Role of horizontal cells in organization of the catfish retinal receptive field.

THE RECEPTIVE-FIELD organi zation of the vertebrate retinal ganglion cell has been the subject of numerous studies. However, the cellular mechanism underlying the receptive field has been explored relatively rarely. One exception can be found in a recent study of the mudpuppy retina where responses were recorded from various retinal neurons (17) and it was shown that the polarization of a bipolar cell by a central spot could be antagonized by an annular illumination. The receptive field in the fish can be as large as 5 mm in diameter (3) and this clearly implies that the signal produced at the periphery of such a field must travel laterally at least 2 mm to reach the receptive-field center. The morphology of the vertebrate retina suggests two possible neuronal structures which could account for the lateral transmission of the signal in a receptive field; one is the row of horizontal cells and the other the amacrine cells. Naka and Rushton (13) have shown in the tenth that the row of horizontal cells behaves as if it were a laminar conductive medium bounded by two parallel membranes and they have referred to this structure as the S space. Any potential change arising within the S space propagates passively according to a given space constant. It is significant that in a recent paper Kaneko (6) could demonstrate in the dogfish electrical coupling among neighboring horizontal cells. In a previous paper (12) we analyzed the receptive field of a channel catfish ganglion cell (referred to here as type B) which responded to a spot of light with an “onoff” discharge and to an annulus with a