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An explanation of contextual modulation by short-range isotropic connections and orientation map geometry in the primary visual cortex

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Okamoto, T., Watanabe, M., Aihara, K., & Kondo, S. (2004). An explanation of contextual modulation by short-range isotropic connections and orientation map geometry in the primary visual cortex. Biological Cybernetics, 91(6), 396-407. doi:10.1007/s00422-004-0528-9.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-D72B-C
Abstract
Recent experimental studies on the primary visual cortex have revealed complicated nonclassical neuronal activities. Contextual modulation on orientation-contrast is one typical example of nonclassical neuronal behavior. This modulation by surrounding stimuli in a nonclassical receptive field is mainly thought to be mediated by short- and long-range horizontal connections within the primary visual cortex. Short-range connections are circularly symmetrical and relatively independent of orientation preferences, while long-range connections are patchy, asymmetrical, and orientation specific. Although this modulation can be explained by long-range specific connections qualitatively, recent studies suggest that long-range connections alone may be insufficient with respect to the balance between two types of connections. Here, in order to clarify the role of short-range connections in the process of contextual modulation, we propose a model of the primary visual cortex with isotropic short-range connections and a geometric orientation map. Computational simulations using the model have demonstrated that contextual modulation can be explained by short-range connections alone. This is due to the interaction between the spatial periodicity of orientation domains and the excitatory-inhibitory regions arising from the propagation of activities.