares baixas é melhor do que a dos jovens. Estes resultados s o consistentes com altera es na sensibilidade ao contraste relacionados ao processo de envelhecimento.
Visual processing of form in human: threshold contrast curves to concentrically symmetric patterns / Processamento visual da forma em humanos: curvas de limiar de contraste para padr es circularmente simétricos
Natanael Antonio dos Santos,Maria Lúcia de Bustamante Simas,Renata Maria Toscano Barreto Lyra Nogueira
Psicologia: Reflex?o e Crítica , 2004,
Abstract: The aim of this work was to measure contrast sensitivity curves to concentrically symmetric patterns in a system of polar coordinates. We measured the contrast thresholds to sine wave gratings, radial frequencies and coupled radial/angular frequencies. Six young adults with corrected-to-normal visual acuity participated in the experiments. The frequencies measured with a forced-choice psychophysical method were 0.2, 0.3, 0.5, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 and 9.0 cpd. Results showed that coupled radial/angular frequencies caused an increase in the sensitivity of at least 1.6 times in relation to radial contrast sensitivity function. These results were in agreement with the model of multiple channels processing of spatial frequencies of stimuli defined in terms of polar coordinates.
Visual processing of form: evidences for angular narrow-band frequency channels in human / Processamento visual da forma: evidências para canais múltiplos de freqüências angulares em humanos
Natanael Antonio dos Santos,Renata Maria Toscano Barreto Lyra Nogueira,Maria Lúcia de Bustamante Simas
Psicologia: Reflex?o e Crítica , 2005,
Abstract: The aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/360o defined in polar coordinates. We measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. The results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360o) filters surrounded on both sides by strong inhibition. These results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.
Visual contrast perception in human beings: psychophysical evidence for high angular frequency channels / Percep o visual de contraste em humanos: evidência psicofísica para canais de freqüência angular alta
Natanael Antonio dos Santos,Maria Lúcia de Bustamante Simas,Renata Maria Toscano Barreto Lyra Nogueira
Psicologia: Reflex?o e Crítica , 2007,
Abstract: The aim of this study was to measure narrow-band frequency response curves for four angular frequency filters. The test frequencies were 32, 48, 64 and 96 cycles/360o. Six humans observers with normal or corrected visual acuity measured nine curves for each filter, with a supra-threshold response summation psychophysical method allied with a forced-choice method. The results showed maximum summation effects at test frequency for filter frequencies 32, 48, 64 and 96 cycles/360o, as well as a strong inhibition for neighboring frequencies. These results are consistent with the existence of narrow-band angular frequency filters in the human visual system either through summation or the inhibition of specific high angular frequency ranges.
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.
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