stereovision question

[P3D John Bercovitz <bercov@xxxxxxxxxx>]

This one is aimed at Jim C and other vision researchers.  I'm 
curious how stereo vision is done in the brain.  I was just 
thinking that folks whose eyes don't track together don't have 
stereo vision.  Sounds reasonable on the surface, but why?  It 
can't be because they can't compare views at all since they still 
have two views, so it must be that somehow the retinas are 
hardwired to the same loci in the brain?  I think I've heard that 
before.  Assuming that's true, how are the comparisons between 
images made?  I would think it would start on a "pixel" level.  
After local differences are noted, how is a global "picture" 
constructed?  I know there is a lot of preprocessing done at the 
retinal level and I wonder what the picture looks like when it 
first comes to the brain on the optic nerves.  I understand that 
the brain has many levels or layers doing the processing.  I 
apologize that this will severely tax the researcher's ability to 
express himself as I certainly don't have all the concepts a 
researcher has.  Anyone want to try an explanation?

Thanks,
John B


------------------------------