Thus, we may conclude that von Helmholtz, Julesz, Pettigrew and Ramachandran are all right; the visual processing of stereo is more complex than we thought. We have no inkling of the physiological mechanisms underlying these interactions. Cells signaling disparity are in V1 (as shown by Pettigrew), but cells that extract illusory contours (from implied occlusion) are extracted in area V2, the next stage up, as shown by Rudiger von der Heydt of Johns Hopkins University. These findings imply that messages from V2 must be fed back to V1 to modulate processing of smaller features. This idea has yet to be tested.
Note: This article was originally printed with the title, "Two Eyes, Two Views."
This article was originally published with the title Two Eyes, Two Views.