Departmental Papers (BE)

Document Type

Journal Article

Date of this Version

February 2001

Comments

Postprint version. Published in Analog Integrated Circuits and Signal Processing, Volume 30, Issue 2, February 2002, pages 121-135.
Publisher URL: http://dx.doi.org/10.1023/A:1013751627357

Abstract

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.

Keywords

neuromorphic systems, analog VLSI, mixed-mode design, CMOS imager, silicon retina, silicon neuron, spatiotemporal filtering, automatic gain control, contrast gain control, direction selectivity

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Date Posted: 03 November 2004

This document has been peer reviewed.