A Summary of My Sunday Thoughts
January 28th, 2007 | No Comments »
My general writing style is to try quickly to outline the complete thought or thoughts and then to go back later and ‘fill in the blanks’ putting the ideas into hopefully reasonably readable text.. In the following you will be treated to the original outline because as I think that it is a rather important summary I will publish here and complete the thoughts in future days.
GCH
The text:
I believe that we should begin to view the eye as Roger Penrose (and I think Koch) proposed as the ‘extension of the neural network of the brain where this network interfaces with external reality’ and not as we have historically considered as the ‘singular organ of vision’. In other words, the eye and brain operating on the same – quantum – principles.
One’s thinking here should start with the points about which I have been writing lately, namely the statement made by Albert Rose that the vision process has evolved to the quantum limit. To quote him exactly:
“It is not conceivable that the sensitivity of the vision process can be significantly enhanced. 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, there is little possibility, outside of increasing absorption, of a further increase in sensitivity. The laws of quantum physics impose a firm limit which has been closely approximated by our existing visual apparatus”
(emphasis in the original, from, Albert Rose, “Vision Human and Electronic” Plenum Press, pp 29-30)
This thought has truly fundamental meaning that seems not to have been seriously considered.
To begin, the ‘retinal signal’, i.e., the isomerization of the retinal molecule following the absorption of a single photon , is of a very small magnitude indeed. In electronics terms it is very difficult to see how this signal, competing against the thermal noise background of the temperature of the body, can be amplified to a useful level (…for transmission to the visual centers of the brain etc.). As I have written, we technologically require either: a.) application of electronic ‘gain’ of values approximating a million or, b.) reduction of thermal conditions (temperature) to a few degrees above absolute zero ( - 273C). Rose with his background in electronic image technology could only assume that the required gain must be present somewhere in the biological system but, he could not even begin to imagine where or how this might come about.
Another group (F.Rieke, D.A. Baylor, “Single-photon detection by rod cells of the retina” Rev. Mod. Phys. 70, 1027 – 1036,1998) make essentially the same point that Rose makes. Their conclusions are so interesting that I will again quote their text exactly:
Abstract: “At low light levels, the visual system detects and counts photon absorptions with a reliability close to limits set by statistical fluctuations in the number of absorbed photons. Thus the rod photoreceptors that provide the input signals to the dark-adapted visual system act as nearly perfect photon counters. This elegant performance is possible because light detection in the rods satisfies four functional requirements: high quantum efficiency, sufficient amplification to produce a measurable response, low dark noise, and low trial-to-trial variability in the elementary response. The rod meets these requirements using biochemical reactions rather than the solid-state reactions of silicon detectors, yet its performance equals or exceeds that of man-made detectors in several ways.”
I have emphasized their last point which might indicate that the subject of biological reactions is understood. But the last paragraph of their conclusions:
“Although our understanding of visual transduction and signal processing has advanced rapidly during the past 15 years, several fundamental questions remain: (1) What mechanisms are responsible for the reproducibility of the rod’s elementary response? (2) How are the rod’s single-photon responses reliably transmitted to the rest of the visual system? (3) What is the molecular basis for the differences in kinetics, sensitivity, and dynamic range of rod and cone photoreceptors? The answers to these and related questions will deepen our understanding of the strategies and capabilities of biological detection”
I believe that the thoughts expressed in their conclusion might lead one to think that the biological reactions mentioned in their Abstract are perhaps not so well understood!
Now back to my line of thought.
Albert Rose and the above referenced investigators both use the construction (erroneously, I believe) that an ‘integration time’ of a fraction of a second or so is inherent in the vision process. Rose comes about this thought naturally as times of this magnitude are involved in photography and electronic imaging as necessary to provide statistically significant signals to form an image. But, as I have written, I believe that this ‘integration time of the eye and vision’ does not correspond at all to the eye alone (or more, precisely the retina alone) but rather encompasses signal transmission from the initial light interaction with the retina over the entire brain/ nervous system to ‘pushing a button’ to record a visual event.
The realm of quantum physics implies consideration of space and time..and very small increments of each. How can the eye detecting at the quantum limit as it does be reconciled with the macro-increments of time that have been assumed?
The answer is that it cannot. The vision process must be operating in very fast time indeed…in a time domain heretofore not considered.
As my thinking has progressed the following model seems reasonable:
The central point is that each of the hundred million or so detection sites on the retina must be considered individually…as a vast array of sensitive devices acting in parallel to detect (or ‘count’) single photons. This is the only way that one can assume that single photon counting can come about…individual, fast counting devices sufficiently sensitive to respond to the energy of a single photon.
And in seeming correspondence, the time scale of operation of these individual devices must be very fast indeed with signal- obscuring noise (see my previous reference) being a time integrated function.
And…I have outlined the probable structure of these receptor-appositional devices.
This line of thinking leads inexorably to the concept of a fleeting ‘quantal image’ impressed on the retina in very short time (probably less than 10-15 seconds). We know very little about such an image as it is buried in the area of physics termed quantum statistics.
And then..how does it come about that the human system perceives and processes such an image. It must convert this image data into a slower (or integrated) form compatible with the human nervous system and human comprehension.
The mechanism I believe is contained in slow transmission through the coherent bundle of fibers that constitute the optic nerve. This nerve bundle of finite length serves the function of ‘slowing the retinal acquired quantal image to human nervous system-responsive time’. It is also possible that this transmission performs a time integration function to allow image information to reach a level of statistical significance.
‘Looking outward’ one must not lose sight of the idea that the retina ‘interrogates the realm of (‘outside’) quantum reality’. I have written and speculated about this.
‘Inward looking’ again, I have been fascinated with the seeming fact that the retinal image is transmitted to the visual centers of the brain as the image itself, i.e., there seems to be a 1:1 spatial correspondence of image pixels or elements existing between retina and brain. The image itself appears in the brain!
If this is so then the geometric rule (my geometric “Rosetta Stone”) that I propose is at the basis of formation of the retina itself must be transmitted to the brain. Might this give some insight into the structure of neural networks contained therein?
Does all of this bring together the elements of the eye and vision, the neural structure of the brain, the realm of quantum physics and, finally, pure geometry? It seems to me that this explanation makes a case for this..
Paraphrasing Einstein: ”Geometry may be at the heart of everything”.
GCH/1/28/07
