(NAS Colloquium) Vision From Photon to Perception (1999) / Chapter Skim
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Circuitry for color coding in the primate retina
Circuitry for color coding in the primate retina
Pages 26-32
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From page 26... ...
Red-green spectral opponency has long been linked to the midget ganglion cells, but an underlying mechanism remains unclear. For example, receptive field mapping argues for segregation of Land M-cone signals to the midget cell center and surround, but horizontal cell interneurons, believed to generate the inhibitory surround, lack opponency and cannot contribute selective L- or M-cone input to the midget cell surround.
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From page 27... ...
This labeled line model predicts a retinal circuitry that can sort out the L- and M-cone signals and deliver them with the appropriate sign to the appropriate part of the receptive field. Identifying the Color Opponent Ganglion Cell Types To explore the labeled line model and determine the retinal circuitry giving rise to red-green and blue-yellow opponency in ganglion cells, the ganglion cell types that transmit these signals must first be identified.
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From page 28... ...
support Hubel and Wiesel's original vision of a cone-type-specific colorcoding circuitry. Strong support for the labeled line model also comes from the anatomy of central midget ganglion cells.
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From page 29... ...
It appears that peripheral midget ganglion cells do not make selective contact with a cone-specific subset of midget bipolar cells, and color opponency greatly diminishes or is absent in the far periphery.
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From page 30... ...
Minced surround model. The lack of L- and M-cone selectivity in the peripheral midget ganglion cells and in the H1 and H2 cells seems to contradict the labeled line model but is consistent with an alternative "mixed surround" model (9, 49, 50~.
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From page 31... ...
In the central retina, midget ganglion cells are synaptically linked to a single cone that drives the receptivefield center; because the center is stronger than the surround, mixed cone input to the surround would still give strong opponency (in this example, L-cone input to the center gives a red-ON response despite a mixed cone input to the surround)
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From page 32... ...
On the one hand, physiological mapping of L- or M-cone inputs supports the labeled line model of cone type-specific connections to both the center and the surround of the midget cell receptive field. The "private line" from a single cone to a single midget ganglion cell can account for a pure cone center response.
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