This work has been carried out in the Neural Networks Research Centre, Helsinki University of Technology, during 1993-1996. While completing the thesis I have participated in several projects of the centre, under the supervision of Academy Professor Teuvo Kohonen. I wish to thank him for guidance and for providing the facilities and financial support necessary for the studies. Most important, however, have been the numerous discussions that have had a fundamental effect on the work, not to mention the contributions of Professor Kohonen in the projects themselves and in co-authoring the majority of the presented publications.
I also wish to thank the other co-workers in the projects that have been included in the thesis, Timo Honkela, Harri Lappalainen, Sirkka-Liisa Joutsiniemi, and Krista Lagus, and also the rest of the personnel of the Neural Networks Research Centre and the Laboratory of Computer and Information Science. Special thanks for comments on the manuscript are due to Timo Honkela, Krista Lagus, Janne Sinkkonen, and Professors Teuvo Kohonen and Erkki Oja.
Numerous other people with whom I have worked and lived in other projects, some of which are hopefully lifelong, deserve many thanks as well. Those acknowledgments relate to some completely different stories, however.
The financial support of the Academy of Finland and the Jenny and Antti Wihuri Foundation is gratefully acknowledged.
Espoo, February 1997