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| '''Orchestrated objective reduction''' ('''Orch-OR''') is a theory of [[consciousness]], which is the joint work of theoretical physicist, [[Roger Penrose|Sir Roger Penrose]], and anesthesiologist [[Stuart Hameroff]]. Mainstream theories assume that consciousness emerges from the brain, and focus particularly on complex [[computation]] at [[synapses]] that allow communication between [[neuron]]s.{{citation needed|date=May 2013}} Orch-OR combines approaches to the problem of [[consciousness]] from the radically different angles of mathematics, physics, and anesthesia.
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| [[Roger Penrose|Penrose]] and [[Stuart Hameroff|Hameroff]] initially developed their ideas quite separately from one another, and it was only in the 1990s that they cooperated to produce the Orch-OR theory. Penrose came to the problem from the view point of mathematics and in particular [[Gödel's incompleteness theorems|Gödel's theorem]], while Hameroff approached it from a career in cancer research and [[anesthesia]] that gave him an interest in brain structures.
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| The mathematical and scientific basis of Orch-OR is rejected by mainstream mathematicians,<ref name=laforte_1998>LaForte, Geoffrey, Patrick J. Hayes, and Kenneth M. Ford 1998.''[http://www.cs.uwf.edu/~glaforte/papers/whyGodel.ps Why Gödel's Theorem Cannot Refute Computationalism]''. Artificial Intelligence, 104:265-286.</ref><ref name=solomon_1996>{{cite journal | authorlink = Solomon Feferman | last = Feferman | first = Solomon | year = 1996 |id = {{citeseerx|10.1.1.130.7027}} | title = Penrose's Gödelian argument | journal = PSYCHE | volume = 2 | pages = 21–32 }}</ref><ref name=krajewski_2007>Krajewski, Stanislaw 2007. ''On Gödel's Theorem and Mechanism: Inconsistency or Unsoundness is Unavoidable in any Attempt to 'Out-Gödel' the Mechanist.'' Fundamenta Informaticae 81, 173-181. Reprinted in [http://books.google.com/books?id=0jSS-3Bl06cC&lpg=PP1&pg=PA173#v=onepage&q&f=falseTopics in Logic, Philosophy and Foundations of Mathematics and Computer Science:In Recognition of Professor Andrzej Grzegorczyk (2008), p. 173]</ref> philosophers,<ref name=mindpapers>http://consc.net/mindpapers/6.1b</ref><ref name=lucas_criticisms>http://users.ox.ac.uk/~jrlucas/Godel/referenc.html</ref><ref name=Boolos_1990>[[George Boolos|Boolos, George]], et al. 1990. ''An Open Peer Commentary on The Emperor's New Mind.'' Behavioral and Brain Sciences 13 (4) 655.</ref><ref name=martin_1993>[[Martin Davis|Davis, Martin]] 1993. ''How subtle is Gödel's theorem? More on Roger Penrose.'' Behavioral and Brain Sciences, 16, 611-612. Online version at Davis' faculty page at http://cs.nyu.edu/cs/faculty/davism/</ref><ref name=lewis_1969>[[David Kellogg Lewis|Lewis, David K.]] 1969.''[http://www2.units.it/etica/2003_1/7_monographica.doc Lucas against mechanism]''. Philosophy 44 231-233.</ref><ref name=putnam_1995>[[Hilary Putnam|Putnam, Hilary]] 1995. ''Review of Shadows of the Mind.'' In Bulletin of the American Mathematical Society 32, 370-373 (also see Putnam's less technical criticisms in his [http://www.nytimes.com/books/97/04/27/nnp/17540.html New York Times review])</ref> and scientists.<ref name=Tegmark2000>{{cite journal|last=Tegmark|first=Max|title=Importance of quantum decoherence in brain processes|journal=Phys. Rev. E|date=April 2000|volume=61|issue=4|pages=4194|doi=10.1103/PhysRevE.61.4194|url=http://pre.aps.org/abstract/PRE/v61/i4/p4194_1|accessdate=18 November 2012}}</ref><ref name=" McKemmish2009">{{cite journal |author=McKemmish, L.K., Reimers, J.R., McKenzie, R.H., Mark, A.E., and Hush, N.S. |title=Penrose-Hameroff orchestrated objective-reduction proposal for human consciousness is not biologically feasible |journal=Physical Review E |volume=80 |pages=021912–021916 |year=2009|url=http://link.aps.org/doi/10.1103/PhysRevE.80.021912 |doi= 10.1103/PhysRevE.80.021912|bibcode = 2009PhRvE..80b1912M |issue=2 }}</ref><ref name="Georgiev2007">{{cite journal |author=Georgiev, D.D. |title=Falsifications of Hameroff-Penrose Orch OR model of consciousness and novel avenues for development of quantum mind theory |journal=NeuroQuantology |volume=5 |issue=1 |pages=145–174 |year=2007 |url=http://philsci-archive.pitt.edu/archive/00003049/}}</ref><ref name=Koch2006>{{cite journal|last=Koch|first=Christof|coauthors=Hepp, Klaus|title=Quantum mechanics in the brain|journal=Nature|date=30 March 2006|volume=440|issue=7084|page=611|doi=10.1038/440611a|url=http://www.nature.com/nature/journal/v440/n7084/full/440611a.html|accessdate=8 August 2013}}</ref><ref name=Hepp2012>{{cite journal|last=Hepp|first=K.|title=Coherence and decoherence in the brain|journal=J. Math. Phys.|date=27 September 2012|volume=53|issue=9|page=095222|doi=10.1063/1.4752474|url=http://jmp.aip.org/resource/1/jmapaq/v53/i9/p095222_s1|accessdate=8 August 2013}}</ref>
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| ==The Penrose–Lucas argument==
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| The Penrose–Lucas argument states that, because humans are capable of knowing the truth of Gödel-unprovable statements, human thought is necessarily [[computable function|non-computable]].<ref name=Penrose1989/>
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| In 1931, mathematician and logician [[Kurt Gödel]] [[Gödel's incompleteness theorems|proved]] that any [[effective procedure|effectively generated]] theory capable of proving basic arithmetic cannot be both [[consistency|consistent]] and [[completeness|complete]]. Furthermore, he showed that any such theory also including a statement of its own consistency is inconsistent. A key element of the proof is the use of [[Gödel numbering]] to construct a "Gödel sentence" for the theory, which encodes a statement of its own incompleteness, e.g. "This theory can't assert the truth of this statement." This statement is ''either'' true but unprovable (incompleteness) ''or'' false and provable (inconsistency). An analogous statement has been used to show that humans are subject to the same limits as machines.<ref>{{Harvnb|Hofstadter|1979|pp=476–477}}, {{Harvnb|Russell|Norvig|2003|p=950}}, {{Harvnb|Turing|1950}} under “The Argument from Mathematics” where he writes “although it is established that there are limitations to the powers of any particular machine, it has only been stated, without sort of proof, that no such limitations apply to the human intellect.”</ref>
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| However, in his first book on consciousness, ''[[The Emperor's New Mind]]'' (1989), Penrose made Gödel's theorem the basis of what quickly became an intensely controversial claim.<ref name=Penrose1989/> He argued that while a formal proof system cannot prove its own inconsistency, Gödel-unprovable results are provable by human mathematicians. He takes this disparity to mean that human mathematicians are not describable as formal proof systems, and are not therefore running a [[computable function|non-computable algorithm]]. Similar claims about the implications of Gödel's theorem were originally espoused by the philosopher [[John Lucas (philosopher)|John Lucas]] of [[Merton College, Oxford]].
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| {{quote|The inescapable conclusion seems to be: Mathematicians are not using a knowably sound calculation procedure in order to ascertain mathematical truth. We deduce that mathematical understanding - the means whereby mathematicians arrive at their conclusions with respect to mathematical truth - cannot be reduced to blind calculation!|Roger Penrose<ref>Roger Penrose. Mathematical intelligence. In Jean Khalfa, editor, What is Intelligence?, chapter 5, pages 107-136. Cambridge University Press, Cambridge, United Kingdom, 1994.</ref>}}
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| ===Criticism of the Penrose–Lucas argument===
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| The Penrose–Lucas argument about the implications of Gödel's incompleteness theorem for computational theories of human intelligence has been widely criticized by mathematicians,<ref name=laforte_1998/><ref name=solomon_1996/><ref name=krajewski_2007/> computer scientists,<ref name=putnam_1995/> and philosophers,<ref name=mindpapers/><ref name=lucas_criticisms/><ref name=Boolos_1990/><ref name=martin_1993/><ref name=lewis_1969/> and the consensus among experts in these fields is that the argument fails,<ref>Bringsford, S. and Xiao, H. 2000. ''[http://kryten.mm.rpi.edu/refute.penrose.pdf A Refutation of Penrose's Gödelian Case Against Artificial Intelligence].'' Journal of Experimental and Theoretical Artificial Intelligence 12: 307-329. The authors write that it is "generally agreed" that Penrose "failed to destroy the computational conception of mind."</ref><ref>In an article at http://www.mth.kcl.ac.uk/~llandau/Homepage/Math/penrose.html L.J. Landau at the Mathematics Department of King's College London writes that "Penrose's argument, its basis and implications, is rejected by experts in the fields which it touches."</ref><ref name="Burgess">Princeton Philosophy professor John Burgess writes in ''[http://www.princeton.edu/~jburgess/Montreal.doc On the Outside Looking In: A Caution about Conservativeness]'' (published in Kurt Gödel: Essays for his Centennial, with the following comments found on [http://books.google.com/books?id=83Attf6BsJ4C&lpg=PP1&pg=PA131#v=onepage&q&f=false pp. 131-132]) that "the consensus view of logicians today seems to be that the Lucas-Penrose argument is fallacious, though as I have said elsewhere, there is at least this much to be said for Lucas and Penrose, that logicians are not unanimously agreed as to where precisely the fallacy in their argument lies. There are at least three points at which the argument may be attacked."</ref> with different authors choosing different aspects of the argument to attack.<ref name="Burgess" /><ref>Dershowitz, Nachum 2005. ''[http://www.cs.tau.ac.il/~nachumd/papers/FourSonsOfPenrose.pdf The Four Sons of Penrose]'', in ''Proceedings of the Eleventh Conference on Logic
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| Programming for Artificial Intelligence and Reasoning (LPAR; Jamaica)'', G. Sutcliffe and A. Voronkov, eds., Lecture Notes in Computer Science, vol. 3835, Springer-Verlag, Berlin, pp. 125-138.</ref>
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| Geoffery LaForte points out that in order to know the truth of an unprovable ''Gödel sentence'', one must already know the formal system is consistent. Referencing [[Paul Benacerraf|Benacerraf]], he then demonstrates that humans cannot prove that they are consistent,<ref name=laforte_1998/> and in all likelihood human brains are inconsistent. He comically points to contradictions from within Penrose's own writings as evidence. Similarly, [[Marvin Minsky]] argues that because humans can construe false ideas to be factual, human mathematical understanding need not be consistent, and consciousness may easily have a deterministic basis.<ref>Marvin Minsky. "Conscious Machines." Machinery of Consciousness, Proceedings, National Research Council of Canada, 75th Anniversary Symposium on Science in Society, June 1991.</ref>
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| [[Solomon Feferman]], a professor of mathematics, logic and philosophy has made criticisms of Penrose's argument.<ref name="Feferman1996">{{cite journal |author=Feferman, S. |title=Penrose's Gödelian argument |journal=Psyche|volume=2 |pages=21–32 |year=1996 |url=http://math.stanford.edu/~feferman/papers/penrose.pdf}}</ref> He faults detailed points in Penrose's second book, ''Shadows of the Mind''. As a mathematician, he{{clarify|date=September 2013|reason = This is what Penrose argues in the book?}} argues that mathematicians do not progress by computer-like or mechanistic search through proofs, but by trial-and-error reasoning, insight and inspiration, and that machines cannot share this approach with humans. However, he thinks that Penrose goes too far in his arguments. Feferman points out that everyday mathematics, as used in science, can in practice be formalized. He also rejects Penrose's [[Platonism]]. | |
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| [[John Searle]] criticizes Penrose's appeal to Gödel as resting on the fallacy that all computational algorithms must be capable of mathematical description. As a counter-example, Searle cites the assignment of [[Vehicle registration plate|license plate number]]s to specific [[vehicle identification number]]s, in order to register a vehicle. According to Searle, no mathematical function can be used to connect a known VIN with its LPN, but the process of assignment is quite simple—namely, "first come, first served"—and can be performed entirely by a computer.<ref>Searle, John R. ''The Mystery of Consciousness''. 1997. ISBN 0-940322-06-4. pp 85–86.</ref>
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| Another critic, [[Charles Seife]], has said, "Penrose, the Oxford mathematician famous for his work on tiling the plane with various shapes, is one of a handful of scientists who believe that the ephemeral nature of consciousness suggests a quantum process."{{citation needed|date=May 2013}}
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| ==Objective reduction==
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| {{main|Penrose interpretation}}
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| ===Motivation===
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| If correct, the Penrose–Lucas argument creates a need to understand the physical basis of non-computational behaviour in the brain.{{citation needed|date=May 2013}} Most physical laws are computable, and thus algorithmic. However, Penrose determined that [[wave function collapse]] was a prime candidate for a non-computable process.
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| In [[quantum mechanics]], particles are treated differently from the macroscopic objects of [[classical mechanics]]. Particles are described not by [[position (vector)|position vectors]], but by [[wave function]]s, which evolve according to the [[Schrödinger equation]]. Non-stationary wave functions are [[linear combination]]s of the [[eigenstate]]s of the system, a phenomenon described by the [[superposition principle]]. When a quantum system interacts with a classical system—i.e. when an [[observable]] is measured—the system appears to [[wave function collapse|collapse]] to a random eigenstate of that [[observable]] from a classical vantage point.
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| If collapse is truly random, then there is no process or algorithm that can deterministically predict its outcome. This provided Penrose with a candidate for the physical basis of the non-computable process that he hypothesized to exist in the brain. However, he disliked the random nature of environmentally-induced collapse, as randomness was not a promising basis for mathematical understanding. Penrose proposed that isolated systems may still undergo a new form of [[wave function collapse]], which he calls objective reduction (OR).{{citation needed|date=April 2012}}
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| ===Details===
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| Penrose sought to reconcile [[general relativity]] and quantum theory using his own ideas about the possible structure of spacetime.<ref name=Penrose1989>{{Cite book |last=Penrose |first= Roger |authorlink=Roger Penrose |title=The Emperor's New Mind: Concerning Computers, Minds and The Laws of Physics |publisher=Oxford University Press |year=1989 |page=480|isbn=0-19-851973-7}}</ref><ref name= Penrose1994>{{Cite book |last=Penrose |first=Roger |authorlink=Roger Penrose |title=Shadows of the Mind: A Search for the Missing Science of Consciousness |publisher=Oxford University Press|year=1989 |page= 457 |isbn=0-19-853978-9}}</ref> He suggested that at the [[Planck scale]] curved [[spacetime]] is not continuous, but discretized. Penrose postulates that each separated [[quantum superposition]] has its own piece of [[spacetime curvature]], a blister in spacetime. Penrose suggests that gravity exerts a force on these spacetime blisters, which become unstable above the Planck scale of <math>10^{-35} \text{m}</math> and collapse to just one of the possible states of the particle. The threshold for Penrose OR is given by his indeterminacy principle ''t'' = ''ħ''/''E'', where ''t'' is the time until OR occurs, ''E'' is the gravitational self-energy or the degree of spacetime separation given by the superpositioned mass, ''ħ'' is the [[reduced Planck constant]]. Thus, the greater the mass-energy of the object, the faster it will undergo OR, and vice versa. Atomic-level superpositions would require 10 million years to reach OR threshold, while an isolated 1 [[kilogram]] object would reach OR threshold in only 10<sup>−37</sup>s. However objects somewhere between these two scales could collapse on a timescale relevant to neural processing.{{citation needed|date=May 2013}}
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| An essential feature of Penrose's theory is that the choice of states when objective reduction occurs is selected neither randomly, as are choices following [[wave function collapse]], nor completely algorithmically. Rather, states are selected by a "non-computable" influence embedded in the [[Planck]] scale of spacetime geometry. Penrose claims that such information is [[Platonism|Platonic]], representing pure mathematical truth, aesthetic, and ethical values at the Planck scale. This relates to Penrose's ideas concerning the three worlds: physical, mental, and the Platonic mathematical world. In his theory, the Platonic world corresponds to the geometry of fundamental spacetime that is claimed to support non-computational thinking.{{citation needed|date=May 2013}}
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| There is no evidence for Penrose's objective reduction, but the theory is considered testable, and plans exist to carry out a relevant experiment.<ref name="Marshall2003">{{cite journal |author=Marshall, W., Simon, C., Penrose, R., and Bouwmeester, D. |title=Towards quantum superpositions of a mirror |journal=Physical Review Letters |volume=91 |issue=13 |pages=130401 |year=2003 |pmid=14525288|arxiv=quant-ph/0210001 |doi=10.1103/PhysRevLett.91.130401 |bibcode=2003PhRvL..91m0401M}}</ref>
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| In August 2013, Penrose and Hameroff reported that the experiments have been carried out by Bandyopadhyay et al., supporting Penrose's theory on six out of the twenty theses he puts forward and invalidating none of the others. They subsequently responded to further critiques from a number of sources, including a 2013 critique from an Australian group led by Reimers.<ref>{{cite news
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| | url=http://www.kurzweilai.net/discovery-of-quantum-vibrations-in-microtubules-inside-brain-neurons-corroborates-controversial-20-year-old-theory-of-consciousness
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| | title=Discovery of quantum vibrations in microtubules inside brain neurons corroborates controversial 20-year-old theory of consciousness
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| | work=KurzweilAI
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| | date=2014-01-16
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| | accessdate=2014-02-01 }}
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| </ref><ref name="Hameroff2013">{{cite journal |author=Stuart Hameroff, Roger Penrose |title=Consciousness in the universe: A review of the ‘Orch OR’ theory|journal=Physics of Life Reviews}} http://www.sciencedirect.com/science/article/pii/S1571064513001188 </ref><ref>{{cite news
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| | url=http://www.brakkegrond.nl/programma/1253/Penrose_Bandyopadhyay_Hameroff/Lezing_Microtubuli_het_grote_debat_over_het_bewustzijn/#eng
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| | title=Penrose, Hameroff & Bandyopadhyay, Lecture: Microtubules and the great debate about consciousness (Lezing: Microtubuli & het grote debat over het bewustzijn)
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| | work=Brakke Grond
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| | date=2014-01-16
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| | accessdate=2014-02-01 }}
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| </ref>
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| ==The creation of the Orch-OR model==
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| When he wrote his first consciousness book, ''The Emperor's New Mind'' in 1989, Penrose lacked a detailed proposal for how such quantum processes could be implemented in the brain. Subsequently, Hameroff read ''The Emperor's New Mind'' and suggested to Penrose that certain structures within brain cells (neurons) were suitable candidate sites for quantum processing and ultimately for consciousness.<ref name= "Hameroff1982">{{cite journal |doi=10.1016/0022-5193(82)90137-0 |author=Hameroff, S.R., and Watt, R.C. |title=Information processing in microtubules |journal=Journal of Theoretical Biology |volume=98 |issue=4 |pages=549–561 |year=1982 |url= http://www.quantumconsciousness.org/documents/informationprocessing_hameroff_000.pdf |pmid=6185798}}</ref><ref name="Hameroff1987">{{cite book |author=Hameroff, S.R. |title=Ultimate Computing |publisher=[[Elsevier]] |year= 1987 |url=http://www.quantumconsciousness.org/ultimatecomputing.html |isbn=0-444-70283-0}}</ref> The Orch-OR theory arose from the cooperation of these two scientists, and was developed in Penrose's second consciousness book ''[[Shadows of the Mind]]'' (1994).<ref name=Penrose1994/>
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| Hameroff's contribution to the theory derived from studying brain cells (neurons). His interest centered on the [[cytoskeleton]], which provides an internal supportive structure for neurons, and particularly on the [[microtubule]]s,<ref name=Hameroff1987/> which are the most important component of the cytoskeleton. As neuroscience has progressed, the role of the cytoskeleton and microtubules has assumed greater importance. In addition to providing structural support, microtubule functions include [[axoplasmic transport]] and control of the cell's movement, growth and shape.<ref name=Hameroff1987/>
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| ===Microtubule condensates===
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| Hameroff proposed that microtubules were suitable candidates for quantum processing.<ref name=Hameroff1987/> Microtubules are made up of [[tubulin]] [[protein]] subunits. The tubulin protein dimers of the microtubules have [[hydrophobic]] pockets which might contain delocalized [[π electron]]s. Tubulin has other smaller non-polar regions, for example 8 [[tryptophan]]s per tubulin, which contain π electron-rich indole rings distributed throughout tubulin with separations of roughly 2 nm. Hameroff claims that this is close enough for the tubulin π electrons to become [[quantum entanglement|quantum entangled]].<ref name=Hameroff_2007>{{cite book |last=Hameroff |first=Stuart |authorlink=Stuart Hameroff |chapter=That's life! The geometry of π electron resonance clouds |title= Quantum aspects of life |editor-last=Abbott |editor1-first=D |editor2-last=Davies |editor2-first=P |editor3-last=Pati |editor3-first=A |url=http://www.quantumconsciousness.org/documents/Hameroff_received-1-05-07.pdf |year=2008 |publisher=World Scientific |pages=403–434 |accessdate=Jan 21, 2010}}</ref> During entanglement, particles' states become inseparably correlated.
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| Hameroff originally suggested the tubulin-subunit electrons would form a [[Bose-Einstein condensate]], but this was discredited.<ref name="Penrose-Hameroff2011"/> He then proposed a Frohlich condensate, a hypothetical coherent oscillation of dipolar molecules. However, this too has been experimentally discredited.<ref name="Reimers2009">{{cite journal|last=Reimers|first=Jeffrey R.|coauthors=McKemmish, Laura K.; McKenzie, Ross H.; Mark, Alan E.; Hush, Noel S.|title=Weak, strong, and coherent regimes of Fröhlich condensation and their applications to terahertz medicine and quantum consciousness|journal=PNAS|date=17 March 2009|volume=106|issue=11|pages=4219–4224|doi=10.1073/pnas.0806273106|url=http://www.pnas.org/content/106/11/4219.full|accessdate=10 June 2013|pmid=19251667|bibcode = 2009PNAS..106.4219R|pmc=2657444}}</ref> Hameroff suggested that such condensate behavior would magnify nanoscopic quantum effects to have large scale influences in the brain.
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| Hameroff proposed that condensates in microtubules in one [[neuron]] can link with microtubule condensates in other neurons and [[glial cell]]s via the [[gap junctions]] of [[electrical synapse]]s.<ref name="Hameroff2006a">{{cite journal |doi=10.1097/00000542-200608000-00024 |author=Hameroff, S.R. |title=The entwined mysteries of anesthesia and consciousness |journal=Anesthesiology |volume=105 |issue=2 |pages=400–412 |year=2006 |pmid=16871075}}</ref><ref name="Hameroff2009">{{cite journal |author= Hameroff, S. |title=The "conscious pilot"—dendritic synchrony moves through the brain to mediate consciousness |journal=Journal of Biological Physics |volume= 36 |pages= 71–93 |year=2009 |doi=10.1007/s10867-009-9148-x |pmid= 19669425 |issue= 1 |pmc= 2791805}}</ref> Hameroff proposed that the gap between the cells is sufficiently small that quantum objects can [[quantum tunneling|tunnel]] across it, allowing them to extend across a large area of the brain. He further postulated that the action of this large-scale quantum activity is the source of 40 Hz [[gamma wave]]s. Here, Hameroff built upon<ref>Specifically, he cites:
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| * {{cite journal |author=Buhl, D.L., Harris, K.D., Hormuzdi, S.G., Monyer, H., and Buzsaki, G. |title=Selective Impairment of Hippocampal Gamma Oscillations in Connexin-36 Knock-Out Mouse In Vivo |journal= Journal of Neuroscience |volume=23 |issue=3|pages=1013–1018 |year=2003 |pmid=12574431}}
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| * {{cite journal |doi=10.1016/S0165-0173(97)00031-3 |author=Dermietzel, R. |title=Gap junction wiring: a 'new' principle in cell-to-cell communication in the nervous system? |journal=Brain Research Reviews |volume=26 |issue=2–3 |pages=176–183 |year=1998 |pmid=9651521}}
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| * {{cite journal |doi=10.1038/28184 |author=Draguhn, A., Traub, R.D., Schmitz, D., and Jefferys, J.G.R. |title=Electrical coupling underlies high-frequency oscillations in the hippocampus in vitro |journal=Nature |volume=394 |issue=6689 |pages=189–192 |year=1998|pmid=9671303|bibcode = 1998Natur.394..189D }}
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| * {{cite journal |author=Fries, P., Schroder, J.-H., Roelfsema, P.R., Singer, W., and Engel, A.K. |title=Oscillatory Neuronal Synchronization in Primary Visual Cortex as a Correlate of Stimulus Selection |journal=Journal of Neuroscience |volume=22 |issue=9|pages=3739–3754 |year=2002 |pmid=11978850}}
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| * {{cite journal |doi=10.1038/47029 |author=Galarreta, M., and Hestrin, S. |title=A network of fast-spiking cells in the neocortex connected by electrical synapses |journal=Nature |volume=402 |issue=6757 |pages=72–75 |year=1999 |pmid=10573418|bibcode = 1999Natur.402...72G }}
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| * {{cite journal |doi=10.1038/47035 |author=Gibson, J.R., Beierlein, M., and Connors, B.W. |title=Two networks of electrically coupled inhibitory neurons in neocortex |journal=Nature |volume=402 |issue=6757 |pages=75–79 |year=1999 |pmid=10573419|bibcode = 1999Natur.402...75G }}
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| * {{cite journal |doi=10.1016/j.bbamem.2003.10.023 |author=Hormuzdi, S.G., Filippov, M.A., Mitropoulou, G., Monyer, H., and Bruzzone, R.|title=Electrical synapses: a dynamic signaling system that shapes the activity of neuronal networks |journal=Biochimica et Biophysica Acta |volume=1662 |issue=1–2 |pages=113–137 |year=2004 |pmid=15033583}}
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| * {{cite journal |doi=10.1016/j.brainresbull.2003.07.004 |author=LeBeau, F.E.N., Traub, R.D., Monyer, H., Whittington, M.A., and Buhl, E.H. |title=The role of electrical signaling via gap junctions in the generation of fast network oscillations |journal=Brain Research Bulletin |volume=62 |issue=1 |pages=3–13 |year=2003 |pmid=14596887}}
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| * {{cite journal |doi=10.1016/S0166-2236(99)01497-6 |author=Velazquez, J.L.P., and Carlen, P.L. |title=Gap junctions, synchrony and seizures |journal=Trends in Neurosciences |volume=23 |issue=2 |pages=68–74 |year=2000 |pmid=10652547}}
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| * {{cite journal |doi=10.1016/S0165-0173(99)00061-2 |author=Rozental, R., and de Carvalho, A.C.C. |title=Introduction |journal=Brain Research Reviews |volume=32 |issue=1 |pages=1–2 |year=2000 |pmid=10751650}}</ref> the much less controversial theory that gap junctions are related to the gamma oscillation.<ref name="Bennett&Zukin2004">{{cite journal |author=Bennett, M.V.L., and Zukin, R.S. |title=Electrical Coupling and Neuronal Synchronization in the Mammalian Brain |journal=Neuron |volume=41 |issue=4 |pages=495–511 |year=2004 |pmid=14980200 |doi=10.1016/S0896-6273(04)00043-1}}</ref>
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| ===Consequences===
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| The Orch-OR theory combines the Penrose–Lucas argument with Hameroff's hypothesis on quantum processing in microtubules. Altogether, it proposes that when condensates in the brain undergo an objective reduction of their wave function, their collapse connects non-computational decision making to experiences embedded in the fundamental geometry of spacetime.
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| The theory further proposes that the microtubules both influence and are influenced by the conventional activity at the synapses between neurons. The ''Orch'' in Orch-OR stands for orchestrated, where ''orchestration'' refers to the hypothetical process by which connective proteins, known as [[microtubule-associated protein]]s (MAPs) influence or orchestrate the quantum processing of the microtubules.
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| Further to this, in 1998, Hameroff made 20 testable predictions related to his proposal.<ref name="Hameroff1998">{{cite journal |author=Hameroff, S.R. |title=Quantum Computation In Brain Microtubules? The Penrose-Hameroff "Orch OR" model of consciousness |journal=[[Philosophical Transactions of the Royal Society A]] |volume=356 |pages=1869–1896 |year=1998 |url=http://www.quantumconsciousness.org/penrose-hameroff/quantumcomputation.html}}</ref> However, most of these proposals have been disproven. The proposed predominance of 'A' lattice microtubules, more suitable for information processing, has been falsified by Kikkawa ''et al.'',<ref name="Kikkawa1994">{{cite journal |author=Kikkawa, M., Ishikawa, T., Nakata, T., Wakabayashi, T., Hirokawa, N. |title=Direct visualization of the microtubule lattice seam both in vitro and in vivo |journal=Journal of Cell Biology |volume=127 |issue=6|pages=1965–1971 |year=1994|pmid=7806574 |url=http://jcb.rupress.org/cgi/content/abstract/127/6/1965 |pmc=2120284 |doi= 10.1083/jcb.127.6.1965}}</ref><ref name="Kikkawa2006">{{cite journal |author=Kikkawa, M., Metlagel, Z. |title=A molecular "zipper" for microtubules |journal=Cell |volume=127 |issue=7 |pages=1302–1304 |year=2006 |pmid=17190594 | doi=10.1016/j.cell.2006.12.009}}</ref> who showed that all in vivo microtubules have a 'B' lattice and a seam. The suggestion of coherent photons has been disproven, as has the existence of gap junctions between neurons and glial cells,<ref name="Binmoller1992">{{cite journal
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| |author = F. J. Binmöller & C. M. Müller
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| |title = Postnatal development of dye-coupling among astrocytes in rat visual cortex
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| |journal = Glia
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| |volume = 6
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| |issue = 2
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| |year = 1992
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| |pages = 127–137
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| |pmid= 1328051
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| |doi=10.1002/glia.440060207
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| }}</ref> and the proposal that photons do not decohere in the retina.<ref name="Georgiev2011">{{cite journal |author=Georgiev, D. |title=Photons do collapse in the retina not in the brain cortex: Evidence from visual illusions |journal=Neuroquantology |volume=9 |issue=2 |pages=206–231 |year=2011 |arxiv=quant-ph/0208053|bibcode = 2002quant.ph..8053G }}</ref>
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| ==Criticism==
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| Hameroff's theory is criticized at every level,<ref name=Tegmark2000/><ref name="Georgiev2007"/> and considered to be an extremely poor model of brain physiology.<ref name="Georgiev2007"/> Primarily, Hameroff requires [[tubulin]] electrons to form either a [[Bose–Einstein condensate|Bose-Einstein]] or Frohlich condensate, both of which have been experimentally disproven.<ref name="Penrose-Hameroff2011"/><ref name="Reimers2009"/>
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| ===Microtubule decoherence===
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| Another objection to Hameroff's hypothesis is that any quantum coherent system in the brain would undergo [[wave function collapse]] due to environmental interaction long before it could ever influence neural processes. [[Max Tegmark]] determined the decoherence timescale of microtubule entanglement to be extremely rapid.<ref name=Tegmark2000/> Tegmark developed a model for time to decoherence, and from this calculated that microtubule quantum states could exist, but would be sustained for only a [[femtosecond]]s (fs) timescale at brain temperatures, far too brief to be relevant to neural processing.
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| In response to Tegmark, physicists Scott Hagan, Jack Tuszynski and Hameroff<ref name="Hagan2002">{{cite journal |doi=10.1103/PhysRevE.65.061901 |author=Hagan, S., Hameroff, S., and Tuszyński, J. |title=Quantum Computation in Brain Microtubules? Decoherence and Biological Feasibility |journal=Physical Review E |volume=65 |pages=061901 |arxiv=quant-ph/0005025 |year=2002|bibcode = 2002PhRvE..65f1901H |issue=6 }}</ref><ref name="Hameroff2006b">{{Cite book |author=Hameroff, S. |contribution=Consciousness, Neurobiology and Quantum Mechanics |editor-last=Tuszynski |editor-first=Jack |title=The Emerging Physics of Consciousness |publisher=Springer |pages=193–253 |year=2006 |postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}</ref> claimed that Tegmark did not address the Orch-OR model, but instead a model of his own construction. This involved superpositions of quanta separated by 24 nm rather than the much smaller separations stipulated for Orch-OR. As a result, Hameroff's group claimed a decoherence time seven orders of magnitude greater than Tegmark's, although still far below 25 ms. Also, Hameroff's group suggested that the [[Debye force|Debye]] layer of counterions could screen thermal fluctuations, and that the surrounding actin [[gel]] might enhance the ordering of water, further screening noise. Also, they suggest incoherent metabolic energy could further order water, and finally that the configuration of the microtubule lattice might be suitable for [[quantum error correction]], a means of resisting quantum decoherence.
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| However, despite Hameroff's objections, most physicists accept Tegmark's analysis, that quantum coherence does not play a major role in [[neurophysiology]].<ref name=Koch2006/><ref name=Hepp2012/>
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| ===Cell biology errors===
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| Hameroff proposed that microtubule coherence reaches the synapses via dendritic lamellar bodies (DLBs), where it could influence [[action potential|synaptic firing]] and be transmitted across the [[synaptic cleft]] to other neurons.<ref name="Georgiev2007"/><ref name="Georgiev2009a">{{cite journal |doi=10.1038/npre.2009.3860.1 |author=Georgiev, D.D. |title=Remarks on the number of tubulin dimers per neuron and implications for Hameroff-Penrose Orch |journal=NeuroQuantology |volume=7 |issue=4 |pages=677–679 |year=2009 |url=http://precedings.nature.com/documents/3860/version/1}}</ref> However De Zeeuw ''et al.'' proved this impossible,<ref name="DeZeeuw1995">{{cite journal |author=De Zeeuw, C.I., Hertzberg, E.L., Mugnaini, E. |title=The dendritic lamellar body: A new neuronal organelle putatively associated with dendrodentritic gap junctions |journal=Journal of Neuroscience |volume=15 |issue=2 |pages=1587–1604 |year=1995 |pmid=7869120}}</ref> by showing that DLBs are located micrometers away from gap junctions.
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| Hameroff's hypothesis requires that cortical dendrites contain primarily 'A' lattice microtubules,<ref name="Hameroff1998"/> but this was experimentally disproved by Kikkawa ''et al''<ref name="Kikkawa1994"/><ref name="Kikkawa2006"/> who showed that all ''in vivo'' microtubules have a 'B' lattice and a seam. It also requires [[gap junctions]] between neurons and glial cells,<ref name="Hameroff1998"/> yet Binmöller ''et al'' proved that these don't exist.<ref name="Binmoller1992"/>
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| Several other criticisms have come to the fore over the years. Papers by Georgiev, D.<ref name="Georgiev2007"/><ref name="Georgiev2009a"/> point to a number of problems with Hameroff's proposals, including a lack of explanation for the probabilistic firing of axonal synapses, an error in the calculated number of the tubulin dimers per cortical neuron.
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| ===Other criticisms===
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| Orch-OR predicts that photons become entangled with [[microtubule]]s instead of decohering in the [[retina]],<ref name="Hameroff1998"/> but this was falsified.<ref name="Georgiev2011"/>
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| In 2009, the debate focused around papers by Reimers ''et al.''<ref name="Reimers2009"/> and McKemmish ''et al.''<ref name=" McKemmish2009"/> and Hameroff's reply to these,<ref name= "Penrose-Hameroff2011">{{cite journal
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| |author= Roger Penrose & Stuart Hameroff
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| |title= Consciousness in the Universe: Neuroscience, Quantum Space-Time Geometry and Orch OR Theory
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| |journal= Journal of Cosmology
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| |volume= 14
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| |issue=
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| |pages=
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| |year= 2011
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| |url= http://journalofcosmology.com/Consciousness160.html
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| }}</ref> which is not regarded as being independently reviewed. The Reimers paper claimed that microtubules could only support 'weak' 8 MHz coherence, but that the Orch-OR proposals required a higher rate of coherence. Hameroff, however, claims that 8 MHz coherence is sufficient to support the Orch-OR proposal. McKemmish ''et al.'' makes two claims; firstly that aromatic molecules cannot switch states because they are delocalised. Hameroff, however, claims that he is referring to the behaviour of two or more electron clouds; secondly McKemmish shows that changes in tubulin conformation driven by GTP conversion would result in a prohibitive energy requirement. Against this, Hameroff claims that all that is required is switching in electron cloud dipole states produced by [[London force]]s.
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| ==See also==
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| * [[Electromagnetic theories of consciousness]]
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| * [[Holonomic brain theory]]
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| * [[Many-minds interpretation]]
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| * [[Penrose interpretation of Quantum Theory|Penrose interpretation]]
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| * [[Quantum Aspects of Life|''Quantum Aspects of Life'' (book)]]
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| * [[Quantum mind]]
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| * [[Mindville]]
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| ==References==
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| {{reflist|2}}
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| ==External links==
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| * [http://www.quantum-mind.co.uk Quantum-Mind]
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| * [http://online.kitp.ucsb.edu/plecture/penrose/ Roger Penrose (1999) Science and the Mind. Kavli Institute for Theoretical Physics Public Lectures, May 12, 1999.]
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| [[Category:Quantum mind]]
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| [[Category:Theories of mind]]
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