Model of a Quantum Super Computer
This keeps me awake at night ...
I think of a synapse as a chemical quantum computer. The synapse is about 20 nm. I visualize blowing it up to a box about 10 cm on a side. That's a magnification of 5 million.
If I spread out a human cortex flat, it's about 1 m on a side and 3 to 6 cells deep. At this magnification, it's a square 5 km on a side. The size of a small city.
Neurons at this scale are 5 m cubes - room size. We have a kind of city layouts of 3 to 6 story buildings from 15 m to 30 m high.
On this scale, we can walk around in our quantum computer like exploring the streets of a city.
Under our feet (under street level), we picture te humming and throbbing business of general city maintenance (like waterworks, electricity). That's the brain stem and cerebellum. Essential parts of the brain that we can ignore for the time being.
Back to the synapses.
Each one is modeled in three parts: the upstream synaptic vesicle (axon), the downstream vesicle (dendrite) and the synaptic cleft.
Actually, one very important input to the conductivity of the synapse is to be in the postsynaptic receptor. The function of this type of receptor is widely studied and the subject of many psychoactive drugs. However, I have found no information on the number of these receptors in the typical synapse. I do know that this number can be dynamically increased or decreased in response (for example) to the action of drugs. Our apparent ignorance of the details is just one illustration of our "frontier of knowledge" and a measure of how far we are from simulating or understanding the "S-function" discussed here.
By implication, we learn that this particular vesicle and its receptors have a big, immediate effect on many phenomena that we refer to as "mental", such as attention and mood. Action at these receptors is theorized to be what is happening with "SSRI" drugs such as Prozac. The word "theorized" is important. Finding out what is happening in a synapse is, to say the least, very difficult. Current technology is right at the edge of being able to influence/detect the action of a neuron, which is relatively huge compared to the synapse. The receptor is even tinier - in the range of protein sizes, apparently in the range of 10 nanometers or less, which happens to be the same size range of the synapse itself. It's obvious that the "pictures" we see of synapses are little more than cartoons: the work of conceptual artists and theorists. It is even possible that what is going on at the synapse will best be characterized as an "electron cloud", in the way we visualize the wave function around a molecule. That would be exactly what I'm aiming at here. It may not be possible to "visualize" the synapse in any better way than visualizing how the S-function varies several times per second. I believe I have seen exactly this approach somewhere in the discussion of internal chemistry in the neuron, although, if memory serves, the derivation was classical rather than quantum.
A re-read of "Foundational Concepts" should allow me to put some more precise numbers into this model. He doesn't shy away from making chemistry visualizable.
My contention that quantum effects are active at the scale of synapses is hardly controversial. For example:
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*In fact, such "hand waving" is equivalent to the "hand waving" we see when a chapter on computer principles is inserted in a book on consciousness. The connection is totally in the mind of the author and never justified by actual facts about brain function. A good example is Dennett's "Consciousness Explained".
I think of a synapse as a chemical quantum computer. The synapse is about 20 nm. I visualize blowing it up to a box about 10 cm on a side. That's a magnification of 5 million.
If I spread out a human cortex flat, it's about 1 m on a side and 3 to 6 cells deep. At this magnification, it's a square 5 km on a side. The size of a small city.
Neurons at this scale are 5 m cubes - room size. We have a kind of city layouts of 3 to 6 story buildings from 15 m to 30 m high.
On this scale, we can walk around in our quantum computer like exploring the streets of a city.
Under our feet (under street level), we picture te humming and throbbing business of general city maintenance (like waterworks, electricity). That's the brain stem and cerebellum. Essential parts of the brain that we can ignore for the time being.
Back to the synapses.
Each one is modeled in three parts: the upstream synaptic vesicle (axon), the downstream vesicle (dendrite) and the synaptic cleft.
for visualization purposes, I picture a box with three chambers where the respective reactions take place. Internal partitions have transmitters and receptors.
Given this, I can settle down to contemplating this 10 cm square computer and what it's doing. What little we know about what's going on is described accessibly in "Foundational Concepts in Neuroscience".
The function of each synapse box is to compute the S-function. S=1 means the synapse "conducts", S=0 means it doesn't. There are no other possibilities At any time, the state of the synapse can be characterized by a Phi function involving the quantum state of all the molecules involve (at least). The Schroedinger wave function gives a probability distribution for S at some later time which I picture to be a fraction of a second later. The wave function "collapses" to S=1 or 0, but the wave function tells us that which value will be selected is unpredictable in principle. The state of the synapse at any one time is a superposition. The synapse is a quantum computer.
We consider quantum effects to dominate due to the scale of the system, but similar conclusions can be drawn from a classical treatment of the system. In principle, it could be described by a few hundred non-linear equations. That would perhaps allow us to describe situations where S is stable at 0 or 1 but there would be domains where the system is unstable or even in a chaotic state. In any case, an analytic solution of this system would be impossible in principle, disallowing a mathematical model that could usefully describe the behavior of the system.
As pointed out elsewhere, there are over 100 trillion of these little computers in our city-sized "brain". That can be compared to about 1 billion hosts (computers) connected to the world wide web.
The lessons I draw from this visualization are:
- This is nothing like a digital computer. Its calculations are quantum as opposed to the deterministic results of any digital computer. Its scale alone is vastly beyond anything we can think of building for a very long time, if ever.
- The brain's "computer" has been "designed" as a relevance detector. We know from experience that it supports what we call a "mind". It is legitimate to ask if this type of architecture is required to support a mind. Many philosophers, such as Daniel Dennet and Ray Kurzweil assume that a mind could be supported by some kind of digital computer. Such assumptions seem to grow from a lack of alternative models along with a suspicious lack of knowledge about brains.
Actually, one very important input to the conductivity of the synapse is to be in the postsynaptic receptor. The function of this type of receptor is widely studied and the subject of many psychoactive drugs. However, I have found no information on the number of these receptors in the typical synapse. I do know that this number can be dynamically increased or decreased in response (for example) to the action of drugs. Our apparent ignorance of the details is just one illustration of our "frontier of knowledge" and a measure of how far we are from simulating or understanding the "S-function" discussed here.
By implication, we learn that this particular vesicle and its receptors have a big, immediate effect on many phenomena that we refer to as "mental", such as attention and mood. Action at these receptors is theorized to be what is happening with "SSRI" drugs such as Prozac. The word "theorized" is important. Finding out what is happening in a synapse is, to say the least, very difficult. Current technology is right at the edge of being able to influence/detect the action of a neuron, which is relatively huge compared to the synapse. The receptor is even tinier - in the range of protein sizes, apparently in the range of 10 nanometers or less, which happens to be the same size range of the synapse itself. It's obvious that the "pictures" we see of synapses are little more than cartoons: the work of conceptual artists and theorists. It is even possible that what is going on at the synapse will best be characterized as an "electron cloud", in the way we visualize the wave function around a molecule. That would be exactly what I'm aiming at here. It may not be possible to "visualize" the synapse in any better way than visualizing how the S-function varies several times per second. I believe I have seen exactly this approach somewhere in the discussion of internal chemistry in the neuron, although, if memory serves, the derivation was classical rather than quantum.
A re-read of "Foundational Concepts" should allow me to put some more precise numbers into this model. He doesn't shy away from making chemistry visualizable.
My contention that quantum effects are active at the scale of synapses is hardly controversial. For example:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5454345/
- https://www.amazon.ca/Quantum-Effects-Biology-Masoud-Mohseni-ebook/dp/B00J8LQMV8/ref=sr_1_1?ie=UTF8&qid=1515004478&sr=8-1&keywords=Quantum+Effects+in+Biology
- https://phys.org/news/2015-07-quantum-physics-startling-insights-biological.html
Study of quantum effects in biological systems now seems to attract enough respectable scientific papers to qualify as a "field", although it's not for sissies. Bottom line: my "S-function" is not wild speculation but, like most quantum wave functions, unobservable and beyond any practical means of calculation.
It is important to emphasize that my introduction of quantum mechanics into this discussion is not equivalent to the hand-waving we see from philosophers who attempt to equate the mystery of consciousness with the mystery (and paradox) in quantum mechanics*. In fact, since 1927, there really hasn't been a mystery or paradox in quantum mechanics - just the struggle of an older generation who expect to "visualize" the process. The current generation of working scientists seems to be totally comfortable with the "paradoxes" of quantum mechanics that still sell a lot of books to the general public. My entire argument could, in principle, be built upon the basis of classical mechanics. The first reference (above) provides the relevant equations for the rate of chemical reactions and an argument that quantum rules lead to the classical rules at "classical" scales. But the "classical" rules do not lead to deterministic behavior of the synapse. They lead to a set of non-linear equations, as discussed elsewhere. I'm not trying to "explain" mental phenomena by invoking quantum mechanics. I'm simply using quantum mechanics because they are the appropriate description of physics at the scale of the synapse.
Bottom line: consciousness is still mysterious, although somehow a bit less mysterious than it was when we thought of the brain as a machine (Descarte's Error). Actual brain behavior gives many hints about the felt reality of consciousness - especially the phenomenon of "re-experiencing", "learning", "feedback", and the integration of sensory data into "perception". It might almost be said that your consciousness is no longer a mystery. I'm still amazed at mine.
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*In fact, such "hand waving" is equivalent to the "hand waving" we see when a chapter on computer principles is inserted in a book on consciousness. The connection is totally in the mind of the author and never justified by actual facts about brain function. A good example is Dennett's "Consciousness Explained".
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