Three-valued logic gates in reaction-diffusion excitable media

It is well established now that excitable media are capable of implementing of a wide range of computational operations, from image processing to logical computation to navigation of robots. The findings published so far in the field of logical computation were concerned solely with realization of boolean logic. This imposed somewhat artificial limitations on a suitability of excitable media for logical reasoning and restricted a range of possible applications of these non-classical computational devices in the field of artificial intelligence. In the paper we go beyond binary logic and show how to implement three-valued logical operations in toy models of geometrically constrained excitable media. We realize several types of logical gates, including Lukasiewicz conjunction and disjunction, and Sobocinski conjunction in cellular automata and FitzHugh-Nagumo models of T-shaped excitable media. (C) 2004 Elsevier Ltd. All rights reserved.