Structure and Function of Orientation Columns in Cat Visual Cortex: a Theoretical Study

We present a detailed model of the pathway from the retina to area 17 of the visual cortex of the adult cat. The model is used to study the orientation tuning of cortical simple cells. It is shown that a combination of unspecific inhibitory mechanisms together with input of aligned receptive fields from the LGN is able to reproduce cortical orientation selectivity and other features of cortical cell behavior. We show by computer simulations and by analytical calculations that Circular inhibition, a novel isotropic intracortical connection scheme introduced by us, results in two anisotropies: orientation tuning and a directional bias. This bias is smaller than experimentally observed values. The directional anisotropy introduced in this way could, however, be the starting point for the development of the true direction specificity found in cortical cells.