FBS Colloquia No.182Cognitive Neuroscience Group

Disparity Defined Edge Response in Early Visual Cortex

Binocular disparity information is an important source for 3D perception. Neurons sensitive to binocular disparity are found in almost all major visual areas in non-human primates. In visual area V4, disparity processes are suggested for the purposes of 3D shape representation and fine disparity perception. However, whether V4 neurons are sensitive to disparity-defined edges used in shape representation is not clear. Also, a functional organization for disparity edge responses has not been demonstrated so far. With intrinsic signal optical imaging, we studied functional organization for disparity edges in monkey visual areas V1, V2 and V4. We found there is an orientation preference functional map in area V4 activated by edges purely defined by binocular disparity. This map is consistent with the orientation map obtained with regular luminance-defined edges, indicating a cue-invariant edge representation in this area. The map pattern is stable among different non-critical parameters of the visual stimuli, while using anti-correlated random dots no longer elicited it. In contrast, such a map is much weaker in V2 and totally absent in V1. These findings reveal a hierarchical processing of 3D shape along the ventral pathway, and the important role V4 plays in shape-from-disparity detection.