Anisotropic receptive field structure of cat horizontal cells

Horizontal (H-)cells were recorded intracellularly in the retinae of optically intact feline eyes in vivo. A small light spot orbiting slowly around the receptive field centers was used to quantify the fine structure and diameter of the receptive fields. Receptive field diameters measured in this way were larger than those measured with centered spots of increasing diameter. All H-units studied showed clearly anisotropic receptive field structures. These results are summarized in polar plots representing the local response generating sites with their corresponding "response plus transport" latencies. It is shown that the anisotropic receptive field properties are not incompatible with the approximately homogenous spatial distribution of H-cell somata reported by Wässle and Rieman (1978) for the axonless type of horizontal cell. Finally it is concluded that each H-cell might be involved in many different locally specialized signal processing activities.