Approximate Geometry Representations and Sensory Fusion

Cs. Szepesvári and A. Lõrincz

Neurocomputing 12, 267--287 (1996)


Abstract


This paper summarizes the recent advances in the theory of self-organizing development of approximate geometry representations based on the use of neural networks. Part of this work is based on the theoretical approach of (Szepesvari, 1993), which is different from that of (Martinetz, 1993) and also is somewhat more general. The Martinetz approach treats signals provided by artificial neuron-like entities whereas the present work uses the entities of the external world as its starting point. The relationship between the present work and the Martinetz approach will be detailed. We approach the problem of approximate geometry representations by first examining the problem of sensory fusion, i.e., the problem of fusing information from different transductors. A straightforward solution is the simultaneous discretization of the output of all transductors, which means the discretization of a space defined as the product of the individual transductor output spaces. However, the geometry relations are defined for the external world only, so it is still an open question how to define the metrics on the product of output spaces. It will be shown that simple Hebbian learning can result in the formation of a correct geometry representation. Some topological considerations will be presented to help us clarify the underlying concepts and assumptions. The mathematical framework gives rise to a corollary on the "topographical mappings" realized by Kohonen networks. In fact, the present work as well as (Martinetz, 1993) may be considered as a generalization of Kohonen's topographic maps. We develop topographic maps with self-organizing interneural connections.


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