Optic Nerve Signals in a Neuromorphic Chip II: Testing and Results

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adaptive circuits
neural systems
neuromorphic engineering
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Zaghloul, Kareem A.

Seeking to match the brain’s computational efficiency [14], we draw inspiration from its neural circuits. To model the four main output (ganglion) cell types found in the retina, we morphed outer and inner retina circuits into a 96 x 60-photoreceptor, 3.5 x 3.3 mm2, 0.35 μm-CMOS chip. Our retinomorphic chip produces spike trains for 3600 ganglion cells (GCs), and consumes 62.7 mW at 45 spikes/s/GC. This chip, which is the first silicon retina to successfully model inner retina circuitry, approaches the spatial density of the retina. We present experimental measurements showing that the chip’s subthreshold current-mode circuits realize luminance adaptation, bandpass spatiotemporal filtering, temporal adaptation and contrast gain control. The four different GC outputs produced by our chip encode light onset or offset in a sustained or transient fashion, producing a quadrature-like representation. The retinomorphic chip’s circuit design is described in a companion paper [Zaghloul and Boahen (2004)].

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Copyright 2004 IEEE. Reprinted from IEEE Transactions on Biomedical Engineering, Volume 51, Issue 4, April 2004, pages 667-675. Publisher URL: http://ieeexplore.ieee.org/xpl/tocresult.jsp?isNumber=28546&puNumber=10 This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.
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