A Brief History of How This Explanation Evolved
Added 11.09.09 THIS WORK IS CONTINUALLY REFERRED TO AS A THEORY. IT IS, HOWEVER, AN EXPLANATION THAT FOR THE FIRST TIME PROVIDES A RATIONAL INTERPRETATION OF THE HISTORIC RETINAL MORPHOLOGY MEASUREMENTS OF OSTERBERG MADE IN 1935. OSTERBERG’S MEASUREMENTS ARE BROADLY ACCEPTED AND ARE REPEATED IN ALMOST EVERY TEXTBOOK ON VISION.
I HAVE BEGUN TO REFER TO RETINAL LIGHT DETECTION SITES AS “NANO-ANTENNAS”. THE EXISTENCE OF SUCH ENTITIES WITH THE TERM “QUANTUM” ATTACHED HAS RECENTLY BEEN REPORTED ‘Quantum antennas’ enable exchange of quantum information between two memory cells
Now to how this singular bit of insight occurred to me in 1991:
For a number of years I directed the Institute of Physics of the School of Medicine of the University of Southern California. During that time I made it a habit of cataloging scientific papers and ideas that seemed to me to be interesting or provocative but which, in the press of daily business, I didn’t have time to pursue. One of these was a patent (U.S. #4,445,050 “A Solar Energy Converter”) that crossed my desk assigned to Alvin M. Marks. I learned subsequently that Dr. Marks was a contemporary of Edwin Land and that there was some controversy between them regarding the initial development of light polarizers. The Marks patent (see the cover page as Figure 1) proposed a solar energy converter formed from “antennas for visible light” with the structures fabricated (I guessed) using contemporary microcircuitry technology. Dimensions of such dipoles would approximate lambda/2n where lambda is light wavelength and n is the refractive index of the absorbing medium. They would thus be of the order of 550 nm divided by 3 (i.e., 2 x 1.5) or about 200 nm in a substrate such as glass or ~70 nm in silicon.. In the light of modern technology such structures could be readily fabricated. I remember discussing the “optical antenna” idea with anyone who I thought might be interested but the response was generally (invariably!) negative – this is the era of photons not classical waves! I put the idea away but never stopped thinking about it…
It turns out to get ahead of the story a bit that I came to believe that Marks missed the mark (!) in that he proposed to conduct the absorbed light energy a distance from it’s dipole absorption site “along a length of wire” to, in the solar energy application, a remote rectifying function (the semiconductor pn junction structure shown in the lower part of his diagram). I propose that this won’t work – the retina of the eye teaches that the absorption site must be immediately adjacent to a quantum dimensioned absorbing mass (the electron).
I discovered, after becoming interested in the geometric vision concept, a second perhaps more prescient antenna patent (U.S. #3,760,257 “Electromagnetic Wave Energy Converter”) by Fletcher and Bailey and assigned to NASA. It turns out, interestingly, that the Fletcher named was James Fletcher then director of NASA and who for some reason had his name placed first on NASA patents. Bailey, a NASA engineer from Florida was the inventor. The second figure from this patent is shown as Figure 2. It becomes a bit more obvious how this antenna concept resembles the receptors of the retina of the eye. In a conversation with Mr. Bailey it became obvious that he truly recognized and argued for recognition of the wave aspects of the absorption of light on surfaces. Again, however, I think that he also missed the mark (although not by much!) in placing the rectifying function – again a pn junction – at the base of each receptor. It doesn’t work this way either!
One line of thought in vision research has in fact treated light as a wave in proposals by Enoch among others modeling the receptors of the retina as light guides (as in “fiberoptic light guides”). This approach assumed that each receptor acted as a refractive index-defined space which did for the first time bring retinal dimensionality into the picture… and, seemingly unrecognized, light guides treat light as a wave! The unsolved problem, however, derives from the wave/particle duality of light and this approach must assume that light energy (somehow and somewhere in the absorption process) evolves into a photon which ultimately interacts with pigments along the receptor length. It is important to note that this approach, as interesting as it might be, never seemed to lead to any new insights into the vision process.
Another totally different development then came to my attention and which fascinated me was Hans Kuhn’s elegant “photon funnel” experiment that used Langmuir Blodgett technigues to embed optical dye molecules in lipid membrane layers. This experiment is described elsewhere on this web page but, in summary, Kuhn found that energy is transduced over tens to hundreds of molecular distances laterally within such an organized lipid layer following the interaction of single photons! I, and at least one other writer, Blinov in Russian Chemical Reviews ( referenced elsewhere) thought this to be a truly seminal experiment. What Kuhn had done was to simulate in controlled self-organized lipid membrane layers the “resonance radiation” discovered in the 1930′s independently by Jelley and Schiebe who had used aggregates of similar optical dyes in solution. Resonance radiation implies that light absorption energy is transduced losslessly (in the Kuhn experiment laterally within the membrane layer) a truly unusual finding. The Kuhn experiment reproduced the resonance effect in organized monolayers by placing octadecane molecules in the interstices between adjacent lipid molecules forming the membrane. This purposefully altered optical absorption behavior from the usual Stokes shifted (energy loss) character to the lossless Schiebe/Jelley resonance behavior. Further, the experiment implies that lateral energy transduction must be mechanical in nature, i.e., phononic or, if lossless, solitonic. A group of us subsequently proposed study of the soliton mechanism and we motivated a number of groups around the world to become interested in this mechanism involved. This effort that continues to this day. An interesting development was the finding by a group of us (with Christiensen and Vitiello) of computer simulations that indicated that a “ring” solitonic mechanism might exist.
The concept of lossless energy transport (the “funnel”) laterally along lipid membrane is thus inherent in the retinal light interaction mechanism that I propose being operative laterally in the thylakoid disks of the retinal receptors. And….in the biological situation, the molecule that substitutes for Kuhn’s space-filling octadecane molecule is cholesterol! I wonder if anyone has ever ascribed this function to the very much maligned cholesterol molecule?
There is one other result from the solid state field that I feel is important to understanding this concept. Dworschak et al (1) and Young et al (2) studied the interaction of pulsed laser radiation with semiconductor surfaces at two wavelengths. In this series of experiments, laser pulses were made incident onto silicon and germanium surfaces with laser intensity controlled so as to cause only partial melting of the surface. The surface was then chilled quickly so as to preserve any structure produced. The result was a periodic “grating” whose period matched the wavelength of the orthogonally incident light energy. When the 1.06 micron wavelength of the neodymium laser was used the grating produced displayed exactly this period. The 10.6 micron wavelength of the CO2 laser produced a period corresponding to this wavelength (shown from Dworschak to the left in Figure 3) . The Young paper goes on to study structures produced by different laser fluences and to discuss possible mechanisms involved but the central finding seems to be the one I have noted, i.e., that the wavelength of incident light is reflected laterally onto a surface… which fundamentally supports the geometrical concept. Another result of the same nature again using the 10.6 micron radiation of the CO2 laser – and copper surfaces – was produced by Siegrist et al (3). Again one sees that the periodicity of the surface structure is related to the orthogonally incident light wavelength with their result shown in the right hand view of Figure 3.
- K. Dworschak, J.E. Sipe, H.M. van Driel, “Transitions Between Ordered and Disordered Solid-Melt Patterns Formed on Silicon by Continuous Laser Beams: Competition Between Electrodynamics and Thermodynamics”, Ref. unknown.
- Jeff F. Young, J.E. Sipe, and H. M. van Driel, “Laser Induced Periodic Surface Structure. III Fluence Regimes, the role of feedback and details of the induced topography in germanium”, Physical Review B, Vol. 30, No.4, 15 August 1984
- Siegrist,M., Kaech,G., Kneubuhl, F.F., “Formation of Periodic Wave Structures on the Dry Surfaces of a Solid by TEA-CO2 Laser Pulses”, App. Phys, Vol.2, 45, 1973
I have used this phenomenon in an attempt to describe how biological photosensitive structures may have evolved. I propose that the induction of these light wavelength-associated periodic surface structures interacted in the distant past with the initial, labile membrane that is extruded under light stimulation from the dark-adapted etioplast. It certainly seems possible that shorter wavelengths formed the primary interaction in what would have been the “initial event”, i.e., formation of the granal regions of such structures. Then, carrying the logic forward, this same phenomenon together with the natural folding tendency of lipid membrane would collaborate to form the second (or “stroma” ) sensitive region. This latter region would, by the reasoning of this concept, form the long wavelength sensitive peak of chlorophyl response, The result is the generally two peak spectral response that is observed. This is a very logical way in which these structures could have formed … and one based on this action of light. See further discussion under “Chloroplasts” elsewhere on this website.With these thoughts and the above (the Marks’ proposal at least) “optical antenna” concept in the back of my mind, and while looking at a diagrammatic representation of the cones and rods of the retina from Cornsweet’s “Visual Perception”, it occurred to me how an antenna concept might be applied to the retina …….essentially….. that “an array of apposed circles of two diameters yields three lengths”….. and all else follows from there!