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Modeling the Formation of Sensory Representations in the Brain
Zitatschlüssel Obermayer2000
Autor Obermayer, K.
Buchtitel Prerational Intelligence: Adaptive Behavior and Intelligent Systems Without Symbols and Logic, Volume 1, Volume 2 Prerational Intelligence: Interdisciplinary Perspectives on the Behavior of Natural and Artificial Systems, Volume 3
Seiten 215 – 232
Jahr 2000
ISBN 978-94-010-3792-1
DOI 10.1007/978-94-010-0870-9_16
Jahrgang 26
Verlag Springer Netherlands
Serie Studies in Cognitive Systems
Zusammenfassung Pattern formation by self-organization is a common phenomenon during brain development. The enormous number of neurons and their connections makes it impossible for organisms to completely prespecify neural connectivity patterns within their genomes. Instead organisms seem to specify processes which then generate the patterns which are observed in the brain. These processes are supposedly much simpler than the actual patterns, and it is our hope that there are only few and that they can be cast into a small set of simple rules. One prominent pattern formation process is the ability of the brain to form spatial representations of sensory information, which are commonly called cortical maps and are characterized by the facts (i) that neurons respond strongly to certain combinations of features, and (ii) that cells with different response properties are arranged across cortex in systematic fashion. Well known examples are the multiple topographic representations of the body surface in the somatosensory areas (Kaas et al. 1979), the various types of acoustic maps in the auditory areas (Suga \& O\\\?Neill 1979; Olsen et al. 1989), the visuomotor maps in the superior colliculus (Tusa et al. 1978; Tusa et al. 1979; Stein \& Meredith 1993), and the retinotopic maps (Dow et al. 1985;), as well as the orientation (Blasdel \& Slaama), ocular dominance (Hubel \& Freeman 1979), motion (Malonek et al. 1993), and stereo maps (Livingstone \& Hubel 1988) in the visual areas of several species. There is also some evidence that spatially localized representations of information may be involved in cognitive tasks like language processing in humans (Hart et al. 1985). Modelling studies have shown that the formation and the plasticity properties of cortical maps can be described by simple dynamical systems (see, e.g., Swindale 1982; Miller et al. 1989; Obermayer et al. 1992; Stein \& Meredith 1993). It seems that the phenomenon of cortical maps and their formation provide an example for our hypothesis: that a small set of \\\"primitives\\\" of information processing and development could account for the variety of phenomena encountered in brain development and function. \\\\\\\\ I illustrate this idea by analysing activity dependent processes, and by investigating their role in cortical map formation. I will mainly concentrate on the development of cortical maps in the primary visual cortex, in particular, on the formation of the ocular dominance and orientation maps in the macaque monkey\\\?s area VI. \\\\\\\\ A comparision with experimental data shows that the developmental rules underlying a simple model based on Hebbian learning are not sufficient to account for both: the formation of orientation and ocular dominance. The abstractized version of the Hebbian approach called the Self-organizing Map generates all the observed phenomena. This approach is generalized and the formation of various types of cortical maps is considered.
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