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BernroiderIon Channels and Quantum Consciousness 1.) Introduction 2.) Quantum entanglement of K+ Ions, multiple Introduction Ion Channels and Consciousness - Gustav Bernroider Bernroider and Roy propose a quantum information system in the brain that is driven by the entangled ion states in the voltage-gated ion channels. These ion channels, situated in the neuron’s membrane are a crucial component of the conventional neuroscience description of axon spiking leading to neural transmitter release at the synapses. The ion channels allow the influx and outflux of ions from the cell driving the fluctuation of electrical potential along the axon, which in turn provides the necessary signal to the synapse. The authors concentrate their attention on the potassium (K+) channel and in particular the configuration of this channel when it is in the closed state. This channel is traditionally seen as having the function of resetting the membrane potential from a firing to a resting state. This is achieved by positively charged potassium (K+) ions flowing out of the neuron through the channel. Recent progress in atomic-level spectroscopy of the membrane proteins that constitute the ion channels and the accompanying molecular dynamic simulations indicate that the organisation of the membrane proteins carries a logical coding potency, and also implies quantum entanglement within ion channels and possibly also between different ion channels. An increasing number of studies show that proteins surrounding membrane lipids are associated with the probabilistic nature of the gating of the ion channels (58. Doyle, 1998, 59. Zhou, 2001, 60. Kuyucak, 2001). The authors draw particularly on the work of MacKinnon and his group, notably his crystallographic X-ray work. (61-64.). The study shows that ions are coordinated by carboxyl based oxygen atoms or by water molecules. An ion channel can be in either a closed or an open state, and in the closed state there are two ions in the permeation path that are confined there. The authors regard this closed gate arrangement as the essential feature with regard to their research work. The open gate presents very little resistance to the flow of potassium ions, but the closed gate is a stable ion-protein configuration. The ion channel serves two functions, selecting K+ ions as the ones that will be given access through the membrane, and then voltage-gating the flow of the permitted K+ ions. In the authors’ view, recent studies also require a change in views both of the ion permeation and of the voltage-gating process. A charge transfer carried by amino acids is involved in the gating process. In the traditional model the charges were completely independent, whereas in the new model there is coupling with the lipids that lie next to the channel proteins. This view, which came originally from MacKinnon, is now supported by other more recent studies . The authors think that the new gating models are more likely to support computational activity, than were the traditional models. Three potassium ions are involved in the ion channel’s closed configuration. Two of these are trapped in the permeation path of the protein, when the channel gate is closed. The filter region of the ion channel is indicated by the recent studies to have five binding pockets in the form of five sets of four carboxyl related oxygen atoms. Each of the two trapped potassium ion are bound to eight of the oxygen atoms, i.e. each of them are bound to two out of the five binding pockets. The author’s calculations predict that the trapped ions will oscillate many times before the channel re-opens, and the calculations also suggest an entangled state between the potassium ions and the binding oxygen atoms. This structure is seen as being delicately balanced and sensitive to small fluctuations in the external field. This sensitivity is viewed as possibly being able to account for the observed variations in cortical responses. Ion Channels & Quantum Computing The theory also relates the results of recent studies of the potassium channel and its electrical properties to the requirements for quantum computing. There have been schemes for quantum computers involving ion traps, based on electostatic interactions between ions held in microscopic traps, that have a resemblance to Bernroider’s interpretation of the possible quantum state of the K+ channel. The authors deny that the rapid decoherence of quantum states in the brain calculated by Tegmark applies to their model. They argue that the ions are not freely moving in the ion filter area of the closed potassium channel, but are held in place by the surrounding electrical charges and the external field. The ions are particularly insulated within the carboxyl binding pockets, and it is suggested the decoherence could be avoided for the whole of the gating period of the channel, which is in the range of 10-13 seconds. Entanglement & Ion Channels The authors also raise the question of whether given quantum coherence in the ion channel, it is possible for the channel states to be communicated to the rest of the cell membrane. This could include connections to other ion channels in the same membrane, possibly by means of quantum entanglement. Bernroider’s work might not be considered to be a fully fledged separate quantum consciousness theory. In the early part of the decade, Bernroider seemed to associate himself with David Bohm’s implicate order, but the lack of much specific neuroscience in Bohm’s version makes it hard to make any definite connection between it and the type of detailed neuroscientific argument offered by Bernroider. Bernroider can be seen to differ from the various quantum brain dynamics theories that derive from Umezawa, in concentrating on quantum mechanics rather than quantum field theory, and in not giving a major role to water. It also varies from Orch OR in focusing on the cell membrane rather than the cytoskeleton and on the axons rather than the dendrites, and by dealing with simple ions rather than Bose condensates. However, it is possible to speculate that wave function collapse under the Bernroider proposals could still result in objective reduction, and thus provide a link to Penrose’s fundamental spacetime geometry. Bernroider’s theory might be seen to represent even more of a challenge to conventional neuroscience than the other quantum consciousness theories. This is because its recruits as its basis the axon membrane and ion channels which form a crucial part of the conventional neuroscience model, and then tries to remodel these core structures on a quantum-driven basis. It is hard to deny that if this theory were to become better substantiated, it would produce in neuroscience a revolution of the most profound kind. Quantum entanglement of K+ Ions, multiple channel states & the role of noise in the brain - Bernroider, G. & Roy, S. (2005) - International Society for Optical Engineering (SPIE) Vol. 5841 Gustav Bernroider of Salzburg University has proposed that quantum coherence and entanglement in the ion channels of neurons underlies information processing in the brain and ultimately consciousness (1&2.). Function & Structure of the Ion Channels Ion channels are a crucial component in the axonal spiking/synaptic firing model of neuronal signalling and information processing. The axonal signal starts from the body of the neuron and proceeds down an extension called the axon, by means of a fluctuation in the difference in electrical potential across the membrane that forms the exterior of the axon. The membrane is formed by a double layer of lipids. The ion channels consist of protein molecules inserted through the lipid bi-layer. The axon fires when sodium (Na+) ions flow in through one set of ion channels, and subsequently returns to its resting state when potassium (K+) ions flow out through another set of ion channels. This process continues down the length of the axon until it reaches the synapse, which it allows to fire, and thus communicate with other neurons. Ion channels are thus a key mechanism in the brain's signalling and information processing. Bernroider bases his theory on recent studies of ion channels. These have been made possible by advances in high-resolution atomic-level spectroscopy and accompanying molecular dynamics simulations. His theory was principally developed in a 2005 paper with co-author Sisir Roy (1.). In this work, they draw particularly on the work of the MacKinnon group, and on studies of the potassium (K+) channel, especially the closed state of this channel. (3-20.) The functioning of the K+ channel occurs in two stages, firstly, the selection of K+ ions in preference to any other species of ion, and secondly voltage-gating that controls the flow of these favoured K+ ions. The authors say that the traditional understanding of both functions has been altered by the recent studies. In its closed state, the channel is now seen to stabilise three K+ ions, two in the permeation filter of the ion channel and one in a water cavity to the intracellular side of this permeation path. In the case of the channel's voltage gating, the electrical charges involved which were previously thought to act independently of the surrounding proteins and lipids, are now seen to be coupled to these proteins and lipids, and are thus involved in the gating process. Atomic-level spectroscopy has revealed the detailed structure of the K+ channel in its closed state. The filter region of the channel has a framework of five sets of four oxygen atoms, which are each part of the carboxyl group of an amino-acid molecule in the surrounding protein. These are referred to as binding pockets, involving eight oxygen atoms in total. Both ions in the channel oscillate between two configurations (1). Bernroider and Roy's calculations lead them to claim that ion permeation can only be understood at the quantum level. Taking this as an initial assumption, they go on to ask whether the resulting model of the ion channel can be related to logic states. Their calculations suggest that the K+ ions and the carboxyl atoms of the binding pockets are two quantum-entangled sub-systems, and they equate this to a quantum computational mapping. The K+ ions that are destined to be expelled from the channel could, in the authors hypothesis, encode information about the state of the oxygen atoms in the axon membrane (1.). In a later paper, presented at the Quantum Mind 2007 conference (2.), Bernroider proposed that different ion channels could be non-locally entangled, thus proposing a quantum process over an extended area of the axon. Given the importance of the ion channels in brain functioning, this model would give quantum coherence and non-locality in the axon membrane an integral role in the brain's signalling and information processing. Further to this, Bernroider and Roy have pointed out a similarity between the structure of the K+ ion channel and some recent proposals for building quantum computers, in which ions are held in microscopic traps (20-27.). The authors argue that their model is well protected against decoherence, which has always been the most cogent criticism of quantum consciousness proposals. In particular, they claim that Tegmark's calculations do not apply to their model (28.). The authors agree that for ions moving freely in water, Tegmark's coherence time of 10^20 seconds would apply. However, they argue that the situation of the ions held in the permeation filter of the ion channel is markedly different, with a temperature about half the prevailing level for the brain, and the ions protected from decoherence by the binding pockets and the adjoining water cavity (1). A New Theory of Quantum Consciousness? It may be debatable as to whether Bernroider's proposals amount to a new theory of quantum consciousness. In a paper in Neuroquantology in 2003 (29.), Bernroider appeared to favour David Bohm's concept of an underlying implicate order from which arises the explicate order of classical physics that we experience in everyday life. However, Bernroider and Roy's 2005 paper and Bernroider's extension of this at the 2007 conference propose a new system of quantum coherence in the brain that is distinct from any of the earlier quantum consciousness models. Bernroider's theory could potentially be a vehicle for transfering consciousness from the implicate into the explicate order of David Bohm. Bernroider differs from Penrose and Hameroff's Orch OR model in his emphasis of the axons and membranes, as opposed to the dendrites and the cytoskeleton. However, there are similarities between the two models in that both of them propose quantum coherence, non-locality and subsequent wave function collpase linked to the brain's macroscopic information processing activity. As it stands, Bernroider's proposals only deal with information processing in the brain rather than consciousness as such. However, it appears possible that wave function collpase in the ion channels might link to Penrose's proposed geometry of space time, just as readily as wave function collapse in the cytoskeleton. Bernroider's theory is distinct from all earlier quantum consciousness theories in locating its mechanism in structures that are central to mainstream theories of the brain's information processing and production of consciousness. If future experimentation were to substantiate the Bernroider proposals, this would involve a revolution in neuroscience of the most profound kind. References:- 1.) Bernroider, G. & Roy, S. (2005) - Quantum entanglement of K+ ions, multiple channel states and the role of noise in the brain - International Society for Optical Engineering (SPIE), vol. 5841 2.) Bernroider, G. & Summhamer, J. (2007) - The role of quantum cooperativity in neural signalling - Quantum Mind 2007 Conference Abstracts 3.) MacKinnon, R. & Yellen (1990) - K channels 4.) Jiang, Y., MacKinnon, R. et al (2003) - X ray structure of a voltage-dependent K+ channel - Nature, 423, pp. 42-8 5.) Jiang, Y. MacKinnon, R. et al (2003) - The principle of gating charge movement in a voltage-dependent K+ channel - Nature, 423, pp. 42-8 6.) Zhou, Y., Morais-Cabral, A., Kaufman, A., & MacKinnon, R. (2001) - Chemistry of ion coordination and hydration revealed in K+ channel-Fab complex at 2.0 A resolution - Nature, 414, pp. 43-8 7.) Morais-Cabral, H., Zhou, H. & MacKinnon, R. (2001) - Energetic optimisation of ion conuction rate by the K+ selectivity filter - Nature, 414, pp. 37-42 8.) Doyle, D., MacKinnon, R. et al (1998) - The structure of the potassium channel: Molecular basis of K+ conduction and selectivity - Science, 280, pp. 69-76 9.) Perozo, E. (1999) - Structural rearrangements underlying K+ channel activation gating - Science, 285, pp. 73-78 10.) Garafoli, S. & Jordan, P. (2003) - Modelling permeation energetics in the KcsA potassium channel - Biophysical Journal, 84, pp. 2814-2830 11.) Miloshevsky, G. & Jordan, P. (2004) - Permeation in ion channels: the interplay of structure and theory - Trends in Neuroscience, 27, (6), pp. 308-314 12.) Armstrong, C. & Hille, B. (1998) - Voltage-gated ion channels and electrical excitability - Neuron, 20, pp. 371-80 13.) Guidoni, L. & Carloni, P. (2002) - Potassium permeation through the KcsA channel: a density functional study - Biochimica et Biophysica Acta, 1563, pp. 1-6 14.) Berneche, S. & Roux, B. (2001) - Energetics of ion conduction through the K+ channel - Nature, 414, pp. 73-7 15.) Ranatunga, K. et al (2001) - Side-chain ionisation states in a potassium channel - Biophysical Journal, 80, pp. 1210-19 16.) Chung, S. et al (2002) - Conducting state properties of the KcsA potassium channel from the molecular and Brownian dynamics simulations - Biophysical Journal, 82, pp. 628-45 17.) Bezanilla, F. (2000) - The voltage sensor in voltage-dependent ion channels - Physiology Review, 80, pp. 555-592 18.) Oliver, D. et al (2004) - Functional conversion between A type and delayed rectifier K+ channels by membrane lipids - Science, 304, pp. 265-70 19.) Roux, B. et al (2000) - Ion channels, permeation and electrostatics: insight into the function of KcsA - Biochemistry, 39, pp. 13295-13306 20.) Kuvucak, S. et al - Models of permeation in ion channels - Rep. Prog. Phys., 64, p.1427 21.) Cirac, J. & Zoller, P. (1995) - Quantum computation with cold trapped ions - Physical Review Letters, 74, pp. 4091-4094 22.) Di Vicenzo, D. (1995) - Two bit gates are universal for quantum computation - Physical Review, A, 51, pp. 1015-22 23.) Cirac, J. & Zoller, P. - A scalable quantum computer with ions in arrays of microtraps - Nature, 404, pp. 579-81 24.) Carlaco, J., Cirac, J. & Zoller, P. - Entangling ions in arrays of microscopic traps - arXiv:quant-ph/00105vl 25.) Monroe, C. (2002) - Quantum information processing with atoms and photons - Nature, 416, pp. 238-46 26.) Milburn, G. et al (2002) - Ion trap quantum computing with warm ions - Fortschr. Phys., 48, pp. 801-10 27.) Duan, L. et al (2004) - Scalable trapped ion computation with a probalistic ion-photon mapping - arXiv:quant-ph/01401020vl 28.) Tegmark, M. (2000) - Importance of quantum coherence in brain processes - Physical Reviews, E61, pp. 4194-4206 29.) Bernroider, G. (2003) - Quantum neurodynamics and the relationship to conscious experience - Neuroquantology, 2: pp. 163-8 |
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