Contour integration in amblyopic monkeys

Kozma, Petra; Kiorpes, Lynne

doi:10.1017/s0952523803205113

Cited by 62 publications

(76 citation statements)

References 66 publications

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“…We propose that binocular suppression during a critical period may play a key role in the bilateral nature of disruptions in RF subfield maps. We previously found that experiencing ocular misalignment for as brief a period as 2 weeks near birth can devastate the ability of V1 or V2 neurons to combine binocular signals (Kumagami et al, 2000;Mori et al, 2002;Zhang et al, 2008), and only 3 d of strabismus can initiate robust binocular suppression in V1 neurons that is comparable in strength to binocular suppression found in adult strabismic monkeys . It is reasonable to think that binocular suppression in our anisometropic amblyopic monkeys caused not only a breakdown of binocular connections, but also weaker and noisier spiking of V1 neurons for stimulation of either eye.…”

Section: Robust Suppression and Bilateral V2 Deficitsmentioning

confidence: 99%

“…Experiencing interocular decorrelation of cortical input signals early in life, because of early ocular misalignment (strabismus) or monocular defocus (anisometropia), is known to cause amblyopia, a disorder of spatial vision. Amblyopic subjects typically show reductions in contrast sensitivity and visual acuity in their affected eye (Hess and Howell, 1977;Levi and Harwerth, 1977;Kiorpes et al, 1998), but also exhibit a broad range of far more complex vision deficits (Hess et al, 1999;Kovács et al, 2000;Chandna et al, 2001;Kozma and Kiorpes, 2003;. For example, amblyopic humans exhibit difficulties in global perceptual tasks that require precise pooling of neighboring local stimulus feature information.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous perceptual studies suggest that the deficits of amblyopes in complex spatial tasks result from "abnormal pooling" of local stimulus information by neurons beyond the striate cortex (V1; Hess et al, 1999;Mussap and Levi, 2000;Chandna et al, 2001;Kozma and Kiorpes, 2003;Simmers and Bex, 2004;. Extrastriate neurons with relatively large receptive fields (RFs) can act as integrators of local stimulus information processed by V1.…”

Section: Introductionmentioning

confidence: 99%

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Early Monocular Defocus Disrupts the Normal Development of Receptive-Field Structure in V2 Neurons of Macaque Monkeys

et al. 2014

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Experiencing different quality images in the two eyes soon after birth can cause amblyopia, a developmental vision disorder. Amblyopic humans show the reduced capacity for judging the relative position of a visual target in reference to nearby stimulus elements (position uncertainty) and often experience visual image distortion. Although abnormal pooling of local stimulus information by neurons beyond striate cortex (V1) is often suggested as a neural basis of these deficits, extrastriate neurons in the amblyopic brain have rarely been studied using microelectrode recording methods. The receptive field (RF) of neurons in visual area V2 in normal monkeys is made up of multiple subfields that are thought to reflect V1 inputs and are capable of encoding the spatial relationship between local stimulus features. We created primate models of anisometropic amblyopia and analyzed the RF subfield maps for multiple nearby V2 neurons of anesthetized monkeys by using dynamic two-dimensional noise stimuli and reverse correlation methods. Unlike in normal monkeys, the subfield maps of V2 neurons in amblyopic monkeys were severely disorganized: subfield maps showed higher heterogeneity within each neuron as well as across nearby neurons. Amblyopic V2 neurons exhibited robust binocular suppression and the strength of the suppression was positively correlated with the degree of hereogeneity and the severity of amblyopia in individual monkeys. Our results suggest that the disorganized subfield maps and robust binocular suppression of amblyopic V2 neurons are likely to adversely affect the higher stages of cortical processing resulting in position uncertainty and image distortion.

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Section: Robust Suppression and Bilateral V2 Deficitsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Early Monocular Defocus Disrupts the Normal Development of Receptive-Field Structure in V2 Neurons of Macaque Monkeys

et al. 2014

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“…Threshold values and standard errors of estimate were obtained by Probit analysis of the log-transformed data sets (Finney, 1971) using a maximum-likelihood technique. We used an iterative method to fit a double-exponential function (Wilson & Bergen, 1979;Kiorpes et al, 1993;Kiorpes & Kiper, 1996;Kozma & Kiorpes, 2003) to both motion and contrastsensitivity data, and extracted the value of peak sensitivity and its location on the abscissa from the fits.…”

Section: Methodsmentioning

confidence: 99%

Development of sensitivity to visual motion in macaque monkeys

Kiorpes

Movshon

2004

Vis Neurosci

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The development of spatial vision is relatively well documented in human and nonhuman primates. However, little is known about the development of sensitivity to motion. We measured the development of sensitivity to direction of motion, and the relationship between motion and contrast sensitivity in macaque monkeys as a function of age. Monkeys (Macaca nemestrina, aged between 10 days and 3 years) discriminated direction of motion in random-dot kinematograms. The youngest monkeys showed directionally selective orienting and the ability to integrate motion signals at large dot displacements and fast speeds. With age, coherence sensitivity improved for all spatial and temporal dot displacements tested. The temporal interval between the dots was far less important than the spatial offset in determining the animals' performance at all but the youngest ages. Motion sensitivity improved well beyond the end of the first postnatal year, when mid-spatial-frequency contrast sensitivity reached asymptote, and continued for at least 3 years. Sensitivity to contrast at high spatial frequencies also continued to develop beyond the end of the first year. We conclude that the development of motion sensitivity depends on mechanisms beyond the low-level filters presumed to limit acuity and contrast sensitivity, and most likely reflects the function of extrastriate visual areas.

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“…and contrast sensitivity across the full range of spatial vision~e.g. "amblyopia index", Kozma & Kiorpes, 2003! to establish a consistent and reliable difference between the eyes.…”

Section: Subjectsmentioning

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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Contour integration in amblyopic monkeys

Cited by 62 publications

References 66 publications

Early Monocular Defocus Disrupts the Normal Development of Receptive-Field Structure in V2 Neurons of Macaque Monkeys

Early Monocular Defocus Disrupts the Normal Development of Receptive-Field Structure in V2 Neurons of Macaque Monkeys

Development of sensitivity to visual motion in macaque monkeys

Sensitivity to visual motion in amblyopic macaque monkeys

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