Rethinking the Process of Vision

I suppose because I have invoked the term “evolution” on a number of occasions the idea that the eye represents an instance of intelligent (i.e., supernatural) “design” has been presented to me. In the best of all worlds at this point in history this would be considered as patent nonsense. Following from my thoughts of light interaction with the retina and the resulting new explanation of the vision process, the eye clearly represents an entirely natural instance of self-organizational biological matter directly objectifying well understood (by humans) laws of physics. By “biological matter” I mean  substances that are a result of the inherent properties of atoms and molecules (i.e., atomic bond angles, etc.) accumulating over very long periods of (evolutionary) time.(a)
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(a.) Long chains of carbon atoms form themselves naturally  into lipid molecules that can subsequently self-organize into ordered mono- or bi- layers on the surface of water (oceans?). These ordered layers of molecules are identical to the membrane of living cells. When such layers are disrupted by sonification (or the wind?) these layers “curl up” into maximum bending radius “miscelles” that are idenitical to the outer coat of some viruses. And on and non……..
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The physical laws involved are the well understood properties of the refraction of light and the, as yet quite not so well understood (by humans) concepts of quantum theory.

In this explanation, it is shown how wavelength sensitive, spatial “antenna” structures (individual receptors) array themselves on the retinal surface in exact accord with the light refractive properties of the lens and body of the structure of the eye. In my view this is a purely natural occurrence. What has not been seen until proposed in this work is the associated  geometric rule that fundamentally and inherently spatially connects this specific assemblage of receptors to light refraction within the eye.  By this I mean my oft-quoted “rule of two diameters” where the admixture of two diameters (the cones and rods) defines an exact center - the central 500 nm wavelength of the visual band (and remembering that the absolute ratio of the two diameters corresponds to the visual band 1.8:1 or 700-400 nm). The eye has no need of a “laboratory” wavelength measurement scheme to define the mid band 550 nm  wavelength - it is uniquely geometrically defined! But this goes on - Edwin Land’s work on color vision is justified as is the basis for understanding that the vision process is in the Fourier domain and on and on….

As I have discussed in recent comments the extraordinary ability of the eye to detect each single light quanta (“The visual process is at an absolute terminal point in the evolutionary chain….to the extent that the visual process now succeeds in counting each absorbed photon” Albert Rose) requires explanation. At least a start down this road is again provided by this work. At the outset I had written in a form that I hoped would be understandable to those working in the vision science field. I consciously downplayed the physics aspects of the explanation though understanding that the quantum aspects of light interaction certainly were present. Specifically, it is certain that the eye evolved to detect light as the wave of classical physics. This is the interpretation of the wavelength- determining, spatial appositional distance between individual retinal receptors. But…a necessary cofactor in the light interaction is that the absorbing mass of the receptor (actually, the electron located within the receptor) must be confined to single electron “quantum confinement” dimension. The overall light interaction is then an ‘interplay” between these to, really spatial, entities. This implies very fundamental physics questions pertaining to the “complementarity” of the wave/particle nature of light. I had not wanted to address this point but it has eventually reared it’s ugly head!  I had contented myself with saying that the the interaction process could be viewed either as a classical or quantum process without violating either theory of physics. But, in attempting to explain the quantum limit of vision (see recent Comments) it seems to become apparent that vision represents a coalescence of the classical and quantum branches of physics - and this occurs in the outer segments of retinal receptors. Quantum reality intrudes in the guise of the “quantum instant” of time that this explanation drives toward (again, see recent Comments). The ultimate explanation of vision is going to involve a new understanding of the coalescence of space and time -with very small spaces and infinitesimal instants of time being inherently involved!

It becomes clear that the only explanation for the retina to detect single quanta is that each individual light reception site possesses the capability for generating a usable signal from the interaction of a single quanta. I have expressed mechanisms that  I believe retinal devices use to accomplish this feat. One is then presented with an entirely new view of the retinal surface - an array of a hundred million light detection sites each capable of interacting with single light quanta (detecting at the “quantum limit”).

The starting point for formation of the visual image therefore involves quantal considerations and occurs in a very short time indeed (discussed previously). A spatial image is therefore “there” in this brief time which may be coherently transmitted to the visual centers of the brain through the millions of individual fibers of the optic nerve. Extraordinary! I have proposed that the heretofore unseen geometric principle (see above) that rules the retina may thus be transferred to, and operative in, the neural processes of the brain.

New insight!

I am going to close this now but I will work on further clarification.

GCH
10/30/06

(Originally written on Saturday, July 8th, 2006)

(I will recycle thoughts as they occur to me to be of particular significance / GCH)

If one can gather in this simple concept of light interaction with the retina of the eye one sees that the fundamental principle involved is that this biological structure evolved to conform to an exact geometrical symmetry. Moreover, this geometrical symmetry overlays the characteristically indefinite structure characteristic of biology and, specifically, of this biological organ. A precise physical principle seems the basis of the biological realm to which evolution conforms!

(I have noted over and over that the admixture of the two sizes of retinal receptors, i.e., the cones and rods, forming the retina are in the ratio of the visible band (1.8:1 or 700-400 nm) and the apposition of one size receptor to the other (i.e., a cone to a rod) defines exact midband. This occurs on the retina at an angle of 7-8 degrees where midband wavelengths are refracted by the structure of the eye.)

The specification of such a geometric center, from which other factors such as wavelength are referenced, explains the color constancy of vision and provides the fixed ‘fulcrum’ necessary to explain Edwin Land’s color vision experiments.

Thus the refraction of light within the eye combined with this geometric principle defines a wavelength of 550 nanometers! What deeper meaning might this finding have? Might considerations of geometrical symmetry be propagated further on via the pathways conducting visual information to the brain and perhaps lead to new explanations for brain function?

I have quoted the enigmatic thought of Einstein that “All is geometry”….???
GCH

Again, it must be stressed that each individual light detecting element of the retina is able to independently introduce a signal contributing to the visual image from the interaction of a single quantum of light. This can be the only basis for the retina “counting” single quantum interactions. As I have said before this is an awesome light detecting array to contemplate! We know of nothing that can compare with it in any of our even advanced technological imaging modalities. This capability in itself requires new thought and I will speculate on this below.

I am going to assume that the hexagonal cone array of the fovea centralis forms the primary (”Marr sketch”) initial stage of the final image. This region comprises an array of 200,000+ individual cone receptors that corresponds, in the sense of this work, to 6 x 200,000 or 1.2 million discrete “light detecting appositional devices” (this follows from each cone receptor being ordered in the hexagonal array). Thus, this small region of the retina approximating one millimeter in area contains a million individual quantum confined electron sites that are connected in parallel (in electronic terms) to the million or so fibers of the optic nerve leading to the visual cortex of the brain. One must envision the entire visual image being coherently transferred from the retina to the brain (in the process being slowed to “a time scale useful to the human nervous system” as previously discussed).

One might think here of the outwardly similar “megapixel arrays” of the imaging technology found in contemporary digital cameras…but there is a distinct difference. The light detecting elements on the silicon imaging chips used in such cameras are connected linearly with signals from the entire array that form an image being electronically “ducted out” during the a millisecond or so time period. Motion is simulated by presenting these single images taken at ~1/30 second intervals to the eye. To the best of our knowledge (discussed below) the eye does not “snap” individual images but rather, in analogue fashion, presents a continually updated stream of image information to the brain.

The element of “time” continually intrudes.

I have come to believe that the final visual image containing detail and color information is “assembled” or “added onto” the primary Marr sketch outline detected by the fovea centralis on the retina itself. This would use the neural connections of the retina to logically introduce information from the green and blue intensity bands (detected at 8 and 20 degrees of retinal angle) to complete the image formation process. This would obviously occur in very fast time (distances are short) but we would already be looking into the past relative to the initial light interaction even at this early stage of the vision process. We would already be past the “pure quantum” or the elusive “timeless instant” of photon detection in the receptor outer segment array.

What physics are involved in the original “quantum instant” of the vision process that occurs in light interaction with the array of spatially quantized receptor outer segments? I readily admit that all of my thinking thus far is “classical” in nature and adds very little to the relevancy of quantum reality to the vision process - which must be there! We are however “closing in” on the meaning of the “instant of time”. I would note that there are still two orders of magnitude of time (from the identified 10^-12 sec “signal initiation time” to the frequency of visible light) remaining to be explained.

GCH
10/13/06

I now step beyond simply proposing an “explanation” for the nature of the vision process to speculation based on where that new explanation leads. I had wished that others would begin this process……and a few are actually beginning to do that!

In recent comments I have made the point that the well documented result that vision has evolved to the “quantum limit”, i.e., that the retina is capable of “counting” single quanta (or photons), � is the key to understanding the process of vision. One must realize that the historic “wave particle duality” dilemma of physics asserts itself here! This single, well documented result that quantum effects are involved at the ultimate limit of vision must be confronted. This association forms the basis for, and provides great insight into understanding the true nature of the process.

NOTE:

To avoid confusion I again remind that the explanation for light interaction that I propose shows (proves) that the eye evolved to detect light as the wave of classical physics. It is the absorbing mass (the electron) of retinal receptors that is quantized being necessarily reduced to “quantum confinement” dimensions for the interaction to occur. The process can then be described either way, i.e., in classical or quantum terms. I use the term “photon” but would rather term it in light of the forgoing a “quantized interaction”.

Based on my initial proposal that the light detection centers of the retina were actually receptor appositions (cone-to-cone, cone-to-rod, etc) and not the receptors themselves (and all that follows from that explanation) single photon sensitivity can only mean that each receptor site acts individually to detect single quanta. This is a daunting thought! The small central fovea contains 200,000+ detection sites – with each site acting individually! Moreover, it follows that the “stopping time” of light within retinal outer segments is in the ephemerally short time of picoseconds (10^-12 sec). It is within this time frame that what might be termed a “quantal image” is “there”. Thus an image composed of millions of individual quantal interactions is resident on the retina in this brief period of time!

I will discuss below whether we should even think of this as a “time” at all or are we now approaching the “instant” of perhaps a new “quantum reality”! We are certainly venturing into the unknown area of physics where wave and particle interact.

But first, I worked for many years in photonic technology developing, among other applications, optical systems capable of single photon detection. In general there are two paths to gaining this level of sensitivity. The first involves use of cryogenic cooling to cool the light detecting element in order to reduce electronic noise and reveal the photon level signal. I remember a system built by an aerospace group in Los Angeles that used a silicon photo detector and that did an admirable job of single photon counting but which required cooling with liquid helium to a few degrees above absolute zero. Another path to attaining this level of sensitivity involves accepting the level of noise and providing a post-detector electronic amplification of a million (10⁶) or so to raise the small single photon signal to a measurable electronic level. This is the route taken by the “vacuum photomultiplier” light detector that can actually detect single (or at most a very few) photons at room temperature. Rose in his analysis (previously referenced) of the vision process could only propose that the eye somewhere contained such an amplifier but he could not explain where or how this might be accomplished in a biological system. The eye, however, is superior to both of these approaches with its ability to detect single photons above room temperature, i.e., at body temperature. How does it accomplish this?

I have proposed that the answer lies in the time scale. In designing radiation detection systems one employs the concept of “matched bandwidths” matching the time in which the signal is absorbed (“is there”) with the “time constant” of the following electronic amplification system. Noise (for example, random thermally induced electrons) is a time-integratable function with the random events appearing in, and integrated over, � time. Shortening the “time constant” of the detection process reduces the number of such events that can occur within the detection window thus reducing the overall noise level. A group of us published a paper on this subject a number of years ago (1.) noting how the effect could be used to increase the sensitivity of radiation detection systems.

(1.) Tove, P.A., Cho, Z.H., Huth, G.C., “The Importance of the Time Scale in Radiation Detection Exemplified by Comparing Conventional and Avalanche Semiconductor Detectors”, Physica Scripta, 13, 83-92, 1976

It would seem that the factors of the vision process as I have outlined above seem to conform to such a detection scenario with the quantum level signals being absorbed in very short, picosecond time. In the initial paper of this web page I discussed the mechanism operative in the light detection device formed between adjacent retinal receptors that seem to conform to these requirements.. See http://www.ghuth.com/?p=58 for a diagram of the structure. This device has the small, sub-micron dimensioned scale required for operation in the very fast time domain. I had proposed that the necessary electrical signal follows from photoisomerization of the retinal molecules contained within each receptor. A correspondent has noted that this reaction has been experimentally shown to occur in this time scale.

“As established experimentally, the quantum of light impinging on a rod and being absorbed by a molecule of rhodopsin ”launches” the photochemical reaction (occurrence of electric impulse) for 0.2 picoseconds”, Ref. El-Sayed, M.A., Tanaka, I., Molin, Y., 1995, Ultrafast Processes in Chemistry and Photobiology, Blackwell Science; Kandoril, H., Shichida, Y., Yoshizawa, T., Photoisomerization in Rhodopsin, Biochemistry, 66, 2001.

From all of this one envisions a “quantal image” comprising millions (corresponding to the number of retinal receptor appositions) of individually quantum receptive “picture elements” at the plane of light interaction with the retinal outer segments. This is an awesome array to contemplate! It must be faced that whatever is occurring here lies in the domain of quantum physics with all of the uncertainty (sic!) that this statement implies.

The term “coherent” (either spatially, temporally or both) seems to apply here and I will revert to what is a classical concept of “an image” being formed and transmitted onward realizing that this probably is not the true state of affairs.

Thus leaving the quantum realm, we assume that the “quantal image” proceeds through retinal neuronal circuitry and thence through the, assumed to be, imaging bundle of the optic nerve to the visual centers of the brain.

It is not clear whether the three (RGB intensity sensitive) Fourier transforms from the retina are processed (synthesized?) in neuronal circuitry on the retina of if this occurs in the brain. The latter would require that three “coherent” quantal images be transferred – in time. My sense is that this does not occur and that only one image is transferred.

One gets the sense of a vision process where an “instant” (in picosecond or less time) quantum defined image (whatever that means!) continually updates an ongoing “vision stream” to the brain. The element of time itself (processing time?, signal transfer time? etc.) is perforce involved in the post-quantal image formation time.

Thus the vision process within itself, following the initial quantum image sensation stage, looks back in time! WE CAN NEVER SEE THE “QUANTUM INSTANT” OF IMAGE FORMATION ON THE RETINA! In another sense we are viewing the abyss of quantum physics. We can never reach the instant that is before our eyes!

I am aware (painfully aware) that none of this breaks any fundamental new ground in understanding the reality of the quantum nature of reality. All that one can now say is that “the classical wave and quantized particle aspects of that reality come into coincidence at the plane of the outer segments of retinal receptors”. � The quantal array of receptors that I propose form the retina and that results in the vanishing “instant” of time that is perceived can said also to exist in the instant � that is “freeze framed” in a photograph! The vision process, however, produces a “moving or continuous instant” and quantum effects are undoubtedly involved. Questions?

I also believe new is the proposal that the well known “arrow of time” of physics exists within the vision process itself. As stated above, we can never know this instant (the “quantized” instant). The instant (timeless?) quantum realm exists on the retina itself but all following is in classical “time”. The ideas of Julian Barbour (“The End of Time, the Next Revolution in Physics” as previously referenced) and Ernst Mach (that reality consists of timeless “sensations”) � that time itself is an illusion become perhaps more real. Using classical; “time � terminology we are always even within ourselves looking into the past!

And too, reaching a fundamental understanding of the Fourier transforming process is involved. I have shown that the vision process is based on this process. Brain Hagan in his brilliant paper (again, previously referenced) presents a geometrical/mathematical explanation that “the wave is the particle” but this does little (at least to me) to provide understanding in this situation. Questions?

I am going to leave this here although I have many other thoughts and will add them shortly.

ADDED:

I learn from my son that sub-retinal neurons (terminology?) are surprisingly (probably only to me!) analogue in nature� . as opposed to neurons in the brain that react digitally. This would seem to support some of the above assertions

GCH
10/04/06

Updated 10/06/06

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