A consideration on visualization of temporal signals by feedback SOM

An Elman-type feedback SOM (EFSOM) is a modified version of the standard SOM for temporal signal processing. It was applied to various kinds of tasks so far, and it showed good performance on temporal signal processing. By the way, one of the major features inspired by the standard SOM is to visualize given data structure into the two-dimensional plane preserving its topology. Then, from the visualization point of view, a working mechanism of the feedback SOM (FSOM), which is an essential part of the EFSOM, is investigated in this paper. As a result of computer simulations, a trajectory of the winner neurons is bifurcated, not overlapped between any two segments, with the help of feedback pathways. This fact implies that the FSOM can deal with the past history, i.e., the context information, appropriately. Furthermore, when continuous pattern is used for training, it is found that signal processing developed in the SOM is quite similar to that for an A/D converter based on the discretized reference vectors.