We explored the contribution to perception of orientation-modulated textures of visual processes selective either for orientation contrast or orientation grouping. To distinguish between these two processes we manipulated the axis of local grouping of texture elements independently of the direction of global orientation modulation. The general question posed was whether visibility of texture st...

Unifying approaches by amongst others Archimedes, Kepler, Goldberg, Caspar and Klug, Coxeter, Conway, extending on a previous formalization of the concept local symmetry preserving (lsp) operations, we introduce formal definition operations plane graphs that preserve orientation-preserving symmetries, but not necessarily orientation-reversing symmetries. This include, e.g., chiral Goldberg Conw...

A recent report suggests that amblyopes are deficient in processing local orientation at supra-threshold contrasts. To determine whether amblyopes are also poor at integrating local orientation signals, we assessed performance for an orientation integration task in which the orientations of static signals are integrated across space. Our results show that amblyopic visual systems can integrate ...

A simple mathematical model for the large-scale circuitry of primary visual cortex is introduced. It is shown that a basic cortical architecture of recurrent local excitation and lateral inhibition can account quantitatively for such properties as orientation tuning. The model can also account for such local effects as cross-orientation suppression. It is also shown that nonlocal state-dependen...

In this paper, we derive a model for analyzing the innuence of local cortical connections on the activities of neurons in V1. A set of orientation columns is arranged according to a measured orientation map. Orientation columns are connected by local excitatory and slightly more distributed inhibitory bers. Based on this geometrical model we demonstrate that (i) sharp and contrast{invariant ori...

We analysed the temporal-frequency characteristics of two functional processes involved in orientation-based texture segregation: local orientation coding and subsequent orientation-contrast coding. Two texture images, in which each micropattern was rotated by 90 degrees, were alternated at various temporal frequencies. A micropattern was a second-derivative (D2) of a Gaussian that loses orient...