Stereoprocessing of cyclopean depth images: horizontally elongated summation fields.

The study evaluated how the detection efficiency varies with the length and width of Gabor wavelets of depth ripple in random element patterns. For local (one-cycle) wavelets, there was no anisotropy with respect to wavelet orientation, implying equal efficiency for processing shear versus compression disparities at threshold. The processing for larger patterns of depth ripple did not correspond to a fixed summation field but varied in size with spatial frequency, and in shape with orientation of depth ripples, up to four cycles of a horizontal bar at 0.5 cy/deg, or 8 degrees of visual angle. The presence of such extended summation fields in only one orientation is incompatible with the idea of local attentional processing, with a single disparity channel or with an adaptive mechanism that could accommodate to any form of disparity image. Thus, these results suggest the presence of a multichannel hypercyclopean level of processing specialized for horizontal depth contours, whose only disparity information is in their surface texture.