P3D Animal Stereopsis (again)

[Dylan The Hippy Wabbit <spacey@xxxxxxxxxxxxx>]

Hi,

Oh man, it's all coming back now.  I've just remembered that with many
mammals the left eye's signals go the the right visual cortex, and vice
versa.  With humans (and presumably other primates) there's a 'knot' in
the optic nerves that sends the left field of view from *both* eyes to the
right brain.

If some body has a severe squint that goes untreated in early life the
brain cells connected to one eye shut up shop and die off, leaving the
sufferer blind in one eye.  I've seen stained sections of such a brain,
and it's fascinating.  The two colours formed a closely interleaved
pattern, indicating that corresponding places in the eyes are dealt with
by neurones right next to each other.  Perfect for comparing the two views
in fine detail.  Ever wonder how those Random Dot Stereograms work?
There's the anatomy behind it.

I should imagine that in the animals that wire their eyes up the other
way, stereopsis is only available at a later processing stage if at all.

On a sillier note Terry Pratchett reckons that, because a bull has widely
spaced eyes with a huge forehead between, they assume that they are *two*
bulls facing opposite directions.  :-D

Dave Spacey

_____________________________________________________________________________

Of Bill Gates, "In fact, he's Ernst Stavro Blofeld as played by Woody 
Allen." - Charles Shaar Murray


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