Departmental Papers (BE)

Document Type

Journal Article

Date of this Version

June 2005

Comments

Copyright 2005 IEEE. Reprinted from IEEE Transactions on Circuits and Systems--I: Regular Papers, Volume 52, Issue 6, June 2005, pages 1049-1060.

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Abstract

Neurons in the mammalian primary visual cortex are selective along multiple stimulus dimensions, including retinal position, spatial frequency, and orientation. Neurons tuned to different stimulus features but the same retinal position are grouped into retinotopic arrays of hypercolumns. This paper describes a neuromorphic implementation of orientation hypercolumns, which consists of a single silicon retina feeding multiple chips, each of which contains an array of neurons tuned to the same orientation and spatial frequency, but different retinal locations. All chips operate in continuous time, and communicate with each other using spikes transmitted by the address-event representation protocol. This system is modular in the sense that orientation coverage can be increased simply by adding more chips, and expandable in the sense that its output can be used to construct neurons tuned to other stimulus dimensions. We present measured results from the system, demonstrating neuronal selectivity along position, spatial frequency and orientation. We also demonstrate that the system supports recurrent feedback between neurons within one hypercolumn, even though they reside on different chips. The measured results from the system are in excellent concordance with theoretical predictions.

Keywords

Address-event representation (AER), Gabor filter, image processing, mixed analog-digital integrated circuits, neural chips, neuromorphic engineering, visual cortex

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Date Posted: 22 November 2005

This document has been peer reviewed.