A Retinomorphic Chip with Parallel Pathways: Encoding INCREASING, ON, DECREASING, and OFF Visual Signals

  • Authors:
  • Kwabena Boahen

  • Affiliations:
  • Penn Bioengineering, 3320 Smith Walk, Philadelphia, PA 19104

  • Venue:
  • Analog Integrated Circuits and Signal Processing
  • Year:
  • 2002

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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 104×96 photoreceptors, 4×52×48 ganglion-cells, a die size of 9.25×9.67 mm2 in 1.2 μm 5 V 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.