We envisage that attachments of MAPs on microtubules "tune" quantum oscillations, and "orchestrate" possible collapse outcomes (Figure 9). Thus we term the particular self-organizing OR occurring in MAP-connected microtubules, and relevant to consciousness, orchestrated objective reduction ("Orch OR"). Orch OR events are thus self-selecting processes in fundamental space-time geometry. If experience is truly a component of fundamental space-time, Orch OR may begin to explain the "hard problem" of consciousness. 

Summary of the Orch OR Model for Consciousness 

 The full details of this model are given in Hameroff and Penrose (1996). The picture we are putting forth involves the following ingredients: 
 

1. Aspects of quantum theory (e.g. quantum coherence) and of the suggested physical phenomenon of quantum wave function "self-collapse" (objective reduction: OR - Penrose, 1994; 1996) are essential for consciousness, and occur in cytoskeletal microtubules (MTs) and other structures within each of the brain's neurons. 
2. Conformational states of MT subunits (tubulins) are coupled to internal quantum events, and cooperatively interact with other tubulins in both classical and quantum computation (Hameroff et al, 1992; Rasmussen et al, 1990 - Figures 4, 5 and 6). 
3. Quantum coherence occurs among tubulins in MTs, pumped by thermal and biochemical energies (perhaps in the manner proposed by Fr”hlich, 1968; 1970; 1975). Evidence for coherent excitations in proteins has recently been reported by Vos et al (1993).

 
It is also considered that water at MT surfaces is "ordered," dynamically coupled to the protein surface. Water ordering within the hollow MT core (acting like a quantum wave guide) may result in quantum coherent photons (as suggested by the phenomena of "super-radiance" and "self-induced transparency" - Jibu et al, 1994; 1995). We require that coherence be sustained (protected from environmental interaction) for up to hundreds of milliseconds by isolation a) within hollow MT cores; b) within tubulin hydrophobic pockets; c) by coherently ordered water; d) sol-gel layering (Hameroff and Penrose, 1996). Feasibility of quantum coherence in the seemingly noisy, chaotic cell environment is supported by the observation that quantum spins from biochemical radical pairs which become separated retain their correlation in cytoplasm (Walleczek, 1995). 
 

4. During pre-conscious processing, quantum coherent superposition/computation occurs in MT tubulins and continues until the mass-distribution difference among the separated states of tubulins reaches a threshold related to quantum gravity. Self-collapse (OR) then occurs (Figures 6 & 7). 

5. The OR self-collapse process results in classical "outcome states" of MT tubulins which then implement neurophysiological functions. According tocertain ideas for OR (Penrose, 1994), the outcome states are "non-computable"; that is, they cannot be determined algorithmically from the tubulin states at the beginning of the quantum computation. 

6. Possibilities and probabilities for post-OR tubulin states are influenced by factors including initial tubulin states, and attachments of microtubule-associated proteins (MAPs) acting as "nodes" which tune and "orchestrate" the quantum oscillations (Figure 9). We thus term the self-tuning OR process in microtubules "orchestrated objective reduction - Orch OR"). 

7. According to the arguments for OR put forth in Penrose (1994), superposed states each have their own space-time geometries. When the degree of coherent mass-energy difference leads to sufficient separation of space-time geometry, the system must choose and decay (reduce, collapse) to a single universe state. Thus Orch OR involves self-selections in fundamental space-time geometry (Figures 10 & 11).

8. To quantify the Orch OR process, in the case of a pair of roughly equally superposed states, each of which has a reasonably well-defined mass distribution, we calculate the gravitational self-energy E of the difference between these two mass distributions, and then obtain the approximate lifetime T for the superposition to decay into one state or the other by the formula T=h/E. Here h is Planck's constant over 2pi. We call T the coherence time for the superposition (how long coherence is sustained). If we assume a coherence time T= 500 msec (shown by Libet, 1979, and others to be a relevant time for pre-conscious processing), we calculate E, and determine the number of MT tubulins whose coherent superposition for 500 msec will elicit Orch OR. This turns out to be about 10^9 tubulins. 

9. A typical brain neuron has roughly 10^7 tubulins (Yu and Baas, 1994). If, say, 10 percent of tubulins within each neuron are involved in the quantum coherent state, then roughly 10^3 (one thousand) neurons would be required to sustain coherence for 500 msec, at which time the quantum gravity threshold is reached and Orch OR then occurs. 

10. We consider each self-organized Orch OR as a single conscious event; cascades of such events would constitute a "stream" of consciousness. If we assume some form of excitatory input (e.g. you are threatened, or enchanted) in which quantum coherence emerges faster, then, for example, 10^10 coherent tubulins could Orch OR after 50 msec (e.g. Figure 8c). Turning to see a bengal tiger in your face might perhaps elicit 10^11 in 5 msec, or more tubulins, faster. A slow emergence of coherence (your forgotten phone bill) may require longer times. A single electron would require more than the age of the universe. 

11. Quantum states are non-local (because of quantum entanglement--or "Einstein-Podolsky-Rosen" (EPR) effects), so that the entire non-localized state reduces all at once. This can happen if the mass movement that induces collapse takes place in a small region encompassed by the state, or if it takes place uniformly over a large region. Thus, each instantaneous Orch OR could "bind" various superpositions which may have evolved in separated spatial distributions and over different time scales, but whose net displacement self-energy reaches threshold at a particular moment. Information is bound into an instantaneous event (a "conscious now"). Cascades of Orch ORs could then represent our familiar "stream of consciousness," and create a "forward" flow of time (Aharonov and Vaidman, 1990; Elitzur, 1996; Tollaksen, 1996).

 
 
It may be interesting to compare our considerations with subjective viewpoints that have been expressed with regard to the nature of the progression of conscious experience. For example, support for consciousness consisting of sequences of individual, discrete events is found in Buddhism; trained meditators describe distinct "flickerings" in their experience of reality (Tart, 1995). Buddhist texts portray consciousness as "momentary collections of mental phenomena", and as "distinct, unconnected and impermanent moments which perish as soon as they arise." Each conscious moment successively becomes, exists, and disappears - its existence is instantaneous, with no duration in time, as a point has no length. Our normal perceptions, of course, are seemingly continuous, presumably as we perceive "movies" as continuous despite their actual makeup being a series of frames. Some Buddhist writings even quantify the frequency of conscious moments. For example the Sarvaastivaadins (von Rospatt, 1995) described 6,480,000 "moments" in 24 hours (an average of one "moment" per 13.3 msec), and some Chinese Buddhism as one "thought" per 20 msec. These accounts, including variations in frequency, are consistent with our proposed Orch OR events. For example a 13.3 msec pre-conscious interval would correspond with an Orch OR involving 4 x 10^10 coherent tubulins, a 0.13 msec interval would correspond with 4 x 10^12 coherent tubulins, and a 20 msec interval with 2.5 x 10^10 coherent tubulins. Thus Buddhist "moments of experience," Whitehead "occasions of experience," and our proposed Orch OR events seem to correspond tolerably well with one another.. 
 

The Orch OR model thus appears to accommodate some important features of consciousness:

The Orch OR model has the implication that an organism able to sustain quantum coherence among, for example, 10^9 tubulins for 500 msec might be capable of having a conscious experience. More tubulins coherent for a briefer period, or fewer for a longer period (E = h bar / T ) will also have conscious events. Human brains appear capable of, for example, 10^11 tubulin, 5 msec "bengal tiger experiences," but what about simpler organisms? 

From an evolutionary standpoint, introduction of a dynamically functional cytoskeleton (perhaps symbiotically from spirochetes, e.g. Margulis, 1975) greatly enhanced eukaryotic cells by providing cell movement, internal organization, separation of chromosomes and numerous other functions. As cells became more specialized with extensions like axopods and eventually neural processes, increasingly larger cytoskeletal arrays providing transport and motility may have developed quantum coherence via the Fröhlich mechanism as a by-product of their functional coordination. 

Another possible scenario for emergence of quantum coherence leading to Orch OR and conscious events is "cellular vision." Albrecht-Buehler (1992) has observed that single cells utilize their cytoskeletons in "cellular vision" - detection, orientation and directional response to beams of red/infra-red light. Jibu et al (1995) argue that this process requires quantum coherence in microtubules and ordered water, and Hagan (1995) suggests the quantum effects/cellular vision provided an evolutionary advantage for cytoskeletal arrays capable of quantum coherence. For whatever reason quantum coherence emerged, one could then suppose that, one day, an organism achieved sufficient microtubule quantum coherence to elicit Orch OR, and had a "conscious" experience. 

 At what level of evolutionary development might this primitive consciousness have emerged? A single cell organism like Paramecium is extremely clever, and utilizes its cytoskeleton extensively. Could a paramecium be conscious? Assuming a single paramecium contains, like each neuronal cell, 10^7 tubulins, then for a paramecium to elicit Orch OR, 100% of its tubulins would need to remain in quantum coherent superposition for nearly a minute. This seems unlikely. 

 Consider the nematode worm C elegans. It's 302 neuron nervous system is completely mapped. Could C elegans support Orch OR? With 3 x 10^9 tubulins, C elegans would require one third of its tubulins to sustain quantum coherent superposition for 500 msec. This seems unlikely, but not altogether impossible. If not C elegans, then perhaps Aplysia with a thousand neurons, or some higher organism. Orch OR provides a theoretical framework to entertain such possibilities. 

Would a primitive Orch OR experience be anything like ours? If C elegans were able to self-collapse, what would it be like to be a worm? (Nagel, 1974) A single, 10^9 tubulin, 500 msec Orch OR in C elegans should be equal in gravitational self-energy (and thus perhaps, experiential intensity) to one of our "everyday experiences." A major difference is that we would have many Orch OR events sequentially (up to, say, 10^9 per second) whereas C elegans could generate, at most, 2 per second. C elegans would also presumably lack extensive memory and associations, and have poor sensory data, but nonetheless, by our criteria a 10^9 tubulin, 500 msec Orch OR in C elegans would be a conscious experience: a mere smudge of known reality, the next space-time move. 

Consciousness has an important place in the universe. Orch OR in microtubules is a model depicting consciousness as sequences of non-computable self-selections in fundamental space-time geometry. If experience is a quality of space-time, then Orch OR indeed begins to address the "hard problem" of consciousness in a serious way. 

Reprinted from Journal of Consciousness Studies (2)1:36-53, 1996 

Correspondence srh@ccit.arizona.edu 
 
 
 
References 
 

Aharonov, Y., and Vaidman, L., (1990) Properties of a quantum system during the time interval between two measurements. Phys. Rev. A. 41:11. 

Albrecht-Buehler, G., (1992) Rudimentary form of "cellular vision" Cell Biol 89, 8288-8292 

Beck, F. and Eccles, J.C. (1992) Quantum aspects of brain activity and the role of consciousness. Proc. Natl. Acad. Sci. USA 89(23):11357-11361. 

Chalmers, D. (1996) Facing up to the problem of consiousness. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA. 

Chalmers, D. (1996) Toward a Theory of Consciousness. Springer-Verlag, Berlin.  

Conze, E., (1988) Buddhist Thought in India, Louis de La Vallee Poussin (trans.), Abhidharmako"sabhaa.syam: English translation by Leo M. Pruden, 4 vols (Berkeley) pp 85-90. 

Di¢si, L. (1989) Models for universal reduction of macroscopic quantum fluctuations. Phys. Rev. A. 40:1165-1174. 

Elitzur, (1996) Time and consciousness: The uneasy bearing of relativity theory on the mind-body problem. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA. 

Everett, H., (1957) Relative state formulation of quantum mechanics. In Quantum Theory and Measurement, J.A. Wheeler and W.H. Zurek (eds.) Princeton University Press, 1983; originally in Rev. Mod. Physics, 29:454-462. 

Fr”hlich, H. (1968) Long-range coherence and energy storage in biological systems. Int. J. Quantum Chem. 2:641-9. 

Fr”hlich, H. (1970) Long range coherence and the actions of enzymes. Nature 228:1093.  

Fr”hlich, H. (1975) The extraordinary dielectric properties of biological materials and the action of enzymes. Proc. Natl. Acad. Sci. 72:4211-4215. 

Ghirardi, G.C., Grassi, R., and Rimini, A. (1990) Continuous-spontaneous reduction model involving gravity. Phys. Rev. A. 42:1057-1064. 

Ghirardi, G.C., Rimini, A., and Weber, T. (1986) Unified dynamics for microscopic and macroscopic systems. Phys. Rev. D. 34:470. 

Goswami, A., (1993) The Self-Aware Universe: How Consciousness Creates the Material World. Tarcher/Putnam, New York. 

Hagan, S., (1995) personal communication 

Hameroff, S.R., Dayhoff, J.E., Lahoz-Beltra, R., Samsonovich, A., and Rasmussen, S. (1992) Conformational automata in the cytoskeleton: models for molecular computation. IEEE Computer (October Special Issue on Molecular Computing) 30-39.  

Hameroff, S.R., and Penrose, R., (1995) Orchestrated reduction of quantum coherence in brain microtubules: A model for consciousness. Neural Network World 5 (5) 793-804. 

Hameroff, S.R., and Penrose, R., (1996) Orchestrated reduction of quantum coherence in brain microtubules: A model for consciousness. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA. 

Jibu, M., Hagan, S., Hameroff, S.R., Pribram, K.H., and Yasue, K. (1994) Quantum optical coherence in cytoskeletal microtubules: implications for brain function. BioSystems 32:195-209. 

Jibu, M., Yasue, K., Hagan, S., (1995) Water laser as cellular "vision", submitted.  

K rolh zy, F., Frenkel, A., and Lukacs, B. (1986) On the possible role of gravity on the reduction of the wave function. In Quantum Concepts in Space and Time, R. Penrose and C.J. Isham (eds.), Oxford University Press. 

Libet, B., Wright, E.W. Jr., Feinstein, B., and Pearl, D.K. (1979) Subjective referral of the timing for a conscious sensory experience. Brain 102:193-224. 

Louria, D., and Hameroff, S. (1996) Computer simulation of anesthetic binding in protein hydrophobic pockets. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA.  

Marshall, I.N. (1989) Consciousness and Bose-Einstein condensates. New Ideas in Psychology 7:73 83. 

Margulis, L., (1975) Origin of Eukaryotic Cells. Yale University Press, New Haven. 

Nagel, T. (1974; 1981) What is it like to be a bat? in The Mind's I. Fantasies and Reflections on Self and Soul. (eds) D.R. Hofstadter and D.C. Dennett, Basic Books, N.Y. pp 391-403, 1981 (Originally published in The Philosophical Review, October, 1974)  

Pearle, P. (1989) Combining stochastic dynamical state vector reduction with spontaneous localization. Phys. Rev. D. 13:857-868.  

Pearle, P., and Squires, E. (1994) Bound-state excitation, nucleon decay experiments and models of wave-function collapse. Phys. Rev. Letts. 73(1):1-5.  

Penrose, R. (1987) Newton, quantum theory and reality. In 300 Years of Gravity S.W. Hawking and W. Israel (eds.) Cambridge University Press.  

Penrose, R. (1989) The Emperor's New Mind, Oxford Press, Oxford, U.K.  

Penrose, R. (1993) Gravity and quantum mechanics. In General Relativity and Gravitation. Proceedings of the Thirteenth International Conference on General Relativity and Gravitation held at Cordoba, Argentina 28 June-4 July 1992. Part 1: Plenary Lectures. (eds. R.J. Gleiser, C.N. Kozameh and O.M. Moreschi) Institute of Physics Publications, Bristol.  

Penrose, R. (1994) Shadows of the Mind, Oxford Press, Oxford, U.K. 

Penrose, R. (1995) On gravity's role in quantum state reduction 

Penrose, R., anmd Hameroff, S.R., What gaps? Reply to Grush and Churchland. Journal of Consciousness Studies 2(2):99-112. 

Rasmussen, S., Karampurwala, H., Vaidyanath, R., Jensen, K.S., and Hameroff, S. (1990) Computational connectionism within neurons: A model of cytoskeletal automata subserving neural networks. Physica D 42:428-449. 

Rensch, B. (1960) Evolution Above the Species Level. Columbia university Press, New York. 

Russell, B. (1954) The Analysis of Matter. Dover, New York. 

Schr”dinger, E (1935) Die gegenwarten situation in der quantenmechanik. Naturwissenschaften, 23:807-812, 823-828, 844-849. (Translation by J. T. Trimmer (1980) in Proc. Amer. Phil. Soc., 124:323-338.) In Quantum Theory and Measurement (ed. J.A. Wheeler and W.H. Zurek). Princeton University Press, 1983. 

Shimony, A., (1993) Search for a Naturalistic World View - Volume II. Natural Science and Metaphysics. Cambridge University Press, Cambridge, U.K. 

Spinoza, B. (1677) Ethica in Opera quotque reperta sunt. 3rd edition, eds. J. van Vloten and J.P.N. Land (Netherlands: Den Haag) 

Stubenberg, L. (1996) The place of qualia in the world of science. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA. 

Tart, C.T., (1995) personal communication and information gathered from "Buddha-1 newsnet" 

Tollaksen, J. (1996) New insights from quantum theory on time, consciousness, and reality. In: Toward a Science of Consciousness - The First Tucson Discussions and Debates, S.R. Hameroff, A. Kaszniak and A.C. Scott (eds.), MIT Press, Cambridge, MA. 

von Rospatt, A., (1995) The Buddhist Doctrine of Momentariness: A survey of the origins and early phase of this doctrine up to Vasubandhu (Stuttgart: Franz Steiner Verlag). 

Vos, M.H., Rappaport, J., Lambry, J. Ch.,Breton, J., Martin, J.L. Visualization of coherent nuclear motion in a membrane protein by femtosecond laser spectroscopy. Nature 363:320-325. 

Walleczek, J. (1995) Magnetokinetic effects on radical pairs: a possible paradigm for understanding sub-kT magnetic field interactions with biological systems. in Biological Effects of Environmental Electromagnetic Fields. M Blank (ed) Advances in Chemistry No 250 American Chemical society Books Washington DC (in press) 

Wheeler, J.A. (1957) Assessment of Everett's `relative state" formulation of quantum theory. Revs. Mod. Phys., 29:463-465. 

Wheeler, J.A. (1990) Information, physics, quantum: The search for links. In (W. Zurek, ed.) Complexity, Entropy, and the Physics of Information. Addison-Wesley. 

Whitehead, A.N., (1929) Science and the Modern World. Macmillan, N.Y. 

Whitehead, A.N., (1929) Process and Reality. Macmillan, N.Y. 

Yu, W., and Baas, P.W. (1994) Changes in microtubule number and length during axon differentiation. J. Neuroscience 14(5):2818-2829. 

Conscious Events as Orchestrated Space-Time Selections (http://www.u.arizona.edu/~hameroff/penrose2.html) by Stuart Hameroff and Roger Penrose - External original version

  

  

My Books

Discover

• Free Books
• Answers FAQ