Narrow-band 1, 2, 3, 4, 8, 16 and 24 cycles/360º angular frequency filters

Oliveira

Nogueira

et al. 2006

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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 decline in contrast sensitivity for older adults at all radial frequencies compared to young adults. Also, contrast sensitivity for sine-wave gratings at all measured frequencies was better, as predicted, for all young adults. Maximum sensitivities in the radial frequency contrast sensitivity function and contrast sensitivity function occurred at 0.25 and 0.5 cycles per degree, respectively, for both young and older adults. These results suggest age-related changes in the contrast sensitivity function for concentric symmetrical stimuli.

mentioning

confidence: 99%

“…Studies on human vision measuring sensitivity to radial frequency stimuli are dispersed, have rarely been conducted on young adults (11)(12)(13) and are non-existent for the older population. Six young adults (19 to 23 years old) and six older adults (60-69 years old) participated in the present investigation.…”

mentioning

confidence: 99%

Mesopic radial frequency contrast sensitivity function for young and older adults

Oliveira

Nogueira

et al. 2006

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“…Since we were also interested in learning how this filtering process could be involved in face detection and/or recognition, in a related study on narrow-band angular frequency filters we presented the face of the night monkey aotus as an example showing that the angular part appears to be somewhat dominant over the radial one, particularly at 1, 2, 3 and 4 cycles (25). We also find it interesting that the aotus has nocturnal habits because if we consider very low angular frequencies such as these, very large portions of the retina would be involved in visually processing information and thus would require (work best under) lower luminance levels.…”

Section: Filtering Of Radial and Angular Frequencies By The Visual Symentioning

confidence: 99%

Contrast sensitivity to radial frequencies modulated by Jn and j n Bessel profiles

Simas

2002

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We measured human contrast sensitivity to radial frequencies modulated by cylindrical (J o ) and spherical (j o ) Bessel profiles. We also measured responses to profiles of j o , j 1 , j 2 , j 4 , j 8 , and j 16 . Functions were measured three times by at least three of eight observers using a forced-choice method. The results conform to our expectations that sensitivity would be higher for cylindrical profiles. We also observed that contrast sensitivity is increased with the j n order for n greater than zero, having distinct orderly effects at the low and high frequency ends. For n = 0, 1, 2, and 4 sensitivity tended to occur around 0.8-1.0 cpd while for n = 8 and 16 it seemed to shift gradually to 0.8-3.0 cpd. We interpret these results as being consistent with the possibility that spatial frequency processing by the human visual system can be defined a priori in terms of polar coordinates and discuss its application to study face perception.

“…Studies on human vision measuring sensitivity to angular frequencies are rare for young adults (11,12) and non-existent for the older population. Six young adults (20-26 years old) and six older adults (60-67 years old) were studied in the present investigation.…”

mentioning

confidence: 99%

“…Measurements were made using a temporal two-alternative forced-choice paradigm (11,12). This paradigm is based on the probability of consecutive correct choices made by the subjects following the presentation of two successive stimuli, in this case, one at mean luminance (6.9 cd/m 2 ) and the other containing one of the angular frequencies.…”

mentioning

confidence: 99%

Comparison of angular frequency contrast sensitivity in young and older adults

Simas

Nogueira

2004

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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 any contrast). Older adults presented a loss in contrast sensitivity at high and medium angular frequencies compared to the young adults (i.e., from 8 to 96 cycles/360º). Contrary to expectation, contrast sensitivity at low angular frequencies, i.e., 2 and 4 cycles/ 360º, was better for the older group than for the younger group. On the other hand, contrast sensitivity for sine-wave gratings at 3 and 4 cpd was higher for young adults as expected. These results suggest agerelated changes in the contrast sensitivity function for angular frequencies.