The spatiotemporal properties of the r-g X-cell channel

Ingling, Carl R.; Martinez-Uriegas, Eugenio

doi:10.1016/0042-6989(85)90077-x

Cited by 80 publications

(24 citation statements)

References 16 publications

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“…We obtained similar equiluminance settings for our minimum-motion technique and for minimum flicker, and other studies have shown similar equiluminance settings for flicker matches at high temporal frequencies and minimum border matches for stimuli with no temporal variation. 2 3 We have also extended the evaluation of equiluminance settings to situations involving perception of static, achromatic forms such as shadow figures' 7 and subjective contours2 8 and still find no evidence of separate luminance pathways for these conditions.29…”

Section: Discussionmentioning

confidence: 99%

“…When two oppositely moving components are summed, motion is seen in the direction of the component of the higher contrast. 16 ,' 7 When the red and green luminances are equal, the contrasts of the two components are equal and no motion, only flicker, is seen. The flicker has two components, a low-contrast luminance flicker of amplitude m and a large-amplitude chromatic flicker.…”

Section: L(xt) = R(x T) + G(x T) =Lr + Lg + 05[m(lr + Lg)mentioning

confidence: 99%

“…1 - 3 These two cell populations project to separate layers of the lateral geniculate (magnocellular and parvocellular, respectively). 6 It has been argued 7 that both are involved in carrying achromatic information; the magnocellular layer is principally nonopponent, and the parvocellular layer, although carrying color-opponent information for low spatial and low temporal frequencies, carries nonopponent information at high spatial and temporal frequencies. This separation of achromatic information into two distinct pathways at an early level calls into question the notion of a monolithic luminance pathway.…”

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confidence: 99%

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Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones

1987

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Equiluminance ratios for red/green, red/blue and green/blue sine-wave gratings were determined by using a minimum-motion heterochromatic matching technique that permitted reliable settings at temporal frequencies as low as 0.5 Hz. The red/green equiluminance ratio was influenced by temporal but not spatial frequency, the green/blue ratio was influenced by spatial but not temporal frequency, and the red/blue ratio was influenced by both. After bleaching of the blue-sensitive cones, there was no change in equiluminance ratios, indicating no contribution of the blue-sensitive cones to the luminance channel even at low temporal and spatial frequencies. The inhomogeneity of yellow pigmentation within the macular region was identified as the source of the spatialfrequency effect on the blue/green ratio.Several studies have shown that pattern information is divided into chromatic and achromatic pathways very early in the visual system.1-Opponency between cone responses contributes to the chromatic pathway, whereas summation of cone responses contributes to the nonopponent, or luminance, pathway. Our paper is concerned with the relative contributions of the different cone mechanisms to the luminance channel at different temporal and spatial frequencies and, in particular, with whether the short-wavelength (B) cones contribute at all.To evaluate the relative contributions to the luminance channel, we determined the null or equiluminance point at which two colors contribute equally. Our stimulus, which will be described shortly, is constructed so that motion is present only if there is a luminance difference between the two colors being evaluated. We also varied the spatial and temporal frequencies used in presenting the stimulus. Cells at the retinal ganglion level can show a range of preferences for spatial and temporal frequency.5 For example, the nonopponent cells respond best to low spatial and high temporal frequencies, whereas the color-opponent cells prefer high spatial and low temporal frequencies. 1 -3 These two cell populations project to separate layers of the lateral geniculate (magnocellular and parvocellular, respectively).6 It has been argued 7 that both are involved in carrying achromatic information; the magnocellular layer is principally nonopponent, and the parvocellular layer, although carrying color-opponent information for low spatial and low temporal frequencies, carries nonopponent information at high spatial and temporal frequencies. This separation of achromatic information into two distinct pathways at an early level calls into question the notion of a monolithic luminance pathway. If there are functionally distinct luminance pathways with different spatiotemporal properties, we may be able to identify them by changes in the relative contributions of the various cone mechanisms, and therefore changes in equiluminance settings, as a function of spatial and temporal frequency.The contribution of the B cones to luminance is currently contested. Results of physiological studies suggest that these c...

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Section: Discussionmentioning

confidence: 99%

Section: L(xt) = R(x T) + G(x T) =Lr + Lg + 05[m(lr + Lg)mentioning

confidence: 99%

mentioning

confidence: 99%

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Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones

1987

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“…At this level, the retinal image is a spatial multiplexing of chromatic cone responses, and there is no reconstruction of full color information at each spatial position. We know that the sampled color responses are still in a mosaic representation at the output of the retina, as illustrated by the behavior of ganglion cell receptive fields [3] (see Fig. 3).…”

Section: A Model Of Retinal Processingmentioning

confidence: 99%

“…Our motivations to use such a workflow is that it is more analogous to the retinal processing of the human visual system (HVS) [3][4][5], as discussed in Section 2. Another motivation is that applying the tone mapping directly to the CFA image requires only one third of the operations.…”

Section: Introductionmentioning

confidence: 99%

Model of retinal local adaptation for the tone mapping of color filter array images

2007

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We present a tone mapping algorithm that is derived from a model of retinal processing. Our approach has two major improvements over existing methods. First, tone mapping is applied directly on the mosaic image captured by the sensor, analogous to the human visual system that applies a nonlinearity to the chromatic responses captured by the cone mosaic. This reduces the number of necessary operations by a factor 3. Second, we introduce a variation of the center/surround class of local tone mapping algorithms, which are known to increase the local contrast of images but tend to create artifacts. Our method gives a good improvement in contrast while avoiding halos and maintaining good global appearance. Like traditional center/surround algorithms, our method uses a weighted average of surrounding pixel values. Instead of being used directly, the weighted average serves as a variable in the Naka-Rushton equation, which models the photoreceptors' nonlinearity. Our algorithm provides pleasing results on various images with different scene content and dynamic range.

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Spectral tuning of opponent channels is spatially dependent

Finkelstein

1988

Color Research & Application

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Psychophysical detection and appearance data suggest that the spectral tuning of opponent pathways varies with test size. The present study examines the effect on spectral sensitivity of the relative size of test and surround fields. Increment thresholds and flashed‐field sensitivities were obtained for 580 nm and 641 nm targets. Three spatial configurations were used. The pattern of sensitivity loss is shown to depend on the spatial relation between test and field; the effect of the spatial relation in turn depends on test wavelength. The findings are explained by the activity of a changing network of spatially and spectrally opponent cells.

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The spatiotemporal properties of the r-g X-cell channel

Cited by 80 publications

References 16 publications

Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones

Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones

Model of retinal local adaptation for the tone mapping of color filter array images

Spectral tuning of opponent channels is spatially dependent

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