Regensburg 2002 – scientific programme

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SYPH: Physik im Hirn - Physical Approaches to Brain Function

SYPH 2: Physik im Hirn - Physical Approaches to Brain Function

SYPH 2.5: Poster

Thursday, March 14, 2002, 15:30–18:00, Poster D

Universal fine structure of orienation pinwheels — •Michael Schnabel, Theo Geisel, and Fred Wolf — Max Planck-Institut fuer Stroemungsforschung, Goettingen

Neurons in primary visual cortex preferentially respond to visual stimuli of a particular orientation, called their preferred orientation. Across cortex, these orienation preferences are arranged in complex 2-D patterns, called orientation maps, which vary in a smooth manner except at characteristic pointlike singularities, called pinwheel centers, which are ubiquuous elements of such patterns. We define an pinwheel-anisotropy α, which uniquely specifies the pattern’s shape in vincinity of individual pinwheels, and investigate the distribution of α values for artificial orientation maps chosen from different ensembles of random fields. We calculate this distribution for isotropic, homogenous and orientation-shift invariant ensembles analytically. Interestingly this distribution is universal, it does not depend on ensemble specific details, e.g. correlation functions. Furthermore, it fits experimental data surprisingly well.