Neurobiology; Communicated by Richard M.€Held, Massachusetts Institute of Technology,
Cambridge, MA, March 3,€1997 (received for review September 30,€1996)
Key words: binocular vision, binocular fusion, stereopsis, simple cell, position disparity, phase disparity. receptive field, reference cell, binary m-sequence.
(346kB, almost as good as a real reprint, directly from the PNAS Web server)
Full Text (~140kB HTML+GIFs, directly from the PNAS Web server)
About PostScript/Acrobat files and free viewers.
There are two possible mechanisms for encoding binocular disparity through simple cells in the striate cortex: a difference in receptive field (RF) position between the two eyes (RF position disparity) and a difference in RF profile between the two eyes (RF phase disparity). Although there have been studies supporting each of the two encoding mechanisms, both mechanisms have not been examined in a single study. Therefore, the relative roles of the two mechanisms have not been determined. To address this issue, we have mapped left and right eye RFs of simple cells in the cat's striate cortex using binary m-sequence noise, and then we have estimated RF position and phase disparities.
We find that RF position disparities are generally limited to small values that are not sufficient to encode large binocular disparities. In contrast, RF phase disparities cover a wide range of binocular disparities and exhibit dependencies on orientation and spatial frequency in a manner expected for a mechanism that encodes binocular disparity. These results indicate that binocular disparity is mainly encoded through RF phase disparity. However, RF position disparity may play a significant role for cells with high spatial frequency selectivity, which are constrained to small RF phase disparities.