dc.contributor.author Levitan, Svetlana en_US dc.date.accessioned 2004-05-31T22:58:14Z dc.date.available 2004-05-31T22:58:14Z dc.date.created 1999-07 en_US dc.date.issued 1999-08-25 en_US dc.identifier.uri http://hdl.handle.net/1903/1017 dc.description.abstract Recent experimental work in neurobiology has defined asymmetries and lateralization in the topographic maps found in mirror-image regions of the sensorimotor cerebral cortex. However, the mechanisms underlying these asymmetries are currently not established, and in some cases are quite controversial. In order to explore some possible causes of map asymmetry and lateralization, several neural network models of cortical map lateralization and asymmetries based on self-organizing maps are created and studied both computationally and theoretically. Activation levels of the elements in the models are governed by large systems of highly nonlinear ordinary differential equations (ODEs), where coefficients change with time and their changes depend on the activation levels. Special metrics for objective evaluation of simulation results (represented as paired receptive field maps) are introduced and analysed. The behavior of the models is studied when their parameters are varied systematically and also when simulated lesions are introduced into one of the hemispheric regions. Some very sharp transitions and other interesting phenomena have been found computationally. Many of these computationally observed phenomena are explained by theoretical analysis of total hemispheric activation in a simplified model. The connection between a bifurcation point of the system of ODEs and the sharp transition in the model's computational behavior is established. More general understanding of topographic map formation and changes under various conditions is achieved by analysis of activation patterns (i.e., $\omega$-limit sets of the above system of ODEs). This is the first mathematical model to demonstrate spontaneous map lateralization and asymmetries, and it suggests that such models may be generally useful in better understanding the mechanisms of cerebral lateralization. The mathematical analysis of the models leads to a better understanding of the mechanisms of self-organization in the topographic maps based on competitive distribution of activation and competitive learning. Also cross-referenced as UMIACS-TR-99-40 en_US dc.format.extent 12097513 bytes dc.format.mimetype application/postscript dc.language.iso en_US dc.relation.ispartofseries UM Computer Science Department; CS-TR-4035 en_US dc.relation.ispartofseries UMIACS; UMIACS-TR-99-40 en_US dc.title Mathematical Modeling of Lateralization and Asymmetries in Cortical Maps en_US dc.type Technical Report en_US dc.relation.isAvailableAt Digital Repository at the University of Maryland en_US dc.relation.isAvailableAt University of Maryland (College Park, Md.) en_US dc.relation.isAvailableAt Tech Reports in Computer Science and Engineering en_US dc.relation.isAvailableAt UMIACS Technical Reports en_US
﻿