Rethinking the Process of Vision

The following text was excerpted from the Wiki entry “Optic Nerve”:

“The optic nerve contains 1.2 million nerve fibers. This number is low compared to the roughly 130 million receptors in the retina, and implies that substantial pre-processing takes place in the retina before the signals are sent to the brain through the optic nerve.”

This is an example of what I believe to be thinking that leads (has led) to a dead end in unraveling the vision process.

In my explanation the rods of the peripheral retina, that constitute the bulk of the above mentioned 130 million receptors, function as the wide angle ‘light meter’ controlling constriction of the light entrance pupil of the eye. It is even understood in vision literature that these peripheral rods are largely connected in parallel in support of this assertion.

It is cones of the fovea and parfovea, together the with lesser number of rods encompassed within approximately 20 degrees of retinal angle that, detecting direction and intensity of the three primary wavelengths, are involved in the image formation process of the eye. There is certainly some pre-processing of visual information involved in the sub-retinal ‘circuitry’ of the retina. The number of optic nerve fibers involved in
transmitting this processed image information then probably will be found to be consistent with the 1.2 million quoted above.

The statement quoted above is critically misleading!

Regarding the optic nerve, I would like to find an electron micrograph of a cross section of the 1.2 million fibers…can anyone help? Specifically, I would like to ascertain if all of the fibers are of the same diameter…..or might they spatially replicate the plan of the retina. I have been told that the visual image of the retina appears as an actual image in the visual centers of the brain. I want to use the term ‘coherent’ here implying that there is a one-to-one correspondence of pixels in the spatial plan of the image appearing in the brain and the initial retinal representation. If this is so it presents the idea that the optic nerve acts as a ‘coherent fiber optic bundle’…might this be so?

I have guessed that the fundamental geometric principle defined on the retina (the ‘rule of two circles’ discussed in the paper) might be carried forward in transmission of the image through the optic nerve and thus might give some clue to the organization of neural networks in the brain.

?????

GCH
3/30/0

Ultimately, vision science must explain the fact that the eye can detect (or “count”) single photons, i.e., that the ultimate level of sensitivity of the process has been reached. An alternative and thought provoking terminology might be that vision actually “interacts with the reality of quantum physics”. There are many in the physics community attempting to address the subject of a quantum connection with neuroscience……and the retina as noted by Roger Penrose is a direct extension of the brain! This subject has not, and could not be, addressed in the literature of vision as long as the eye was perceived to be the analogue of a “camera” with, usual for that line of thought, image integration times of the order of photographic film, i.e., on a macro time scale of the order of fractions of a second. This is the view that seems tacitly assumed in the entirety of vision science even to this day.

From a technological viewpoint a glaring disconnect appears here. The only way that the field of photonics knows of to detect light at this low level in contemporary imaging systems (“photomultipler” tubes, etc.) is to either apply large electronic amplification (not at all evident or possible in biological systems) or, to reduce the temperature of the system to close to absolute zero to reduce signal obscuring noise. Neither of these considerations is evident in the eye and, moreover, vision accomplishes this feat even above room ambient at body temperature.

My explanation, in contrast to the above, posits that the retina actually can be shown to consist of a logically spaced array (of a 100 million or so) of discrete light detection
elements each of which displays electronic characteristics consistent with the requirements for detecting single quanta. Considering individual lightdetection elements (or devices) isbthe only way to explain detection at this ultimate level of sensitivity. The characteristics of such individual devices includes both the physical size of the element (in this case the sub-optical wavelength dimensions characterized by the appositiona“electromagnetic antenna” distances between retinal receptors) and, consideration of a reduced time scale reaching at least into the sub-picosecond (10-12 sec) time domain to reduce random (thermally generated) electronic noise that would otherwise obscure the quantum signal (electronic noise is a time integrated function and shorter time reduces the number of discrete unwanted electronic noise events inclusive in any detection “time window”.

The total image information that is acquired may extend even to femtosecond (10-15 sec) time or less supported by data that this is the “switching time” for the fundamental retinal chromophore molecule in the rhodopsin complexes contained in receptors of the retina. This image can therefore be said to be “quantum noise limited”. THERE IS REALLY NOTHING NEW IN THIS STATEMENT - THE IMAGE FORMATION PROCESS ON THE RETINA SPATIALLY INTERROGATES THE REALM OF QUANTUM PHYSICS! How then is such an ephemeral (i.e., in time) signal perceived by the much slower human nervous system and the brain? I have proposed that known mechanisms involved in transmission of this image information (coherently!) through the two million or so individual fibers comprising the optic nerve accomplishes this function. The transmission mechanism for this process has historically been assumed as being ionic but a new hypothesis proposes that signal transmission may actually be phononic or, coherently, as lossless solitons (nature would use lossless solitons!). I might suppose that some sort of time integration of acquired “quantal image” information must occur somewhere in this process. .a new window for the vision/mind process into what I term “quantum reality” is provided by this logic.

From the above it should be obvious that in both space and time this explanation approaches the realm of quantum physics.

And there is much more …..this explanation finds that a simple and heretofore unrecognized geometric construction is fundamental to light interaction with the retina. Refer to the “Rosetta Stone” diagram in the paper where, following the realization that an “antenna spatial dimensionality” is involved in the detection of electromagnetic radiation,
the rule follows that: “an array of circles of two diameters leads to three appositional lengths and that this corresponds to the trichromicity of vision” and that the “the absolute diameters of these circles defines the wavelength band”, and…further, that “the ratio of these diameters defines the width of the band detected” (the ratio of the diameters of cone and rod retinal receptors corresponds to the visual band from 400-700 nm). Also crucial to the vision process, an exact “geometric center” (thus wavelength) is defined that I believe is the reference for determining color in the eye.

About the physics involved….this new explanation does not refute any tenet of either classical or quantum physics. It simply notes that, using the assumption of “optical antenna lengths” rather than the pure quantum construction that “a photon interacts…”, it becomes obvious that the retina evolved to detect light as the wave of classical physics
but necessarily adjacent to the recognized concept of “quantum confined electron” regions widely accepted in contemporary quantum electronics. I go no further than this… simply an observation that the nanostructure of the retina is so structured. It fascinates me that in such a nanostructure the quantum and classical realms can be viewed as being spatially “side-by-side” (Bohr’s complementarity?)…and that the process can be viewed“ from either side” either as a quantum or classical interaction process. As opposed to historically inaccurate views….this explanation provides, for the first time, a basis for extending thinking about the vision process into the realm of quantum reality.

I would propose that an alternative (and more correct) way to view the structure of the retina is as a “spatially defined array of quantum wires”. The real function of cones and rods is spatial with their role being to define the distance between such quantum wires!

GCH
3/27/07

From Garrison Keillor’s “Writer’s Almanac” of March 13th (I heartily recommend the RSS feed for this site!). From Act 2 of Henrik Ibsen’s play Ghosts that opened in 1891:

“I almost think we’re all of us Ghosts… It’s not only what we have inherited from our father and mother that walks in us. It’s all sorts of dead ideas, and lifeless old beliefs, and so forth. They have no vitality, but they cling to us all the same, and we can’t get rid of them. Whenever I take up a newspaper, I seem to see Ghosts gliding between the lines. There must be Ghosts all the country over, as thick as the sand of the sea. And then we are, one and all, so pitifully afraid of the light.”

I think perhaps appropriate to the realm of science!

Segueing to……….. from the New York Times of the same date: “Growing Older, and Adjusting to the Dark” (Science Times, p.D7)…..again the same old stuff over and over again about “cones giving us color vision” and that “….rods provide only black and white images..” Tsk, tsk!!!

I think that another summary of my explanation for light interaction with the retina and the vision process is in order:

1.) The visual image is formed on the retina from light falling on the matrix of cones and rods extending from the all-cone fovea to approximately 20 degrees of retinal angle.

2.) The hues of color are determined by determination of a ratio of light falling on either side of a fundamental, geometrically-determined reference point (’primary green’) at 7-8 degrees of retinal angle..exactly as Edwin Land deduced. This point corresponds on the retina to where there are - a sufficient density of rods to completely surround each cone. Land showed that a slight shift of this reference point (and assuming that the diffractive properties of the eye do not change) can drastically change perception of the hues of color. A slight shift of this point (by, for example, genetic alteration of the size ratio of retinal receptors) is in my mind undoubtedly the explanation for ‘color blindness’ - and NOT the ‘absence of one of the classes of cones’ that, in fact, do not exist at all.

3.) The all-cone fovea itself extending to one degree of retinal angle is responsive solely to long wavelength (’primary red’) and, in fact, specifically defines the exact long wavelength end of the the visual band.

4.) The transition to predominantly rod density from the 7-8 degree ce mid-point reference to approximately twenty degrees detects the short wavelength (’primary blue’) input to the image.

5.) The three ‘primary wavelength’ regions described above detect the varying intensity of these wavelengths and are not a spectral response as universally assumed.

6.) The predominantly rod-containing peripheral retina beyond 20 degrees serves the sole function of a ‘wide angle light meter’ controlling the mechanical action of pupillary constriction that limits light entrance into the eye. This region is solely short wavelength (blue) sensitive and exactly defines the short wavelength limit of the visual band…a dangerous point being adjacent to the biologically-damaging UV region. In addition to being sensitive to the intensity of light , pupillary constriction is solely short wavelength sensitive being controlled by the response of the peripheral retina.

7.) The ratio of the sizes of the cones to rods on the human retina is ~1.8:1 corresponding to the visible band from 700-400 nm.

8.) A mix of two receptor diameters must be present to produce the sensation of color. The response of a retina with receptors of only one diamter would have a monochromatic response.

9.) The absolute diameter of retinal receptors determines (by setting center-to-center appositional length) the wavelength sensed. Smaller receptors connote shorter wavelength response (insects and birds / UV) and larger receptors sensing intothe near infrared region of the spectrum (fish).

I would guess that the comment in the NYT piece about “the less responsive muscles in the iris…” is the primary effector of reduced night vision with aging. Constriction of the pupil of the eye (as I have noted above) is mechanical and I would assume subject to decline ..as all of our other muscles are! Perhaps eye exercises would forestall this decline…?

The comment “There is also evidence that as we age we lose more rods than cones” and “But an autopsy study of older adults found that while the cones remain intact, almost third of the rods in the macula (generally the imaging region as defined above) had been lost”. Maybe so….but if true ..perception of color would change with age!! This seems amenable to experiment. Has this ever been investigated?

I have also noted the possible relationship between the short wavelength limit-controlling function of the all-rod peripheral retina and the onset of the condition of macular degeneration. Once one realizes that the the absolute wavelength response determined by this region is perilously close to biologically damaging ultraviolet radiation one can speculate about this connection. Moreover, following from this explanation it is the diameter of rod receptors in an individual that sets this limit..which must be genetically inheritable.

GCH

3/1/07