arXiv subjects

Myoung Won Cho

Publications and source records attributed to Myoung Won Cho.

5 recordsLinked to original sources

arXiv2015

Two symmetry breaking mechanisms for the development of orientation selectivity in a neural system

Orientation selectivity is a remarkable feature of the neurons located in the primary visual cortex. Provided that the visual neurons acquire orientation selectivity through activity-dependent Hebbian learning, the development process could be understood as a kind of symmetry breaking phenomenon in the view of physics. The key mechanisms of the development process are examined here in a neural system. Found is that there are at least two different mechanisms which lead to the development of orientation selectivity through breaking the radial symmetry in receptive fields. The first, a simultaneous symmetry breaking mechanism, bases on the competition between neighboring neurons, and the second, a spontaneous one, bases on the nonlinearity in interactions. It turns out that only the second mechanism leads to the formation of a columnar pattern which characteristics accord with those observed in an animal experiment.

q-bio.NC↗

arXiv2004

General representation of collective neural dynamics with columnar modularity

We exhibit a mathematical framework to represent the neural dynamics at cortical level. Our description of neural dynamics with columnar and functional modularity, named fibre bundle representation (FBM) method, is based both on neuroscience and informatics, whereas they correspond with the conventional formulas in statistical physics. In spite of complex interactions in neural circuitry and various cortical modification rules per models, some significant factors determine the typical phenomena in cortical dynamics. The FBM representation method reveals them plainly and gives profit in building or analyzing the cortical dynamic models. Not only the similarity in formulas, the cortical dynamics can share the statistical properties with other physical systems, which validated in primary visual maps. We apply our method to proposed models in visual map formations, in addition our suggestion using the lateral interaction scheme. In this paper, we will show that the neural dynamic procedures can be treated through conventional physics expressions and theories.

q-bio.NC↗

arXiv2004

Different ocular dominance map formation by influence of orientation columns in visual cortices

In animal experiments, the observed orientation preference (OP) and ocular dominance (OD) columns in the visual cortex of the brain show various pattern types. Here, we show that the different visual map formations in various species are due to the crossover behavior in anisotropic systems composed of orientational and scalar components such as easy-plane Heisenberg models. We predict the transition boundary between different pattern types with the anisotropy as a main bifurcation parameter, which is consistent with experimental observations.

q-bio.NC↗

arXiv2003

Instability of planar vortices in two-dimensional easy-plane Heisenberg model with distance-dependent interactions

It is known that magnetic vortices in two dimensional Heisenberg models with easy-plane anisotropy exhibit an instability depending on the anisotropy strength. In this paper, we study the statistic behavior of the two-dimensional easy-plane Heisenberg models with distance-dependent interactions, $J_{xy}(r)$ and $J_z(r)$ for in-plane and out-of-plane components. We develop analytical and numerical methods for accurate determination of critical anisotropy, above which out-of-plane vortices are stable. In particular, we explore the vortex formation of the Gaussian-type interaction model and determine the critical anisotropy accurately for square, hexagonal and triangular lattices.

cond-mat.str-el↗

arXiv2003

Understanding visual map formation through vortex dynamics of spin Hamiltonian models

The pattern formation in orientation and ocular dominance columns is one of the most investigated problems in the brain. From a known cortical structure, we build spin-like Hamiltonian models with long-range interactions of the Mexican hat type. These Hamiltonian models allow a coherent interpretation of the diverse phenomena in the visual map formation with the help of relaxation dynamics of spin systems. In particular, we explain various phenomena of self-organization in orientation and ocular dominance map formation including the pinwheel annihilation and its dependency on the columnar wave vector and boundary conditions.

physics.bio-ph↗