Abstract
Different types of texture modulation provide different information about surface shape. Here we investigate centre-surround interactions between different types of texture modulation, specifically whether the ‘quilt’ version of an orientation-modulated (OM) stimulus is processed by a different mechanism from the contrast-modulated (CM) stimuli from which it is constructed. The OM quilt stimulus (Landy & Oruc, 2002) is constructed from two CM stimuli with orthogonal carrier-orientations combined 180 deg out-of-phase. Thus, there is a symmetry between a CM stimulus composed of two, orthogonal-in-carrier-orientation, in-phase CM stimuli, with an OM stimulus in which the two CM components are out-of-phase: both types of modulation can be constructed from the same set of micropatterns. Although some evidence suggests that for at threshold modulations the OM quilt stimulus is processed differently from its CM counterpart, this has not been determined for suprathreshold modulations. To examine centre-surround interactions between different types of micropattern-constructed OM and CM gratings, we used the tilt illusion in which the surround/inducer grating of a particular orientation biases the perceived orientation of a central test-grating. We measured both small-angle attraction (3 deg surround orientation) (Akgoz, Gheorghiu & Kingdom, 2022) and large-angle repulsion (30 deg surround orientation) effects in the tilt illusion. We compared the effects between ‘same’ (both either OM or CM) versus ‘different’ (OM centre/ CM surround; CM surround/ OM centre) centre-surround types of texture modulations, and for different centre-surround phase-relationships (in-phase, anti-phase, quadrature, random). Our results indicate that overall, there is only partial selectivity for ‘same’ versus ‘different’ conditions. Selectivity is greatest for the in-phase small-angle attraction condition and least for the CM surround/ OM center condition. To conclude, the partial transfer between CM and OM stimuli for suprathreshold modulations and its phase selectivity suggest that quilt OM and its CM counterpart share some common mechanisms.