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Penrose & Hameroff 3Articles relevant to the Penrose/Hameroff model of quantum consciousness 1.) Anesthesia, consciousness & hydrophobic pockets 2.) Conduction pathways in microtubules, biological quantum computation and consciousness - Stuart Hameroff et al 3.) Search for quantum & classical modes of information processing in microtubules 4.) Gaps in Penrose's Toilings - Grush & Garland 5.) Reply to Grush & Garland - Penrose & Hameroff 6.) Cytoskeletal involvement in neuronal learning - Dayhoff & Hameroff 7.) Falsification of Penrose/Hameroff - Georgiev 8.) Dissipationless waves - Georgiev & Glazebrook 9.) Mathematical Intelligence - Giuseppe Longo 10.) Neural mechanism that randomises behaviour - Carpenter 11.) Hybrid Cognition - Worden Anaesthesia, consciousness and hydrophobic pockets Stuart Hameroff www.quantumconsciousness.org This article examines ideas about the action of anesthetic gases on proteins, and the possibility that quantum features are involved in the process. Studies made in recent decades ( Wulf & Featherstone (1957), Franks and Lieb (1982-94) and Halsey (1989)) indicate that anaesthetic gases act on hydrophobic regions of proteins. Van der Waals forces are suggested to act between anaesthetic molecules and non-polar amino acids. The post-synaptic receptors for neurotransmitters such as GABA, serotonin and acetylcholine are the areas most susceptible to anaesthetics, and they allow both excitatory and inhibitory functions to be effected. However, anaesthetics appear to effect a wide range of proteins including receptors, ion channels, second messengers and cytosleletal proteins including microtubules. The mode of operation of anaesthetics is taken to be suggestive of the involvement of quantum activity in consciousness. Protein function depends on the shape and conformation of the protein involved. Proteins are created out of chains of amino-acids. The folding of protein depends on the attractions and repulsions of amino-acid side groups. The main driving force in proteins are non-polar amino acids, repelled by water and attracted by van der Waals forces. They are non-polar but polarisable. Computer simulation or prediction of the folding of protein has proved difficult, with the suggestion of the possible need for quantum computing. Anaesthetics are suggested to prevent conformational switching in protein, possibly by inhibiting electron mobility, which may be required for protein dynamics. The implication of the article is that these features are linked to consciousness. References:- (1) Beck F, Eccles J.C. (1982), Quantum aspects of brain activity and the role of consciousness: Proceeding of the National Academy of Science: USA 89 (23) 11357-11361 (2) Franks N.P. and Lieb W.R. (1984), Do general anaesthetics act by competitive binding to specific receptors: Nature 310, 599-601 (3) Halsey M.J. (1989) Molecular mechanism of anaesthetics: General Anaesthesia – Fifth Edition (4) Wulf R.J, Featherstone R.M. (1957), A correlation of van der Waals constants with anaesthetic potency Conduction pathways in microtubules, biological quantum computation and consciousness Stuart Hameroff, Alex Nip, Mitchell Porter & Jack Tuszynski Biosystems, 64, 2002, pp.149-168 The article examines the plausibility of quantum computing in the brain. In respect of this, Hameroff views proteins as information processing or computing systems. In a quantum computer, superpositions of particles would be in two or more states or locations simultaneously. Classic computers utilise binary bits of 1 or 0. Quantum computers have superpositions of 1 and 0 at the same time. These superposed particles are called qbits. The qbits are entangled with one another. When the wave function collapses, the resulting classical data is the output for the computer. Quantum computers are expected to be particularly effective as search engines. This advantage may be particularly relevant for perception and hence survival in living organisms. Quantum computation has become more feasible since proposals for quantum error correction. This would involve an algorithm running on a computer that detects and corrects any localised decoherence that might otherwise lead to the collapse of the whole system. It has been suggested that microtubules could support an algorithm for quantum error connection. Hameroff suggests that the folding of protein could be based on a quantum computation. He also suggests that the structure of microtubules could be favourable to quantum error correction, and some amino acid groupings such as tryptophan and histidine may be involved in this. Fröhlich originally proposed (1968) that there could be quantum dipole oscillation in hydrophobic pockets in order to regulate protein conformation. Roitberg et al (1995) demonstrated functional protein vibrations that depend on quantum effects centred in two hydrophobic areas. Matsumo (2001) claimed to observe quantum coherence in actin. Actin is related to cytoskeletal contraction. Meyers and Overton showed a correlation between anaesthetic potency and solubility in lipids. At the time, it was assumed that this meant the lipids in cell membranes, but Wulf and Featherstone (1957), Frank and Lieb (1982-94), Halsey (1989) and others suggest they act in hydrophobic pockets in target proteins. The solubility is indicated to be an effect of van der Waals forces. The anaesthetics act on neurotransmitter receptors, such the GABA and serotonin receptors, second messenger proteins, enzymes and tubulins. A molecule just entering a hydrophobic pocket may not be enough, it must be the right type of molecule. Hallucinogen are seen to bind at serotonin receptors. This paper examines amino acid pathways in microtubules such as those for tryptophan and histidine and their possible involvement in electron mobility and quantum tunneling. Hameroff suggests that the conditions in microtubules could allow tunnelling over 3nm rather than the more normal one nanometer. Conformational states of tubulin are also suggested to be determined by London forces within the tubulin interiors. Electron conduction between tryptophan and histidine amino acids may be important in this respect. References:- Beck F, Eccles J.C. (1982), Quantum aspects of brain activity and the role of consciousness: Proceeding of the National Academy of Science: USA 89 (23) 11357-11361 Franks N.P. and Lieb W.R. (1984), Do general anaesthetics act by competitive binding to specific receptors: Nature 310, 599-601 Fröhlich H, (1968) Long range coherence and energy storage in biological systems: Int J. Quant Chem 2 6419 Fröhlich H, (1970) Long range coherence and the action of enzymes: Nature 728 1993 Fröhlich H, (1975) The extra dielectric properties of biological materials and the action of enzymes: Proceedings of the National academy of Science 72 4215 Halsey M.J. (1989) Molecular mechanism of anaesthetics: General Anaesthesia – Fifth Edition Wulf R.J, Featherstone R.M. (1957), A correlation of van der Waals constants with anaesthetic potency Quantum & classical modes of information processing in microtubules Stuart Hameroff & Jack Tuszzynski Biochemical energy is provided to microtubules in several ways, including from tubulin bound GTP which is hydrolysed to GDP. Van der Waals forces operate between the amino-acid side groups . Hameroff suggests that the tubulins could be the computing bits of a calculating system. Hameroff and Tuszynski say that by using the Protein Data Bank and the Tinker molecular dynamic package, they have demonstrated quite a high negative charge on tubulin at normal pH, with 40% of this concentrated in the tail-like ‘C’ terminal of the monomer. It is also indicated that mapping of electrostatic charges in the tubulin shows two wells of positive charge near the junction between the alpha and the beta monomers, which mapping work suggests would result in quantum tunnelling. W. Bras (1) has demonstrated microtubules align parallel to magnetic fields, and this is also considered as likely to allow electron tunnelling. Work by Binhi et al (2) indicates the existence of unpaired electron spins for networks in protein interiors, which are shielded from the environment and lead to functional quantum interaction at physiological temperatures. The conclusion of the article is that work on microtubules and the component tubulins suggests several mechanisms for quantum information processing. References:- (1) W. Bras, Magnetically aligned microtubules: PHD thesis, John Moore University (2) V.N. Binhi & A. V. Savin, Molecular gyroscopes and biological effects of weak extremely low frequency magnetic fields: Physical Review E 65: 051912 1&8211: 0519 R.R. Rizi et al, Intermolecular zero quantum coherence in the human brain: Magnetic resonance medecine: 43 627-32 (2000) W. Richter et al: Functional magnetic resonance imaging with intermolecular multiple quantum coherence: Magnetic resonance imaging 8, 489-494 (2000) Gap’s in Penrose’s Toilings Rick Grush and Patricia Churchland Philosophy Dept., University of California San Diego Journal of Consciousness Studies, 2, No. 1, 1995, pp. 10-29 The core part of this article is the Grush and Churchland’s discussion of the soundness of the processes by which mathematical truth is ascertained. The authors say that for convenience they will grant Penrose’s claims that human mathematicians are not using a knowable sound algorithm in exercising mathematical understanding, and thus arriving at ascertainible or unassailable mathematical truths. They also go along with his claim that there is no sound but unknowable algorithm. Instead they concentrate their discussion on the soundness of the brain procedures involved. They basically argue against the soundness of such procedures. They point out, and Penrose agrees with them in saying, that mathematicians sometimes make errors. The authors admit that anyone can make an error while applying a fundamentally sound procedure but they argue that the complexities of mathematics make it hard to distinguish an error of application from an unsound procedure. Therefore they claim that Penrose can only substantiate his claim by specifying procedures that are short enough for it to be easily checked that the application of procedures has been correct. The authors point to the case of the famous 19th century mathematician, Cauchy, who denied the possibility of the existence of infinite sets. The existence of such sets is now a basic part of mathematics as taught to students. The authors argue from this that there are no sound procedures, but only procedures that are usually reliable, or which are useful on a trial and error basis. Penrose replied to Grush and Churchland in the next volume of the Journal of Consciousness Studies. In his reply, he decides to concentrate the argument on the question of Pi 1 sentences, which assert that particular computations, such as Goldbach’s conjecture and the Lagrange theorem do not halt. He considers that these sentences are in principle accessible by human reasoning and insight. In contrast to Grush/Churchlands contention that mathematicians use trial and error and general reliability, Penrose claims that mathematical understanding is more precise than anything in science or philosophy. Penrose accepts that individual mathematicians make errors, but says the point is that there is an argument to be found which gives access to the mathematical truth. The rest of the Grush/Churchland article is a disappointment relative to the reasonably coherent discussion of mathematical truth. As philosophers, they are more plausible in terms of arguments relative to logic and maths than in physics or neuroscience, where Penrose and Hameroff are better placed in terms of scientific knowledge. They appear to waste a lot of time on the proposition attributed to Penrose that quasicrystals are evidence of non-algorithmic physical processes. In fact, Penrose suggested that their relationship might be non-local, rather than non-algorithmic. More to the point, even if there was nothing unusual about the quasi crystals it is not apparent why this would by itself falsify the OR form of quantum wave reduction proposed by Penrose. The attack on Hameroff’s proposals for microtubules as the basis of quantum activity in the brain contains factual errors. Grush/Garland claim physiological evidence that consciousness can occur without microtubules. This turns out to be based on two claims relating to the drug colchicine used in the treatment of gout. Colchicine depolymerises microtubules without patients losing consciousness. However, Penrose/Hameroff point out that the blood/brain barrier prevents most of the drug from reaching the brain. It was further claimed that when colchicine was delivered direct to the brains of animals they also did not lose consciousness. The Penrose/Hameroff reply is that brain microtubules are more stable than microtubules in the rest of the body, not having polymerisation cycles, nor the exposed beta plus ends found in body microtubules. Grush/Garland also come up with the rather strange objection that the microtubules do not extend the full length of the axons to the actual synapse. The answer is that the connection is made by other elements of the cytoskeleton without which the microtubules could not even perform their known function of transporting neurotransmitter and other molecules to the synapses. This answer also applies to their connection with the cell membrane and the dendritic spines. There was a further argument about anaesthetics. G&C claiming ion channels are the main target for anaesthetic gases. P&H do not deny the importance of these, but argue that the same changes that happen in hydrophobic pockets in membrane proteins also happen in microtubules, with the action on the latter ablating consciousness. G&C reasonably ask how quantum activity in microtubules in individual neurons could be extended across the wider brain. In this article, Hameroff has suggested communication via gap junctions. While this is also very controversial it does provide a structure to fill the apparent gap pointed out by G&C. The Grush & Garland article, published in 1995, have begun to look a bit dated. There are references to ‘promising research programmes’ presumably in the area of mainstream ideas about consciousness, whereas there is sadly little sign now that we are any closer to a a mainstream theory of consciousness, and this nowadays beginning to be openly acknowledged by mainstream science. Instead, recent papers suggest a much greater caution as to the timescale needed to establish nature of consciousness on the part of both neuroscientists and some AI experts. In contrast, Hameroff can at least point to the correlation of cytoskeletal activity and synaptic function, which G&C claimed to be unconnected plus some evidence for the existence of quantum coherence in the brain. In particular, G&C also give a large amount of space in their article to neural net computers. These were very much in vogue in the 1990’s because they used or at least simulated the parallel processing of data seen to be used by the brain. There seem to have been hopes that neural nets would break the log jam in AI and robotics. As late as the turn of the century, Max Tegmark suggested that the promise of neural net computers leading to an understanding of consciousness, suggested that there was little need to look to the quantum level for an explanation. Little now seems to be heard about neural nets, suggesting that this route to imitating the brain has not proved very fruitful. P&H merely point out that whatever the merits of neural nets, they are certainly based on a sequence of algorithms and have no bearing on mathematical understanding relative to Gödel. Despite the many shortcoming of the Grush and Garland article it is often referred to a definitive refutation of the whole of the Penrose/Hameroff model, without even a reference to the existence of a reply by Penrose and Hameroff. Reply to Grush & Garland Roger Penrose & Stuart Hameroff Journal of Consciousness, 1995, 2 (2) pp. 99-112 and: www.quantumconsciousness.org One interesting thing about this reply is that exists at all. Commentators on quantum consciousness are apt to quote The Grush & Churchland article as a comprehensive dismissal of the Penrose/Hameroff model, without even mentioning that there was a reply, let alone bothering to discuss any of the points raised. Penrose and Hammeroff claim that Grush & Churchland’s (G&C) arguments are misleading and that with respect to the physiological evidence of the brain they are factually incorrect. With respect to Penrose and non-computability, their main argument is said to hinge on the statement that mathematical thinking can contain errors. Penrose says that he does not deny this, but does not see it as invalidating the Gödel argument. Penrose also say that G&C claim that he said that in some and perhaps in all instances human thought was sound but non-algorithmic. He states that this is incorrect, and that he never denied that human thought and even rigorous mathematical thinking could be in error. Penrose says that he wishes to restrict the argument to Pi 1 sentences, which are sentences that assert that a particular computation does not halt. An example of a Pi 1 sentence is the Goldbach conjecture, which states that ‘every even number greater than 2 is the sum of two prime numbers. It is an assertion that the computation does not halt in the sense that it says that a programme looking for an even number that was not the sum of two primes would never find it and would therefore never come to a halt. Penrose says the issue is as to how accessible to human reason Pi 1 sentences are. G&C also claimed that there was no evidence that non-computability was involved in quantum gravity. Penrose replied that there was some evidence. This relates to the work of Geroch and Hartle, which showed that there was no algorithm for certain problems related to the superposition of four dimensional space-time, which is in turn closely related to Penrose’s version of quantum gravity. The latter part of the reply is devoted to G&C’s criticisms relative to the physiology of the brain. They claimed that a drug called colchicine, which is used for the treatment of gout, acts by depolymerising microtubules, but does not result in the loss of consciousness. In reply, Hameroff says that this argument fails to take account of differences between microtubules in the body and microtubules in the brain. The brain microtubules are much more stable. In its medical use colchicine does not penetrate to the brain, being excluded by the blood-brain barrier, but in animal experiments, where it has been administered to the brain, it is shown that brain microtubules do not depolymerise. Grush & Churchland argue that if microtubules were responsible for consciousness, consciousness would be distributed through out the body, because there are microtubules in all cells. Against this, Hameroff stresses the substantial differences between body cell microtubules and neuron microtubules, the latter being in much denser networks, particularly in the dendrites. G&C also queried how microtubules communicated with the cell membrane and in particular with the synapses, since axons stop some way short of the synapses. Hameroff answers that the connections are made by smaller cytoskeletal proteins and some incoming communication is via second messengers. They also question how microtubules encode information. Hameroff points the suitability of the cyclical lattice for information, although more complex arguments for amino acid structures and quantum tunnelling appear in later papers. He also quotes Vassilev (1985) for evidence of signal transmission. Here again, there seems to have been some more recent data for signalling since the Penrose/Hameroff reply was published. References:- (1) Vassilev P. et al, (1985) Intermembrane linkage mediated by tubulin: Biochem. Biophys Res Comm. 126 pp 559-65 Jibu M, Hagan S, Hameroff S, Pribram K.H., Yasue K, (1994) Quantum optical coherence in cytoskeletal microtubules: Biosystems 32 pp 105-209 Jibu M, Yasue K, Hagan S, (1995) Water laser as cellular vision Oedaira H. and Osaka A.C. (1989) Water in biological systems: Kodansha Scientific Cytoskeletal involvement in neuronal learning Judith Dayhoff, Stuart Hameroff et al European Biophysics Journal, 1994, 23:79, 93 Experimental evidence suggests that the cytoskeleton may be involved in information processing, cognition and learning. Mileusne et al (1980) (1) correlated tubulin production with peaks in learning. Cronly-Dillon (1994) (2) also correlated increase and reduction of tubulin production in the visual cortex to learning. Conventionally learning is associated with synaptic plasticity. Both Lynch & Baudry (1987) (3) and Friedrich (1990) (4) suggest that LTP depends on the rearrangement of the synaptic cytoskeleton. Matsumoto and Saka (1977) (5)and Hirokawa (6) (1991) suggested links to excitability of membrane receptors and ion channels and to synaptic transmission. Desmond and Levy (1998) (7) found changes in dendritic spines mediated by cytoskeletal actin during learning. Kwak and Matus (1988) (8) and Aoki and Siekevit (1985) (9) suggested that microtubules depolymerised in the event of lack of input. The last quoted found that signalling in and regulation of dendritic spines depended on phosphorylation of microtubule associated proteins (MAPs). References:- (1) Mileusne et al (1980) (2) Cronly-Dillon (1974) Possible involvement of microtubules in memory fixation: J. Exp. Biol 61 443-454 (3) Lynch & Baudry (1987) (4) Friedrich (1990) Protein structure, the primary substrata for memory: Neuroscience 35 (5) Matsumat & Saka (1977) (6) Hirokawa (1991) (7) Desmond & Levy (1998) (8) Kwak & Matus (1981) (9) Aoki C. & Siekevit P. (1985) Journal of Neuroscience 5 2465 2483 Falsification of Hameroff-Penrose ORCH OR model of consciousness and novel advances for development of quantum mind theory Danko Georgiev Laboratory of Molecular Pharmacology, Kanazawa University, Japan November 2006 Georgiev entitles his article, a ‘Falsification of Penrose-Hameroff, but in contrast to most critics, the author appears to accept the possibility of Penrose’s objective reduction and its link to consciousness, and concentrate on looking at alternatives to Hameroff’s ideas for how this might be implemented in the brain. It is at least refreshing in the quantum mind area to find criticism based on detailed factual argument rather than sweeping condemnations based on no particular logic or information. Georgiev is critical of Hameroff’s idea that the microtubules related to consciousness are only in the dendrites and not in the axons. He regards split brain experiments, which show a degree of independence between the two hemispheres when the corpus callosum was cut, as an indication that the severance of axons running between the two hemispheres, also leads to a loss of quantum coherence between the hemispheres. He sees this as evidence that microtubules in both the dendrites and the axons are involved in consciousness. Hameroff’s model suggested that processing in the axons was purely classical. Georgiev moves on to attack Hameroff’s idea that quantum coherence could extend over significant areas of the brain via tunnelling at gap junctions. The gap junctions looked a likely point at which quantum coherence could extend between neurons because the cell membranes are only four nanometres apart. However Georgiev argues that the microtubules and the related dendritic lamellar structures are too far away from the gap junctions for these to provide a possible way of transferring quantum coherence. The most important difference between Georgiev and Hameroff, however, is their approach to quantum decoherence within neurons. Hameroff developed an argument for the possible shielding of microtubules by ordered water, which could allow coherence to be sustained for as long as 25ms, bringing into line with the 40Hz thalamo-cortical oscillation. Georgiev, however, is more interested in the very short timescale of only 10-15 picoseonds associated with enzymatic functions in proteins. The speed of this process is necessary to counteract the underlying trend towards thermal equilibrium/increased entropy. Georgiev doubts whether the microtubules could perform their normal functions if they were tied into 25 ms decoherence periods. He thinks that it is more feasible for the microtubules to be locked into a protein related cycle of 10-15 picoseconds. He also thinks that it makes more sense for the microtubules to be exposed to rather than shielded from the electromagnetic field. He feels that the results of Penfield and Dobelle that show electrical impulses directly impacting consciousness would not be possible in the Hammerof model. He also argues that the Debye layer cannot produce electrical shielding. Jibu and Yasue are cited for the their work relative to quantum field theory which suggest that the field is linked to the tubulin tail. Georgiev posits microtubular control of the firing of synapses. He feels that in a classical structure the large number of synapses, the probability of only 15-30% that individual synapses will fire, would create a chaotic situation unless there is some form of sub-neuronal control. The Hammeroff model with only dendritic consciousness, does not allow any direct management of synaptic firing. This is also in effect a criticism of all mainstream models of brain function and consciousness, where there is never any suggestion of any such control of firing. This too would be vulnerable to the chaotic breakdown suggested by Georgiev. Georgiev advocates pre-synaptic quantum computing to deal with the problem of synaptic control. He argues that classical error correction is not feasible. His view of consciousness is slightly different from Penrose’s. Whereas Penrose sees consciousness deriving from the collapses of the wave function, Georgiev thinks this is just computing, and that consciousness is simply a fundamental experience of quantum systems. Georgiev thinks that many views of decoherence in the brain are wrong because their authors assume that the cytoplasm is in thermal equilibrium or is a thermal bath. However, this is not the case, because living organisms are a long way from thermal equilibrium. It is the continuous supply of energy, i.e. non-thermal equilibrium that maintains the structure of organisms. Georgiev says that biophysical modelling suggests that Fröhlich type or Bose-Einstein condensation could arise for 10-15 picoseconds in biological tissues. Danko Georgiev & James Glazebrook Informatica, 2006, 30, pp. 221-232 The paper discusses quantum mechanical processes and soliton interactions in microtubules that could underly sub-neuronal information processing. This is seen as a possible basis for mind and memory. Solitons are dissipationless waves and are common both in quantum theory and biophysics. Neurons are regulated by strings of self-assembling proteins that constitute the cytoskeleton. Microtubules organise the intracellular space, and tune the activity of enzymes anchored to the microtubules. The microtubules are composed of dimers with α and β systems. GTP is tied to the β tubulin and hydrolyses and stores energy in the wall of the microtubule. Studies by D.L. Sackett (1995) (1) and Jiminez et al showed that microtubules were not smooth tubes, but that each tubulin had a 4-5nm tail, often referred to as a C-terminal tail. The alpha and beta tubulins have slightly different tail structures and the tails are extremely sensitive to environmental conditions and electrical fields. Microtubules are involved in vesicle transport using motor proteins such as kinase bound to microtubules. C-terminal tails modulate kinasin function. Quantum tunnelling may be related to C-tail action. References:- Jiminez M.A. et al Helicity of alpha and beta protein: Protein Science 8 (1999) 788-799 Sackett D.L. Structure and function in the tubulin dimer: Subcellular Biochemist Proteins 24 255-302 Mathematical Intelligence, Infinity & Machines Giuseppo Longo Journal of Consciousness Studies, vol. 6, 1999, Nov/Dec. The article attempts to refute Penrose’s argument that the Gödel theorem indicates that there is some form of non-computable processing in the human brain. The reasoning is difficult for the non-specialist to follow. However, the gist appears to be an argument that proofs that go beyond formal systems can be derived from numerous mental and historical experiences, some of them from outside mathematics. The problem that does not appear to be dealt with is whether or not these may not themselves involve non-computable processes. A Neural Mechanism that Randomnises Behaviour R.H.S. Carpenter Physiology Laboratory, University of Cambridge Journal of Consciousness Studies, vol. 6, No. 1, 1999, pp. 13-22 The abstract starts by pointing out that the time taken to react voluntarily to stimulus is far longer than can be accounted for by known nervous system processing. The strength of response is shown to rise in proportion to the incoming sensory data, until a critical level at which action is taken is reached. However, the rate of rise fluctuates randomly from trial to trial. This claim is based on studies of neurons in the frontal eye field and the time taken between presenting a visual stimulus and making a saccade (an eye movement). The saccade itself is very quick, lasting only 20-30ms, but the system is not designed for speed in other respects. The average gap between presentation of the stimulus and the saccade is 200ms. Normal processing in the nervous system is claimed to account for at most one third of this time. The shortest route from the retinal receptors to the eye muscles passes through the superior colliculus and should take only 60ms. However, the colliculus receives input that comes ultimately from the parietal cortex and the frontal eye fields. The control is inhibitory, otherwise the eyes would be constantly darting towards each and every stimulus. The blanket inhibition has to be lifted for a saccade to be made. The colliculus lacks the information to make useful decisions, because it registers only where things are in space, but not what they are. The biggest problem is seen to be in a series of trials the response time varies over a surprisingly large range. While the average saccadic latency is 200ms, on some 5% of trials the latency is either less than 150ms or more than 300ms. In the first stage of the latency period neurons distinguish between a target stimulus and distractors. This takes about the same period of time, about 70ms, whether the eventual latency period is short or long, so the whole of the variability is concentrated in the latter part of the latency period. The article suggests that this means that the variability is not due to noise in the sensory pathways, but to something introduced by the brain. The randomness of the reaction times is seen as a function of deliberate randomisation by neural processes in the brain. Carpenter says that the underlying process is obscure, although he points out that its is consistent with the Penrose/Hameroff model, and that the delay periods involved are similar to those seen in Libet’s experiments. Carpenter goes on to speculate as to what evolutionary advantage would favour randomisation. He argues that there would be an adaptive advantage in the resulting unpredictability, as opposed to deterministic responses that would be easier for a predator or prey to predict. References:- Carpenter, R.H.S. Oculomotor procrastination in Eye Movements Cognition and Visual Perception (1981) Carpenter, R.H.S. Movement of the Eyes (1988) Carpenter, R.H.S. Human saccadic latency to targets of differing contrast and probability: Evidence for neural randomisation Carpenter, R.H.S. and Williams M.L.L. Neural computation of log likelihood in the control of saccadic eye movements Nature 377 pp59-62 Hybrid Cognition R.P. Worden ex Cambridge, Caltech & Cern Journal of Consciousness Studies, 6, No. 1, 1999, pp. 70-90 The article proposes that cognition is supported by a 3D model of local space stored in Bose-Einstein condensates, which couple to neurons in the thalamus. This structure is also suggested to be the basis of consciousness. This is seen as likely to be favoured by evolution as an efficient means of storing data as well as being consistent with the properties of consciousness. The author argues that neuroscience has so far only uncovered 2D maps in the brain, and that it would be much more economical for the brain to have evolved a 3D map. Against this, it could be argued that much of the lay out of the brain is not very economical, with vision processed at the back of the brain, and the right side of the body handled by the left side of the brain and visa versa. In fact, the lay out seems to be positively aimed at maximising the length of nerve tracts needed. In fact, it has been argued that this might be a way of extending quantum coherent structures over a large area of information processing. The author suggests that there is nothing implausible with the idea that neurons could couple with a wave, as this is exactly what they do in the retina, where they couple with light waves. He reminds us that neurons can couple to signals at very low intensities, and this might extend to systems that have not yet been detected. He also points out that given the known information capacity of neurons, it is hard to work how they perform some functions as fast as they in fact do. This ties in somewhat with those who argue for quantum computing in the brain, on the grounds that no classical computer could handle the amount of processing needed to achieve basic perception of objects within a reasonable time. He also points out that, as it stands, neuroscience does not give us a clear distinction between conscious and unconscious activity. The article also suggests that there is a control mechanism to direct the attention of the proposed 3D model. There is stated to be evidence in favour of thalamic reticular nucleus performing such as role (Newman, 1995 & 1996) (1&2). The thalamic reticular could be directed by inputs from the rear of the cortex, where objects and their position are recognised, and from the midbrain reticular which orientates to new stimuli and the prefrontal. The article recalls the past theories of Bose-Einstein condensates or other quantum coherence in the brain, starting with Fröhlich (1968) (3), who proposed a metabolic energy pumping mechanism to sustain a condensate, and also Umezawa (1993) (4), Vitiello (1995) (5), Hameroff (1994) (6) and Gershenfeld & Chuang (1997) (7). The author admits that rapid decoherence in the brain is a problem for all these theories, but does not go into how it might be prevented. Marshall (1989) (8) appeared to advance the view that the Bose-Einstein condensates were themselves conscious, and would as such experience the local 3D map stored in the thalamus. This is therefore seen as the basis of consciousness and it does not require a further observer behind or beyond it. The 3D map and the single quantum state condensate theory of consciousness appears also to solve the binding problem, explaining how it is all brought together in one place. The article also points to evidence (Bogen, 1995) (9) that damage to the thalamus and particularly the Intra-Laminar Nuclei, interrupts consciousness, which is not the case with most other areas of the brain. The author feels that the theory bridges the explanatory gap found in consciousness theories based on classical physics. However, he feels that the theory nonetheless has something in common with some of the more popular mainstream theories of consciousness. The Global Workspace theory of Baars & Newmann (10 & 11), where the workspace broadcasts the results of computations to different neural modules is seen a s similar to the proposed 3D mastermap. Damasio’s theory (12) involving somatosensory data and a body model in consciousness and cognition is seen as having similarities to the body’s role in the 3D mastermap. However, it is pointed out that all these theories leave an explanatory gap in that all the systems described could function without consciousness. Churchland (1995) (13) has tries to bridge this gap, with identity theory, which tries to say that neural activity is consciousness in the same way that molecular motion is heat. The author feels that the identity theory does not account for most of the properties of consciousness. He also points out that identity theory does not provide an explanation for the distinction between conscious and unconscious activity in the brain. A century of increasingly detailed examination of the brain and neurons has not thrown up a plausible distinction between conscious and unconscious areas or functions, and is not apparent in any detailed study of a particular area of neurons. A further criticism might be that it does not provide the detailed cause and effect sequence that we demand from science. Thus when we say that heat is molecular motion, we also know from current science that the sufficiently rapid motion of molecules changes the bonds between particles in such a way that phase changes between solid, liquid and gas or chemical changes such as burning occur. It is not just a correlation between molecule motion and heat, there is also an observable detailed process. There are all sorts of correlations between neural activity and consciousness but existing mainstream neuroscience has no detailed mechanisms such as breaking or forming of bonds between molecules that shows how consciousness arises. It is pointed out that quantum theories of consciousness fall into two groups, collapse theories such as those of Stapp (14) and Penrose/Hameroff (15), where consciousness is related to the collapse of the wave function, and state theories, such as the one discussed here, where consciousness resides in a particular quantum state. Worden claims that decoherence is a much greater problem for collapse theories than for state theories. The main problem with this theory is that it offers no particular reason why a quantum condensate should be conscious. In this it is no different from mainstream theories based on classical physics, going right back to Descartes, which simply decree that a particular brain feature or process is conscious or consciousness. The Penrose/Hameroff model, which also posits condensates in the brain links their collapse to the fundamental space-time geometry which provides the non-computable element in human thinking. One may not like the various assumptions and speculations involved in the model, but is does provide a reason why consciousness should arise at this level. References:- (1) Newman, J. (1995) Thalamic contributions to attention and consciousness Consciousness and Cognition, 4, pp.172-93 (2) Newman, J.(1996) Thalamocortical foundations of conscious experience (3) Fröhlich, J. (1968) Long range coherence and energy storage in biological systems International Journal of Quantum Chemistry (4) Umezawa, H. (1993) Advanced Field Theory: Micro, Macro and Thermal Physics New York, AIP (5) Vitiello, G. (1995) Dissipation and memory capacity in the quantum brain model International Journal of Modern Physics, 9B, pp. 973-89 (6) Hameroff, S. (1994) Quantum coherence in microtubules Journal of Consciousness Studies, 1 (1) pp. 91-118 (7) Hameroff, S & Penrose R. (1996) Orchestrated Reduction of quantum coherence in microtubules Towards a Science of Consciousness , ed. S. Hameroff MIT Press (8) Gershenfeld, N & Chuang, I (1997) Bulk spin-resonance quantum computation Science, 275, pp. 350-6 (9) Marshall, I. (1989) Consciousness and Bose-Einstein condensates New Ideas in Psychology, 7, 73-83 (10) Bogen, J. (1995) On the Neurophysiology of consciousness Consciousness and Cognition, 4 (1) pp. 52-62 (11) Baars, B. (1988) A Cognitive Theory of Consciousness (Cambridge Unoversity Press) (12) Newman, J and Baars, B. (1993) A neural attentional model for access to consciousness Concepts in Neuroscience, 4, pp. 255-90 (13) Damasio, A. (1994) Descartes Error Putnam (14) Churchland, P.S. (1995) Can Neurobiology Teach us anything about consciousness (15) Stapp, H.P. (1993) Mind, Matter and Quantum Mechanics Verlag Springer (16) Stapp H. (1996) The Hard Problem: A Quantum Approach Journal of Consciousness Studies, 3 (3) pp. 194-210 Bohm, D. & Hiley, B (1993) The Undivided Universe Routledge Cairn-Smith, A. (1996) Evolving the Mind: On the nature of matter and the origin of consciousness Cambridge University Press Carpenter, R. & Williams, M. (1995) Neural computation of likelihood in the saccadic control of eye movement Nature, 377, pp. 59-62 Chalmers, D. (1995) Facing up to the problem of consciousness Journal of Consciousness Studies, 2 (3) pp. 200-19 Chalmers, D. (1996) The Conscious Mind Oxford University Press Lockwood, M (1989) Mind, Brain and Consciousness Blackwell Penrose, R. (1989) Shadows of the Mind Oxford University Press Pribram, K. (1971) Languages of the Brain Prentice Hall Pribram, K. (1991) Brain and Perception Lawrence Erlbaum Associates Wigner, E. (1961) Remarks on the mind-body problem in The Scientist Speculates Princeton University Press Worden, R. (1995) An optimal yardstick for cognition Psycoloquy, 7 Zohar, D (1990) The Quantum Self Bloomsbury |
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