Horizontal Cell

Receptive Field

In this simulation, the horizontal cell simply averages all the photoreceptor outputs. It establishes spatial context to which the bipolar cells can use to compare the outputs of the photoreceptors.

In addition, the horizontal cell does a low-pass termporal filtering.  You can see this if you suddenly apply a wide field stimulus to the entire photoreceptor array. You will see that the horizontal cell takes some time to respond.

Real horizontal cells form a lateral mesh of cells underlying the photoreceptors. These horizontal cells are laterally coupled by ohmic junctions, so the horizontal cells form a true resistive, or spreading, network.

We only modeled a single horizontal cell because the computation of a true spreading network is expensive, and would not buy us much for such a small spatial extent.