PURPOSE. To compare the effects of aging on two shapediscrimination tasks: a closed shape task (r... more PURPOSE. To compare the effects of aging on two shapediscrimination tasks: a closed shape task (radial frequency [RF] patterns) and a Glass pattern coherence task (discrimination of global shape signal from textured noise). We hypothesized that aging would impair the extraction of shape from texture more than the discrimination of closed shapes, consistent with evidence that aging impairs the ability to suppress irrelevant information when segmenting contours from noise.
Purpose Contrast sensitivity testing is an important part of visual assessment and can identify v... more Purpose Contrast sensitivity testing is an important part of visual assessment and can identify visual deficits that go undetected by measuring visual acuity (VA) alone. Despite this, contrast sensitivity testing is rarely performed clinically due to the expensive processes required and limited test availability, with few spatial frequencies used. Further, gratings can be difficult for subjects to learn and results are often not standardized. We developed and tested a convenient, inexpensive protocol using Snellen optotypes to measure the CSF using a widely available computerised VA chart. Effects of blur and neutral density (ND) light attenuation were analysed to evaluate the technique under different conditions.Methods 34 eyes of 34 subjects were tested monocularly under photopic conditions. Subjects had corrected VA of 6/4.8 (or better) and normal ocular health. A computerised chart (Luneau) was used to measure contrast sensitivity thresholds across 19 spatial frequencies between...
Our experiments explore whether contour processing of closed shapes is altered by healthy aging. ... more Our experiments explore whether contour processing of closed shapes is altered by healthy aging. Contour processing was measured using a closed contour (circle or ellipse) constructed of Gabor elements. The contour was presented either on a blank background or embedded in noise (identical Gabor elements of random orientation). Twenty-one older (age range: 61-80 years) and 21 younger (age range: 22-38 years) adults participated in three experiments: 1) the number of Gabors comprising the contour was fixed (10, 12 or 15) and the threshold aspect ratio required to discriminate the shape (circle versus ellipse) was measured; 2) orientation jitter was added to the Gabor elements comprising the contour and shape aspect ratio discrimination thresholds were measured; and 3) the aspect ratio was fixed (three times the individual threshold aspect ratios) and the threshold number of elements required to determine the shape was measured. Older adults required a larger number of elements to discriminate the global contour shape (F(1, 41) = 15, p < 0.001), even when stimulus saliency was matched for contrast sensitivity and aspect ratio threshold. This finding is consistent with other recent work showing deteriorations in cortically mediated visual processing with age.
To compare the effects of aging on two shape-discrimination tasks: a closed shape task (radial fr... more To compare the effects of aging on two shape-discrimination tasks: a closed shape task (radial frequency [RF] patterns) and a Glass pattern coherence task (discrimination of global shape signal from textured noise). We hypothesized that aging would impair the extraction of shape from texture more than the discrimination of closed shapes, consistent with evidence that aging impairs the ability to suppress irrelevant information when segmenting contours from noise. Fourteen younger (19-38 years) and 14 older (62-72 years) adults participated. Contrast-detection thresholds were measured for the RF and Glass stimuli, and then shape-discrimination tasks were performed using stimuli of 5-fold each individual's contrast threshold. The threshold sinusoidal amplitude for the discrimination of an RF3 (triangular) versus an RF4 (square) was measured, in addition to the threshold signal coherence level for the discrimination of concentric from radial Glass patterns. Older adults had elevated shape-discrimination thresholds: RF: mean older = 27 second arc, younger = 18 second arc, t(26) = -3.14, P < 0.01; Glass patterns mean coherence: older = 29%, younger = 16%, t(26) = -5.67, P < 0.01. Relative to younger adult performance, the Z-scores for older adult performance on the Glass task were higher than the RF task (paired t-test; P < 0.05). Shape perception is not robust to the effects of aging. Greater deficits were manifest for the discrimination of shape from texture than for the discrimination of closed contours.
... Prix indicatif 385,32 Ajouter au panier le livre de SCHUMAN Joel S., PULIAFITO Carmen A., F... more ... Prix indicatif 385,32 Ajouter au panier le livre de SCHUMAN Joel S., PULIAFITO Carmen A., FUJIMOTO James G. Date de parution : 05-2004 Langue : ANGLAIS 250p. 17.8x11.1 Paperback Disponible chez l'éditeur (délai d'approvisionnement : 15 jours). ...
PURPOSE. To compare the effects of aging on two shapediscrimination tasks: a closed shape task (r... more PURPOSE. To compare the effects of aging on two shapediscrimination tasks: a closed shape task (radial frequency [RF] patterns) and a Glass pattern coherence task (discrimination of global shape signal from textured noise). We hypothesized that aging would impair the extraction of shape from texture more than the discrimination of closed shapes, consistent with evidence that aging impairs the ability to suppress irrelevant information when segmenting contours from noise.
Purpose Contrast sensitivity testing is an important part of visual assessment and can identify v... more Purpose Contrast sensitivity testing is an important part of visual assessment and can identify visual deficits that go undetected by measuring visual acuity (VA) alone. Despite this, contrast sensitivity testing is rarely performed clinically due to the expensive processes required and limited test availability, with few spatial frequencies used. Further, gratings can be difficult for subjects to learn and results are often not standardized. We developed and tested a convenient, inexpensive protocol using Snellen optotypes to measure the CSF using a widely available computerised VA chart. Effects of blur and neutral density (ND) light attenuation were analysed to evaluate the technique under different conditions.Methods 34 eyes of 34 subjects were tested monocularly under photopic conditions. Subjects had corrected VA of 6/4.8 (or better) and normal ocular health. A computerised chart (Luneau) was used to measure contrast sensitivity thresholds across 19 spatial frequencies between...
Our experiments explore whether contour processing of closed shapes is altered by healthy aging. ... more Our experiments explore whether contour processing of closed shapes is altered by healthy aging. Contour processing was measured using a closed contour (circle or ellipse) constructed of Gabor elements. The contour was presented either on a blank background or embedded in noise (identical Gabor elements of random orientation). Twenty-one older (age range: 61-80 years) and 21 younger (age range: 22-38 years) adults participated in three experiments: 1) the number of Gabors comprising the contour was fixed (10, 12 or 15) and the threshold aspect ratio required to discriminate the shape (circle versus ellipse) was measured; 2) orientation jitter was added to the Gabor elements comprising the contour and shape aspect ratio discrimination thresholds were measured; and 3) the aspect ratio was fixed (three times the individual threshold aspect ratios) and the threshold number of elements required to determine the shape was measured. Older adults required a larger number of elements to discriminate the global contour shape (F(1, 41) = 15, p < 0.001), even when stimulus saliency was matched for contrast sensitivity and aspect ratio threshold. This finding is consistent with other recent work showing deteriorations in cortically mediated visual processing with age.
To compare the effects of aging on two shape-discrimination tasks: a closed shape task (radial fr... more To compare the effects of aging on two shape-discrimination tasks: a closed shape task (radial frequency [RF] patterns) and a Glass pattern coherence task (discrimination of global shape signal from textured noise). We hypothesized that aging would impair the extraction of shape from texture more than the discrimination of closed shapes, consistent with evidence that aging impairs the ability to suppress irrelevant information when segmenting contours from noise. Fourteen younger (19-38 years) and 14 older (62-72 years) adults participated. Contrast-detection thresholds were measured for the RF and Glass stimuli, and then shape-discrimination tasks were performed using stimuli of 5-fold each individual's contrast threshold. The threshold sinusoidal amplitude for the discrimination of an RF3 (triangular) versus an RF4 (square) was measured, in addition to the threshold signal coherence level for the discrimination of concentric from radial Glass patterns. Older adults had elevated shape-discrimination thresholds: RF: mean older = 27 second arc, younger = 18 second arc, t(26) = -3.14, P < 0.01; Glass patterns mean coherence: older = 29%, younger = 16%, t(26) = -5.67, P < 0.01. Relative to younger adult performance, the Z-scores for older adult performance on the Glass task were higher than the RF task (paired t-test; P < 0.05). Shape perception is not robust to the effects of aging. Greater deficits were manifest for the discrimination of shape from texture than for the discrimination of closed contours.
... Prix indicatif 385,32 Ajouter au panier le livre de SCHUMAN Joel S., PULIAFITO Carmen A., F... more ... Prix indicatif 385,32 Ajouter au panier le livre de SCHUMAN Joel S., PULIAFITO Carmen A., FUJIMOTO James G. Date de parution : 05-2004 Langue : ANGLAIS 250p. 17.8x11.1 Paperback Disponible chez l'éditeur (délai d'approvisionnement : 15 jours). ...
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