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	Provedor de dados BJMBR (4) Autor Nogueira,R.M.T.B.L. (4) Santos,N.A. (4) Simas,M.L.B. (3) Costa,T.L. (1) Oliveira,A.B. (1) Pereira,A.G.F. (1) Mais... Palavra-chave Contrast sensitivity (4) Forced-choice method (2) Radial frequency (2) Spatial frequency (2) Aging (1) Angular frequency (1) Bessel functions (1) Circular gratings (1) Human aging (1) Linear gratings (1) Multiple channels (1) Sine-wave gratings (1) Spatial vision (1) Visual form processing (1) Mais... Tipo do documento Info:eu-repo/semantics/article (2) Info:eu-repo/semantics/other (2) Ano 2013 (1) 2006 (1) 2005 (1) 2004 (1) País Brazil (4) Idioma Inglês (4)		Ordenar por:  Relevância Autor Título Ano Registros recuperados: 4 Primeira ... 1 ... Última Differential effects of aging on spatial contrast sensitivity to linear and polar sine-wave gratings BJMBR Costa,T.L.; Nogueira,R.M.T.B.L.; Pereira,A.G.F.; Santos,N.A.. Changes in visual function beyond high-contrast acuity are known to take place during normal aging. We determined whether sensitivity to linear sine-wave gratings and to an elementary stimulus preferentially processed in extrastriate areas could be distinctively affected by aging. We measured spatial contrast sensitivity twice for concentric polar (Bessel) and vertical linear gratings of 0.6, 2.5, 5, and 20 cycles per degree (cpd) in two age groups (20-30 and 60-70 years). All participants were free of identifiable ocular disease and had normal or corrected-to-normal visual acuity. Participants were more sensitive to Cartesian than to polar gratings in all frequencies tested, and the younger adult group was more sensitive to all stimuli tested. Significant... Tipo: Info:eu-repo/semantics/article Palavras-chave: Contrast sensitivity; Circular gratings; Linear gratings; Aging; Spatial vision. Ano: 2013 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2013001000855 Comparison of angular frequency contrast sensitivity in young and older adults BJMBR Santos,N.A.; Simas,M.L.B.; Nogueira,R.M.T.B.L.. The aim of the present study was to measure contrast sensitivity curves for angular frequencies in the range between 2 and 96 cycles/360º in older human adult volunteers and to compare these measurements with the more usual contrast sensitivity functions for sine-wave gratings. All subjects were free of identifiable ocular disease and had normal acuity. We measured the contrast thresholds for young adults (N = 6; age range, 20-26 years) and older adults (N = 6; age range, 60-67 years) using the psychophysical forced-choice method. In this paradigm the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., either a sine-wave grating or an angular frequency stimulus), or another neutral stimulus at mean luminance (without... Tipo: Info:eu-repo/semantics/other Palavras-chave: Human aging; Spatial frequency; Angular frequency; Contrast sensitivity; Forced-choice method. Ano: 2004 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2004000300014 Radial frequency stimuli and sine-wave gratings seem to be processed by distinct contrast brain mechanisms BJMBR Simas,M.L.B.; Nogueira,R.M.T.B.L.; Santos,N.A.. An assumption commonly made in the study of visual perception is that the lower the contrast threshold for a given stimulus, the more sensitive and selective will be the mechanism that processes it. On the basis of this consideration, we investigated contrast thresholds for two classes of stimuli: sine-wave gratings and radial frequency stimuli (i.e., j0 targets or stimuli modulated by spherical Bessel functions). Employing a suprathreshold summation method, we measured the selectivity of spatial and radial frequency filters using either sine-wave gratings or j0 target contrast profiles at either 1 or 4 cycles per degree of visual angle (cpd), as the test frequencies. Thus, in a forced-choice trial, observers chose between a background spatial (or radial)... Tipo: Info:eu-repo/semantics/article Palavras-chave: Sine-wave gratings; Spatial frequency; Radial frequency; Bessel functions; Multiple channels; Contrast sensitivity. Ano: 2005 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2005000300013 Mesopic radial frequency contrast sensitivity function for young and older adults BJMBR Santos,N.A.; Oliveira,A.B.; Nogueira,R.M.T.B.L.; Simas,M.L.B.. The objective of the present study was to determine contrast sensitivity curves of concentric circular patterns with radial frequencies of 0.25, 0.5, 1.0, 2.0, and 4.0 cycles per degree in young and older adult volunteers. These parameters were also compared with sensitivity contrasts for sine-wave gratings. All participants had normal acuity vision and were free of identifiable ocular illness. Contrast sensitivity was measured in 6 young adults aged 19 to 23 years and 6 older adults aged 60 to 69 years using the psychophysical forced-choice method. In this paradigm the volunteers had to decide which of two stimuli contained the above radial frequencies at low contrast levels. The other neutral stimulus was gray with homogeneous luminance. We detected a... Tipo: Info:eu-repo/semantics/other Palavras-chave: Visual form processing; Radial frequency; Contrast sensitivity; Forced-choice method. Ano: 2006 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2006000600012 Registros recuperados: 4 Primeira ... 1 ... Última

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