Spatio–temporal Sensitivity of the Retina: A Physical Model

In the quest to understand how the retina encodes moving images, we analyze the spatiotemporal behavior of a simple dynamic model proposed by Yagi [2]. This model is physical—it is built out of resistors, capacitors, and transconductances. It based on the distal retina of the turtle and includes all the known synaptic interactions. Interesting questions that are addressed are how the outer plexiform acheives speed invariant encoding of contrast while multiplexing the speed information onto the same channel for latter extraction at the inner— plexiform. The predictions of the model are compared with available spatio—temporal measurements from pshycophisical and physiological experiments on cats and humans. The