TCB Publications - Abstract

Edgar Erwin, Klaus Obermayer, and Klaus Schulten. Formation of dimension-reducing somatotopic maps. In Samir I. Sayegh, editor, Proceedings of the Fourth Conference on Neural Networks and Parallel Distributed Processing, pp. 115-126. Indiana University at Fort Wayne, 1992.

ERWI92 The somatosensory cortex of humans and higher animals contains a map of the body surface with a largely topographically ordered connectivity between tactile skin receptors and cortical neurons. Merzenich, et. al., have extensively studied the hand region of the somatotopic map in areas 3b and 1 of the cortex in a number of adult owl and squirrel monkeys [10]. They found that the maps are highly individual to a particular animal and change even in adult animals in response to the frequency of sensory stimuli received, although some general map characteristics do seem to be constant between individuals. In an earlier model [14] based on the self-organizing feature map algorithm [5,6], we showed that some aspects of the formation of the somatotopic cortical maps may be explained by an input-driven, self-organizing process. However, our earlier model treated the hand as a true three-dimensional cortical array. Our model cortical maps reproduce many features of the experimental maps well. However, in order for the model to produce maps with the relative locations of map features showing the same tendency to be correlated as in the experimentally observed maps, it is necessary that the initial pattern of connectivity contain a bias toward the representation of the dorsal surface in particular regions of the largely topographic map of the glabrous surface. This finding then suggests how specific the biological pattern of connectivity between skin receptors and the cortex might need to be before an activity-based refinement of the map structure begins. Due to the high computational requirements, our model was implemented on the Connection Machine CM-2.

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