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Quantum EvidenceArticles relative to experiments and other evidence for quantum coherence in the brain/quantum consciousness 1.) Introduction 2.) Coherent control of isomerisation - Prokhorenko 3.) Pizzi experiment 4.) Protons as neurotransmitters 5.) A neural mechanism that randomises behaviour 6.) Consciousness, neurobiology & quantum mechanics 7.) Quantum coherence in photosynthetic systems 8.) Quantum effects in cytoskeletal proteins 9.) Quantum & Classical Modes of Information Processing in Microtubules 10.) Photon echo experiments at Starlab Introduction: Evidence for Quantum Coherence in the Brain There is a limited amount of evidence for the existence of quantum coherence in the brain. This does not refer to condensates, but it does undermine the basic argument that quantum coherence of any kind could not exist in the brain for a useful length of time. In 2000 coherence was detected in an experimemt aimed at finding improves MRI methods. The experimemt was conducted at Princeton by W. Warren, W. Richter et al. In another experiment, also in 2000, Zizzi et al detected quantum coherence in the frontal, pre-motor, parietal and visual areas of the cortex. The most interesting factor here was that the duration of the coherence was around 25ms, which could be viewed as related to the 40Hz gamma oscillation between the cortex and the thalamus. Finally in 2006, V. Prokhorenka at the University of Toronto showed that a process of isomerisation was steered by quantum wave effects. The conclusion in this experiment was that the wave properties of matter can be observed and even manipulated in systems as large and complex as the brain. Coherent Control of Isomerisation in Bacteriorrhodopsin Prokhorenko, V. Dept. of Chemistry and Physics, University of Toronto Science, 1st September 2006: Vol 313 no. 5791, pp. 1257-1261 An experiment demonstrated optical control of the primary step of photoisomerisation of retinal molecules. Pulses involved in the process were phase sensitive at intensities that were too low to access electronic states. It was therefore concluded that isomerisation was steered through quantum interference effects. The result thus shows that the wave properties of matter can be observed and manipulated in a system as large and complex as a protein. Modern spectroscopic techniques have produced evidence of interference at the molecular level, and have used it to steer chemical reactions. However, these involved small molecules or ions. Very complex protein molecules looked to be a different situation. The thing to look at is the degree of conserved phase relationships or quantum coherence within a chemical process in a protein environment. Some excitation pulses can manipulate a process faster than random thermal activity can act to cause decoherence. Photoisomerisation of the retinal molecule in rhodopsin proteins is one of the fastest biological processess in this respect. It has been the subject of intense investigation. Pizzi Experiment Dept of Information Technologies, Milan University. The experiment used human neurons grown from a common stock of neural stem cells, but separated from one another in electromagnetically shielded basins. One sample is exposed to laser pulses that generates event related potentials. The unstimulated culture was shown to generate bursts of potentials in synchrony with the stimulated culture. References:- Pizzi, R. et al (2004) Non-local correlation between human neural networks in Donker, E. et al Eds. Quantum Information and Computation 11. Proceedings of Spies 436: 107-117 Protons as Neurotransmitters Nature, March 2008 and Beg et al in Cell Professor Eric Jorgensen of the University of Utah and his team have demonstrated that free protons can bind to receptor sites on muscles. The relevant study was carried out on nematode worms (c.elegans). The authors studied the defecation cycle of c. elegans. The muscle contractions involved in this cycle are not directed by neurons but by signalling using protons or hydrogen ions, the positively charged part of the hydrogen atom. Instead of using neurotransmitters, the PBO-4 protein in the intestinal cell membrane facing muscle cells exchanges H+ protons for sodium ions (Na+). The protons thus released act as chemical signals to activate ion channels in muscle cells. The PBO-5 protein expressed in other muscle cells is seen as a likely receptor for protons. The protons are released in pulses, and the fluctuations in the concentration of protons controls the defecation cycle of c. elegans. This is correlated to calcium ion release, and the two processes could be linked by the sodium ion concentration in the cytoplasm. The proton-sodium ion exchanges found in the intestines of c. elegans are also expressed in the mammalian brain, and Beg et al suggest that these exchanges could be involved in learning and memory. Jorgensen comments that mice that lack proton receptors cannot learn, suggesting that proton signalling may be involved in the learning process. This study is considered likley to open up research into other non-classical forms of neurotransmission. Jorgensen's findings were published in the journal 'Cell'. 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 paper starts by pointing out that the time taken to react voluntarily to stimulis 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. 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 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 of 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 that 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 actually 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. Consciousness, Neurobiology & Quantum Mechanics: The Case for Connection Stuart Hameroff In: The Emerging Physics of Consciousness, Ed. J. Tuszynski Springer, 2006 ISBN-13 978-3-540-23890-4 Hameroff summarises his proposals in the early part of the chapter. He thinks that consciousness arises in the dendrites of neurons that are connected by gap junctions to form 'hyperneurons', and that these are related to the gamma synchrony. Axonal spikes and synapses are seen as making inputs to and receiving outputs from the microtubular process as part of an interactive systems. In general, Hameroff argues that the emerging evidence of neurobiology has moved in favour of the ORCH OR model over the last decade, not withstanding the continued unpopularity of the theory. Hameroff classifies all the mainstream approaches to consciousness as 'classical functionalism'. Functionalism takes no account of what the brain is made of or of anything finer grained than the level of neuron-to-neuron connections. It beleives that these connections could be copied in another material such as silicon, and that the resulting construct would be conscious. However, Hameroff argues that although axonal spikes and synaptic connections play a key role in information processing in the brain, they may not be the main currency of consciousness. He argues that quantum processing in microtubules within the dendrites and gap junctions between dendrites are the basis of consciousness. The main case against quantum processing in the brain has always been the view that it would decohere faster than the time taken for any useful biological process. Hameroff accepts that this is in principle a valid argument. However, he claims that a gelatinous non-liquid ordered state can arise in the neuronal interior, and provide screening for microtubules against the rest of the environment. A further objection to quantum processing was that even if it arose in one neuron, it would difficult to communicate across the brain. This was countered by the suggestion that there could be quantum tunneling at gap junctions between neurons. In recent years, gap junctions have been discovered to be more widespread in the brain than was previously thought. They are also related to the 40 Hz gamma synchrony. This oscillation was at one time promoted by Crick and Koch as the most promising correlate of consciousness. However, the idea fell from favour with mainstream neuroscience, when it was discovered that the gamma synchrony correlated with dendritic activity rather than axonal spiking. Backward referral in time The recent evidence of neurobiology suggests periodicity in perception and reaction times, notably the gamma synchrony and the alpha and theta waves. The former has sometimes been promoted as a correlate of consciousness and the latter related to visual activity. Hameroff also touches on the famous Libet experiment that demonstrated a 500ms timelag between a stimulus and the perception entering consciousness. The subject is not aware of this time lag as a result of so-called backward referral in time. Hameroff thinks that the backward referral in time should be taken seriously. The mainstream has tended to favour something resembling the Dennett 'multiple drafts' concept, which would involve an after the event reconstruction of what had happened. Hameroff prefers an alternative suggestion by Roger Penrose. Penrose proposed that the bain sent information backward through time. This is not as far fetched as it sounds, since the laws of physics, as embodied in the Maxwell and Schrodinger equations, do not preclude backward travel in time. It is just that we do not experience objects or even rays of light arriving from the future, and there is a further argument in the form of the 'grandfather paradox' by which we could travel into the past and kill our own grandfather. This is presented as an argument against macroscopic objects travelling into the past. However, Einstein's equations have been shown to allow for a repeated return to certain points in the past. This is derived from the concept of tilting of light cones, as used in relativity, where a sufficiently strong gravitational field can tilt the light cones so that they comes full circle, making what is called a closed timelike curve. Penrose has suggested that while macroscopic objects may be prevented from going back in time, quantum states might be able to make a 500ms journey into the past. However, it does not appear to preclude a 500ms adjustment within the brain. Learning & Memory Hameroff points out that changes in dendrites can lead to increased synaptic activity. This is basic to ideas about learning, memory and neural correlates of consciousness. The changes in dendrites involve the number and arrangement of receptors and the arrangement of dendritic spines and dendrite to dendrite connections. Axon potentials or spikes have been assumed to be the main basis of consciousness, but Hammerof suggests that there could be other candidates. Electrodes implanted into the brain detect mainly the activity of dendritic gap junctions plus inhibitory chemical synapses. Thus detected synchrony derives from dendrites rather than axonal spikes. The main function of dendrites is seen to be the handling of input signal into the neuron which may eventually result in an axon spike. However, this is not the whole story, since many cortical neurons have dendrites but no axons. Here dendrites interact with other dendrites. Also there can be extensive dendritic activity with no spikes. The evidence suggests that there are complex logic functions in the dendrites, and these may oscillate over a wide area, while remaining below the axon spiking threshold. Many post-synaptic receptors send signals into the dendrite cytoskeleton. Gamma Synchrony Gamma synchronies, in the 30-70Hz range, have aroused interest as possible correlates of consciousness. Gray and Singer (1) found coherent gamma oscillations in the brain that were dependent on visual stimulation. It was suggested that this synchrony could solve the binding problem, which is the problem of how the different inputs into the brain are bound together into a single conscious experience. It was suggested that the synchrony reflected the activity of a relevant assembly of neurons. Varela (2) noted that synchrony operated whenever the processing of spatially separated parts of the brain were brought together in consciousness. Gamma synchrony has been demonstrated across cortical areas, hemispheres and the sensory/motor modalities. The synchrony is involved in a range of brain activities including perception of sound, REM dream sleep, attention, working memory, face recognition and somatic perception. Also gamma decreases during general anesthesia and returns on waking from this. Hameroff regards gamma synchrony as the best overall correlate of consciousness. He further addresses the question of how the gamma synchrony is mediated. There is coherence over large areas of the brain sometimes including multiple cortical areas and both hemispheres of the brain, with zero or near zero phase lag. If the synchrony was based on the axon/synapse system a considerable lag would be expected. Hameroff points to gap junctions as an alternative to synapses for connections between neurons. Neurons that are connected by gap junctions depolarise synchronously. Gap junctions play a more important role in the adult brain than was previously supposed. Numerous studies (3) show that gap junctions mediate the gamma synchrony. A neuron may have many gap junction connections, but not all of them are necessarily open at the same time. The opening and closing of the junctions may be regulated by the microtubules. Hameroff suggests that cells connected by gap junctions may in fact constitute a cell assembly, with the added advantage of snchronous excitation. Cortical inhibitory neurons are particularly studded with gap junctions, possibly connecting each cell to 20 to 50 others (4). The axons of these neurons tend to form inhibitory GABA chemical synapses on the dendrites of other interneurons. Screening of Microtubules Hameroff moves on to discuss the role of the cytoskeleton, which is seen to determine the structure, growth and function of neurons. Actin is the main constituent of dendritic spines and is present throughout the neuronal interior. Actin can depolymerise into a dense network, and when this happens the interior of the cell is converted from an aqueous solution into a gelatinous state. Furthermore, when this happens the whole of the cytoskeleton forms a negatively charged matrix around which water molecules are bound into an ordered state (5). It is particularly remarked that the neurotransmitter glutamate binding to NMDA and AMPA receptors cause gel states in actin spines (6). Cytoskeletal functions include microtubules and actin enabling the growth of axons and dendrites, and transport of molecules that maintain and regulate synapses. Dendrites The cytoskeleton of the dendrites is distinctive from both non-neuronal cells and the axons of neuronal cells. The microtubules as opposed to the continous ones found in axons and have mixed polarity. This appears a sub-optimal arrangement from a normal structural point of view, and it is suggested that in conjunction with microtubule associated proteins (MAPs) this arrangement may be optimal for information processing. These microtubule/MAP arrangements are connected to synaptic receptors on the dendrite membrane by a variety of calcium and sodium influxes, actin and other inputs (7). Alterations in the microtubule/MAPs network in the dendrites correlate with the arrangement of dendrite synapatic receptors (8). Studies (9) demonstrate that the cytoskeleton is also involved in signal transmission. It is suggested that the microtubule lattice could be more than just convenient wiring. The lattice is well designed to represent and process information. The microtubule is thus comprised of pieces of tubulin capable of representing bits of information. Tubulin switches between two conformations. It is suggested that tubulin conformational states could interact with with neighbouring tubulin by means of dipole interactions. The dipole-coupled conformation for each tubulin could be determined by the six surrounding tubulins. Hameroff describes protein conformation as a delicate balance between contervailing forces. Proteins are chains of amino acids that fold into three dimensional conformations. Folding is driven by van der Waals forces between hydrophobic amino acid groups. These groups can form hydrophobic pockets in some proteins. These pockets are critcal to the folding and regulation of protein. Amino acid side groups in these pockets interact by van der Waals forces. Nonpolar atoms and molecules can have instantaneous dipoles. Hameroff discusses the process of anesthesia that erases consciousness, but leaves many non-conscious functions intact. Anesthetic gas molecules are soluble in a lipid-like hydrophobic environment. Such areas are present in the brain in the lipid regions of cell membranes and in hydrophobic pockets within proteins. It is suggested that anesthetic gas molecules interact with amino acid groups via London forces, altering the normal action of London forces on the conformation of protein. Hameroff further looks at quantum information processing. Quantum superpositions, where the quantum waves represent multiple possibilities for the state of a particle, are known to persist until quanta are either measured or naturally interact with the rest of the environment. Penrose suggests that this wave function collapse is a real event. He sees superposition as a separation in the underlying spacetime geometry. Each quanta is embedded in a bit of space, and as superpositions grow a blister or separation appears in spacetime. If the separation between superpositions grows to more than the Planck length collapse occurs. The normal quantum wave collapse is seen as an entirely random choice of the state of a quantum particle, from amongst the various superpositions of states. However, these collapses involve interaction with the environment. Penrose suggests that a quanta, which does not interact with the environment will undergo objective reduction (OR) when the separation between superpositions begins to exceed the Planck length. He also suggests that while the normal collapse is totally random, OR is not totally random, but involves a non-computable process. This is suggested because Penrose thinks that the brain manifests a non-computational aspect, and that the wave function collapse is the only place in the universe where such a thing can exist. Penrose also proposes that OR based quantum computation occurs in the brain. It is important to stress that quantum computing as such is not expected to generate consciousness. In the quantum computers which many are now trying to develop quantum collapse will occur as a result of measurement or interaction with the environment. It is only in the event of OR that non-computability and consciousness could be brought into play. Hameroff goes on to look at some of the detail of the theory that he and Penrose developed as to how consciousness could be based in microtubules in the brain. They suggest that quantum compuations take place in microtubules orchestrated by the inputs of synapse via MAPs. Hence the theory is often known as Orch OR, for orchestrated objective reduction. The computations are suggested to persist for 25ms, which would link them to the 40 Hz gamma synchrony. The computations are terminated by objective reduction. It is proposed that in dendrites, the tubulin sub-units of the microtubules interact by dipole coupling so as process information. The tubulin conformation is governed by quantum London forces, so that the tubulins can exist as quantum superpositions of different conformations. In superposition the tubulins would be qbits in a quantum computer, computing by means of non-local entanglement with other tubulin qbits. This entanglement would not just be with tubulins in the same microtubule, but other microtubules in the same dendrite, and in other dendrites connected by gap junctions. It should be remembered that neurons connected by gap junctions can be viewed as a single hyperneuron and the hyperneuron can be seen as a conventional neuron assembly. Dendritic Interiors The dendritic interiors alternate between two states as a result of the polymerisation of actin protein. In the depolymerised form the interior of the neuron is aqueous and microtubules signal and process information classically. There are synaptic inputs to the microtubules during this phase. When actin polymerises, the interior of the dendrite becomes quasi-solid of gelatinous, and water near to the proteins beomes ordered as a result of the actin gelation. Debye layers of counterions may also shield the microtubules, due to the charged C-termini tails on the tubulins. This is suggested to make the microtubules sufficiently isolated from the environment for quantum superposition to occur in the tubulins. Coherent pumping of energy and quantum error correction may also help to prevent decoherence. Quantum error correction involves a code that can detect and correct decoherence in a quantum system. The geometry of a quantum computer lattice could be formed so as to be resistant to decoherence. Microtubules are suggested to have a structure which is particularly suitable for error correction. When the superpositions in the microtubules are reduced, the result can be used to regulate axon firing and changes in synapses. Hameroff claims to refute Tegmark's attempt to disprove the Penrose/Hameroff model. This is significant as Tegmark's criticism of Orch OR has been widely accepted as a satisfactory dismissal of the theory, and responses to Tegmark are habitualy ignored. Tegmark calculated microtubule decoherence time as being 10^-13 seconds, which would certainly be much too short for any neural activity. However, he worked on the basis of his own model for quantum activity in microtubules, which was never proposed by Penrose/Hameroff. For some reason he did not choose to address the Penrose/Hameroff model. This invalidates his particular approach, whatever the truth is about decoherence, but it has not prevented his work from being quoted as an absolutely reliable refutation of Orch OR. Tegmark based his calculation on a 24nm separation of solitons from themselves along the microtubules, whereas Orch OR proposes a superposition separation distance six orders of magnitude smaller. Capability of Being Tested or Falsified The ability of a theory to be falsified is the acid test of a scientific theory. The Orch Or model is claimed to stand up well in this respect. In 1998 twenty testable predictions of Orch OR were published. Four of these have actually been validated over the last decade, being, signalling along microtubules (9), correlation of synaptic function and cytoskeleton (10), action of psychoactive drugs on microtubules (11) and gap junction mediation of gamma synchrony (12). Others are currently being tested. The 16 untested predictions are:- 1) Microtubule stabilising drugs could treat brain diseases (13). 2) Laser spectroscopy could demonstrate coherent oscillation in microtubules (14). 3) Correlation of vibrational states of microtubule networks with cell activity. 4) Correlation of cytoskeletal networks with memory and neural behaviour 5) Preponderance of 'A lattice' microtubules in dendrites, as these are more suited to information processing. 6) Demonstration of non-local correlations between tubulins on same and different microtubules. 7) Superconducting devices could detect quantum coherence in microtubules. 8) Coherent photons will be detected from microtubules. 9) Dendritic microtubules surrounded by cross linked actin gels. 10) Cycles of gelation linked to gamma synchrony. 11) Gelation cycles regulated by calcium ions associated with microtubules. 12) Quantum tunnelling across gap junctions. 13) Non-local correlation between tubulins in different neurons. 14) Neural mass involved in cognitive tasks is inversely proportional to preconscious time, as in E=hbar/t. 15) Gap junction connections with retinal glial cells. 16) Testing of objective reduction (OR). Will test if isolated quantum superpositions self-collapse according to E=hbar/t (15). The theory is 'fundamentalist' in assuming that consciousness has to be a fundamental property of the universe that is accessed by the brain. Penrose's OR relates to the fundamental level of the universe, where at 10^-35 m, the continuity of spacetime breaks down and becomes quantised. This is proposed as the level where non-computable processes and possibly qualia are embedded. The rarity of consciousness in the universe is because only in a structure like the brain is it possible to isolate relatively large superpositions, such as nanograms of tubulin. Gregory Engel et al Dept. of Chemistry, University of California, Berkeley Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems Nature, vol 446, pp. 782-786, 12 April 2007 This paper points out that photosynthetic complexes are adapted to capture light, and put its energy into long-term storage. This process has normally been described in classical terms, and quantum coherence has been to a good extent ignored in the traditional analysis. However, the possibility of quantum coherence has been predicted, and in this paper the authors describe evidence for long-lived quantum coherence being involved in energy transfer within photosynthetic systems. The wavelike process is thought to account for the efficiency of the sytem, because it allows the sampling of large areas of phase space, in order to find the most efficient path, or to transfering energy to the area in the lowest energy state. The Engel et al experiment involved electronic spectroscopy to observe the evolution of electronic coherence. Quantum beating was found to last for 660 fs, which was much more than the 250 fs estimated for conventional models. Conventional models had assumed that quantum coherence would be rapidly destroyed, and had therfore not factored it into their models of photosynthetic systems. By contrast, the authors conclude that long-lived quantum coherence must play an active role in photosynthetic systems. A quantum coherent system allows sampling in order to direct energy to the lowest energy state. The system is viewed as performing a quantum computation, in which it senses many states simultaneously and from these selects the correct answer. This is seen as analogous to Grover's algorithm, allowing both the discovery of the lowest energy state and the transfer of coherence. This is more efficent than any classical search engine. Protein is seen as providing the structure in which coherence can be preserved and at the same time modulating the coherence as a result of the local dielectric environment. 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 paper 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. Mershin is mainly interested in experimentation at the protein-to-atom 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 building blocks of the microtubules. Protein is the work horse of all life forms, with its activity ranging over signaling, energy transduction, movements and catalysis of reactions. Mershin has worked on testing the suggestion that microtubules are not just structural, but are also involved in neural processing. His first test was the effedct 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, and 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. The interaction between tubulin dipoles and water molecule dipoles is basic to ideas of ferroelectricity along MTs and possible emission of coherent photons. 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. 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 hysrophobic 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 often quoted attack on quantum consciousness. Mershin's own point against Tegmark 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 transfer to occur. The paper discusses recent experiments involving quantum entanglement at room temperatures. Error correction and allowance for redundancy, because each qbit corresponds to a large number of particles, allows quantum coherence to continue despite contact with the environment. It is thought not impossible that similar circumstances could arise in biological systems. Mershin moves on to discuss what are 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 amongst a number of similar states. Mershin discusses the possibility of quantum teleportation in biological tissue. Quantum teleportation is a non-local correlation that occurs without any transfer of mass or energy. 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. Then the state of microtubule A is 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. Alteration of 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. The article proposes equipment and experiments that could test for 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 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 that 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 paper 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) Photon echo experiments at Starlab Pierre St. Hilaire, Dick Biermann & Stuart Hameroff www.starlab.org The authors claim that quantum consciousness models are testable, which is the acid test of a scientific theory as opposed to conventional or classical theories, which are claimed not to be testable. Physicists, Pierre St.Hilaire and Dick Bierman devised a test for evidence of quantum coherence in the retina, the most conveniently accessible part of the brain. Their scheme was to send two separate laser pulses to the part of the retina being studied. This is expected to cause rhodopsin molecules in the rod and cone cells to become quantum coherent. If the coherent state persists for longer than the time between the two laser pulses, then some atoms in the system precess back towards their original state, and they emit a photon in the process of doing this. This is known as a ‘photon echo’. This could be detected, and if detected it would be indicative of quantum coherence in the retina. Structures in the retina such as rhodopsin could in principle be shown to sustain macroscopic quantum coherence. No existing experiments of this kind were known to the authors, but research into the isomerisation of rhodopsin suggests the presence of quantum coherence. |
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