Color opponent cell

D Zmura and Lennie assume that red-green as well as blue-yellow color opponent cells are used to arrive at stable hue descriptors. They represent the chromatic sensitivity of a cell using a three-dimensional chromaticity space as shown in Figure 8.10. The white point is denoted by W. The white point describes the steady state of adaptation of the cell. The vector C represents the most effective choice of chromatic contrast, which will activate the cell. The preferred hue of the cell can be found by projecting the vector C onto... 

The output from the red-green and the blue-yellow color opponent cells defines a two-dimensional coordinate system. A cell that responds maximally to red light can be constructed using the outputs from the red-green as well as the blue-yellow channel. Let x be the output of the red-green channel and let y be the output of the blue-yellow channel. A cell, which computes its output z according to... 

Most cells of the interblob region respond to lines or bars of a particular orientation. They do not respond to color or show any color opponency. In contrast to the cells found inside the blobs, the receptive field of the cells found in the interblob region is very small. The response characteristic of the neurons of the interblob regions is arranged... 

Dufort and Lumsden (1991) proposed a model for color categorization and color constancy. In their model, color constancy is achieved by using the output from double opponent cells... 

Twig G, Levy H, Perlman I (2003) Color opponency in horizontal cells of the vertebrate redna. Prog Redn Eye Res 22 31-68. 

Color processing in VI is confined to small circular areas, known as blobs, in which double-opponent cells are found. They display a center/surround behavior based on the red reen and yeUow-blue axes but lack orientation selectivity. The V1 blobs were first identified by their uptake of certain enzymes, and only later was their role in color vision discovered [Livingstone and Hubei, 1984]. The blobs are especially prominent in layers 2 and 3, which receive input from the P cells of the LGN. 

VI mainly connects to area V2, which surrounds VI (Tov6e 1996). Area V2 seems to be organized into three types of stripes, the so-called thick, thin, and interstripes. The stripes seem to be used to process visual orientation (thick stripes), color (thin stripes), and retinal disparity (interstripes). Adjacent stripes respond to the same region of the visual field. Neurons of layer 4B of V1 connect to the thick stripes. Cells found inside the thick stripes are selective for orientation and movement. Many of the cells also respond to retinal disparity. The neurons of the blobs are connected to the thin stripes. These cells are not orientation selective. More than half of these cells respond to color. Most show a double opponent characteristic. The cells of the interblob region connect to the interstripes. Neurons of the interstripe region respond to different orientations but neither to color nor to motion. A condition know as chromatopsia is caused by damage to certain parts of VI and V2. Individuals who suffer from chromatopsia are not able to see shape or form. However, they are still able to see colors. 

The retinal ganglion cells already encode chromatic opponency in their neuronal signals. These signals are decoded and processed by the striate cortex. The responses of 41 % of the striate cells [19] show a chromatic opponency as well. This indicates sensitivity for wavelength variations and therefore color processing in the visual cortex. 

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