The open- and closed-loop gain-characteristics of the cone/horizontal cellsynapse in goldfish retina

Under constant light-adapted conditions, vision seems to be rather linear. However, the processes underlying the synaptic transmission between cones a nd second-order neurons (bipolar cells and horizontal cells) are highly non linear. In this paper, the gain-characteristics of the transmission from co nes to horizontal cells and from horizontal cells to cones are determined w ith and without negative feedback from horizontal cells to cones. It is sho wn that 1) the gain-characteristic from cones to horizontal cells is strong ly nonlinear without feedback from horizontal cells, 2) the gain- character istic between cones and horizontal cells becomes linear when feedback is ac tive, and 3) horizontal cells feed back to cones via a linear mechanism. In a quantitative analysis, it will be shown that negative feedback linearize s the synaptic transmission between cones and horizontal cells. The physiol ogical consequences are discussed.