Release from cross-orientation suppression facilitates 3D shape perception.

Cross-orientation suppression (COS) in striate cortex has been implicated in the efficient encoding of visual stimuli. We show that release from COS facilitates the decoding of 3-D shape. In planar surfaces overlaid with textures, slanting the surface can increase the visibility of the component parallel to the slant. Since this component provides the orientation flows that signify 3-D shape, the enhancement of visibility facilitates 3-D slant perception. Contrast thresholds reveal that this enhancement results from a decrease in COS when 3-D slant creates a frequency mismatch between texture components. We show that coupling compressive nonlinearities in LGN neurons with expansive nonlinearities in cortical neurons can model the frequency-specific component of suppression.