Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] images in eye

Among the many things that are processed close to the eye is color vision.
It really does not follow the traditional 3 color model very well. The eye
looks at boundaries and renormalizes so you can see the "actual" color of an
object independently of illumination. Now of course cameras do not work
this way, so the 3 color theory should be called an engineering color
theory. Incidentally there are 2 different possible inherited color filters
for blue so others may not see color the same way if they have the other
filter.

Some other curious factors are that some people who have poor or no color
vision have had it "restored" by wedge shaped glasses that put different
colors at different depths.

Then there are many people who do not have binocular vision, and rely only
on other cues for depth. I knew one who could not see depth except when
looking through a stereoscope. He became an instant 3-d photography addict.

It is truly amazing how the brain and eye can unscramble the stimulations!

John M. Clement
Houston, TX



At 01:15 PM 5/13/2008, Marc Kossover, you wrote:

From: Anthony Lapinski <Anthony_Lapinski@pds.org>
Sent: Tuesday, May 13, 2008 10:23:03 AM

Many were surprised to learn
that the images on their retina are also inverted. Our brains somehow
make
us see things normally. I figure it's complicated, but does anyone
know
the exact mechanism by which the brain "flips" these retinal images so
that we see them as upright? Did evolution play any role in this?

The brain doesn't flip the image back over. There is no "inner you"
that looks at the image made by the retina.

Further the bundle of nerves in optic nerve don't maintain
orientation as it takes the information to the brain. The brain just
gets a muddle, but that's okay. The brain learns as you learn to see
that a particular sets of sensory responses corresponds to
particular things seen. This method is very flexible since it allows
you to make sense of objects and events without having to have those
objects built into your genome. On the other hand, it does mean that
you need time to learn to make sense of these senory impressions,
which can take years.

Marc "Zeke" Kossover
The Jewish Community High School of the Bay

Further to Zeke's note, I will regurgitate some random recollections
of the relevant material.
The seminal experiments on the visual pathways were undertaken by a
couple of Harvard researchers using monkeys, cats etc. (Torstein
Wiesel and David Hubel 1968 on...) for which they later shared a
Nobel with a split brain experimenter (The 1981 Phys & Med)
They established that visual processing starts at an early stage by
direct probing of visually stimulated animals, some of which
responses were specialized for particular dynamic visual image motion.
The visual neurones fire fastest in lowest light, and slow with
increasing illumination. They typically can detect light in single
photon fluxes though at low quantum efficiency of less than
10% There are movement sensors
specialized for various directions and orientations and a merge and
crossover point in the main nerve bundle pathway. The optic bundles
map much more than a spatial orientation of the images.


Brian Whatcott Altus OK Eureka!

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l