A new test of contour integration deficits in patients with a history of disrupted binocular experience during visual development

Kovács, Ilona; Polat, Uri; Pennefather, P M; Chandna, Arvind; Norcia, Anthony M.

doi:10.1016/s0042-6989(00)00008-0

Cited by 107 publications

(105 citation statements)

References 25 publications

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“…also performed well on the present task, Figure 13. Examples of displays used in the experiments presented in Kovács et al (2000) of contours made of local Gabor units. A: Easy.…”

Section: Resultsmentioning

confidence: 99%

“…and R.N. participated in this study, and we used the data from the neurologically intact participants reported in Kovács et al (2000) against which to compare their thresholds.…”

Section: Methodsmentioning

confidence: 99%

“…A staircase procedure was used to establish threshold. For more details, the reader is referred to Kovács et al (2000).…”

Section: Methodsmentioning

confidence: 99%

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What does visual agnosia tell us about perceptual organization and its relationship to object perception?

Behrmann¹,

Kimchi²

2003

Journal of Experimental Psychology: Human Perception and Perfor

124

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The authors studied 2 patients, S.M. and R.N., to examine perceptual organization and its relationship to object recognition. Both patients had normal, low-level vision and performed simple grouping operations normally but were unable to apprehend a multielement stimulus as a whole. R.N. failed to derive global structure even under optimal stimulus conditions, was less sensitive to grouping by closure, and was more impaired in object recognition than S.M. These findings suggest that perceptual organization involves a multiplicity of processes, some of which are simpler and are instantiated in lower order areas of visual cortex (e.g., collinearity). Other processes are more complex and rely on higher order visual areas (e.g., closure and shape formation). The failure to exploit these latter configural processes adversely affects object recognition. to the patients for their good-hearted and continued involvement in these experiments.

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“…also performed well on the present task, Figure 13. Examples of displays used in the experiments presented in Kovács et al (2000) of contours made of local Gabor units. A: Easy.…”

Section: Resultsmentioning

confidence: 99%

“…and R.N. participated in this study, and we used the data from the neurologically intact participants reported in Kovács et al (2000) against which to compare their thresholds.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

What does visual agnosia tell us about perceptual organization and its relationship to object perception?

Behrmann¹,

Kimchi²

2003

Journal of Experimental Psychology: Human Perception and Perfor

124

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show abstract

“…McKee et al, 2003!. Recent work has shown a much broader range of deficits in amblyopes that are not easily explained by or correlated with the basic loss in spatial vision. For example, contour integration and other tasks that require spatial integration are impaired in amblyopia~Hess et al, 1997; Hess & Demanins,1998;Kovács et al, 2000;Mussap & Levi, 2000;Chandna et al, 2001;Kozma & Kiorpes, 2003!. Such "high-level Although low-level orientation discrimination is largely found to be normal in amblyopes~e.g.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity to visual motion in amblyopic macaque monkeys

2006

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Amblyopia is usually considered to be a deficit in spatial vision. But there is evidence that amblyopes may also suffer specific deficits in motion sensitivity as opposed to losses that can be explained by the known deficits in spatial vision. We measured sensitivity to visual motion in random dot displays for strabismic and anisometropic amblyopic monkeys. We used a wide range of spatial and temporal offsets and compared the performance of the fellow and amblyopic eye for each monkey. The amblyopes were severely impaired at detecting motion at fine spatial and long temporal offsets, corresponding to fine spatial scale and slow speeds. This impairment was also evident for the untreated fellow eyes of strabismic but not anisometropic amblyopes. Motion sensitivity functions for amblyopic eyes were shifted toward large spatial scales for amblyopic compared to fellow eyes, to a degree that was correlated with the shift in scale of the spatial contrast sensitivity function. Amblyopic losses in motion sensitivity, however, were not correlated with losses in spatial contrast sensitivity. This, combined with the specific impairment for detecting long temporal offsets, reveals a deficit in spatiotemporal integration in amblyopia which cannot be explained by the lower spatial resolution of amblyopic vision.

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“…1-4), including reductions in visual acuity (VA), contrast-sensitivity function (CSF), and vernier acuity as well as spatial distortion (5), abnormal spatial interactions (6, 7), and impaired contour detection (8,9). In addition, amblyopic individuals suffer from binocular abnormalities such as impaired stereoacuity and abnormal binocular summation.…”

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confidence: 99%

Improving vision in adult amblyopia by perceptual learning

Polat

Ma-Naim

Belkin

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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389

401

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Practicing certain visual tasks leads, as a result of a process termed ''perceptual learning,'' to a significant improvement in performance. Learning is specific for basic stimulus features such as local orientation, retinal location, and eye of presentation, suggesting modification of neuronal processes at the primary visual cortex in adults. It is not known, however, whether such low-level learning affects higher-level visual tasks such as recognition. By systematic low-level training of an adult visual system malfunctioning as a result of abnormal development (leading to amblyopia) of the primary visual cortex during the ''critical period,'' we show here that induction of low-level changes might yield significant perceptual benefits that transfer to higher visual tasks. The training procedure resulted in a 2-fold improvement in contrast sensitivity and in letter-recognition tasks. These findings demonstrate that perceptual learning can improve basic representations within an adult visual system that did not develop during the critical period.A mblyopia is characterized by several functional abnormalities in spatial vision (for reviews see refs. 1-4), including reductions in visual acuity (VA), contrast-sensitivity function (CSF), and vernier acuity as well as spatial distortion (5), abnormal spatial interactions (6, 7), and impaired contour detection (8,9). In addition, amblyopic individuals suffer from binocular abnormalities such as impaired stereoacuity and abnormal binocular summation. The visual deficiencies are thought to be irreversible after the first decade of life (10-12), by which time the developmental maturation window has been terminated. The loss of vision is thought to result from abnormal operation of the neuronal network within the primary visual cortex, particularly of orientation-selective neurons and their interactions (13). The perceptual learning procedure described in this study was designed to train this network by efficiently stimulating these neuronal populations and effectively promoting their spatial interactions.Spatial interactions in human vision can be probed by contrast detection of a localized target in the presence of flankers (Fig. 1). These experiments show that the contrast threshold of a foveal Gabor signal (GS) is reduced in the presence of cooriented and coaligned (collinear) high-contrast GS flankers (14-18). The excitatory interaction is range-dependent and is maximal for target-flanker separation of approximately three times the GS wavelength. Smaller separations can raise the target threshold, depending on flanker contrast and phase (19). Singleunit recordings suggest that the underlying mechanisms reside within the primary visual cortex (20,21). Neuronal responses in the visual cortex are tuned for location, orientation, and spatial frequency. Recent evidence from studies in the cat and the monkey (20,(22)(23)(24)(25) shows that neuronal responses in the primary visual cortex are modulated by remote image parts, with both excitatory and inhibitory effects observ...

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A new test of contour integration deficits in patients with a history of disrupted binocular experience during visual development

Cited by 107 publications

References 25 publications

What does visual agnosia tell us about perceptual organization and its relationship to object perception?

What does visual agnosia tell us about perceptual organization and its relationship to object perception?

Sensitivity to visual motion in amblyopic macaque monkeys

Improving vision in adult amblyopia by perceptual learning

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