NONLINEAR PROCESSES IN PERCEIVED REGION SEGREGATION - ORIENTATION SELECTIVITY OF COMPLEX CHANNELS

Models incorporating linear spatial-frequency- and orientation-selective channels explain many aspects of visual texture segregation. The inability of such models to fully explain texture segregation results, indicates that non-linear processes are also involved. One non-linearity that has been suggested is complex channels consisting of two stages of linear filtering separated by a rectification-type non-linearity (much like cortical complex cells). Here we further demonstrate the usefulness of complex channels in explaining texture segregation results and investigate the orientation-selectivity of the first stage of such complex channels. Our results suggest that the first stage is much more selective for orientation than are lateral geniculate nucleus cells, but that the first-stage orientation bandwidth is rather wide with some interaction occuring between perpendicular orientations.