Departmental Papers (BE)

Document Type

Journal Article

Date of this Version

February 2001


Retinomorphic chips may improve their spike-coding efficiency by emulating the primate retina's parallel pathways. To model the four predominant ganglion-cell types in the cat retina, I morphed outer and inner retina microcircuits into a silicon chip, Visio1. It has 104 x 96 photoreceptors, 4 x 52 x 48 ganglion-cells, a die size of 9.25 x 9.67 mm2 in 1.2 µm 5V CMOS, and consumes 11.5 mW at 5 spikes/second/ganglion-cell. Visio1 includes novel subthreshold current-mode circuits that model horizontal-cell autofeedback, to decouple spatial filtering from local gain control, and model amacrine-cell loop-gain modulation, to adapt temporal filtering to motion. Different ganglion cells respond to motion in a quadrature sequence, making it possible to detect edges of one contrast or the other moving in one direction or the other. I present results from a multichip 2-D motion system, which implements Watson and Ahumada's model of human visual-motion sensing.


Postprint version. Published in Analog Integrated Circuits and Signal Processing, Volume 30, Issue 2, February 2002, pages 121-135.
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neuromorphic systems, analog VLSI, mixed-mode design, CMOS imager, silicon retina, silicon neuron, spatiotemporal filtering, automatic gain control, contrast gain control, direction selectivity



Date Posted: 03 November 2004

This document has been peer reviewed.