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Penrose & Hameroff 6Penrose-Hameroff: 6 Contains further articles related to Penrose/Hammeroff quantum consciousness theory 1.) Experimental tests of quantum effects in cytoskeletal protein - Mershin 2.) Recurrent quantum neural network - Behera 3.) Microtubules as a quantum Hopfield network - Behrman 4.) Refutation of Penrose' Godelian Case - Bringsjord & Xiao 5.) Beyond the doubting of the shadow - Roger Penrose 6.) Quantum computing in microtubules - Stuart Hameroff 7.) Funda-Mentality: Is the conscious mind linked to a basic level of the universe - Stuart Hameroff 8.) Quantum consciousness: Reply to Speir & Thomas Towards experimental tests of quantum effects in cytoskeletal proteins A. Mershin et al Centre for biomedical engineering, MIT In: Tuszynski, J. Ed. The Emerging Physics of Consciousness Springer ISBN-13 978-3-540-23890-4 The article starts by emphasising the need for more experimental work on biological tissue. The author mentions experiments by Nancy Woolf on the dendritic expression of MAP2 (1. Woolf) and on learning and memory in fruit flies by Mershin's own group. This is experimentation on the cell down to the scale of individual proteins, which can produce results that are consistent with the existence of quantum coherence. Mershin is now mainly interested in experimentation at the atomic scale. He claims that it is slowly being recognised that quantum mechanics (QM) has a role to play in protein functions such as enzyme actions (2. Ball & Ritz). The paper looks in particular at information based processing in protein, with an emphasis on cytoskeletal proteins and especially the tubulin subunits of the microtubules. Mershin has worked on testing the suggestion that microtubules are not just structural but are also involved in neural information processing. His first test was the effect on memory of a minimal disruption of the microtubule network. It was shown that olfactory memory in fruit flies suffered when microtubules (MTs) and microtubule associated proteins (MAPs) were disturbed. This was taken to suggest a role in memory and probably also in information processing (3.Mershin). The next step was to test whether microtubule proteins were processing 'bits' either at the classical or quantum level. The tests showed a high dipole moment in the tubulins that make up the MTs, which was relevant because MT processing theories often involve dipoles. The geometry of the microtubule, with a 13 protofilament assymetrical lattice has been suggested as a possible basis for quantum error correction (4. Koruga). These experiments are said to have opened up further experimental possibilities, including a test for quantum coherence and entanglement in biological tissue. Tubulin is a common protein in all eukaryotic cells, mainly concentrated in the cytoskeleton and especially common in the brain. MTs constitute a major part of the cytoskeleton . MTs are comprised of tubulin dimers. The structure of MTs has been extensively studied. The amount of energy needed for a change in the conformation of tubulin protein is 200x greater than that needed for a silicon switch in a computer and 30x greater than thermal noise at room temperature. This would allow the tubulins to act as information processors. Preliminary experiments to measure the electric field round MTs suggests that they could be ferroelectric, thus allowing abrupt orientations of the dipoles (5. Jelinek). The possibility of energy-loss- free transport along microtubules has been theoretically demonstrated (6. Mavramotos). Models for excitation in MTs all depend on the dipole moment of tubulin and its ability to flip while in the polymerised state. Such flips are the basis of predictions of quantum superposition and entanglement in MTs. It is suggested that Mershin's group could be close to doing an experiment to test for quantum coherence and entanglement involving biomolecules. Mershin discusses the question of quantum decoherence at brain temperatures. He mentions that instances of quantum coherence at room temperature have been demonstrated. In a recent experiment a macroscopic quantity of cesium gas remained entangled for 0.5ms despite contact between the gas and the environment. The reason for the relatively long decoherence period was the large amount of spins (7. Julsgard). Ferroelectricity is basic to the QM activity proposed by this model. The ordering of the tubulin dimers' electrical dipoles will be due to interaction with the dipoles of water molecules in the hollow core of the microtubules. It is argued that this interaction is substantially protected from the environment. If there is isolation, the region of the MT between the inner wall of the dimer and the water at the centre of the hollow core of the MT can be treated as a site for the electromagnetic or QED cavities. These isolated regions inside the microtubule form the basis for quantum coherence in this model, as opposed to the wave guide system proposed by Hameroff. QED cavities are well known for being able to sustain coherent electromagnetic radiation in their interior. The interaction of the cavities with the inner dimer walls leads to the development of coherent dimer states along the MTs. The interior of the microtubule seems to contain ordered water, which makes the existence of the electric dipole moment likely. It has been suggested that each of the protein dimers has a hydrophobic pocket. The electrons in these pockets are suggested to have two possible conformations. The electric dipole moment for the tubulin molecule has been determined, and this is now seen as an important area for study. Mershin's calculations suggest that quantum mechanical events may be responsible for superefficient energy and signal transfer. It is suggested that the interaction between water dipoles and quantised radiation plays the role of cavity modes that produce quantum coherent solitons across the MT network. The calculated decoherence time for this system is greater than the time required for energy transport across the system. Mershin is highly critical of Tegmark's oft quoted attack on quantum consciousness. Mershin's criticism of Tegmark's paper is that he does not allow for possible isolation from the environment within the MTs. This paper also discusses the function of ordered water in biological systems. Recent studies indicate that the transfer of energy in liquid water is quicker than expected (8. Woutensen). This might be due the presence of kink solitons. In biological tissue, this might be suited to loss free energy transfer between biomolecules or along biological structures, such as MTs that are covered with water both inside and in the central cavity. It is predicted that hydrophobic areas would retain excited states longer than the hydrophilic areas, and that this would help to isolate electrons within the hydrophobic pockets. Given the appropriate environmental isolation in parts of the system, it is seen as theoretically possible for there to be quantum coherence of tubulin dimers on MTs on a macroscopic scale and over a sufficiently long timescale for dissipationless energy and signal rtansfer to occur. The paper discusses recent experiments involving quantum entanglement at room temperatures. Error correction allowes for redundancy, because each qbit corresponds to a large number of particles that allow for coherence, despite contact with the environment. It is thought not impossible that similar circumstances could arise in biological systems. Mershin moves on to discuss the implications if coherence and entanglement exist in biological systems. It is pointed out that such systems might be adaptive for organisms. Quantum coherence could facilitate rapid choice for a range of similar states. Mershin discusses the possibility of quantum teleportation in biological tissue, a hypothesis that even the much derided original Penrose/Hameroff model seemed to have avoided. Quantum teleportation is a non-local correlation that occurs without any transfer of mass, energy or conventional information. Possible 'teleportation' is suggested to involve three microtubules. Microtubule A could send its state to microtubule C, if they were both entangled with microtubule B. Microtubule A, described as the sender molecule, makes a measurement, which in real life might involve binding with a MAP and the state of microtubule A is then 'teleported' to microtubule C, which is described as the receiver microtubule. No energy, mass or information has been transferred but the quantum states of one microtubule have been transferred to the other. From here, Mershin goes back to discussing less exotic possibilities. It is claimed that the existence of quantum coherent states along the microtubules suggest the possibility that the MTs can act as logic gates. This could arise at a type of node of three MTs connected by MAPs. The quantum states make the interaction probabalistic. The outcome is influenced by the geometry of the MTs. Changes in the lengths of the MTs and the binding sites of the MAPs can alter the probabilities of the outcome. In this model, called the 'guitar string' model, it is suggested that four MAPs could 'clamp' six MTs at different nodes. A small set of MTs with a small number of binding sites could produce a large web of processing. Objections to the possibility of quantum coherence, are claimed by the authors, to be most often based on the assumption of equilibrium in biological systems. But tubulin, for instance, is not an equilibrium system but a dissipative system where energy is constantly being pumped in and out. Mershin's group's own calculations suggests that tubulin could sustain quantum coherence for timespans in the order of microseconds. In addition, in a tubulin molecule with 17,000 atoms, the electric dipole moment state may depend on only a handful of electrons. Unpaired electrons in the dimers could couple to water molecule dipoles in the interior of the microtubule. Detection of such coupling would demonstrate the existence of quantum modes in the ordered water of the MT. The article proposes equipment and experiments that could test for such quantum properties in biological tissue. References:- 1) Woolf, Nancy et al (1994) Neuroreport, 5, pp. 1045-48 + Woolf, Nancy et al (1999) Brain Research, 821 (1) pp. 241-9 2) Ball, P. (2004) Nature, 431 + Ritz, T. et al (2002) Chem. Phys. Chem., 3 pp. 243-248 3) Mershin, A. et al (2004) Learning and Memory, 11 (2) pp. 277-287 + Mershin, A. et al (2004) Biosystems, 77, pp. 73-85 + Mershin, A.et al (1999) Proceedings of the Academy of Athens, 74, pp. 123-173 4) Koruga, D. (1985) Ann. New York Academy of Science, 466, pp. 953-957 5) Jelinek, F. et al (1999) Bioelectrochemistry and Bioenergetics, 48, pp. 261-266 7) Julsgaard et al (2001) Nature, 413, pp. 400-212 6) Mavratmos, N., Mershin, A. & Nanopoulos, D. (2002) International Journal of Modern Physics B, 16 (24) pp. 3623-3642 + Mavratmos, N. & Nanopoulos, D. (1998) International Journal of Modern Physics B, B12, pp. 517-527 + Mavratmos, N. (1999) Bioelectrochemistry and Bioenergetics, 48, pp. 120-128 8) Wouternsen, H. (1999) Nature, 402, pp. 507-510 Hameroff, S. (1974) American Journal of Clinical Medecine, 2, pp. 163-173 Hameroff, S. (1998) Toxicology Letters, pp. 100-101, pp. 31-39 Harcoche, S. (1994) Cavity Quantum Electrodynamics Academic Press Luduena, R. (1998) International Review of Cytology, 178, pp. 207-275 Satiric, M., Tuszynski, J. & Zakula, B. (1993) Physical Review E, 48 (1) pp. 589-97 Satiric, M., Zekovic, S., Tuszynski, J. & Pokorny, J. (1998) Physical Review E, 58, pp. 6333-6340 Tegmark, M. (2000) Physics Review E, 61, pp. 4194-42000 Zhang, S. (2003) Nature Biotechnology, 21 (10) pp. 1171-1178 Recurrent Quantum Neural Network & its Applications Laxmidhar Behera, Indrani Kar & Avshalom Elitzur Indian Institute of Technology, & Bar-Ilan Institute, Israel In: Tuszynski, J. Ed. The Emerging Physics of Consciousness Springer ISBN-13 978-3-540-23890-4 This chapter sidesteps the whole question of whether quantum activity exists in the brain, and goes straight to discussing the need for some sort of quantum effect to explain some of the things that the brain is able to do, particularly the saccade movements of the eyes. The model proposed here suggests that there is a quantum process that effects the average behaviour of a neural lattice. The authors remind us that some of the tasks humans perform with ease, such as more difficult forms of pattern recognition are still beyond the capacity of super computers. The authors look for a quantum mechanical explanation of the abilities of orgnisms in this respect, and the chapter discusses human eye movement from this respect. Simulations of brains produce some interesting insights in this respect. When the eye tracks a target, a related wave packet moves not in a continous classical manner but in a discrete quantum manner, which is considered similar to the 'jumps' and 'rests' involved in saccidic eye movement. Eye movements relative to static scenes are not continous but involve discrete 'jumps'. If the information is new or difficult to interpret there are more erratic pauses and even a process of flip back and forth between different images. This again is similar to the movement of quantum wave packets in simulations. Eye tracking experiments show that smooth eye movements contain errors, which are corrected by saccades that bring the eye back to the required position. After one or two quick saccades the eye usually becomes adjusted to the target. Saccadic and smooth movements are seen to combine to keep track of the visual target. The authors suggests a view of neural information processing where quantum processing effects a neural lattice with spatial structure. This is known as a Recurrent Quantum Neural Network model or (RQNN). This is distinct from other models. This quantum based model is said to be very succesful in explaining the actual nature of eye movements, and to be 1,000x more accurate than conventional models. The authors hope that their work will encourage researchers to study the brain from a quantum perspective. Microtubules are mentioned as the most plausible location for quantum activity in the brain, with electrons inside hydrophobic pockets localised towards either to the A or B end of the tubulin dimer and capable of being in a superposition of these states. Apart from this, the authors simply describe their model as idealised, and decide to remain silent on the question of the actual physical structure of quantum information processing or the problem of decoherence. References:- Behera, L. & Sundaram, B. (2004) Proceedings, International Conference on Intelligent sensors Behera, L. et al (1996) IEE Trans Neural Networks, 7 (6) pp. 1401-1414 Behera, L. et al (1998) IEE Proceedings Control Theory and Applications, 145 (2) pp. 134-40 Behrman, E. et al (2002) Physical Review Letters Behrman, E. et al (2000) Information Sciences, 128, (3-4) pp. 257-69 Davydov, A. (1982) Biology and Quantum Mechanics Pergamon Press Gupta, S. & Zia, R. (2001) Journal of Computer and System Sciences, 63 (3) pp. 355-383 Hagan, S., Hameroff, S. & Tuszynski, J. (2002) Physical Review E, 65, pp. 061901 Atmanspacher, H. (2004) Discrete Dynamics, 8, pp. 51-73 Mershin, A., Nanapoulos, D. & Skoulakis, E. (1999) Proceedings of the Academy of Athens, 74, pp. 148-79 Tuszynski, J., Hamerof, S., Sataric, M. et al (1995) Journal of Theoretical Biology, 174, pp. 371-380 Microtubules as a Quantum Hopfield Network Elizabeth Behrman, K. Gaddam, J. Steck & S. Skinner Wichita University In: Tuszynski, J. Ed. The Emerging Physics of Consciousness Springer ISBN-13 978-3-540-23890-4 Behrman's group set out to examine the Penrose/Hameroff model from a mathematical point of view. The concept is modelled as a quantum Hopfield network (QHN) with tubulin as qbits. The whole question of decoherence and exact physical structure is sidestepped, with a general assumption that the system is screened from the environment. The group looked for stable states in the form of local minima. It is acknowledged that the algorithmic approach of existing computers runs up against capacity problems with tasks such as pattern recognition or problems with many possible solutions, such as the travelling salesman problem ( 1. Haykin ). It is suggested that a neural type computer might construct its own algorithms, since these have proved difficult to write for quantum computers, and might also be suitable for quantum error correction ( 2. Allaudin, Behrman, Chuang ). Hopfield demonstrated that his network could implement associative memory, and even solve problems such as the travelling salesman problem. After repeated updating such a network might reach a stable point. With neurons this would mean that at this point all neurons remained in their existing state once they had examined the input, and the output would constitute the memory recall. The authors have simulated a quantum neural network with the same structure as a microtubule (MTs). The model is very simplified, with the microtubule represented as a two-state system. The network of qbits evolve towards a local minima and store information. MTs have the most versatile structure of any of the various components of the cytoskeleton. They determine cell shape and movement, transport vesicles and organelles, such as mitochondria and chromosomes. In terms of length, MTs can extend to macroscopic length, and are composed of small double molecules or dimers, made of the protein, tubulin. These dimers are arranged in a skewed hexagonal lattice, and each tubulin is in contact with six neighbours. The dimers are 8 nm long, and each monomer is 4 nm long. The dimers are comprised of alpha and beta tubulin molecules, with the negative charge concentrated on the alpha tubulin, which creates an orientated dipole in the dimer. The MT is an assembly of orientated dipoles. Other couplings result giving piezoelectric properties that may be important for MT signalling and assembly/disassembly. The network is enormously expanded in relation to the number of particles in superposition. Information propagates from one qbit to another and the output is the lowest energy state of the qbit. During processing the polarisation at one end of the MT can be translated to another at the other end. With both input and output as a superposition the MT is acting as a quantum computer. Looking forward, the authors say that new work is in process that would involve calculations relevant to quantum entanglement. References:- 1) Haykin, S (1999) Neural Networks: A Comprehensive Foundation Prentice Hall 2) Allaudin, R. et al (2002) International Joint Conference on Neural Networks, 3 pp. 2732-7 + Behrman, E. et al (2000) Information Sciences, 128, pp. 257-69 + Chuang, I. (2005) Bulletin of the American Physical Society Allaudin, R. et al (2005) IEEE Transactions on Neural Networks Behrman, E. et al (1983) Journal of Chemical Physics, 79, pp. 6277-81 Hagan, S., Hameroff, S. & Tuszynski, J. (2002) Physical Review E, 65 Hopfield, J. (1982) Proceedings of the National Academy of Sciences USA, 79, pp. 2554-8 Hameroff, S. & Penrose, R. (1996) Mathematics and Computers in Simulation, 40, pp. 453-80 Shor, P. (1997) SIAM Journal of Computing, 26, pp. 1484-1509 Tuszynski, J, Hameroff, S. & Hurylak, P. (1998) Philosophical Transactions of the Royal Society of London A, pp. 1897-1926 A refutation of Penrose's Godelian case against artificial intelligence Selmer Bringsjord & Hong Xiao Dept. of Philosophy & Cognitive Science Dept. of Computer Science Rensselaer Polytechnic Institute February 2000 This paper is sometimes glibly quoted as a complete refutation of the arguments relative to the Godel theorem and the brain, but in reality the opinions of the authors are much more mixed. The authors emphasise the distinction between 'Strong Artificial Intelligence' (AI) and 'Weak Artificial Intelligence.' The former claims that the sensation of subjective consciousness could be created by some appropriate computation on a manmade computer. The latter only claims that computers can potentially simulate all the functions of the human mind but would not become conscious in the process. Penrose has adopted a third position, proposing that Godel's theorem means that computers cannot perform some of the functions of the brain, such as those involved in mathematical understanding, and by extension it would also appear that they cannot produce consciousness. The first named author of this paper, Selmer Bringjord, takes the intermediate position of opposing strong AI, but accepting weak AI. He has published 13 formal arguments against strong AI. However, he accepts the weak AI position, and claims to expose fallacies in Penrose's reasoning relative to weak AI, as outlined in 'Shadows of the Mind' and subsequent discussions in Psyche. This involves complex and technical logical processes, which can be accessed at www.citeseer.ist.psu.edu/320350. Bringjord, at the same time argues that when proponents of strong AI, such as Laforte, Hayes and Ford (LaForte et al 1998) have attacked the Godelian case against strong AI, they have fallen into exactly the same fallacies as Penrose. Bringsjord also critical of Penrose's scholarship relative to strong AI, but does not think that this represents any refutation of his or Bringjord's position on strong AI. Bringsjord believes that it is possible to derive the denial of strong AI from Godelian facts. At the same time, he thinks that his own paper 'Argument from Infinitary Reasoning' (Bringsjord 1997b) captures Penrose's core intuitions better than any appeal to Godel. Because Penrose is a mathematician, he has argued outwards from concepts of mathematical understanding and truth, while consciousness as such has followed from this. The emphasis on mathematical understanding requires a refutation of weak AI. However, a non-computational basis for consciousness and the qualia only requires a refutation of strong AI. Beyond the doubting of a shadow Roger Penrose Psyche A reply to commentaries on on 'Shadows of the Mind' published in Psyche This article covers Penrose’s replies to various attacks on his second consciousness book, ‘Shadows of the Mind’ in the interdisciplinary journal ‘Psyche.’ Penrose points out the apparent implausibility of the suggested ways of getting round the implications of Gödel’s theorem, such as an unknowable algorithm, or unsound mathematical reasoning. He remarks on the ‘almost religious fervour’ and often abusive manner of many of the supporters of the computationalist view, and on the fact that even more moderate commentators tend to assume, what they are supposed to be proving, that computationalism has to be right, and that the Gödelian argument cannot be serious. This should not surprise. It is not necessary to read very much scientific literature or discussion forum material related to consciousness, to get the picture of a whole body of opinion that has an essentially metaphysical stance rooted in the obsolete assumptions of 19th century physics. Patricia Churchland’s approach in her criticism of Penrose is interesting in this respect. She remarks that a majority of logicians reject Penrose’s view and appears to consider this a conclusive argument against the Gödelian case, apparently removing the necessity to present any actual argument. But on closer examination, a lot of this majority view comprises a fixed metaphysical stance rather than a reasoned argument. Penrose says that most the Psyche commentator’s criticisms have been directed at the Gödelian aspect of ‘Shadows in the Mind’, rather than the discussion relative to objective reduction of the wave function or the possible instantiation of quantum coherent processes in the brain. Some critics appear to argue that there is no need to discuss these other aspects, because they have disproved the Gödelian case. Penrose, however, says that the arguments from physics and biology could stand up even without Gödel. This appears to be reasonable. The fact that mathematical understanding was computationally based would still leave us looking for a description of consciousness, which might still be non-computational or in some way linked to fundamental physics. A non-mathematician might well have approached the whole thing differently, avoiding the fraught issue of mathematical reasoning, and going straight to the problem of deriving consciousness from matter. Similarly the arguments about the microtubules relate only to biological factors, and are not at all linked to Gödel. Penrose first discusses the arguments of David Chalmers, the only one of his Psyche critics for whom he seems to have much patience. Chalmers argued that it was contradictory ‘to know that we are sound’ with reference here to mathematical understanding, but Penrose takes the view that the whole point of mathematical procedures is that they instil a belief in their proof procedures and their soundness. A good part of the discussion about the Gödel theorem and its consequences is taken up with arguments about mathematicians who make errors, that is situations where mathematical understanding is not apparently sound. Penrose’s argument is that he is thinking in terms of either an idealisation or at least the development of human mathematical understanding over the medium to longer term. He is concerned with what mathematicians are able to perceive in principle by methods of mathematical proof, while short term errors of understanding are seen as correctable, and given time mathematical arguments usually become correct. Some of the critics point to longer term errors of understanding such as Kempe’s attempt to prove the four-colour theorem and Frege’s inconsistent formal set theory, but Penrose views these as correctable errors. Penrose is particularly critical of one commentator, Drew McDermott in this respect. McDermott claimed ‘to have torn Penrose’s arguments to shreds’, but Penrose remarks that McDermott went of at a tangent, and did not actually discuss the arguments given in ‘Shadows of the Mind.’ McDermott is seen to have a problem with the concept that guaranteeable mathematical assertions may not be computable, but Penrose asserts that this is the way mathematics works. David Chalmers, to a limited extent, appears to agree with Penrose in the view that mathematicians have an underlying sound competence, even if it sometimes goes astray. Penrose claims that many of the Psyche critics twist the argument away from his claim that the principles underlying proof procedures that are common to mathematicians might be accessible to the common understanding of the mathematical community, and towards a spurious claim that an individual mathematician has his/her own algorithm. Hans Moravec’s arguments are derided as being a travesty in this respect. Penrose also counters claims that the slightest flaw in any part of the Gödelian section of ‘Shadows of the Mind’ would demolish the argument, by saying that there is not one but several separate lines of argument. Penrose expresses surprise at the manner in which attacks on the Gödelian argument seem to degenerate into attacks on mathematics itself, or at least on the idealised mathematical reasoning which is the basis of mathematics and also of science that is expressed in mathematical terms. Tim Maudlin suggested that the Gödelian argument was false because the output of a human being was finite, and therefore in principle a finite computer could simulate a person’s action. Penrose claims that this would invalidate the principle of deduction from observation. Thus the solar system is finite, and its data could form the output of a computer, but without providing any of the theories by which we understand the solar system. He also points out that it is not sufficient to have a computer with pre-designed or ‘canned’ answers, because there is a complexity explosion in the number of answers that may be needed. In any cases, canned answers are said not to work in the case of the P sentences, which are sentences stating whether or not a programme halts. The trouble with a computer with such canned answers for P sentences is that according to Penrose they derive from something non-computable in the mind of the original programmer. In answer to the question of how one would tell whether something was non-computable or not, Penrose says that this has to derive from experiment and observation. Experiments that relate to Newtonian physics reveal a deterministic structure, but this is not the case in areas of quantum physics, and a future theory that merges quantum and relativity theory may be based on experiments that reveal non-computability. Some critics have reasonably argued that the explanatory power of a quantum theory of consciousness will be no better than classical theories of consciousness. It is not clear how consciousness arises from neurons or protein etc., but it could equally well be said that it is not clear how it would arise from atoms, electrons etc, both neurons and atoms being physical objects that give in themselves no particular indication of being conscious. Penrose says that this is not his proposition, but rather that non-computability arises from the new physics that he proposes. Some critics, such as Bernard Baar, object to the idea of a major change in physics as being unnecessary, but it is fair to say that this reveals a lack of awareness of the problems in physics, particularly the incompatibility between quantum and relativity theory. Baars, Stanley Klein and Tim Maudlin are also both criticised for failing to grasp what is intended in the discussion of the objective reduction of the wave function. Penrose says that he has concentrated on the issue of ‘understanding’, but feels that non-computable processes must also be essential for other aspects of conscious mentality. Consciousness is viewed as having an active and a passive side. Freewill relates to the active side, although Penrose is neutral as to whether true free will exists. The passive side relates to awareness and particularly the qualia. Anything that shed light on ‘understanding’ is also felt to shed light on qualia. Critics have raised the issue of whether there are things that humans can in principle do better than robots. Penrose says that this applies to anything that requires understanding. He refers to a series of chess problems that were devised to be either easy for humans and hard for computers, or the other way round. The deciding factor was whether or not they required understanding of the objective of the game. This test showed an almost complete separation between human and computer aptitudes. Penrose remarks that Daniel Dennett seems to have tried to claim that Penrose is saying that human abilities did not arise by evolution. Penrose says that he has no reason to say this if, as Penrose claims, non-computability is present in the natural world. Only a small part of the Psyche discussions are related to biology, but Penrose does deal with one supposed refutation advanced by Grush and Churchland and also by Edelman to the effect that the drug, colchicine, used for the treatment of gout, depolymerises microtubules, but does not effect consciousness. It is pointed out that the blood-brain barrier does not allow significant amounts of the drug to enter the brain. It is true that consciousness remains even when colchicine is administered directly to the brain, but this is because the neural microtubules are much more stable than those in the rest of the body and do not undergo a polymerisation cycle in the same way. Quantum computing in microtubules - An inta-neural correlate of consciousness? Stuart Hameroff Dept. of Anesthiology & Psychology University of Arizona One popular model for a neural correlate of consciousness involves thalamo-cortical feedback loops with connections to the hippocampus. These neurons are suggested to oscillate synchronously in the 30-70Hz range, known popularly as the 40Hz or gamma synchrony oscillation. The paper continues by pointing out various puzzling features of consciousness, notably the binding of perceptions into a unitary sense of consciousness, the sensation of having free will, the experience of the flow of time, qualia or subjective experience. The paper notes that the philosopher, David Chalmers, claims that conscious experience does not appear to be necessary to the functioning of organisms. It also discusses the reductive/functionalist views of consciousness prevalent in mainstream neuroscience and philosophy. Hameroff accepts that the brain performs computation, but suggests that this may not be the whole of the story. In the mainstream theories, consciousness is often proposed to emerge at a critical level of complexity, but there is not even speculation as to when this level is reached, or why a particular level should prove critical. Hameroff considers that the standard neuron and neuronal synapse model of the brain is too simple, because it does not allow for processing that may occur within the neuron. He points to increasing evidence that microtubules and other components of the cytoskeleton convey signals and process information. The ability of single cell organisms to navigate is taken as evidence for information processing within cells. Hameroff argues that the whole concept of the brain as computer rather begs the question of what type of computer is involved. It is considered possible that present day classical computers are an early stage of technology that may be superseded by quantum computers, and that it is quantum rather than classical computing that drives information processing in the brain. Hameroff considers that the mainstream model of the brain overlooks several physiological features. In contrast to the one-to-one responses within silicon computers only 15% of action potentials reaching a synapse result in the release of neurotransmitters, introducing a probabilistic element into the basic processing of the brain. The variability of reaction times in neural processes suggests an element of random activity in the brain. Gap junctions are of relatively little account in mainstream theory, but Hameroff indicates that they mediate the thalamo-cortical 40Hz oscillations, which have themselves often been identified as possible neural correlates of consciousness. This is related to processing between dendrites, which is also downplayed in mainstream accounts of the brain. Hameroff enlarges on Penrose’s claim that consciousness arises from the geometry of fundamental spacetime, accessed via quantum wave collapses in the brain. Space is considered as non-continuous and composed of discrete elements in many versions of modern physics. In the 1970s, Penrose developed the idea of spin networks, coding for the configurations and volumes of space. This concept is close to the theory of loop quantum gravity, in which the rearrangement of the geometry of spacetime is indicated to be self-organising. These hypothetical networks, exist at the Planck length, and are suggested to encode conscious experience including qualia. Penrose has proposed that access to this fundamental level comes from so-called objective reduction (OR) of the wave function. Wave function collapse as a result of measurement or decoherence in the environment has a random outcome. Penrose proposes that wave functions that do not interact with the environment could reduce of their own accord, and that this latter process could be neither random nor deterministic but non-computable. If such a process occurred in the brain, it would require something with long-range order and suitable for information processing. Microtubules are here considered to be the best candidates for this, although membrane proteins, ions and clathrins are also considered to be possibilities. Microtubules are composed of subunits of the protein tubulin, a dimer composed of two 4nm monomers. The tubulin dimers are arranged in a slightly twisted hexagonal lattice, giving different relationships for each subunit and its six neighbours. The tubulins have dipoles and the microtubules as a whole are orientated assemblies of dipoles. Biochemical energy is provided to microtubules by tubulin bound GTP hydrolysed to GDP and by phosphorylated microtubule associated proteins (MAPs). Each tubulin has an intra-protein hydrophobic region. These are suggested as sites for anaesthetic binding, and also for quantum events related to the configuration of protein. Via MAP attachements microtubules influence the form and function of cells, including synaptic connections. Other cytoskeletal proteins such as actin connect microtubules to synapses and dendritic spines. The tubulin subunits in microtubules undergo various conformational changes. Monomers can shift as much as 29? from the vertical axis of the tubulin dimer In the 1960’s and 1970’s, the physicist Herbert Fröhlich proposed that protein conformation was driven by dipole oscillation with the hydrophobic pockets in proteins. He theorised that sets of protein dipoles could undergo coherent excitation if supplied with energy. This energy could be drawn from the surrounding thermal bath in biological tissue, and would pump the coherence of the hydrophobic dipoles. Microtubules are embedded in the cytoplasm within the cell. The cytoplasm goes through alternating phases of being a a liquid or solution (sol) and a gelatinous phase (gel). The transition from sol to gel is driven by actin polymerisation. Hameroff suggests that during the gel phase quantum states within the microtubules could be isolated from the environment. The gel depolymerises back to a liquid state by means of calcium ions which effect actin. The cytoplasm sol/gel cycle is vital to the overall functioning of the cell. It has been shown that cycles of actin gelation correlate with neurotransmitter release (Miyamoto, 1994) and (Muallem et al, 1995). Gap junctions are seen as a possible means by which quantum states could be communicated across large areas of the brain. Neurons connected by gap junctions fire synchronously as a kind of hyperneuron (Kandel et al, 1991). Gap junctions have now been shown to be widespread throughout the brain (Micevych and Abelson, 1991). Funda-Mentality: Is the conscious mind linked to a basic level of the universe? Stuart Hameroff Dept. of Anesthesiology & Psychology, Univerisity of Arizona Hameroff defines three main approaches to explaining consciousness: (1.) The dominant reductionist or functionalist approach sees consciousness as deriving from neural networks, more or less as described by existing neuroscience. (2) Dualists, who propose a ‘spirit stuff’ distinct from matter and energy as described by science, in order to account for consciousness. (3) So-called fundamentalists that see consciousness as being or being related to fundamental properties of matter or spacetime, which science must be extended in order to describe. Hameroff’s own views fall into the third category. Building on proposals from Roger Penrose, he suggests that consciousness/subjective experience is accessed in fundamental spacetime via quantum processes in the brain. These processes involve Penrose’s objective reduction (OR) of the wave function linking the brain to processes embedded in the fundamental spacetime geometry, in another words at the ground level of the universe. It is now a conventional view that at the smallest scale spacetime is not continuous but is quantised into discrete units or networks. Penrose has suggested that spacetime could comprise a web of quantum spins or spin networks. The dynamic evolution of these networks is proposed to define four dimensional spacetime. Penrose thinks that Einstein’s general relativity applies down to the very small scale, and that in effect everything, all energy and matter, is made up out of particular arrangements of these spacetime networks. The physicist, Lee Smolin, has built on this, to relate these self-organising spacetime networks to the flow of time. Penrose’s objective reduction and Hameroff’s suggestions for quantum processing in the brain are proposed as a link between biological tissue and fundamental spacetime. This link requires Penrose’s proposed objective reduction (OR) of the quantum wave. This is distinct from the normal wave function collapse that results from interaction with the environment or a deliberate measurement of the quantum wave. Penrose suggests that the superpositions of the quantum wave represent separate spacetime curvatures. These become unstable and rapidly collapse to a specific state if the curvatures become separated by more than the Planck length of 10-35m. While the normal wave function collapse is random in its choice of a specific state, Penrose suggests that objective reduction could be a non-computational process, something which is neither deterministic nor random. It is further suggested that volitional acts may be the result of superpositions, which are objectively reduced and decided by a non-computational process. Hameroff has proposed the microtubules as the most likely candidate site for quantum processing in the brain. It is suggested that quantum processing is shielded within either hydrophobic pockets within the tubulin protein subunits of the microtubules or possibly in the hollow core of the microtubule. The quantum process is proposed to extend over macroscopic areas of the brain by means of gap junctions between neurons. Quantum consciousness: Reply to Spier & Thomas Stuart Hameroff Trends in Cognitive Science In this paper, Hameroff replies to criticisms of the Orch OR model by Spier and Thomas. Hameroff justifies the unusual nature of the proposals in the Orch OR model, and its integration of ideas from neuroscience, computing and physics, by the fact new concepts are required to solve ‘the hard problem’ of consciousness. The theory is argued to be non-dualist, because it is based on in fact merely an extension of existing physical sciences including neuroscience. The theory stems from Penrose’s notion that there is an element of non-computability within brain processes. Most physical processes are deterministic, and Penrose has singled out wave function collapse as the only non-deterministic aspect of nature. This is conventionally understood as being a random process, not apparently of much value to human cognition. Penrose, however, proposes an additional form of wave function collapse, objective reduction (OR), which is suggested to occur when the quantum wave is not collapsed by interaction with the environment or by a measurement. The quantum wave represents superpositions of the different possible states of a quantum particle. Each superposition of a particle is viewed as having its own spacetime geometry, with each superposition possessing a slightly different geometry, and the separation between these comprising a form of blister or bubble in spacetime. When this separation reaches the Planck length, it reaches a critical threshold of instability, and rapidly collapses to a single state of the particle. It is suggested that in this case the choice of state is not random, but based on a non-computable process that is neither deterministic nor random. This process is suggested to be based on the configuration of networks that make up and drive the dynamic development of spacetime. Hameroff suggests that qualia, raw subjective experiences such as the redness of red, are encoded in the spin networks that may constitute space time. The sensation of having free will is also suggested to be a function of this non-computable process. Penrose sometimes describes the spacetime where mathematical understanding and other aspects of the mind are suggested to be encoded as the Platonic realm. This refers back to Plato’s idea that the physical world reflected ideals or ideas embodied in a separate realm. This has tended to be a target of ridicule for modern critics, such as Patricia Churchland. Spiers and Thomas advance the somewhat odd objection to Orch OR that if human ideas were derived from a Platonic realm or Platonic logic all human opinions would be the same. Hameroff’s counter view is that spacetime geometry is dynamic and evolving, and also that only part of the influence on individual minds derives from spacetime, with the mind also be governed by conventional inputs from inheritance and environment. Spier and Thomas appear to have something of a mantra to the effect that protein molecules are the basic computational elements in neurons. Hameroff in fact agrees with this, but suggests that the conformation is governed by quantum van der Waals forces, occurring mainly in hydrophobic pockets within the proteins. Anaesthetic molecules which oblate consciousness are thought to bind in such pockets. Spier and Thomas somewhat weaken their case by trundling out the old argument that microtubules are too unstable to form a basis for consciousness. This at least is easily answered by the fact that brain microtubules are much more stable and form part of a dense cytoskeletal structure. The argument moves on to the issue of single celled creatures, such as paramecium. Hameroff has suggested that these can navigate and respond to their environment without a nervous system as a result of microtubule processing. Spier and Thomas counter with the example of bacteria, which can also navigate themselves but lack microtubules. Hameroff quotes a study (Lowe & Amos, 1.) indicating that bacteria have protein based circuits resembling tubulin, the protein from which microtubules are built. References:- 1.) Lowe, J. & Amos, L. (1998) - Crystal structure of the bacterial cell-division protein - Nature, 1998, 391, pp. 203-206 Smolin, L. (1997) - Life of the Cosmos - Oxford Press Franks, N. & Lieb, W. (1982) - Molecular mechanisms of general anesthesia - Nature, 1982, 361 pp. 349-351 |
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