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Re: [Phys-l] images in eye

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!