title: Mexican hats and pinwheels in visual cortex.
abstract: Many models of cortical function assume that local lateral connections are specific with respect to the preferred features of the interacting cells and that they are organized in a Mexican-hat pattern with strong "center" excitation flanked by strong "surround" inhibition. However, anatomical data on primary visual cortex indicate that the local connections are isotropic and that inhibition has a shorter range than excitation. We address this issue in an analytical study of a neuronal network model of the local cortical circuit in primary visual cortex. In the model, the orientation columns specified by the convergent lateral geniculate nucleus inputs are arranged in a pinwheel architecture, whereas cortical connections are isotropic. We obtain a trade-off between the spatial range of inhibition and its time constant. If inhibition is fast, the network can operate in a Mexican-hat pattern with isotropic connections even with a spatially narrow inhibition. If inhibition is not fast, Mexican-hat operation requires a spatially broad inhibition. The Mexican-hat operation can generate a sharp orientation tuning, which is largely independent of the distance of the cell from the pinwheel center.
authors.affiliation: Courant Institute of Mathematical Sciences and Center for Neural Science, New York University, New York, NY 10012, USA. kkj@cns.nyu.edu
authors.forename: Kukjin
authors.initials: K
authors.lastname: Kang
authors.forename: Michael
authors.initials: M
authors.lastname: Shelley
authors.forename: Haim
authors.initials: H
authors.lastname: Sompolinsky
mesh_terms: D000818:Animals; D002415:Cats; D000882:Haplorhini; D006801:Humans; D015233:Models, Statistical; D008962:Models, Theoretical; D016202:N-Methylaspartate / Q000494:pharmacology; D009415:Nerve Net; D009474:Neurons / Q000166:cytology; D009991:Oscillometry; D013569:Synapses; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology*
chemical_list: D016202:N-Methylaspartate