Winner-Take-All Networks of O(N) Complexity

Two general types of inhibition mediate activity in neural systems: subtractive inhibition, which sets a zero level for the computation, and multiplicative (nonlinear) inhibition, which regulates the gain of the computation. We report a physical realization of general nonlinear inhibition in its extreme form, known as winner-take-all We have designed and fabricated a series of compact, completely functional CMOS integrated circuits that realize the winner-take-all function, using the full analog nature of the medium. This circuit has been used successfully as a component in several VLSI sensory systems, that perform auditory localization (Lazzaro and Mead, in press) and visual stereopsis (Mahowald and Delbruck, 1988). Winner-take-all circuits with over 170 inputs function correctly in these sensory systems. We have also modified this global winner-take-all circuit, realizing a circuit that computes local nonlinear inhibition. The circuit allows multiple winners in the network, and is well suited for use in systems that represent a feature space topographically and that process several features in parallel. We have designed, fabricated, and tested a CMOS integrated circuit that computes locally the winner-take-all function of spatially ordered input.