!Converted with LaTeX2HTML 95.1 (Fri Jan 20 1995) by Nikos Drakos (firstname.lastname@example.org), CBLU, University of Leeds >
In order to evidence how the orientation map modulates the effects of inhibition, we compared the results with those obtained with random arrangements of orientation preferences (not shown). The lesser specificity in orientation tuning as well as the absence of the additional periodic sidebands obtained with these random maps, suggest a dependence between the inhibitory schemata and the regular organization of the orientation maps. More precisely, we observed that the efficacy of recurrent inhibition in generating periodic RFs is strongly influenced by the rate at which preferred orientations change across cortical plane with respect to the distance (d) between clusters of the inhibitory field. Low orientation gradients, as they occur in iso-orientation domains (see figure 3a-b), give rise to extensive RFs with parallel elongated subregions, whereas high orientation gradients, as in proximity of singularities (see figure 3c) or fractures (see figure 3d), lead to smaller RFs with poor spatial structure. Indeed, high orientation gradients in the areas subjected to inhibition, break the self-reinforcing mechanisms which induce positive and negative correlations, that are responsible of highly structured RFs.