Percepção e processamento visual da forma: discutindo modelos teóricos atuais

Santos, Natanael Antonio dos; Simas, Maria Lúcia de Bustamante

doi:10.1590/s0102-79722001000100013

Cited by 14 publications

(83 citation statements)

References 90 publications

(83 reference statements)

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“…Além de ser um dos principais indicadores das funções visuais (Wilson, Levi, Maffei, Rovamo & De Valois, 1990), ela descreve de forma eficiente o desempenho do sistema visual em níveis diferentes de contrastes, fornecendo, inclusive, o limite entre o mundo a baixo contraste, que é, entretanto, percebido, e o mundo a baixo contraste, que nunca se vê (Santos & Simas, 2001). A FSC é uma medida clássica que permite descrever mecanismos sensoriais básicos, fornecendo uma das descrições mais completas do sistema visual (Adams & Courage, 2002;Wilson et al, 1990).…”

Section: Função De Sensibilidade Ao Contraste E Percepção Visualunclassified

Sensibilidade ao contraste de freqüências radiais em crianças de 4 a 7 anos e adultos

Santos

França

Simas

2008

Psicol. Reflex. Crit.

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Resumo O objetivo deste trabalho foi medir a sensibilidade ao contraste para freqüências radiais (FSCr) de 0,25 a 2 cpg em crianças (4 a 7 anos) e adultos. Foram estimados limiares de contraste para 25 participantes (vinte crianças e cinco adultos jovens), utilizando o método psicofísico da escolha forçada. Os participantes apresentavam acuidade visual normal. Os resultados mostraram que as curvas (FSCr) de crianças de 4 a 7 anos melhoraram de forma significativa com a idade. Os resultados mostraram ainda que a FSCr de crianças de 7 anos é mais baixa do que a de adultos jovens. Estes resultados sugerem que o desenvolvimento da percepção visual de contraste para estímulos radiais ocorre gradualmente se prolongando além dos 7 anos. Palavras-chave: Sensibilidade ao contraste; desenvolvimento visual; crianças; freqüência radial; método da escolha forçada. AbstractThe aim of this work was to measure contrast sensitivity for radial frequencies (rCSF) in the range between 0.25-2 cpd in children (4 to 7 years of age) and young adults. Contrast thresholds were estimated for 25 participants (twenty children and five adults) using the psychophysical forced-choice method at low luminance levels. All the cts participants had normal acuity. The results showed that the curves (rCSF) of the 4, 5, 6 and 7 years old improved significantly with age. The results also showed that the rCSF for 7 year old children was lower than in young adults. These results suggest that the development of contrast sensitivity for radial stimuli increases gradually even after turning 7 years old.

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Section: Função De Sensibilidade Ao Contraste E Percepção Visualunclassified

Sensibilidade ao contraste de freqüências radiais em crianças de 4 a 7 anos e adultos

Santos

França

Simas

2008

Psicol. Reflex. Crit.

Self Cite

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“…Contrast sensitivity function (CSF), an important measure of visual function and the first analysis performed by the visual cortex 13, 14 , may be used to assess the performance of the visual system. Luminance contrast differences, which are perceived as lightness differences, can be identified and quantified through spatial frequency responses 13, 14 .…”

Section: Introductionmentioning

confidence: 99%

“…Luminance contrast differences, which are perceived as lightness differences, can be identified and quantified through spatial frequency responses 13, 14 .…”

Section: Introductionmentioning

confidence: 99%

Effects of smoking and smoking abstinence on spatial vision in chronic heavy smokers

Fernandes

Almeida

Santos

2017

Sci Rep

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Cigarette smoke is a complex chemical mixture, involving health-damaging components such as carbon monoxide, ammonia, pyridine, toluene and nicotine. While cognitive functions have been well documented in heavy smokers, spatial vision has been less characterized. In the article, we investigated smoking effects through contrast sensitivity function (CSF), a rigorous procedure that measures the spatial vision. Data were recorded from 48 participants, a group of non-smokers (n = 16), a group of chronic and heavy cigarette smokers (n = 16) and deprived smokers (n = 16); age range 20–45 years. Sinewave gratings with spatial frequencies ranging from 0.25 to 20 cycles per degree were used. All subjects were free from any neurological disorder, identifiable ocular disease and had normal acuity. No abnormalities were detected in the fundoscopic examination and in the optical coherence tomography exam. Contrary to expectations, performance on CSF differed between groups. Both smokers and deprived smokers presented a loss of contrast sensitivity compared to non-smokers. Post-hoc analyses suggest that deprived smokers were less sensitive at all spatial frequencies. These results suggest that not only chronic exposure to cigarette compounds but also withdrawal from nicotine affected spatial vision. This highlights the importance of understanding diffuse effects of smoking compounds on visual spatial processing.

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“…Do ponto de vista psicofísico um canal ou um filtro corresponde a uma estrutura visual independente que lida com uma faixa estreita de freqüência espacial (Santos, 1999;Santos & Simas, 2001a).…”

Section: Filtros De Freqüências Espaciais No Sistema Visualunclassified

Percepção e processamento visual da forma em humanos: filtros de freqüências radiais de 1 e 4 cpg

Santos

Simas

2002

Psicol. Reflex. Crit.

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banda estreita operando no sistema visual humano através do processo de somação ou inibição em faixa de freqüências específicas. Palavras-chave: Processamento visual de forma; filtro radial; freqüência radial; somação de supra-limiar. Perception and Visual Processing of Form in Humans: Radial Frequency Filters of 1 and 4 cpd AbstractThe aim of this work was to measure narrow-band frequency response curves for two radial frequency filters, spatial stimuli modulated by cylindrical Bessel profiles, J 0 , 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.

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Percepção e processamento visual da forma: discutindo modelos teóricos atuais

Cited by 14 publications

References 90 publications

Sensibilidade ao contraste de freqüências radiais em crianças de 4 a 7 anos e adultos

Sensibilidade ao contraste de freqüências radiais em crianças de 4 a 7 anos e adultos

Effects of smoking and smoking abstinence on spatial vision in chronic heavy smokers

Percepção e processamento visual da forma em humanos: filtros de freqüências radiais de 1 e 4 cpg

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