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Cytochrome Oxidase, Texture Fields, and Texture Flows

When the visual cortex is stained for the metabolic enzyme cytochrome oxidase and is viewed from above, a periodic array of ``blobs'' appear intercalated within a lattice of lower cytochrome oxidase activity. Allman and Zucker have proposed that the distinction between the ``blobs'' and the lattice is related to two different modes for representing stimulus variables. Scalar variables related to intensity-variables (e.g. contrast, color) of the stimulus are represented in the blobs, and are encoded over a broad dynamic range in which firing rate is proportional to the intensity variable (e.g. contrast). In the surrounding lattice of lower cytochrome oxidase activity geometrical variables are carried by cells with orientation preferences and lead to different representational requirements. One consequence of our hypothesis for coding in visual cortex is that texture density, or the number of texture elements per unit area, is processed differently from the geometric structure of the texture elements. In particular, we propose that texture density is coded within the cytochrome oxidase system and texture orientation is coded within the interblob system. Psychophysical experiments in the Kolers' paradigm are currently underway to verify this proposal.

P. Breton, J. Allman (Caltech), S.W. Zucker

Thierry Baron
Mon Nov 13 10:43:02 EST 1995