A mechanism for spatial brightness contrast enhancement and a basis for the duplicity of vision.

Cones are connected to bipolar cells connected to rods by processes extending laterally from the cone terminals (Sjöstrand, 1958). The cone connections have been studied further in the rabbit retina. Structurally these connections are typical synaptic connections. It can be deduced that these connections must affect the onresponses of bipolar cells connected to rods in such a way that spatial brightness contrast is enhanced. The connections raise the threshold for rod vision and slow down the changes in the membrane potential of on-bipolar cells. These effects offer an explanation for the duplicity of vision.