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A complex-valued Hopfield neural network (CHNN) is a model of a multistate Hopfield neural network, and has been applied to the storage of multilevel data. Weak noise tolerance, however, is a disadvantage of CHNNs. Symmetric CHNNs (SCHNNs), modified CHNNs, improve the noise tolerance of CHNNs. In the present work, we study the global and local minima of SCHNNs with one training pattern. In CHNNs, the global minima are the training and rotated patterns, and there are no local minima. In SCHNNs, it has been hard to determine all the global and local minima. It is thought that the global minima are the training and reversed patterns, and that there are no local minima in most cases. In the present work, however, we find many local minima, and show that they are very weak attractors, which reduce noise tolerance very little. In addition, we determine all the global minima of SCHNNs. [ABSTRACT FROM AUTHOR]

In this letter, we will clarify the redundancy of the parameters of the complex-valued neural network. The results may be summarized as follows. There exist the four transformations which can cause the redundancy of the parameters of the complex-valued neural network, including the two transformations which can cause the redundancy of the parameters of the real-valued neural network (i.e., the interchange of the two hidden neurons and the sign flip of the parameters on the hidden neurons). [Copyright &y& Elsevier]