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Re: [Phys-l] inversion goggles





From: Anthony Lapinski <Anthony_Lapinski@pds.org>
Sent: Thu, May 12, 2011 12:13:57 PM

P.S. I'm still trying to figure out how our brain flips inverted images on
our retina so we see the world as upright. My eye doctor once told me that
this is initially not true for newborns -- that they literally see the
world inverted! Wow!


The situation is even more complicated than most people present. This is hard
to
explain without pictures, but I'll do my best. After all the image isn't just
upside down, but flipped left to right as well.

Have you ever seen a coherent fiber optic bundle, sometimes called an image
conduit? It is a collection of fiber optic strands designed in such a way that
the fiber that starts at the top left on one end is the top left on the other
end, the fiber that is directly to the right to the fiber on the top left on
one
end is directly to the right to the top left fiber on the other end, and so on.
You can see an example of that here.
<http://www.plastecs.com/images/taper%20letters.jpg>

You might think that the nerves that connect our eyes to our optical cortex in
the brain work that way, but I strongly suspect that they don't. The nerves do
not remain coherent nor organized and get crossed by the time they make it to
our brain.

So an image that starts out on the retina

0000000
0000000
1111111
0000000
0000000

might map to

0000101
0010000
1001001
0000000
0001000

on the cortex. Part of learning how to see is learning what spots on the cortex
are actually next to each other in the retina.

I heard a radio report, but now can't find the citation, that babies learn to
associate the brain mappings to the retina mappings by wiggling their fingers
and toes. Their brains know that fingers, toes, arms and legs are solid objects
and so the moving spots on the brain most all be next to each other on the
retina.

So, flipping the image over is hardly the biggest problem. It is just part of
an
even worse problem.

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

The most important bit is this: Your brain doesn't have a right side up and and
an upside down. A little person isn't inside your head looking at a screen
trying to make out the world.

Marc "Zeke" Kossover