Path dissociation of visual signals entering the cortex: Disparity, contour orientation and position

Whether position and orientation shifts induced by monocular context also act as a disparity for purposes of stereoscopy was investigated experimentally in order to examine the extent to which lateral spatial localization and stereoscopic depth share circuitry. A monocular tilt illusion in a line does not lead to a commensurate depth tilt of that line in binocular view, nor does a position shift in a bisection task caused by a gap within monocular dynamic random noise produce the commensurate depth displacement. Interocular transfer of monocularly-induced shifts, which might explain such findings, was eliminated as a factor. The results can therefore be interpreted as indicators of channeling and ordering of spatial signals paths in the visual cortex and imply that two-dimensional contextual interactions operate at a processing level beyond where disparity has already been extracted.

Research highlights► Two- and three-dimensional visual signals enter the brain via the retina. ► Processing for stereoscopy follows a separate path. ► Experiments reveal the point of bifurcation of the two classes of signals.