title: An explanation of contextual modulation by short-range isotropic connections and orientation map geometry in the primary visual cortex.
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.
authors.affiliation: Department of Quantum Engineering and Systems Science, University of Tokyo Graduate School of Engineering, 7-3-1 Hongo, 113-8654 Tokyo. Bunkyo-ku, Japan. gogogo@aihara.jst.go.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Okamoto
authors.forename: Masataka
authors.initials: M
authors.lastname: Watanabe
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Aihara
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kondo
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D003118:Color Perception / Q000502:physiology; D006801:Humans; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010507:Periodicity; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*