Norman, J. FarleyShapiro, Hannah K.Sanders, Karli N.Sher, Abdallah F....
5页
查看更多>>摘要:In this study 28 younger and older observers discriminated the global shapes of objects that were defined by differences in texture. The judged stimulus patterns were 3-point micropattern textures. On any given trial, a texture-defined shape (either a vertically- or horizontally-oriented rectangle) was presented; the observers' task was to discriminate between the two rectangles. The task difficulty was manipulated by varying the deviation from colinearity of each of the individual 3-point texture elements between figure and background (the larger the difference in deviation between figure and ground, the higher the discrimination performance). The results revealed a substantial effect of age. In order for the older observers to reliably discriminate the shape of the target rectangle (with a d' value of 1.5), they needed differences from colinearity that were 54.4 percent larger than those required for the younger observers. While older adults can utilize differences in texture to perceive global shape, their ability is nevertheless significantly impaired.
Norman, J. FarleyShapiro, Hannah K.Sanders, Karli N.Sher, Abdallah F....
5页
查看更多>>摘要:In this study 28 younger and older observers discriminated the global shapes of objects that were defined by differences in texture. The judged stimulus patterns were 3-point micropattern textures. On any given trial, a texture-defined shape (either a vertically- or horizontally-oriented rectangle) was presented; the observers' task was to discriminate between the two rectangles. The task difficulty was manipulated by varying the deviation from colinearity of each of the individual 3-point texture elements between figure and background (the larger the difference in deviation between figure and ground, the higher the discrimination performance). The results revealed a substantial effect of age. In order for the older observers to reliably discriminate the shape of the target rectangle (with a d' value of 1.5), they needed differences from colinearity that were 54.4 percent larger than those required for the younger observers. While older adults can utilize differences in texture to perceive global shape, their ability is nevertheless significantly impaired.
Novozhilova, SashaReynaud, AlexandreHess, Robert F.
8页
查看更多>>摘要:Short term monocular deprivation modulates ocular dominance, such that the previously deprived eye's contribution to the binocular percept increases, supposedly as a result of changes in contrast-gain. Therefore, the processing time of the previously patched eye would be expected to speed up as a result of an increase in contrast gain. In order to test this hypothesis, this study examines the effects of short-term monocular deprivation on interocular synchronicity. The present study uses a paradigm based on the Pulfrich phenomenon. The stimulus used for testing consists of elements defining a cylinder rotating in depth, that allows measurement of any interocular delay. The interocular delay was measured at baseline before patching and at outcome, after one hour of monocular deprivation with an opaque or translucent patch. Contrary to expectations, short-term monocular deprivation induces an interocular delay, albeit not always significant, in the previously patched eye. The amplitude of this effect is larger with opaque patching compared to translucent patching. These results are the first report of a non-beneficial effect - i.e. a slowing down in the processing time of the previously patched-eye. They indicate that the plasticity effects of monocular deprivation are not exclusively mediated by contrast gain mechanisms and that light adaptation mechanisms might also be involved in the plasticity resulting from shortterm monocular deprivation.
Novozhilova, SashaReynaud, AlexandreHess, Robert F.
8页
查看更多>>摘要:Short term monocular deprivation modulates ocular dominance, such that the previously deprived eye's contribution to the binocular percept increases, supposedly as a result of changes in contrast-gain. Therefore, the processing time of the previously patched eye would be expected to speed up as a result of an increase in contrast gain. In order to test this hypothesis, this study examines the effects of short-term monocular deprivation on interocular synchronicity. The present study uses a paradigm based on the Pulfrich phenomenon. The stimulus used for testing consists of elements defining a cylinder rotating in depth, that allows measurement of any interocular delay. The interocular delay was measured at baseline before patching and at outcome, after one hour of monocular deprivation with an opaque or translucent patch. Contrary to expectations, short-term monocular deprivation induces an interocular delay, albeit not always significant, in the previously patched eye. The amplitude of this effect is larger with opaque patching compared to translucent patching. These results are the first report of a non-beneficial effect - i.e. a slowing down in the processing time of the previously patched-eye. They indicate that the plasticity effects of monocular deprivation are not exclusively mediated by contrast gain mechanisms and that light adaptation mechanisms might also be involved in the plasticity resulting from shortterm monocular deprivation.
She, ZhihuiHung, Li-FangArumugam, BaskarBeach, Krista M....
13页
查看更多>>摘要:Although reduced ambient lighting (-50 lx) does not increase the degree of form-deprivation myopia (FDM) in chickens or infant monkeys, it does reduce the probability that monkeys will recover from FDM and that the normal age-dependent reduction in hyperopia will occur in monkeys reared with unrestricted vision. These findings suggest that low ambient lighting levels affect the regulatory mechanism responsible for emmetropization. To study this issue, infant rhesus monkeys (age - 24 days) were reared under dim light (55 +/- 9 lx) with monocular -3D (dim-light lens-induced myopia, DL-LIM, n = 8) or +3D spectacle lenses (dim-light lens-induced hyperopia, DL-LIH, n = 7) until approximately 150 days of age. Refractive errors, ocular parameters and subfoveal choroidal thickness were measured periodically and compared with normal-light-reared, lens-control monkeys (NL-LIM, n = 16; NL-LIH, n = 7). Dim light rearing significantly attenuated the degree of compensatory anisometropias in both the DL-LIM (-0.63 +/- 0.77D vs. -2.11 +/- 1.10D in NL-LIM) and DL-LIH treatment groups (-0.18 +/- 1.93D vs. +1.71 +/- 0.39D in NL-LIH). These effects came about because the treated and fellow control eyes had a lower probability of responding appropriately to the eye's effective refractive state. Vision-induced interocular differences in choroidal thickness were only observed in monkeys that exhibited compensating refractive changes, suggesting that failures in detecting the relative magnitude of optical errors underlay the abnormal refractive responses. Our findings suggest that low ambient lighting levels reduce the efficacy of the vision-dependent mechanisms that regulate refractive development.
She, ZhihuiHung, Li-FangArumugam, BaskarBeach, Krista M....
13页
查看更多>>摘要:Although reduced ambient lighting (-50 lx) does not increase the degree of form-deprivation myopia (FDM) in chickens or infant monkeys, it does reduce the probability that monkeys will recover from FDM and that the normal age-dependent reduction in hyperopia will occur in monkeys reared with unrestricted vision. These findings suggest that low ambient lighting levels affect the regulatory mechanism responsible for emmetropization. To study this issue, infant rhesus monkeys (age - 24 days) were reared under dim light (55 +/- 9 lx) with monocular -3D (dim-light lens-induced myopia, DL-LIM, n = 8) or +3D spectacle lenses (dim-light lens-induced hyperopia, DL-LIH, n = 7) until approximately 150 days of age. Refractive errors, ocular parameters and subfoveal choroidal thickness were measured periodically and compared with normal-light-reared, lens-control monkeys (NL-LIM, n = 16; NL-LIH, n = 7). Dim light rearing significantly attenuated the degree of compensatory anisometropias in both the DL-LIM (-0.63 +/- 0.77D vs. -2.11 +/- 1.10D in NL-LIM) and DL-LIH treatment groups (-0.18 +/- 1.93D vs. +1.71 +/- 0.39D in NL-LIH). These effects came about because the treated and fellow control eyes had a lower probability of responding appropriately to the eye's effective refractive state. Vision-induced interocular differences in choroidal thickness were only observed in monkeys that exhibited compensating refractive changes, suggesting that failures in detecting the relative magnitude of optical errors underlay the abnormal refractive responses. Our findings suggest that low ambient lighting levels reduce the efficacy of the vision-dependent mechanisms that regulate refractive development.
Mestre, ClaraBedell, Harold E.Diaz-Douton, FernandoPujol, Jaume...
14页
查看更多>>摘要:The near point of convergence test is widely used to evaluate binocular vision. It assesses the ability of the eyes to converge at short distances. Although the test consists of a pure symmetrical vergence task, small involuntary saccades occur concurrently. The main goal of this study was to analyze saccadic characteristics as a function of vergence demand when testing the near point of convergence. To this purpose, the eye movements of 11 participants were registered with an eye-tracker while they performed the near point of convergence test by following a target that traveled forward and backward on a motorized bench. Saccade amplitude increased and, on average, saccade rate decreased with vergence demand. In general, the direction of the concurrent vergence movement had no significant effect on saccade characteristics. However, each individual subject showed idiosyncratic behavior. Most saccades tended to be corrective in terms of both binocular disparity and individual fixation position errors. In particular, most participants tended to correct the fixation position error of the dominant eye.
Mestre, ClaraBedell, Harold E.Diaz-Douton, FernandoPujol, Jaume...
14页
查看更多>>摘要:The near point of convergence test is widely used to evaluate binocular vision. It assesses the ability of the eyes to converge at short distances. Although the test consists of a pure symmetrical vergence task, small involuntary saccades occur concurrently. The main goal of this study was to analyze saccadic characteristics as a function of vergence demand when testing the near point of convergence. To this purpose, the eye movements of 11 participants were registered with an eye-tracker while they performed the near point of convergence test by following a target that traveled forward and backward on a motorized bench. Saccade amplitude increased and, on average, saccade rate decreased with vergence demand. In general, the direction of the concurrent vergence movement had no significant effect on saccade characteristics. However, each individual subject showed idiosyncratic behavior. Most saccades tended to be corrective in terms of both binocular disparity and individual fixation position errors. In particular, most participants tended to correct the fixation position error of the dominant eye.
查看更多>>摘要:In this study, we investigated the processes of coordination, adaptation, and calibration during the development of colour naming and colour constancy, and we tested whether colour term knowledge is related to colour constancy. We measured category membership and prototypes with 163 Munsell chips in preschool children (3 to 4-year-old) under neutral, green, and red illuminations, and compared their results to those of adults. We introduced an index of colour term maturity based on the similarity of children's colour term use to adults, and a colour category constancy index that quantifies the variation in colour categorisation that is specific to illumination changes. Results showed that illumination changes affected children's consistency of colour categorisation, but only to a small extent. However, colour term maturity and illumination-specific effects on consistency strongly varied in this age range. Correlations between colour term maturity and illumination specific consistency indicated that colour constancy increases with colour term acquisition; but those results depended on the type of illumination changes (between neutral, green, and red). Together, our findings suggest that children progressively fine-tune and recalibrate the meaning of colour terms through processes of coordination and adaptation that are also involved in the calibration of colour constancy.
查看更多>>摘要:In this study, we investigated the processes of coordination, adaptation, and calibration during the development of colour naming and colour constancy, and we tested whether colour term knowledge is related to colour constancy. We measured category membership and prototypes with 163 Munsell chips in preschool children (3 to 4-year-old) under neutral, green, and red illuminations, and compared their results to those of adults. We introduced an index of colour term maturity based on the similarity of children's colour term use to adults, and a colour category constancy index that quantifies the variation in colour categorisation that is specific to illumination changes. Results showed that illumination changes affected children's consistency of colour categorisation, but only to a small extent. However, colour term maturity and illumination-specific effects on consistency strongly varied in this age range. Correlations between colour term maturity and illumination specific consistency indicated that colour constancy increases with colour term acquisition; but those results depended on the type of illumination changes (between neutral, green, and red). Together, our findings suggest that children progressively fine-tune and recalibrate the meaning of colour terms through processes of coordination and adaptation that are also involved in the calibration of colour constancy.