Copyright 1996-2000 by Donald R. Tveter, don@dontveter.com, commercial use is prohibited. This material cannot be quoted at length or posted elsewhere on the net or included in CD ROM collections. Short quotations are permitted provided proper attribution is given. But better yet, since I'm hardly an expert on the subject, don't quote me.
For a long time scientists have ASSUMED that human thought is being produced by the neurons in the brain and that these neurons also somehow store memories as well. This has never been proven but it has become THE TRUTH anyway because there were no other known structures in the brain where computing and memory storage could possibly take place. Also quite often some expert will tell you how many bits of information the brain can store, this despite the fact that no one knows how information is stored in the brain.
Also for a long time the only alternative to the brain as a neurocomputer has been the idea that there is a human soul where thinking is done and where memories are stored but since the materialists ABSOLUTELY HATE this idea it was declared to be "unscientific". However with the arrival of quantum mechanics came the idea that quantum mechanical waves and fields actually are the spiritual portion of the universe that religions have always talked about. This idea is supposed to go back at least as far as Sir James Jeans in 1929. If this is the case then Science has already been studying spirit we just don't know that yet. Materialists HATE this idea as well. (Test question: why would they hate it anyway? True, quantum mechanical waves and fields are not matter but if they're real physical stuff of some sort and not just a mathematical construction, what's the harm?)
With the only other alternative to explain thinking being that a human soul or spirit is involved the neuron as a switch theory did not have any competition and so it became THE TRUTH. But a new candidate has appeared on the scene: the cytoskeleton. It is a collection of hollow fibers (microtubules) made out of a protein called tubulin. Until recently the only known use for the cytoskeleton was as a skeleton that maintains the shape of a cell and in some cases the tubes extend beyond the cell and are the cilia used for instance in paramecia to enable them to swim around. The microtubules consist of molecules of tubulin that can be in two different states depending on the presence or absence of an electron, a nice digital system. Microtubules are even designed around a well-known digital error correcting code. The microtubules may also support optical computing. For a good description of microtubules (as a .tex or .ps file) see the article by Dimitri Nanopoulos. For html articles (with pictures) see the articles Orchestrated Objective Reduction of Quantum Coherence in Brain Microtubules: The "Orch OR" Model for Consciousness and Conscious Events as Orchestrated Space-Time Selections by Roger Penrose and Stuart Hameroff.
Some evidence for information processing by the microtubules comes from studies of paramecia which seem to show that they can learn:
For example, a number of studies have observed paramecia swimming and escaping from capillary tubes in which they could turn around. In general, results showed that with practice the ciliates took successively less and less time to escape, indicative of a learning mechanism ( French, 1940; Applewhite and Gardner, 1973; Fukui and Asai, 1976). Many other experiments suggest paramecia can learn to swim in patterns and through mazes and have a short-term memory, although some of these behaviors depend on their environment ( Applewhite, 1979;). [Hameroff et. al. 1993]
If neurons are responsible for learning in multi-celled animals it is hard to explain how a one-celled animal with NO neurons can learn. The theory is that the cytoskeleton is the nervous system of the paramecium and the cytoskeleton is a miniature computer. The gist of the article quoted above is to explore ways of doing computing using microtubules without considering quantum mechanical effects. The authors of that article also estimate that a paramecium (or a neuron or some other cell) could move around bits at the rate of 10^13 bits per second. Thus every cell with microtubules (this is almost all cells) may contain a computer. A human brain counting only the use of 10^11 neurons and allowing for some redundancy would move around 10^23 bits per second according to this article. Another estimate I've seen is 10^28 bits per second. In either case this is rather a lot more than a digital computer can manage at this time and if this is what is going on then it will be a while before digital computers can compete with the brain. (There is an online article by Joel Henkel where he speculates how quantum effects could account for learning in paramecia, again more than I can follow but for the sake of people who may be interested I think I should list it.)
But its also being proposed that the microtubules in each cell could be used for quantum computing. Quantum computing is more sophisticated and much faster than digital computing because each bit in a quantum computer (a q-bit) can simultaneously take on a large number of values (quantum superpositions). If the brain uses quantum computing then there is enormously more computing power in the brain than anyone has suspected and this will make producing a conventional digital computer equivalent in power to the human mind a really difficult problem, more than likely the development of real artificial intelligence will then require the development of quantum computers.
There are a number of proposals on how quantum mechanics would enter into thinking using the microtubules. Physicist Roger Penrose proposes that some effect of quantum gravity would cause the collapse of the wave function describing the states of the electrons in the microtubules and that this collapse produces a conscious thought. (See the Penrose book, Shadows of the Mind and/or the Stuart Hameroff Website) Physicist Dimitri Nanopoulos and his associates have already proposed a theory of quantum gravity that produces such a collapse. The Nanopoulos article can be found online..
Both the above ideas depend on an interpretation of quantum mechanics known as the Copenhagen or Bohr interpretation. Most physicists tend to accept this interpretation but because it contains such confusing results other physicists have looked for other interpretations that make more sense. One of these interpretations comes from physicist David Bohm. In his formulation he splits the Schroedinger wave equation into two parts, one part describes definite classical-like particles located at definite locations in space while the other part results in a quantum force that moves the particles around. There is an online article by Bohm on this theory and how he speculates it may relate to the study of mind. There is also a reasonably good book by Bohm called Wholeness and the Implicate Order.
Just recently physicist Jack Sarfatti has been proposing a new version of the Bohm interpretation where the particle acts back on its wavefuntion (something that does not happen in the current dominant theories of quantum mechanics). In this theory its the back action that generates consciousness. Jack has an online paper on this idea. He also has a number of websites that address this and other cutting edge ideas in modern physics, a couple of which are:
Thus there are lots possibilities to choose from at the moment.
Besides quantum computing there are theories by Vitiello (Vitiello1, Vitiello3, Vitiello4) and Nanopoulos and others concerning ways to store memories in quantum mechanical systems. The Vitiello model is said to be able to store an unlimited number of memories in the sense that a new memory can always be added without damaging any of the old ones.
Of course if much of what goes on the human mind is handled at the level of QM a certain amount of processing and some memory functions would still be handled at the level of neurons.
Another line of argument for the brain as a quantum computer comes from the idea that consciousness and related human abilities need to be explained. First note that there are at least three significant schools of thought on the subject of consciousness. First, quite often AI researchers use the following chain of reasoning: The brain is in effect some kind of digital computer and therefore if the brain is thinking then the digital computer is thinking. Likewise if the brain is intelligent the digital computer must then be intelligent. And if the brain experiences consciousness then computers can too, a position that reduces consciousness down to, well, nothing but an illusion of some kind. Let me document this with a quote from a page by Anne Foerst, the Theological adviser to the Cog project at MIT. The page title is: ``Cog'', A Humanoid Robot and the Question of Imago Dei The context is that Dr. Foerst is arguing against the idea that there are things that computers cannot do (see the book by Stuart and Hubert Dreyfus, What Computers Can't Do: The Limits of Artificial Intelligence) and here she talks about consciousness:
The Cog builders' argument against this type of attack is twofold. First, they argue that phenomena like consciousness are an illusion; consciousness for instance arises because our brain is complex enough to abstract and categorize certain processes and analyze them [10, p.12] and emotions arise from chemical reactions in the body and their reflections and responses in the brain [12, pp.127]. Using this materialistic approach towards all complex phenomena which seem to be exclusive for humans, they can, secondly, argue that Cog is built accordingly to all these materialistic findings; as Cog becomes increasingly complex it might develop the same complexity and, hence, develop the same illusions.
I have to say this: people in the Cog project and other AI researchers HAVE to promote the idea that consciousness is an illusion that will somehow appear in a computer because if consciousness is an honest physical phenomenon and it is necessary for human-level AI then their digital computers won't be able to reach human-level abilities and that's a good reason to cut off their funding.
A second important view of consciousness is that there is something about the biochemisty of life that makes consciousness possible so digital computers cannot manage it. Consciousness would be some kind of physical process of some sort, a process that can be stopped by a blow to the head or the use of certain drugs and gases. In this view either molecules in the brain are moving around in a coordinated way, or electrons are moving around in a coordinated way (as in super-conductivity) or photons are moving in a coordinated way (as in a laser). There is some reason to think that the electrons moving around in the microtubules are involved in consciousness because anesthetics inhibit the movement of these electrons and as they do people lose consciousness.
The third major view of consciousness is that it still some physical process but one that involves quantum mechanical waves and fields. In recent times Roger Penrose created the debate over what a quantum brain could do vs. what a digital computer can do in his book, The Emperor's New Mind. Penrose believes that quantum effects are necessary for consciousness and consciousness is necessary to produce human-levels of intelligence.
Another feature of the human mind that has to be explained (if you're willing to grant that these phenomena exist!) is mind-reading and predicting the future. In the materialist interpretation of reality these things can't happen so they don't and anyone who says they do is nuts. But the reports of such things are persistent among the general population and among scientists who are looking for such phenomenon even though such things don't occur very consistently. In quantum mechanics it appears that small particles like light and electrons do base their movements on conditions that exist in the future so in this sense they "know" the future. Since this happens it easy to speculate that mind-reading and predicting the future can also happen using quantum mechanical principles. (More on this in another section someday. It appears to me that psychic phenomenon cannot happen in any sort of reliable fashion because it produces inconsistencies that the universe cannot tolerate.)
Physicist Guiseppe Vitiello has a short article prepared for the Tucson II conference on consciousness that argues that Quantum Mechanics (or as he says really Quantum Field Theory) is relevant to the study of consciousness.