Color opponency in cone-driven horizontal cells in carp retina. Aspecific pathways between cones and horizontal cells.

The spectral and dynamic properties of cone-driven horizontal cells in carp retina were evaluated with silent substitution stimuli and/or saturating background illumination. The aim of this study was to describe the wiring underlying the spectral sensitivity of these cells. We will present electrophysiological data that indicate that all cone-driven horizontal cell types receive input from all spectral cone types, and we will present evidence that all cone-driven horizontal cell types feedback to all spectral cone types. These two findings are the basis for a model for the spectral and dynamic behavior of all cone-driven horizontal cells in carp retina. The model can account for the spectral as well as the dynamic behavior of the horizontal cells. It will be shown that the strength of the feedforward and feedback pathways between a horizontal cell and a particular spectral cone type are roughly proportional. This model is in sharp contrast to the Stell model, where the spectral behavior of the three horizontal cell types is explained by a cascade of feedforward and feedback pathways between cones and horizontal cells. The Stell model accounts for the spectral but not for the dynamic behavior of the horizontal cells.