View source for Physics:Quantum mind

{{Short description|Fringe hypothesis}}
The '''quantum mind''' or '''quantum consciousness''' is a group of hypotheses proposing that local physical laws and interactions from [[Physics:Classical mechanics|classical mechanics]] or connections between neurons alone cannot explain [[Philosophy:Consciousness|consciousness]],<ref name="Quantum Approaches to Consciousness">{{cite web|url=http://plato.stanford.edu/entries/qt-consciousness/|title=Quantum Approaches to Consciousness|publisher=Stanford Encyclopedia of Philosophy|orig-year=First published Tue Nov 30, 2004 |date=May 19, 2011}}</ref> positing instead that [[Physics:Quantum mechanical|quantum-mechanical]] phenomena, such as [[Quantum entanglement|entanglement]] and [[Physics:Quantum superposition|superposition]] that cause nonlocalized quantum effects, interacting in smaller features of the brain than cells, may play an important part in the brain's function and could explain critical aspects of consciousness. These scientific hypotheses are as yet unvalidated, and they can overlap with [[Physics:Quantum mysticism|quantum mysticism]].

== History ==

[[Biography:Eugene Wigner|Eugene Wigner]] developed the idea that quantum mechanics has something to do with the workings of the mind.<ref name="Wigner1961">{{cite book
 | last1 = Wigner
 | first1 = Eugene
 | title = Philosophical Reflections and Syntheses
 | chapter = Remarks on the Mind-Body Question
 | year = 1961
 | editor = Good, Irving John
 | publisher = Heinemann
 | location = London
 | pages = 284–302
 | doi = 10.1007/978-3-642-78374-6_20
| isbn = 978-3-540-63372-3
 }}</ref> He proposed that the [[Physics:Wave function collapse|wave function collapse]]s due to its interaction with consciousness. [[Biography:Freeman Dyson|Freeman Dyson]] argued that "mind, as manifested by the capacity to make choices, is to some extent inherent in every electron".<ref>{{cite book |last1=Dyson |first1=Freeman |title=Infinite in All Directions: Gifford Lectures Given at Aberdeen, Scotland April–November 1985 |date=2004 |publisher=Perennial |location=New York |isbn=0060728892 |page=297 |edition=1st Perennial}}</ref>

Other contemporary physicists and philosophers considered these arguments unconvincing.<ref>{{cite book |last1=Searle |first1=John R. |title=The Mystery of Consciousness |date=1997 |publisher=New York Review of Books |location=New York |isbn=9780940322066 |pages=[https://archive.org/details/mysteryconscious00sear/page/n69 53]–88 |edition=1st |url-access=limited |url=https://archive.org/details/mysteryconscious00sear}}</ref> Victor Stenger characterized quantum consciousness as a "myth" having "no scientific basis" that "should take its place along with gods, unicorns and dragons".<ref>{{cite magazine |last=Stenger |first=Victor |author-link=Victor J Stenger |title=The Myth of Quantum Consciousness |magazine=The Humanist |volume=53 |issue=3 |date=May–June 1992 |pages=13–15 |url=http://www.colorado.edu/philosophy/vstenger/Quantum/QuantumConsciousness.pdf |archive-url=https://web.archive.org/web/20080517015350/http://www.colorado.edu/philosophy/vstenger/Quantum/QuantumConsciousness.pdf |archive-date=2008-05-17 |url-status=dead}}</ref>

[[Biography:David Chalmers|David Chalmers]] argues against quantum consciousness. He instead discusses how [[Physics:Quantum mechanics|quantum mechanics]] may relate to [[Philosophy:Mind–body dualism|dualistic consciousness]].<ref name="Chalmers2003">{{cite book| author1=Stephen P. Stich |author2=Ted A. Warfield |title=The Blackwell Guide to Philosophy of Mind |url=https://books.google.com/books?id=NEGK_ZStddkC&q=dualistic+consciousness&pg=PA126 |date=15 April 2008 |work=Blackwell Philosophy Guides |publisher=John Wiley & Sons |page=126 |isbn=9780470998755}}</ref> Chalmers is skeptical that any new physics can resolve the [[Philosophy:Hard problem of consciousness|hard problem of consciousness]].<ref name="Chalmers1995">{{cite journal |author=Chalmers |first=David J. |year=1995 |title=Facing Up to the Problem of Consciousness |url=http://consc.net/papers/facing.html |journal=Journal of Consciousness Studies |volume=2 |issue=3 |pages=200–219}}</ref><ref name="Chalmers1997">{{cite book |last1=Chalmers |first1=David J. |title=The Conscious Mind: In Search of a Fundamental Theory |date=1997 |publisher=Oxford University Press |location=New York |isbn=978-0-19-511789-9 |edition=Paperback}}</ref><ref name="Chalmers">{{cite book |author=Chalmers |first=David |url=https://archive.org/details/consciousmindins00chal |title=The Conscious Mind: In Search of a Fundamental Theory |publisher=Oxford University Press |year=1996 |isbn=978-0-19-510553-7 |language=en-us |url-access=registration}}</ref> He argues that quantum theories of consciousness suffer from the same weakness as more conventional theories. Just as he argues that there is no particular reason why particular macroscopic physical features in the brain should give rise to consciousness, he also thinks that there is no particular reason why a particular quantum feature, such as the EM field in the brain, should give rise to consciousness either.<ref name=Chalmers/>

==Approaches==

===Bohm===

[[Biography:David Bohm|David Bohm]] viewed [[Physics:Quantum mechanics|quantum theory]] and [[Physics:Theory of relativity|relativity]] as contradictory, which implied a more fundamental level in the universe.<ref name="Bohm1980">{{cite book |last1=Bohm |first1=David |title=Wholeness and the Implicate Order |date=2002 |publisher=Routledge |location=Hoboken |isbn=0203995155 |edition=Online-Ausg.}}</ref> He claimed that both quantum theory and relativity pointed to this deeper theory, which he formulated as a quantum field theory. This more fundamental level was proposed to represent an undivided wholeness and an implicate order, from which arises the explicate order of the universe as we experience it.<ref>{{cite book |last1=Bohm |first1=David |title=Wholeness and the implicate order. |date=1980 |publisher=Routledge & Kegan Paul |isbn=9780415289795 |edition=Repr. |location=London, England |language=en}}</ref>

Bohm's proposed order applies both to matter and consciousness. He suggested that it could explain the relationship between them. He saw mind and matter as projections into our explicate order from the underlying implicate order. Bohm claimed that when we look at matter, we see nothing that helps us to understand consciousness.<ref>{{cite web |last1=Raggett |first1=Simon |title=https://www.facebook.com/QuantumMind |url=http://quantum-mind.co.uk/theories/david-bohm/the-implicate-order/ |website=Quantum Mind |access-date=11 September 2023}}</ref>

Bohm discussed the experience of listening to music. He believed that the feeling of movement and change that make up our experience of music derive from holding the immediate past and the present in the brain together. The musical notes from the past are transformations rather than memories. The notes that were implicated in the immediate past become explicate in the present. Bohm viewed this as consciousness emerging from the implicate order.{{citation needed|date=January 2023}}

Bohm saw the movement, change or flow, and the coherence of experiences, such as listening to music, as a manifestation of the implicate order. He claimed to derive evidence for this from [[Biography:Jean Piaget|Jean Piaget]]'s work on infants.<ref name="Piaget1956">{{cite book |last1=Piaget |first1=Jean |title=Jean Piaget: selected works. (The Origin of Intelligence in the Child) |date=1997 |publisher=Routledge |isbn=9780415168861 |edition=Repr. |location=London, England |language=en-uk}}</ref> He held these studies to show that young children learn about time and space because they have a "hard-wired" understanding of movement as part of the implicate order. He compared this hard-wiring to [[Biography:Noam Chomsky|Chomsky's]] theory that grammar is hard-wired into human brains.{{citation needed|date=January 2023}}

Bohm never proposed a specific means by which his proposal could be falsified, nor a neural mechanism through which his "implicate order" could emerge in a way relevant to consciousness.<ref name="Bohm1980"/> He later collaborated on [[Biography:Karl H. Pribram|Karl Pribram]]'s [[Philosophy:Holonomic brain theory|holonomic brain theory]] as a model of quantum consciousness.<ref>{{cite book |last1=Wade |first1=Jenny |title=Changes of Mind: A Holonomic Theory of the Evolution of Consciousness |date=1996 |publisher=State University of New York Press |isbn=9780791428498 |location=Albany, New York |language=en-us}}</ref>

According to philosopher [[Biography:Paavo Pylkkänen|Paavo Pylkkänen]], Bohm's suggestion "leads naturally to the assumption that the physical correlate of the logical thinking process is at the classically describable level of the brain, while the basic thinking process is at the quantum-theoretically describable level".<ref>{{cite journal |author=Pylkkänen |first=Paavo |title=Can quantum analogies help us to understand the process of thought? |url=http://philpapers.org/archive/PYLCQA.1.pdf |journal=Mind & Matter |volume=12 |pages=61–91 [75] |number=1}}</ref>

It was suggested by theoretical physicists [[Biography:David Bohm|David Bohm]] and [[Biography:Basil Hiley|Basil Hiley]] that [[Philosophy:Thought#The mind-body problem|mind and matter]] both emerge from an "implicate order".<ref>Basil J. Hiley. ''Particles, fields, and observers'', Volume I The Origins of Life, Part 1 Origin and Evolution of Life, Section II The Physical and Chemical Basis of Life, pp. 87–106 ([http://www.bbk.ac.uk/tpru/BasilHiley/Frontiersoflife.pdf PDF]).</ref> [[Biography:Basil Hiley#Mind and matter|Bohm and Hiley's approach to mind and matter]] is supported by philosopher [[Biography:Paavo Pylkkänen|Paavo Pylkkänen]].<ref>Basil J. Hiley, Paavo Pylkkänen: ''Naturalizing the mind in a quantum framework''. In Paavo Pylkkänen and Tere Vadén (eds.): Dimensions of conscious experience, Advances in Consciousness Research, Volume 37, John Benjamins B.V., 2001, {{ISBN|90-272-5157-6}}, [https://books.google.com/books?hl=en&lr=&id=CCX1NhhpQNQC&pg=PA119 pages 119–144]</ref> Pylkkänen underlines "unpredictable, uncontrollable, indivisible and non-logical" features of conscious thought and draws parallels to a philosophical movement some call "post-phenomenology", in particular to [[Biography:Pauli Pylkkö|Pauli Pylkkö]]'s notion of the "aconceptual experience", an unstructured, unarticulated and pre-logical experience.<ref>{{cite journal |author=Paavo Pylkkänen|title=Can quantum analogies help us to understand the process of thought?|journal=Mind & Matter |volume=12 |number=1|pages=61–91|url=http://his.diva-portal.org/smash/record.jsf?pid=diva2%3A741236}} p.&nbsp;83–84.</ref>

===Penrose and Hameroff===

{{main|Philosophy:Orchestrated objective reduction}}
Theoretical physicist [[Biography:Roger Penrose|Roger Penrose]] and anaesthesiologist [[Biography:Stuart Hameroff|Stuart Hameroff]] collaborated to produce the theory known as "[[Philosophy:Orchestrated objective reduction|orchestrated objective reduction]]" (Orch-OR). Penrose and Hameroff initially developed their ideas separately and later collaborated to produce Orch-OR in the early 1990s. They reviewed and updated their theory in 2013.<ref>{{cite web |url=http://www.sciencedaily.com/releases/2014/01/140116085105.htm |title=Discovery of quantum vibrations in 'microtubules' inside brain neurons supports controversial theory of consciousness |publisher=ScienceDaily |date=2014-01-16 |access-date=2017-12-28}}</ref><ref name="elsevier">{{cite web |url=http://www.elsevier.com/about/press-releases/research-and-journals/discovery-of-quantum-vibrations-in-microtubules-inside-brain-neurons-corroborates-controversial-20-year-old-theory-of-consciousness |title=Discovery of Quantum Vibrations in "Microtubules" Inside Brain Neurons Corroborates Controversial 20-Year-Old Theory of Consciousness |publisher=Elsevier |date=2014-01-16 |access-date=2017-12-28}}</ref>

Penrose's argument stemmed from [[Gödel's incompleteness theorems]]. In his first book on consciousness, ''[[The Emperor's New Mind]]'' (1989),<ref name="Emperor">{{cite book |last1=Penrose |first1=Roger |url=https://archive.org/details/emperorsnewmind00roge |title=The Emperor's New Mind |date=1989 |publisher=Penguin Books |isbn=0-14-01-4534-6 |location=New York, New York |language=en-us}}</ref> he argued that while a formal system cannot prove its own consistency, Gödel's unprovable results are provable by human mathematicians.<ref name="Godel2012">{{cite book |last1=Gödel |first1=Kurt |title=On Formally Undecidable Propositions of Principia Mathematica and Related Systems |date=1992 |publisher=Dover Publications |location=New York |isbn=0486669807 |edition=Reprint}}</ref> Penrose took this to mean that human mathematicians are not formal proof systems and not running a computable algorithm. According to Bringsjord and Xiao, this line of reasoning is based on fallacious [[Philosophy:Equivocation|equivocation]] on the meaning of computation.<ref>Bringsjord, 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]].</ref> In the same book, Penrose wrote: "One might speculate, however, that somewhere deep in the brain, cells are to be found of single quantum sensitivity. If this proves to be the case, then quantum mechanics will be significantly involved in brain activity."<ref name="Emperor" />{{rp|400}}

Penrose determined that [[Physics:Wave function collapse|wave function collapse]] was the only possible physical basis for a non-computable process. Dissatisfied with its randomness, he proposed a new form of wave function collapse that occurs in isolation and called it ''objective reduction''. He suggested each quantum superposition has its own piece of spacetime curvature and that when these become separated by more than one [[Planck length]], they become unstable and collapse.<ref name="emperornewmind">{{cite book |last1=Penrose |first1=Roger |url=https://archive.org/details/emperorsnewmindc1999penr |title=The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics |date=1999 |publisher=Oxford University Press |isbn=0192861980 |edition=New |location=Oxford, England |language=en-uk |url-access=registration}}</ref> Penrose suggested that ''objective reduction'' represents neither randomness nor algorithmic processing but instead a non-computable influence in [[Physics:Spacetime|spacetime]] geometry from which mathematical understanding and, by later extension, consciousness derives.<ref name="emperornewmind"/>

Hameroff provided a hypothesis that [[Biology:Microtubule|microtubule]]s would be suitable hosts for quantum behavior.<ref>{{cite book |last1=Penrose |first1=Roger |url=https://archive.org/details/shadowsofmindsea00penr_0 |title=Shadows of the Mind: A Search for the Missing Science of Consciousness |date=1995 |publisher=Oxford University Press |isbn=0198539789 |edition=Repr. (with corrections) |location=Oxford [u.a.] |language=en}}</ref> Microtubules are composed of [[Biology:Tubulin|tubulin]] [[Biology:Protein dimer|protein dimer]] subunits. The dimers each have [[Chemistry:Hydrophobic|hydrophobic]] pockets that are 8&nbsp;nm apart and may contain delocalized π electrons. Tubulins have other smaller non-polar regions that contain π-electron-rich [[Chemistry:Indole|indole]] rings separated by about 2&nbsp;nm. Hameroff proposed that these electrons are close enough to become entangled.<ref name= Hameroff_2007>{{cite book |last=Hameroff |first=Stuart |chapter=That's life! The geometry of π electron resonance clouds |editor-last=Abbott |editor-first=D. |editor2-last=Davies |editor2-first=P. |editor3-last=Pati |editor3-first=A. |title=[[Biology:Quantum Aspects of Life|Quantum Aspects of Life]] |chapter-url=http://www.quantumconsciousness.org/documents/Hameroff_received-1-05-07.pdf |year=2008 |publisher=World Scientific  |pages=403–434 |access-date=Jan 21, 2010}}</ref> He originally suggested that the tubulin-subunit electrons would form a [[Physics:Bose–Einstein condensate|Bose–Einstein condensate]], but this was discredited.<ref name="Penrose-Hameroff2011">{{cite journal |last1=Penrose |first1=Roger |last2=Hameroff |first2=Stuart |name-list-style=amp |year=2011 |title=Consciousness in the Universe: Neuroscience, Quantum Space-Time Geometry and Orch OR Theory |url=http://journalofcosmology.com/Consciousness160.html |url-status=dead |journal=Journal of Cosmology |volume=14 |archive-url=https://web.archive.org/web/20140207124412/http://journalofcosmology.com/Consciousness160.html |archive-date=February 7, 2014}}</ref> He then proposed a Frohlich condensate, a hypothetical coherent oscillation of dipolar molecules, but this too was experimentally discredited.<ref>{{cite journal |last=Reimers |first=Jeffrey R. |author2=McKemmish, Laura K. |author3=McKenzie, Ross H. |author4=Mark, Alan E. |author5= 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 |bibcode=2009PNAS..106.4219R |pmid=19251667 |pmc=2657444 |doi-access=free}}</ref>

In other words, there is a missing link between physics and neuroscience.<ref>{{cite journal |last1=van den Noort |first1=Maurits |last2=Lim |first2=Sabina |last3=Bosch |first3=Peggy |date=2016-10-28 |title=Towards a theory of everything: The observer's unconscious brain |journal=Nature |volume=538 |issue=7623 |pages=36–37 |bibcode=2016Natur.538...36D |doi=10.1038/538036a |doi-access=free}}</ref> For instance, the proposed predominance of A-lattice microtubules, more suitable for information processing, was falsified by Kikkawa ''et al.'',<ref name="Kikkawa1994">{{cite journal |vauthors=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 |pmc=2120284 |doi= 10.1083/jcb.127.6.1965}}</ref><ref name="Kikkawa2006">{{cite journal |vauthors=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 |s2cid=31980600 |doi-access=free }}</ref> who showed that all in vivo microtubules have a B&nbsp;lattice and a seam. The proposed existence of gap junctions between neurons and glial cells was also falsified.<ref name="Binmoller1992">{{cite journal |last1=Binmöller |first1=F. J. |last2=Müller |first2=C. M. |name-list-style=amp |year=1992 |title=Postnatal development of dye-coupling among astrocytes in rat visual cortex |journal=Glia |volume=6 |issue=2 |pages=127–137 |doi=10.1002/glia.440060207 |pmid=1328051 |s2cid=548862}}</ref> Orch-OR predicted that microtubule coherence reaches the synapses through dendritic lamellar bodies (DLBs), but De&nbsp;Zeeuw ''et al.'' proved this impossible<ref name="DeZeeuw1995">{{cite journal |vauthors=De Zeeuw CI, Hertzberg EL, 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 |pmc=6577840 |doi=10.1523/JNEUROSCI.15-02-01587.1995}}</ref> by showing that DLBs are micrometers away from gap junctions.<ref>{{cite journal |last=Hameroff |first=S. |date=2013-08-12 |title=Consciousness, the brain, and spacetime geometry |journal=Annals of the New York Academy Sciences |volume=929 |issue=1 |pages=74–104 |bibcode=2001NYASA.929...74H |doi=10.1111/j.1749-6632.2001.tb05709.x |pmid=11349432 |s2cid=12399940}}</ref>

In 2014, Hameroff and Penrose claimed that the discovery of quantum vibrations in microtubules by Anirban Bandyopadhyay of the [[Organization:National Institute for Materials Science|National Institute for Materials Science]] in Japan in March 2013<ref>{{cite journal |title= Atomic water channel controlling remarkable properties of a single brain microtubule: correlating single protein to its supramolecular assembly |date=2014-05-14 |pmid=23567633 |doi=10.1016/j.bios.2013.02.050 |volume=47 |journal=Biosens Bioelectron |pages=141–148 |vauthors=Sahu S, Ghosh S, Ghosh B, Aswani K, Hirata K, Fujita D, Bandyopadhyay A |url=https://zenodo.org/record/889377 }}</ref> corroborates Orch-OR theory.<ref name="elsevier"/><ref>{{cite web |last=Osborne |first=Hannah |title=Quantum Vibrations in Brain Opens 'Pandora's Box' of Theories of Consciousness |url=https://uk.news.yahoo.com/quantum-vibrations-brain-opens-39-pandora-39-box-160301481.html |website=Yahoo News UK |date=2014-01-16 |access-date=2014-08-04}}</ref> Experiments that showed that anaesthetic drugs reduce how long microtubules can sustain suspected quantum excitations appear to support the quantum theory of consciousness.<ref name=Lewton>{{cite news |last1=Lewton |first1=Thomas |title=Quantum experiments add weight to a fringe theory of consciousness |url=https://www.newscientist.com/article/2316408-quantum-experiments-add-weight-to-a-fringe-theory-of-consciousness/ |access-date=20 April 2022 |url-access=subscription |website=New Scientist |date=18 April 2022}}</ref>

In April 2022, the results of two related experiments at the University of Alberta and [[Organization:Princeton University|Princeton University]] were announced at [[Philosophy:The Science of Consciousness|The Science of Consciousness]] conference, providing further evidence to support quantum processes operating within microtubules. In a study [[Biography:Stuart Hameroff|Stuart Hameroff]] was part of, Jack Tuszyński of the University of Alberta demonstrated that anesthetics hasten the duration of a process called delayed luminescence, in which microtubules and tubulins {{Nowrap|re-emit}} trapped light. Tuszyński suspects that the phenomenon has a quantum origin, with [[Physics:Superradiance|superradiance]] being investigated as one possibility. In the second experiment, Gregory D. Scholes and Aarat Kalra of [[Organization:Princeton University|Princeton University]] used lasers to excite molecules within tubulins, causing a prolonged excitation to diffuse through microtubules further than expected, which did not occur when repeated under anesthesia.<ref>{{cite web|last1=Lewton|first1=Thomas|date=18 April 2022|title=Quantum experiments add weight to a fringe theory of consciousness|url=https://www.newscientist.com/article/2316408-quantum-experiments-add-weight-to-a-fringe-theory-of-consciousness/|url-access=subscription|access-date=23 April 2022|website=New Scientist}}</ref><ref>{{cite web|last1=Tangermann|first1=Victor|title=Experiment Suggests That Consciousness May Be Rooted in Quantum Physics|url=https://futurism.com/human-consciousness-quantum-physics|website=www.futurism.com|publisher=Camden Media Inc|access-date=24 April 2022}}</ref> However, diffusion results have to be interpreted carefully, since even classical diffusion can be very complex due to the wide range of length scales in the fluid filled extracellular space.<ref>{{cite journal|last1=Nicholson|first1=Charles|title=The Secret World in the Gaps between Brain Cells|journal=Physics Today|date=May 2022|volume=75|issue=5|pages=26–32|doi=10.1063/PT.3.4999|bibcode=2022PhT....75e..26N|s2cid=248620292}}</ref> Nevertheless, [[Organization:University of Oxford|University of Oxford]] quantum physicist Vlatko Vedral told that this connection with consciousness is a really long shot.

Also in 2022, a group of Italian physicists conducted several experiments that failed to provide evidence in support of a gravity-related quantum collapse model of consciousness, weakening the possibility of a quantum explanation for consciousness.<ref>{{cite news|title=Collapsing a leading theory for the quantum origin of consciousness|url=https://phys.org/news/2022-06-collapsing-theory-quantum-consciousness.html|work=phys.org|date=13 June 2022}}</ref><ref>{{cite journal|last1=Derakhshani|first1=Maaneli|last2=Diósi|first2=Lajos|last3=Laubenstein|first3=Matthias|last4=Piscicchia|first4=Kristian|last5=Curceanu|first5=Catalina|title=At the crossroad of the search for spontaneous radiation and the Orch OR consciousness theory|journal=Physics of Life Reviews|date=1 September 2022|volume=42|pages=8–14|doi=10.1016/j.plrev.2022.05.004|pmid=35617922|bibcode=2022PhLRv..42....8D|s2cid=248868080}}</ref>

Although these theories are stated in a scientific framework, it is difficult to separate them from scientists' personal opinions. The opinions are often based on intuition or subjective ideas about the nature of consciousness. For example, Penrose wrote:<ref>{{cite web |last1=Daniel |first1=Dennett |title=Edge Conversation Chapter 10: Intuition Pumps, and response by Roger Penrose |url=https://www.edge.org/conversation/daniel_c_dennett-chapter-10-intuition-pumps |website=Edge.com |access-date=20 Feb 2018}}</ref>
<blockquote>
[M]y own point of view asserts that you can't even simulate conscious activity. What's going on in conscious thinking is something you couldn't properly imitate at all by computer.... If something behaves as though it's conscious, do you say it is conscious? People argue endlessly about that. Some people would say, "Well, you've got to take the operational viewpoint; we don't know what consciousness is. How do you judge whether a person is conscious or not? Only by the way they act. You apply the same criterion to a computer or a computer-controlled robot." Other people would say, "No, you can't say it feels something merely because it behaves as though it feels something." My view is different from both those views. The robot wouldn't even behave convincingly as though it was conscious unless it really was—which I say it couldn't be, if it's entirely computationally controlled.
</blockquote>

Penrose continues:<ref name="Penroseedge">{{cite web |last1=Penrose |first1=Roger |title=Edge Conversation Chapter 14: Consciousness Involves Noncomputable Ingredients |url=https://www.edge.org/conversation/roger_penrose-chapter-14-consciousness-involves-noncomputable-ingredients |website=Edge.com |access-date=20 Feb 2018}}</ref>
<blockquote>
A lot of what the brain does you could do on a computer. I'm not saying that all the brain's action is completely different from what you do on a computer. I am claiming that the actions of consciousness are something different. I'm not saying that consciousness is beyond physics, either—although I'm saying that it's beyond the physics we know now.... My claim is that there has to be something in physics that we don't yet understand, which is very important, and which is of a noncomputational character. It's not specific to our brains; it's out there, in the physical world. But it usually plays a totally insignificant role. It would have to be in the bridge between quantum and classical levels of behavior—that is, where quantum measurement comes in.
</blockquote>

===Umezawa, Vitiello, Freeman===

[[Biography:Hiroomi Umezawa|Hiroomi Umezawa]] and collaborators proposed a quantum field theory of memory storage.<ref>{{cite journal |author1=Ricciardi L. M.  |author2=Umezawa H. | year = 1967 | title = Brain physics and many-body problems | journal = Kibernetik | volume = 4 | issue = 2 | pages = 44–48 | doi=10.1007/BF00292170 |pmid=5617419 |s2cid=29289582 }}</ref><ref>{{cite journal |last1=Ricciardi |first1=L. M. |last2=Umezawa |first2=H. |year=2004 |editor-last=Gordon |editor-first=G. G. |editor2=Pribram |editor2-first=K. H. |editor3=Vitiello |editor3-first=G. |title=Brain physics and many-body problems |journal=Brain and Being |location=Amsterdam |publisher=John Benjamins Publishing Company |pages=255–266 |orig-year=1967}}</ref> Giuseppe Vitiello and Walter Freeman proposed a dialog model of the mind. This dialog takes place between the classical and the quantum parts of the brain.<ref>G. Vitiello, ''My Double Unveiled''. John Benjamins, 2001.</ref><ref>{{cite journal |last1=Freeman |first1=W. |last2=Vitiello |first2=G. |year=2006 |title=Nonlinear brain dynamics as macroscopic manifestation of underlying many-body dynamics |journal=Physics of Life Reviews |volume=3 |issue=2 |pages=93–118 |arxiv=q-bio/0511037 |bibcode=2006PhLRv...3...93F |doi=10.1016/j.plrev.2006.02.001 |s2cid=11011930}}</ref><ref>{{citation |author1=Atmanspacher |first=H. |title=Quantum Approaches to Consciousness. A critical survey article in Stanford University Encyclopedia of Philosophy |year=2006 |chapter=Quantum Approaches to Consciousness |chapter-url=https://plato.stanford.edu/entries/qt-consciousness |publisher=Metaphysics Research Lab, Stanford University}}</ref> Their quantum field theory models of brain dynamics are fundamentally different from the Penrose–Hameroff theory.{{citation needed|date=January 2023}}

====Quantum brain dynamics====
In [[Biology:Neuroscience|neuroscience]], '''quantum brain dynamics''' (QBD) is a hypothesis to explain the function of the [[Biology:Brain|brain]] within the framework of [[Physics:Quantum field theory|quantum field theory]].{{citation needed|date=January 2023}}

As described by Harald Atmanspacher, "Since quantum theory is the most fundamental theory of matter that is currently available, it is a legitimate question to ask whether quantum theory can help us to understand consciousness."

<blockquote>The original motivation in the early 20th century for relating quantum theory to consciousness was essentially philosophical. It is fairly plausible that conscious free decisions (“free will”) are [[Incompatibilism|problematic in a perfectly deterministic world]], so quantum randomness might indeed open up novel possibilities for free will. (On the other hand, randomness is problematic for goal-directed volition!)<ref>
{{cite web
 | url = http://plato.stanford.edu/entries/qt-consciousness/
 | title = Quantum Approaches to Consciousness
 | last = Atmanspacher
 | first = Harald
 | date = 2 June 2015
 | orig-year = 30 November 2004
 | website = Stanford Encyclopedia of Philosophy
 | publisher = Center for the Study of Language and Information (CSLI), Stanford University
 | access-date = 17 February 2016
}}
</ref></blockquote>

Ricciardi and Umezawa proposed in 1967 a general theory of quanta of long-range [[Physics:Coherence|coherent]] waves within and between brain cells, and showed a possible mechanism of memory storage and retrieval in terms of Nambu–Goldstone bosons.<ref name="Umezawa1967">{{cite journal 
|vauthors=Ricciardi LM, Umezawa H |title = Brain and physics of many-body problems
|journal = Kybernetik
|volume = 4
|year = 1967
|issue = 2
|pages = 44–48
|doi=10.1007/bf00292170
 |pmid = 5617419
|s2cid = 29289582
}}</ref> This was later developed into a theory encompassing all biological cells and systems in the quantum biodynamics of Del Giudice and co-authors.<ref name="DelGiudice1986">{{cite journal 
|vauthors=Del Giudice E, Doglia S, Milani M, Vitiello G |title =  Electromagnetic field and spontaneous symmetry breaking in biological matter
|journal = Nucl. Phys. B
|volume = 275
|year = 1986
|issue = 2
|pages = 185–199
|doi=10.1016/0550-3213(86)90595-x
|bibcode = 1986NuPhB.275..185D
}}</ref><ref name="DelGiudice1988">{{cite journal 
|vauthors = Del Giudice E, Preparata G, Vitiello G 
|title =  Water as a free electric dipole laser
|journal = Physical Review Letters
|volume = 61
|year = 1988
|issue = 9 
|pages = 1085–1088
|doi=10.1103/physrevlett.61.1085
|pmid = 10039515 
|bibcode = 1988PhRvL..61.1085D 
}}</ref> Mari Jibu and Kunio Yasue later popularized these results and discussed the implications towards consciousness.<ref name="Jibu1995">{{cite book
  |vauthors=Jibu M, Yasue K | title = Quantum Brain Dynamics: An Introduction
  | publisher =  John Benjamins
  | series = 
  | location = Amsterdam
  | year = 1995
  | doi =  
  | isbn = 
}}</ref><ref name="Jibu1997">{{cite journal 
|vauthors=Jibu M, Yasue K |title =  What is mind? Quantum field theory of evanescent photons in brain as quantum theory of consciousness
|journal = Informatica
|volume = 21
|year = 1997
|pages = 471–490
}}</ref><ref>{{cite web|last1=Yasue |first1=Kunio |title=Quantum Monadology |url=http://cognet.mit.edu/posters/TUCSON3/Yasue.html |website=Toward a Science of Consciousness |url-status=dead |archiveurl=https://web.archive.org/web/20140625024817/http://cognet.mit.edu/posters/TUCSON3/Yasue.html |archivedate=June 25, 2014 }}</ref>

Umezawa emphasizes that macroscopic and microscopic ordered states are both of quantum origin according to quantum field theory and points out the shortcomings of classical neuronal models in describing them.<ref>{{cite book |last1=Umezawa |first1=Hiroomi |title=Advanced Field Theory: Micro, Macro, and Thermal Physics |publisher=American Institute of Physics Press |year=1993 |isbn=1-56396-456-2 |language=en-us}}</ref> In 1981, theoretical exploration of the [[Physics:Ising model|Ising model]] in {{pslink|Ising model|Cayley tree topologies and large neural networks|nopage=y}} yielded an exact solution on closed trees with arbitrary branching ratios greater than two, exhibiting an unusual [[Physics:Phase transition|phase transition]] in local-apex and long-range site-site correlations.<ref>{{cite thesis |first=Peter F. |last=Barth | year=1981 | title=Cooperativity and the Transition Behavior of Large Neural Nets | pages=1–118 | type= M.Sc. Thesis | publisher= University of Vermont |oclc=8231704 }}</ref><ref>{{cite journal |last1=Krizan |first1=J. E. |last2=Barth |first2=P. F. |author-link2=Peter F. Barth |last3=Glasser |first3=M. L. |year=1983 |title=Exact Phase Transitions for the Ising Model on the Closed Cayley Tree |journal=Physica |publisher=North-Holland Publishing Company |volume=119A |pages=230–242 |doi=10.1016/0378-4371(83)90157-7}}</ref> This finding directly raises the possibility of multiple cooperative modes being present in ordering states long-range within neural networks and their constituents, with Barth cooperative effects of the closed tree Ising model (structurally and connectivity dependent, with critical point a function of branching ratio and site-to-site energies of interaction)<ref>{{cite thesis|first=Peter F. |last=Barth | author-link=Peter F. Barth |year=1981 | title=Cooperativity and the Transition Behavior of Large Neural Nets | pages=58–59, 99 | type= M.Sc. Thesis | publisher= University of Vermont |oclc=8231704 }}</ref> and Umezawa ordering of states (less structure dependent and with significantly greater degrees of freedom)<ref>{{cite book |last1=Umezawa |first1=Hiroomi |title=Advanced Field Theory: Micro, Macro, and Thermal Physics |publisher=AIP (American Institute of Physics) Press|year=1993 |isbn=1563964562 }}</ref> independently or collectively guiding overall long-range macroscopic ordering often associated with higher cognitive functions in QBD.

===Pribram===

[[Biography:Karl H. Pribram|Karl Pribram]]'s [[Philosophy:Holonomic brain theory|holonomic brain theory]] (quantum holography) invoked quantum mechanics to explain higher-order processing by the mind.<ref>{{cite journal |author=Pribram |first=K. H. |year=1999 |title=Quantum holography: Is it relevant to brain function? |journal=Information Sciences |volume=115 |issue=1–4 |pages=97–102 |doi=10.1016/s0020-0255(98)10082-8}}</ref><ref>{{cite journal |author=Pribram |first=K. H. |year=2004 |title=Consciousness Reassessed |journal=Mind and Matter |volume=2 |pages=7–35}}</ref> He argued that his holonomic model solved the [[Binding problem|binding problem]].<ref>Pribram, K. (1999) Status Report: Quantum Holography and the Braln. Acta Polyiechnica Scandinavica: Emergence Complexity, Hierarchy, Organization, Vol. 2, pp.&nbsp;33–60.</ref> Pribram collaborated with Bohm in his work on quantum approaches to mind and he provided evidence on how much of the processing in the brain was done in wholes.<ref>Pribram, K. H. Holography, holonomy and brain function. Elsevier's Encyclopedia of Neuroscience, 1999.</ref> He proposed that ordered water at [[Biology:Dendrite|dendritic]] membrane surfaces might operate by structuring [[Physics:Bose–Einstein condensate|Bose–Einstein condensation]] supporting quantum dynamics.<ref>{{cite journal |last1=Jibu |first1=M. |last2=Pribram |first2=K. H. |last3=Yasue |first3=K. |year=1996 |title=From conscious experience to memory storage and retrieval: The role of quantum brain dynamics and boson condensation of evanescent photons |journal=International Journal of Modern Physics B |volume=10 |issue=13n14 |pages=1735–1754 |bibcode=1996IJMPB..10.1735J |doi=10.1142/s0217979296000805}}</ref>

===Stapp===

[[Biography:Henry Stapp|Henry Stapp]] proposed that quantum waves are reduced only when they interact with consciousness. He argues from the {{clarify span|orthodox quantum mechanics of [[Biography:John von Neumann|John von Neumann]]|"Orthodox" usually means Copenhagen interpretation, but von Neumann and Wigner developed their own, with "consciousness causes collapse". Which one is implied here?|date=June 2021}} that the quantum state collapses when the observer selects one among the alternative quantum possibilities as a basis for future action. The collapse, therefore, takes place in the expectation that the observer associated with the state. Stapp's work drew criticism from scientists such as David Bourget and Danko Georgiev.<ref name=Bourget>
{{cite journal
 |last=Bourget |first=D.
 |year=2004
 |title=Quantum Leaps in Philosophy of Mind: A Critique of Stapp's Theory
 |journal=[[Philosophy:Journal of Consciousness Studies|Journal of Consciousness Studies]]
 |volume=11 |issue=12 |pages=17–42
}}</ref><ref name="Georgiev2012">
{{cite journal
 |last1=Georgiev |first1=D.
 |year=2012
 |title=Mind efforts, quantum Zeno effect and environmental decoherence
 |journal=[[Physics:NeuroQuantology|NeuroQuantology]]
 |volume=10 |issue=3 |pages=374–388 |doi=10.14704/nq.2012.10.3.552
}}</ref><ref name="Georgiev2015">
{{cite journal
 |last1=Georgiev |first1=D.
 |year=2015
 |title=Monte Carlo simulation of quantum Zeno effect in the brain
 |journal=International Journal of Modern Physics B
 |volume=29 |issue= 7|pages=1550039 |doi=10.1142/S0217979215500393 |arxiv=1412.4741
|bibcode=2015IJMPB..2950039G|s2cid=118390522
 }}</ref><ref name="Georgiev2017">{{cite book |last=Georgiev |first=Danko D. |url=https://books.google.com/books?id=OtRBDwAAQBAJ |title=Quantum Information and Consciousness: A Gentle Introduction |publisher=CRC Press |year=2017 |isbn=9781138104488 |location=Boca Raton, Florida |language=en-us |oclc=1003273264}}</ref>

===David Pearce===

British philosopher [[Biography:David Pearce (philosopher)|David Pearce]] defends what he calls physicalistic idealism ("the non-materialist physicalist claim that reality is fundamentally experiential and that the natural world is exhaustively described by the equations of physics and their solutions") and has conjectured that unitary conscious minds are physical states of quantum coherence (neuronal superpositions).<ref>{{cite web |last1=Pearce |first1=David |title=Non-Materialist Physicalism: An experimentally testable conjecture |url=https://www.physicalism.com |access-date=15 Feb 2018}}</ref><ref>{{cite web |last1=Pearce |first1=David |title=Quantum computing: the first 540 million years: Abstract of talk given at Tucson conference 'Toward a Science of Consciousness' (2010) |url=https://www.hedweb.com/philsoph/quantum-computer.html |access-date=18 Feb 2018}}</ref><ref name="Pearcevideo">{{cite web |last1=Pearce |first1=David |title=The Binding Problem of Consciousness |url=https://www.youtube.com/watch?v=8xizbtklciA  |archive-url=https://ghostarchive.org/varchive/youtube/20211213/8xizbtklciA |archive-date=2021-12-13 |url-status=live|website=YouTube.com}}{{cbignore}}</ref><ref>{{cite web |last1=Pearce |first1=David |title=Schrödinger's Neurons: David Pearce at the '2016 Science of Consciousness' conference in Tucson |url=https://www.youtube.com/watch?v=2N6j1pHiEA4  |archive-url=https://ghostarchive.org/varchive/youtube/20211213/2N6j1pHiEA4 |archive-date=2021-12-13 |url-status=live|website=YouTube.com |access-date=18 Feb 2018}}{{cbignore}}</ref> This conjecture is, according to Pearce, amenable to falsification, unlike most theories of consciousness, and Pearce has outlined an experimental protocol describing how the hypothesis could be tested using [[Astronomy:Interferometry|matter-wave interferometry]] to detect [[Physics:Wave interference|nonclassical interference patterns]] of [[Physics:Quantum superposition|neuronal superpositions]] at the onset of [[Physics:Quantum decoherence|thermal decoherence]].<ref name="Pearce">{{cite web |last1=Pearce |first1=David |title=Non-Materialist Physicalism: An experimentally testable conjecture, Section&nbsp;6 |url=https://www.physicalism.com/#6 |access-date=15 Feb 2018}}</ref> Pearce admits that his ideas are "highly speculative", "counterintuitive", and "incredible".<ref name="Pearcevideo" />

===Catecholaminergic Neuron Electron Transport (CNET)===

CNET is a hypothesized neural signaling mechanism in catecholaminergic neurons that would use quantum mechanical electron transport.<ref>{{Cite journal |last=Rourk |first=Christopher John |date=September 2018 |title=Ferritin and neuromelanin "quantum dot" array structures in dopamine neurons of the substantia nigra pars compacta and norepinephrine neurons of the locus coeruleus |journal=Biosystems |volume=171 |pages=48–58 |doi=10.1016/j.biosystems.2018.07.008 |pmid=30048795 |s2cid=51722018 |issn=0303-2647|doi-access=free }}</ref><ref>{{Citation |last=Rourk |first=Christopher J. |title=Functional neural electron transport |date=2020 |url=http://dx.doi.org/10.1016/bs.aiq.2020.08.001 |work=Quantum Boundaries of Life |series=Advances in Quantum Chemistry |volume=82 |pages=25–111 |publisher=Elsevier |doi=10.1016/bs.aiq.2020.08.001 |isbn=9780128226391 |s2cid=229230562 |access-date=2022-10-23}}</ref> The hypothesis is based in part on the observation by many independent researchers that electron tunneling occurs in ferritin, an iron storage protein that is prevalent in those neurons, at room temperature and ambient conditions.<ref>{{Cite journal |last1=Xu |first1=Degao |last2=Watt |first2=Gerald D. |last3=Harb |first3=John N. |last4=Davis |first4=Robert C. |date=2005-03-25 |title=Electrical Conductivity of Ferritin Proteins by Conductive AFM |url=http://dx.doi.org/10.1021/nl048218x |journal=Nano Letters |volume=5 |issue=4 |pages=571–577 |doi=10.1021/nl048218x |pmid=15826089 |bibcode=2005NanoL...5..571X |issn=1530-6984}}</ref><ref>{{Cite journal |last1=Kumar |first1=Karuppannan Senthil |last2=Pasula |first2=Rupali Reddy |last3=Lim |first3=Sierin |last4=Nijhuis |first4=Christian A. |date=2015-12-28 |title=Long-Range Tunneling Processes across Ferritin-Based Junctions |url=http://dx.doi.org/10.1002/adma.201504402 |journal=Advanced Materials |volume=28 |issue=9 |pages=1824–1830 |doi=10.1002/adma.201504402 |pmid=26708136 |s2cid=2238319 |issn=0935-9648}}</ref><ref>{{Cite journal |last1=Kolay |first1=J. |last2=Bera |first2=S. |last3=Rakshit |first3=T. |last4=Mukhopadhyay |first4=R. |date=2018-02-07 |title=Negative Differential Resistance Behavior of the Iron Storage Protein Ferritin |url=http://dx.doi.org/10.1021/acs.langmuir.7b04356 |journal=Langmuir |volume=34 |issue=9 |pages=3126–3135 |doi=10.1021/acs.langmuir.7b04356 |pmid=29412680 |issn=0743-7463}}</ref><ref>{{Cite journal |last1=Gupta |first1=Nipun Kumar |last2=Karuppannan |first2=Senthil Kumar |last3=Pasula |first3=Rupali Reddy |last4=Vilan |first4=Ayelet |last5=Martin |first5=Jens |last6=Xu |first6=Wentao |last7=May |first7=Esther Maria |last8=Pike |first8=Andrew R. |last9=Astier |first9=Hippolyte P. A. G. |last10=Salim |first10=Teddy |last11=Lim |first11=Sierin |last12=Nijhuis |first12=Christian A. |date=2022-09-23 |title=Temperature-Dependent Coherent Tunneling across Graphene–Ferritin Biomolecular Junctions |url=http://dx.doi.org/10.1021/acsami.2c11263 |journal=ACS Applied Materials & Interfaces |volume=14 |issue=39 |pages=44665–44675 |doi=10.1021/acsami.2c11263 |pmid=36148983 |pmc=9542697 |issn=1944-8244}}</ref> The hypothesized function of this mechanism is to assist in action selection, but the mechanism itself would be capable of integrating millions of cognitive and sensory neural signals using a physical mechanism associated with strong electron-electron interactions.<ref>{{Citation |last1=Kouwenhoven |first1=Leo P. |title=Electron Transport in Quantum Dots |date=1997 |url=http://dx.doi.org/10.1007/978-94-015-8839-3_4 |work=Mesoscopic Electron Transport |pages=105–214 |place=Dordrecht |publisher=Springer Netherlands |isbn=978-90-481-4906-3 |access-date=2022-10-23 |last2=Marcus |first2=Charles M. |last3=McEuen |first3=Paul L. |last4=Tarucha |first4=Seigo |last5=Westervelt |first5=Robert M. |last6=Wingreen |first6=Ned S.|doi=10.1007/978-94-015-8839-3_4 }}</ref><ref>{{Cite journal |last1=Basov |first1=D. N. |last2=Averitt |first2=Richard D. |last3=van der Marel |first3=Dirk |last4=Dressel |first4=Martin |last5=Haule |first5=Kristjan |date=2011-06-02 |title=Electrodynamics of correlated electron materials |url=http://dx.doi.org/10.1103/revmodphys.83.471 |journal=Reviews of Modern Physics |volume=83 |issue=2 |pages=471–541 |doi=10.1103/revmodphys.83.471 |arxiv=1106.2309 |bibcode=2011RvMP...83..471B |s2cid=118437353 |issn=0034-6861}}</ref><ref>{{Cite journal |last1=Dykman |first1=M. I. |last2=Fang-Yen |first2=C. |last3=Lea |first3=M. J. |date=1997-06-15 |title=Many-electron transport in strongly correlated nondegenerate two-dimensional electron systems |url=http://dx.doi.org/10.1103/physrevb.55.16249 |journal=Physical Review B |volume=55 |issue=24 |pages=16249–16271 |doi=10.1103/physrevb.55.16249 |bibcode=1997PhRvB..5516249D |issn=0163-1829}}</ref> Each tunneling event would involve a collapse of an electron wave function, but the collapse would be incidental to the physical effect created by strong electron-electron interactions.{{citation needed|date=January 2023}}

CNET predicted a number of physical properties of these neurons that have been subsequently observed experimentally, such as electron tunneling in substantia nigra pars compacta (SNc) tissue and the presence of disordered arrays of ferritin in SNc tissue.<ref>{{Cite journal |last=Rourk |first=Christopher J. |date=May 2019 |title=Indication of quantum mechanical electron transport in human substantia nigra tissue from conductive atomic force microscopy analysis |url=http://dx.doi.org/10.1016/j.biosystems.2019.02.003 |journal=Biosystems |volume=179 |pages=30–38 |doi=10.1016/j.biosystems.2019.02.003 |pmid=30826349 |s2cid=73509918 |issn=0303-2647}}</ref><ref>{{Cite journal |last1=Sulzer |first1=David |last2=Cassidy |first2=Clifford |last3=Horga |first3=Guillermo |last4=Kang |first4=Un Jung |last5=Fahn |first5=Stanley |last6=Casella |first6=Luigi |last7=Pezzoli |first7=Gianni |last8=Langley |first8=Jason |last9=Hu |first9=Xiaoping P. |last10=Zucca |first10=Fabio A. |last11=Isaias |first11=Ioannis U. |last12=Zecca |first12=Luigi |date=2018-04-10 |title=Neuromelanin detection by magnetic resonance imaging (MRI) and its promise as a biomarker for Parkinson's disease |url=http://dx.doi.org/10.1038/s41531-018-0047-3 |journal=npj Parkinson's Disease |volume=4 |issue=1 |page=11 |doi=10.1038/s41531-018-0047-3 |pmid=29644335 |pmc=5893576 |issn=2373-8057}}</ref><ref>{{Cite journal |last1=Friedrich |first1=I. |last2=Reimann |first2=K. |last3=Jankuhn |first3=S. |last4=Kirilina |first4=E. |last5=Stieler |first5=J. |last6=Sonntag |first6=M. |last7=Meijer |first7=J. |last8=Weiskopf |first8=N. |last9=Reinert |first9=T. |last10=Arendt |first10=T. |last11=Morawski |first11=M. |date=2021-03-22 |title=Cell specific quantitative iron mapping on brain slices by immuno-µPIXE in healthy elderly and Parkinson's disease |journal=Acta Neuropathologica Communications |volume=9 |issue=1 |page=47 |doi=10.1186/s40478-021-01145-2 |pmid=33752749 |pmc=7986300 |issn=2051-5960 |doi-access=free }}</ref><ref>{{Cite journal |last1=Xiong |first1=Nian |last2=Huang |first2=Jinsha |last3=Zhang |first3=Zhentao |last4=Zhang |first4=Zhaowen |last5=Xiong |first5=Jing |last6=Liu |first6=Xingyuan |last7=Jia |first7=Min |last8=Wang |first8=Fang |last9=Chen |first9=Chunnuan |last10=Cao |first10=Xuebing |last11=Liang |first11=Zhihou |last12=Sun |first12=Shenggang |last13=Lin |first13=Zhicheng |last14=Wang |first14=Tao |date=2009-11-18 |title=Stereotaxical Infusion of Rotenone: A Reliable Rodent Model for Parkinson's Disease |journal=PLOS ONE |volume=4 |issue=11 |pages=e7878 |doi=10.1371/journal.pone.0007878 |pmid=19924288 |pmc=2774159 |bibcode=2009PLoSO...4.7878X |issn=1932-6203|doi-access=free }}</ref> The hypothesis also predicted that disordered ferritin arrays like those found in SNc tissue should be capable of supporting long-range electron transport and providing a switching or routing function, both of which have also been subsequently observed.<ref>{{Cite journal |last1=Bera |first1=Sudipta |last2=Kolay |first2=Jayeeta |last3=Pramanik |first3=Pallabi |last4=Bhattacharyya |first4=Anirban |last5=Mukhopadhyay |first5=Rupa |date=2019 |title=Long-range solid-state electron transport through ferritin multilayers |url=http://dx.doi.org/10.1039/c9tc01744e |journal=Journal of Materials Chemistry C |volume=7 |issue=29 |pages=9038–9048 |doi=10.1039/c9tc01744e |s2cid=198849306 |issn=2050-7526}}</ref><ref>{{Cite journal |last1=Rourk |first1=Christopher |last2=Huang |first2=Yunbo |last3=Chen |first3=Minjing |last4=Shen |first4=Cai |date=2021-06-16 |title=Indication of Highly Correlated Electron Transport in Disordered Multilayer Ferritin Structures |url=http://dx.doi.org/10.31219/osf.io/7gqmt |access-date=2022-10-23 |doi=10.31219/osf.io/7gqmt |s2cid=241118606 }}</ref><ref>{{Cite journal |last1=Labra-Muñoz |first1=Jacqueline A. |last2=de Reuver |first2=Arie |last3=Koeleman |first3=Friso |last4=Huber |first4=Martina |last5=van der Zant |first5=Herre S. J. |date=2022-05-15 |title=Ferritin-Based Single-Electron Devices |journal=Biomolecules |volume=12 |issue=5 |pages=705 |doi=10.3390/biom12050705 |pmid=35625632 |pmc=9138424 |issn=2218-273X|doi-access=free }}</ref>

Another prediction of CNET was that the largest SNc neurons should mediate action selection. This prediction was contrary to earlier proposals about the function of those neurons at that time, which were based on predictive reward dopamine signaling.<ref>{{Cite journal |last=Schultz |first=Wolfram |date=1998-07-01 |title=Predictive Reward Signal of Dopamine Neurons |journal=Journal of Neurophysiology |volume=80 |issue=1 |pages=1–27 |doi=10.1152/jn.1998.80.1.1 |pmid=9658025 |s2cid=52857162 |issn=0022-3077|doi-access=free }}</ref><ref>{{Cite journal |last=Schultz |first=Wolfram |date=2016-02-02 |title=Reward functions of the basal ganglia |url=http://dx.doi.org/10.1007/s00702-016-1510-0 |journal=Journal of Neural Transmission |volume=123 |issue=7 |pages=679–693 |doi=10.1007/s00702-016-1510-0 |pmid=26838982 |pmc=5495848 |issn=0300-9564}}</ref> A team led by Dr. Pascal Kaeser of Harvard Medical School subsequently demonstrated that those neurons do in fact code movement, consistent with the earlier predictions of CNET.<ref>{{Cite journal |last1=Liu |first1=Changliang |last2=Goel |first2=Pragya |last3=Kaeser |first3=Pascal S. |date=2021-04-09 |title=Spatial and temporal scales of dopamine transmission |url=http://dx.doi.org/10.1038/s41583-021-00455-7 |journal=Nature Reviews Neuroscience |volume=22 |issue=6 |pages=345–358 |doi=10.1038/s41583-021-00455-7 |pmid=33837376 |pmc=8220193 |issn=1471-003X}}</ref> While the CNET mechanism has not yet been directly observed, it may be possible to do so using quantum dot fluorophores tagged to ferritin or other methods for detecting electron tunneling.<ref>{{Cite journal |last1=Garg |first1=Mayank |last2=Vishwakarma |first2=Neelam |last3=Sharma |first3=Amit L. |last4=Singh |first4=Suman |date=2021-07-08 |title=Amine-Functionalized Graphene Quantum Dots for Fluorescence-Based Immunosensing of Ferritin |url=http://dx.doi.org/10.1021/acsanm.1c01398 |journal=ACS Applied Nano Materials |volume=4 |issue=7 |pages=7416–7425 |doi=10.1021/acsanm.1c01398 |s2cid=237804893 |issn=2574-0970}}</ref>

CNET is applicable to a number of different consciousness models as a binding or action selection mechanism, such as [[Integrated information theory|Integrated Information Theory]] (IIT) and [http://www.scholarpedia.org/article/Sensorimotor_theory_of_consciousness Sensorimotor Theory] (SMT).<ref>{{Cite journal |last=Rourk |first=Chris |date=2022-01-06 |title=Application of the Catecholaminergic Neuron Electron Transport (CNET) Physical Substrate for Consciousness and Action Selection to Integrated Information Theory |journal=Entropy |volume=24 |issue=1 |pages=91 |doi=10.3390/e24010091 |pmid=35052119 |pmc=8774445 |bibcode=2022Entrp..24...91R |issn=1099-4300|doi-access=free }}</ref> It is noted that many existing models of consciousness fail to specifically address action selection or binding. For example, O’Regan and Noë call binding a “pseudo problem,” but also state that “the fact that object attributes seem perceptually to be part of a single object does not require them to be ‘represented’ in any unified kind of way, for example, at a single location in the brain, or by a single process. They may be so represented, but there is no logical necessity for this.”<ref>{{Cite journal |last1=O'Regan |first1=J. Kevin |last2=Noë |first2=Alva |date=October 2001 |title=A sensorimotor account of vision and visual consciousness |url=http://dx.doi.org/10.1017/s0140525x01000115 |journal=Behavioral and Brain Sciences |volume=24 |issue=5 |pages=939–973 |doi=10.1017/s0140525x01000115 |pmid=12239892 |issn=0140-525X}}</ref> Simply because there is no “logical necessity” for a physical phenomenon does not mean that it does not exist, or that once it is identified that it can be ignored. Likewise, [[Philosophy:Global workspace theory|global workspace theory]] (GWT) models appear to treat dopamine as modulatory,<ref>{{Cite journal |last1=Volzhenin |first1=Konstantin |last2=Changeux |first2=Jean-Pierre |last3=Dumas |first3=Guillaume |date=2022-01-25 |title=Multilevel Development of Cognitive Abilities in an Artificial Neural Network |url=http://dx.doi.org/10.1101/2022.01.24.477526 |access-date=2022-10-23 |journal=Proceedings of the National Academy of Sciences of the United States of America|volume=119 |issue=39 |pages=e2201304119 |doi=10.1073/pnas.2201304119|biorxiv=10.1101/2022.01.24.477526 |pmid=36122214 |pmc=9522351 |bibcode=2022PNAS..11901304V }}</ref> based on the prior understanding of those neurons from predictive reward dopamine signaling research, but GWT models could be adapted to include modeling of moment-by-moment activity in the striatum to mediate action selection, as observed by Kaiser. CNET is applicable to those neurons as a selection mechanism for that function, as otherwise that function could result in seizures from simultaneous actuation of competing sets of neurons. While CNET by itself is not a model of consciousness, it is able to integrate different models of consciousness through neural binding and action selection. However, a more complete understanding of how CNET might relate to consciousness would require a better understanding of strong electron-electron interactions in ferritin arrays, which implicates the [[Physics:Many-body problem|many-body problem]].

===Experiments===
In 2022, neuroscientists reported experimental [[Physics:Magnetic resonance imaging|MRI]] results that so far appear to imply nuclear proton [[Physics:Spin|spins]] of bulk water in the [[Biology:Brain|brain]]s of human participants were [[Quantum entanglement|entangled]], suggesting [[Cognition|brain functions]] that operate non-classically which may support quantum mechanisms being involved in consciousness as the signal pattern declined when human participants fell asleep. However, the results are far from unambiguous and if such brain functions indeed exist and are involved in conscious cognition, the extent and nature of their involvement in consciousness remains unknown.{{Explain|date=December 2022}}<ref>{{cite news |last1=Firtina |first1=Nergis |date=20 October 2022 |title=Our brains could use quantum computation – here's how |work=interestingengineering.com |url=https://interestingengineering.com/science/brain-quantum-computation-consciousness |access-date=17 November 2022}}</ref><ref>{{cite journal |last1=Kerskens |first1=Christian Matthias |last2=López Pérez |first2=David |title=Experimental indications of non-classical brain functions |journal=Journal of Physics Communications |date=1 October 2022 |volume=6 |issue=10 |pages=105001 |doi=10.1088/2399-6528/ac94be |bibcode=2022JPhCo...6j5001K |language=en |issn=2399-6528|doi-access=free|arxiv=1806.07998 }}</ref>

==Criticism==

These hypotheses of the quantum mind remain hypothetical speculation, as Penrose and Pearce admit in their discussions. Until they make a prediction that is tested by experimentation, the hypotheses aren't based on empirical evidence. In 2010, [[Biography:Lawrence Krauss|Lawrence Krauss]] was guarded in criticising Penrose's ideas. He said: "Roger Penrose has given lots of new-age crackpots ammunition... Many people are dubious that Penrose's suggestions are reasonable, because the brain is not an isolated quantum-mechanical system. To some extent it could be, because memories are stored at the molecular level, and at a molecular level quantum mechanics is significant."<ref name="Krauss">{{cite web|last1=Boyle|first1=Alan|title=How to Spot Quantum Quackery|url=https://www.nbcnews.com/science/how-spot-quantum-quackery-6c10403763|website=NBC News Science News|date=20 September 2010 |access-date=8 Mar 2018}}</ref> According to Krauss, "It is true that quantum mechanics is extremely strange, and on extremely small scales for short times, all sorts of weird things happen. And in fact, we can make weird quantum phenomena happen. But what quantum mechanics doesn't change about the universe is, if you want to change things, you still have to do something. You can't change the world by thinking about it."<ref name="Krauss"/>

The process of testing the hypotheses with experiments is fraught with conceptual/theoretical, practical, and ethical problems.

===Conceptual problems===

The idea that a quantum effect is necessary for consciousness to function is still in the realm of philosophy. Penrose proposes that it is necessary, but other theories of consciousness do not indicate that it is needed. For example, [[Biography:Daniel Dennett|Daniel Dennett]] proposed a theory called [[Philosophy:Multiple drafts model|multiple drafts model]], which doesn't indicate that quantum effects are needed, in his 1991 book ''Consciousness Explained''.<ref name="dennett1"/> A philosophical argument on either side isn't scientific proof, although philosophical analysis can indicate key differences in the types of models and show what type of experimental differences might be observed. But since there isn't a clear consensus among philosophers, there isn't conceptual support that a quantum mind theory is needed.<ref>{{cite web |last1=Myrvold |first1=Wayne |title=Philosophical Issues in Quantum Theory |url=https://plato.stanford.edu/entries/qt-issues/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=11 September 2023 |date=2022}}</ref>

There are computers that are specifically designed to compute using quantum-mechanical effects. [[Quantum computing]] is [[Computation|computing]] using [[Physics:Quantum mechanics|quantum-mechanical]] phenomena, such as [[Physics:Quantum superposition|superposition]] and [[Quantum entanglement|entanglement]].<ref>{{cite journal |url=http://cba.mit.edu/docs/papers/98.06.sciqc.pdf |title=Quantum Computing with Molecules |journal=Scientific American |first1=Neil |last1=Gershenfeld |first2=Isaac L. |last2=Chuang |author-link2=Isaac L. Chuang |date=June 1998|volume=278 |issue=6 |pages=66–71 |doi=10.1038/scientificamerican0698-66 |bibcode=1998SciAm.278f..66G }}</ref> They are different from [[Binary number|binary]] [[Digital electronic computer|digital electronic computer]]s based on [[Engineering:Transistor|transistor]]s. Whereas common digital computing requires that the data be encoded into binary digits ([[Bit|bit]]s), each of which is always in one of two definite states (0 or 1), quantum computation uses [[Qubit|quantum bits]], which can be in [[Physics:Quantum superposition|superpositions]] of states. One of the greatest challenges is controlling or removing [[Physics:Quantum decoherence|quantum decoherence]]. This usually means isolating the system from its environment, as interactions with the external world cause the system to decohere. Some quantum computers require their qubits to be cooled to 20&nbsp;millikelvins in order to prevent significant decoherence.<ref>{{cite journal |last1=Jones |first1=Nicola |title=Computing: The quantum company |journal=Nature |date=19 June 2013 |volume=498 |issue=7454 |pages=286–288 |doi=10.1038/498286a |pmid=23783610 |bibcode=2013Natur.498..286J |doi-access=free}}</ref> As a result, time-consuming tasks may render some quantum algorithms inoperable, as maintaining the state of qubits long enough eventually corrupts the superpositions.<ref>{{cite arXiv |last1=Amy |first1=Matthew |last2=Matteo |first2=Olivia |last3=Gheorghiu |first3=Vlad |last4=Mosca |first4=Michele |last5=Parent |first5=Alex |last6=Schanck |first6=John |title=Estimating the cost of generic quantum pre-image attacks on SHA-2 and SHA-3 |date=November 30, 2016 |eprint=1603.09383 |class=quant-ph}}</ref> Currently, there aren't any confirmed [[Formal equivalence checking|formal equivalencies]] between the functioning of quantum computers and the human brain. Some hypothetical models of quantum mind have proposed mechanisms for maintaining quantum coherence in the brain, but they have yet to be thoroughly demonstrated to operate as such.{{citation needed|date=January 2023}}

[[Quantum entanglement]] is a physical phenomenon often invoked for quantum mind models. This effect occurs when pairs or groups of [[Physics:Particle|particle]]s interact so that the [[Physics:Quantum state|quantum state]] of each particle cannot be described independently of the other(s),<ref name="Georgiev2021">{{cite journal
 | last1 = Georgiev
 | first1 = Danko D.
 | title = Quantum information in neural systems
 | journal = Symmetry
 | volume = 13
 | issue = 5
 | pages = 773
 | year = 2021
 | doi = 10.3390/sym13050773
 | s2cid = 233714776
 | arxiv = 2105.01410
| bibcode = 2021Symm...13..773G
 | doi-access = free
 }}</ref> even when the particles are separated by a large distance. Instead, a quantum state has to be described for the whole system. [[Measurement#Quantum mechanics|Measurements]] of physical properties such as [[Position (vector)|position]], [[Physics:Momentum|momentum]], [[Physics:Spin|spin]], and [[Physics:Polarization (waves)|polarization]], performed on entangled particles are found to be [[Correlation|correlated]]. If one particle is measured, the same property of the other particle immediately adjusts to maintain the conservation of the physical phenomenon. According to the formalism of quantum theory, the effect of measurement happens instantly, no matter how far apart the particles are.<ref>{{cite journal | last =Matson | first =John | title =Quantum teleportation achieved over record distances | journal =Nature | date =13 August 2012 | url =http://www.nature.com/news/quantum-teleportation-achieved-over-record-distances-1.11163 | doi =10.1038/nature.2012.11163 | s2cid =124852641 }}</ref><ref name=Griffiths2004>{{citation | author=Griffiths, David J. |title=Introduction to Quantum Mechanics (2nd ed.) | publisher=Prentice Hall |year=2004 |isbn=0-13-111892-7}}.</ref> It is not possible to use this effect to transmit classical information at faster-than-light speeds<ref>[[Biography:Roger Penrose|Roger Penrose]], ''The Road to Reality: A Complete Guide to the Laws of the Universe'', London, England, 2004, p.&nbsp;603.</ref> (see [[Physics:Faster-than-light#Quantum mechanics|Faster-than-light § Quantum mechanics]]). Entanglement is broken when the entangled particles [[Physics:Quantum decoherence|decohere]] through interaction with the environment—for example, when a measurement is made<ref name="Peres1993">Asher Peres, ''[[Quantum Theory: Concepts and Methods| Concepts and Methods]]'', Kluwer, 1993; {{ISBN|0-7923-2549-4}} p.&nbsp;115.</ref> or the particles undergo random collisions or interactions. According to Pearce, "In neuronal networks, ion–ion scattering, ion–water collisions, and long-range Coulomb interactions from nearby ions all contribute to rapid decoherence times; but thermally induced decoherence is even harder experimentally to control than collisional decoherence." He anticipated that quantum effects would have to be measured in femtoseconds, a trillion times faster than the rate at which neurons function (milliseconds).<ref name="Pearce"/>

Another possible conceptual approach is to use quantum mechanics as an analogy to understand a different field of study like consciousness, without expecting that the laws of quantum physics will apply. An example of this approach is the idea of [[Physics:Schrödinger's cat|Schrödinger's cat]]. [[Biography:Erwin Schrödinger|Erwin Schrödinger]] described how one could, in principle, create entanglement of a large-scale system by making it dependent on an elementary particle in a superposition. He proposed a scenario with a cat in a locked steel chamber, wherein the cat's survival depended on the state of a [[Physics:Radioactive decay|radioactive]] atom—whether it had decayed and emitted radiation. According to Schrödinger, the Copenhagen interpretation implies that ''the cat is both alive and dead'' until the state has been observed. Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; he intended the example to illustrate the absurdity of the existing view of quantum mechanics.<ref name="Schrodinger1935">
{{cite journal
| first=Erwin |last=Schrödinger
| title=Die gegenwärtige Situation in der Quantenmechanik (The present situation in quantum mechanics)
| language=de
| journal=Naturwissenschaften
| doi=10.1007/BF01491891
| volume=23
| issue=48
| pages=807–812
| bibcode=1935NW.....23..807S
| date=November 1935
| s2cid=206795705}}</ref> But since Schrödinger's time, physicists have given other [[Physics:Interpretations of quantum mechanics|interpretations of the mathematics of quantum mechanics]], some of which regard the "alive and dead" cat superposition as quite real.<ref name="Polkinghorne">{{cite book
 |last1       = Polkinghorne
 |first1      = J. C.
 |title       = The Quantum World
 |publisher   = Princeton University Press
 |date        = 1985
 |pages       = 67
 |url         = https://books.google.com/books?id=lp4JPYnLrtEC&q=%22schrodinger's+cat%22+%22alive+dead&pg=PA67
 |isbn        = 0691023883
 |url-status  = live
 |archive-url = https://web.archive.org/web/20150519001623/https://books.google.com/books?id=lp4JPYnLrtEC&pg=PA67&dq=%22schrodinger's+cat%22+%22alive+dead
 |archive-date = 2015-05-19
}}</ref><ref name="Tetlow">{{cite book |last1=Tetlow |first1=Philip |url=https://books.google.com/books?id=Rk7O3EG0Xn4C&q=%22alive+and+dead%22&pg=PA321 |title=Understanding Information and Computation: From Einstein to Web Science |date=2012 |publisher=Gower Publishing, Limited |isbn=978-1409440406 |pages=321 |language=en |archive-url=https://web.archive.org/web/20150519001741/https://books.google.com/books?id=Rk7O3EG0Xn4C&pg=PA321&dq=%22alive+and+dead%22 |archive-date=2015-05-19 |url-status=live}}</ref> Schrödinger's famous [[Thought experiment|thought experiment]] poses the question, "''when'' does a quantum system stop existing as a superposition of states and become one or the other?" In the same way, one can ask whether the act of making a decision is analogous to having a superposition of states of two decision outcomes, so that making a decision means "opening the box" to reduce the brain from a combination of states to one state. This analogy about decision-making uses a formalism derived from quantum mechanics, but doesn't indicate the actual mechanism by which the decision is made. In this way, the idea is similar to [[Quantum cognition|quantum cognition]]. This field clearly distinguishes itself from the quantum mind, as it is not reliant on the hypothesis that there is something micro-physical quantum-mechanical about the brain. Quantum cognition is based on the quantum-like paradigm,<ref>{{cite journal |last1=Khrennikov |first1=A. |year=2006 |title=Quantum-like brain: Interference of minds |journal=Biosystems |volume=84 |issue=3 |pages=225–241 |doi=10.1016/j.biosystems.2005.11.005 |pmid=16427733|arxiv=quant-ph/0205092 }}</ref><ref>Khrennikov, A. Information Dynamics in Cognitive, Psychological, Social, and Anomalous Phenomena (Fundamental Theories of Physics) (Volume 138), Kluwer, 2004.</ref> generalized quantum paradigm,<ref>{{cite journal | last1 = Atmanspacher | first1 = H. | last2 = Römer | first2 = H. | last3 = Walach | first3 = H. | year = 2002 | title = Weak quantum theory: Complementarity and entanglement in physics and beyond | journal = Foundations of Physics | volume = 32 | issue = 3 | pages = 379–406 | doi=10.1023/a:1014809312397| s2cid = 118583726 }}</ref> or quantum structure paradigm<ref>{{cite journal | last1 = Aerts | first1 = D. | last2 = Aerts | first2 = S. | year = 1994 | title = Applications of quantum statistics in psychological studies of decision processes | journal = Foundations of Science | volume = 1 | pages = 85–97 | doi = 10.1007/BF00208726 }}</ref> that information processing by complex systems such as the brain can be mathematically described in the framework of quantum information and quantum probability theory. This model uses quantum mechanics only as an analogy, but doesn't propose that quantum mechanics is the physical mechanism by which it operates. For example, quantum cognition proposes that some decisions can be analyzed as if there is interference between two alternatives, but it is not a physical quantum interference effect.{{citation needed|date=January 2023}}

===Practical problems===

Quantum mechanics is a mathematical model that can provide some extremely accurate numerical predictions. [[Biography:Richard Feynman|Richard Feynman]] called quantum electrodynamics, based on the quantum-mechanics formalism, "the jewel of physics" for its [[Physics:Precision tests of QED|extremely accurate predictions]] of quantities like the anomalous magnetic moment of the electron and the [[Physics:Lamb shift|Lamb shift]] of the [[Physics:Energy level|energy level]]s of [[Chemistry:Hydrogen|hydrogen]].<ref name=feynbook>{{cite book |last=Feynman |first=Richard |year=1985 |isbn=978-0-691-12575-6 |title=QED: The Strange Theory of Light and Matter |publisher=Princeton University Press}}</ref>{{rp|Ch. 1}} So it is not impossible that the model could provide an accurate prediction about consciousness that would confirm that a quantum effect is involved. If the mind depends on quantum mechanical effects, the true proof is to find an experiment that provides a calculation that can be compared to experimental measurement. It has to show a measurable difference between a classical computation result in a brain and one that involves quantum effects.{{citation needed|date=January 2023}}

The main theoretical argument against the quantum-mind hypothesis is the assertion that quantum states in the brain would lose coherency before they reached a scale where they could be useful for neural processing. This supposition was elaborated by [[Biography:Max Tegmark|Max Tegmark]]. His calculations indicate that quantum systems in the brain decohere at sub-picosecond timescales.<ref name="Tegmark2000">{{cite journal |doi=10.1103/PhysRevE.61.4194 |pmid=11088215 |author=Tegmark, M. |title= Importance of quantum decoherence in brain processes |journal=Physical Review E |volume=61 |pages=4194–4206 |year=2000 |bibcode=2000PhRvE..61.4194T |arxiv=quant-ph/9907009 |issue=4 |s2cid=17140058 }}</ref><ref name="Seife">{{cite journal |author=Seife |first=Charles |date=4 February 2000 |title=Cold Numbers Unmake the Quantum Mind |journal=Science |volume=287 |issue=5454 |page=791 |doi=10.1126/science.287.5454.791 |pmid=10691548 |s2cid=33761196}}</ref> No response by a brain has shown computational results or reactions on this fast of a timescale. Typical reactions are on the order of milliseconds, trillions of times longer than sub-picosecond timescales.<ref>{{cite journal |last1=Yuhas |first1=Daisy |title=Speedy Science: How fast can you react? |journal=Scientific American |date=May 24, 2012 |url=https://www.scientificamerican.com/article/bring-science-home-reaction-time/ |access-date=18 Feb 2018}}</ref>

Daniel Dennett uses an experimental result in support of his [[Philosophy:Multiple drafts model|multiple drafts model]] of [[Physics:Color phi phenomenon|an optical illusion]] that happens on a time scale of less than a second or so. In this experiment, two different-colored lights, with an angular separation of a few degrees at the eye, are flashed in succession. If the interval between the flashes is less than a second or so, the first light that is flashed appears to move across to the position of the second light. Furthermore, the light seems to change color as it moves across the visual field. A green light will appear to turn red as it seems to move across to the position of a red light. Dennett asks how we could see the light change color before the second light is observed.<ref name="dennett1">{{cite book |author=Dennett |first=Daniel C. |title=Consciousness Explained |publisher=Little, Brown & Company |year=1991 |language=en}}</ref> Velmans argues that the [[Cutaneous rabbit illusion|cutaneous rabbit illusion]], another illusion that happens in about a second, demonstrates that there is a delay while modelling occurs in the brain and that this delay was discovered by [[Biography:Benjamin Libet|Libet]].<ref name="vel">{{cite journal |author=Velmans, M. |title=Is Consciousness Integrated? |journal=Behavioral and Brain Sciences |volume=15 |issue=2 |pages=229–230 |doi=10.1017/s0140525x00068473 |year=1992 |s2cid=145232451 }} (Commentary on Dennett & Kinsbourne "Time and the observer", BBS, 1992, 15(2): 183–201.)</ref> These slow illusions that happen at times of less than a second don't support a proposal that the brain functions on the picosecond time scale.{{citation needed|date=January 2023}}

According to David Pearce, a demonstration of picosecond effects is "the fiendishly hard part – feasible in principle, but an experimental challenge still beyond the reach of contemporary molecular matter-wave interferometry. [...] The conjecture predicts that we'll discover the interference signature of sub-femtosecond macro-superpositions."<ref name="Pearce" />

Penrose says:<ref name="Penroseedge"/>
<blockquote>
The problem with trying to use quantum mechanics in the action of the brain is that if it were a matter of quantum nerve signals, these nerve signals would disturb the rest of the material in the brain, to the extent that the quantum coherence would get lost very quickly. You couldn't even attempt to build a quantum computer out of ordinary nerve signals, because they're just too big and in an environment that's too disorganized. Ordinary nerve signals have to be treated classically. But if you go down to the level of the microtubules, then there's an extremely good chance that you can get quantum-level activity inside them.

For my picture, I need this quantum-level activity in the microtubules; the activity has to be a large-scale thing that goes not just from one microtubule to the next but from one nerve cell to the next, across large areas of the brain. We need some kind of coherent activity of a quantum nature which is weakly coupled to the computational activity that Hameroff argues is taking place along the microtubules.{{citation needed|date=January 2023}}

There are various avenues of attack. One is directly on the physics, on quantum theory, and there are certain experiments that people are beginning to perform, and various schemes for a modification of quantum mechanics. I don't think the experiments are sensitive enough yet to test many of these specific ideas. One could imagine experiments that might test these things, but they'd be very hard to perform.
</blockquote>

Penrose also said in an inverview:
<blockquote>
...whatever consciousness is, it must be beyond computable physics.... It's not that consciousness depends on quantum mechanics, it's that it depends on where our current theories of quantum mechanics go wrong. It's to do with a theory that we don't know yet.<ref name="Penrose 2023">{{cite journal |last1=Brooks |first1=Michael |title=Cosmic Thoughts |journal=New Scientist |date=Autumn 2023 |volume=256 |issue=3413 |pages=34–37 |doi=10.1016/S0262-4079(22)02094-2 |bibcode=2022NewSc.256...46P |s2cid=253724922 |url=https://www.newscientist.com/article/mg25634130-100-roger-penrose-consciousness-must-be-beyond-computable-physics/ |access-date=November 3, 2023}}</ref>
</blockquote>

A demonstration of a quantum effect in the brain has to explain this problem or explain why it is not relevant, or that the brain somehow circumvents the problem of the loss of quantum coherency at body temperature. As Penrose proposes, it may require a new type of physical theory, something "we don't know yet."<ref name="Penrose 2023"/>

===Ethical problems===
[[Biography:Deepak Chopra|Deepak Chopra]] has referred a "quantum soul" existing "apart from the body"<ref name="Hameroff2012">{{cite book
 | last1 = Hameroff
 | first1 = Stuart R.
 | last2 = Chopra
 | first2 = Deepak
 | chapter = The "Quantum Soul": A Scientific Hypothesis
 | year = 2012
 | editor-last1 = Moreira-Almeida
 | editor-first1 = Alexander
 | editor-last2 = Santos
 | editor-first2 = Franklin Santana
 | title = Exploring Frontiers of the Mind-Brain Relationship
 | publisher = Springer
 | location = New York
 | pages = 79–93
 | doi = 10.1007/978-1-4614-0647-1_5
 | isbn = 978-1-4614-0647-1
 | quote = When the blood stops flowing, energy and oxygen depleted and microtubules inactivated or destroyed (e.g., near death experience (NDE)/out-of-body experience (OBE), death), it is conceivable that the quantum information which constitutes consciousness could shift to deeper planes and continue to exist purely in space-time geometry, outside the brain, distributed nonlocally. Movement of consciousness to deeper planes could account for NDEs/OBEs, as well as, conceivably, a soul apart from the body.
}}</ref> and human "access to a field of infinite possibilities".,<ref name="Chopra2021">{{cite journal
 | last1 = Chopra
 | first1 = Deepak
 | title = What is wholeness? The consciousness view
 | journal = Global Advances in Health and Medicine
 | volume = 10
 | issue = 
 | pages = 21649561211043794
 | year = 2021
 | doi = 10.1177/21649561211043794
 | pmid = 34497737
 | pmc = 8419538
 | quote = The snake biting its tail solves the problem of consciousness, but you have to look at it closely and let its meaning sink in. The snake biting its tail symbolism points to something that has no beginning or end, is immune to death, extends infinitely in all directions, and gives humans access to a field of infinite possibilities.
}}</ref> and other [[Physics:Quantum mysticism|quantum mysticism]] topics such as [[Unsolved:Quantum healing|quantum healing]] or quantum effects of consciousness. Seeing the human body as being undergirded by a "quantum-mechanical body" composed not of matter but of energy and information, he believes that "human aging is fluid and changeable; it can speed up, slow down, stop for a time, and even reverse itself", as determined by one's state of mind.<ref name=ageless>{{cite book |first1=Deepak |last1=Chopra |title=Ageless Body, Timeless Mind: The Quantum Alternative to Growing Old |publisher=Random House |url=https://archive.org/details/agelessbodytimel0000chop |url-access=registration |page=[https://archive.org/details/agelessbodytimel0000chop/page/6 6] |date=1997 |isbn=9780679774495 }}</ref> [[Biography:Robert Todd Carroll|Robert Carroll]] states that Chopra attempts to integrate [[Philosophy:Ayurveda|Ayurveda]] with quantum mechanics to justify his teachings.<ref name="skepdic-web" >{{citation |url=http://www.skepdic.com/chopra.html |work=[[Philosophy:The Skeptic's Dictionary|The Skeptic's Dictionary]] |first=Robert Todd |last=Carroll |title=Deepak Chopra |date=May 19, 2013 }}.</ref> Chopra argues that what he calls "quantum healing" cures any manner of ailments, including cancer, through effects that he claims are based on the same principles as quantum mechanics.<ref name=AshmanBarringer2005/> This has led physicists to object to his use of the term ''quantum'' in reference to medical conditions and the human body.<ref name=AshmanBarringer2005>{{cite book |editor1-first=Keith |editor1-last=Ashman |editor2-first=Phillip |editor2-last=Barringer |title=After the Science Wars: Science and the Study of Science |chapter=Chapter 9: Voodoo medicine in a scientific world |first=Robert L. |last=Park |author-link=Robert L. Park |chapter-url=https://books.google.com/books?id=XImEAgAAQBAJ&pg=PA137 |date=September 1, 2005 |publisher=Routledge |isbn=978-1-134-61618-3 |pages=137–}}</ref> Chopra said: "I think quantum theory has a lot of things to say about the [[Physics:Observer effect|observer effect]], about non-locality, about correlations. So I think there’s a school of physicists who believe that consciousness has to be equated, or at least brought into the equation, in understanding quantum mechanics."<ref name="dawkins1">{{cite web |last1=Chopra |first1=Deepak |title=Richard Dawkins Plays God: The Video (Updated) |url=https://www.huffingtonpost.com/deepak-chopra/richard-dawkins-plays-god_b_3467484.html |website=Huffington Post |access-date=5 Mar 2018 |date=2013-06-19}}</ref> On the other hand, he also claims that "[quantum effects are] just a metaphor. Just like an electron or a photon is an indivisible unit of information and energy, a thought is an indivisible unit of consciousness."<ref name="dawkins1"/> In his book ''Quantum Healing'', Chopra stated the conclusion that [[Quantum entanglement|quantum entanglement]] links everything in the Universe, and therefore it must create consciousness.<ref name=dnews>{{cite news |last1=O'Neill |first1=Ian |title=Does Quantum Theory Explain Consciousness? |url=http://news.discovery.com/space/does-quantum-theory-explain-consciousness-110526.htm |access-date=August 11, 2014 |work=Discovery News |publisher=Discovery Communications, LLC |date=May 26, 2011}}</ref>

According to Daniel Dennett, "On this topic, ''Everybody's an expert...'' but they think that they have a particular personal authority about the nature of their own conscious experiences that can trump any hypothesis they find unacceptable."<ref>{{cite book |last1=Dennett |first1=Daniel |title=From Bacteria to Bach and Back: The Evolution of Minds |date=Feb 2017 |publisher=W. W. Norton and Company |location=New York |isbn=978-0393242072 |edition=1st}}</ref>

While quantum effects are significant in the physiology of the brain, critics of quantum mind hypotheses challenge whether the effects of known or speculated quantum phenomena in biology scale up to have significance in neuronal computation, much less the emergence of consciousness as phenomenon. Daniel Dennett said, "Quantum effects are there in your car, your watch, and your computer. But most things—most macroscopic objects—are, as it were, oblivious to quantum effects. They don't amplify them; they don't hinge on them."<ref name="Penroseedge"/>

==See also==
{{Div col|colwidth=20em}}
* [[Artificial consciousness]]
* Bohm interpretation of quantum mechanics
* Coincidence detection in neurobiology
* [[Biology:Critical brain hypothesis|Critical brain hypothesis]]
* [[Physics:Electromagnetic theories of consciousness|Electromagnetic theories of consciousness]]
* Evolutionary neuroscience
* Hameroff-Penrose Orchestrated Objective Reduction
* [[Philosophy:Hard problem of consciousness|Hard problem of consciousness]]
* [[Philosophy:Holonomic brain theory|Holonomic brain theory]]
* [[Physics:Many-minds interpretation|Many-minds interpretation]]
* [[Philosophy:Mechanism|Mechanism]]
* [[Biology:Neuroplasticity|Neuroplasticity]]
* [[Quantum cognition]]
* [[Quantum neural network]]
{{Div col end}}

==References==
{{reflist|30em}}

==Further reading==
{{refbegin}}
* {{cite book |last=Georgiev |first=Danko D. |title=Quantum Information and Consciousness: A Gentle Introduction |publisher=CRC Press |year=2017 |location=Boca Raton, Florida |language=en-us |url=https://books.google.com/books?id=OtRBDwAAQBAJ |isbn=9781138104488 |oclc=1003273264}}
* {{cite book |first=David |last=Hodgson |title=The Mind Matters: Consciousness and Choice in a Quantum World |url={{google books |plainurl=y |id=wrvAQgAACAAJ}} |year=1993 |publisher=Clarendon Press |isbn=978-0-19-824068-6 |language=en}}
* {{cite journal |last1=Koch |first1=Christof |last2=Hepp |first2=Klaus |title=Quantum mechanics in the brain |journal=Nature |year=2006 |volume=440 |issue=7084 |pages=611–612 |doi=10.1038/440611a |pmid=16572152 |bibcode=2006Natur.440..611K |s2cid=5085015 |doi-access=free}}
* {{cite journal |last1=Litt |first1=Abninder |last2=Eliasmith |first2=Chris |last3=Kroon |first3=Frederick W. |last4=Weinstein |first4=Steven |last5=Thagard |first5=Paul |title=Is the brain a quantum computer? |journal=Cognitive Science |year=2006 |volume=30 |issue=3 |pages=593–603 |url=http://watarts.uwaterloo.ca/~celiasmi/Papers/litt%20et%20al.2006.quantum%20brain.cogsci.pdf |doi=10.1207/s15516709cog0000_59 |pmid=21702826 |doi-access=free}}
* {{cite book |title=Mind, Brain, and the Quantum: The Compound 'I' |first=Michael |last=Lockwood |url={{google books |plainurl=y |id=wUducgAACAAJ}} |year=1995 |language=en |publisher=Basil Blackwell}}
* [[Biography:Johnjoe McFadden|McFadden, Johnjoe]] (2000) [http://www.surrey.ac.uk/qe/quantumevolution.htm ''Quantum Evolution''] HarperCollins. {{ISBN|0-00-255948-X}}; {{ISBN|0-00-655128-9}} . Final chapter on the quantum mind.
* {{cite magazine |title=Can quantum hints in the brain revive a radical consciousness theory? |first=George |last=Musser |date=17 January 2024 |magazine=New Scientist |url=https://www.newscientist.com/article/mg26134740-800-can-quantum-hints-in-the-brain-revive-a-radical-consciousness-theory/ |access-date=2024-01-19}} 
* {{cite book |title=Quantum Enigma: Physics Encounters Consciousness |first1=Bruce |last1=Rosenblum |first2=Fred |last2=Kuttner |edition=2nd |language=en-uk |year=2011 |url=http://quantumenigma.com/ |isbn=9780199753819 |publisher=Oxford University Press}}
* {{cite book |last=Schrödinger |first=Erwin |title=What is Life?: With Mind and Matter and Autobiographical Sketches |publisher=Cambridge University Press |series=Canto Classics |year=2012 |location=Cambridge |language=en |url=https://archive.org/download/WhatIsLife_201708/What%20is%20Life.pdf |isbn=978-1107604667}}
* {{cite book |first=Hermann |last=Weyl |title=Mind and Nature |url={{google books |plainurl=y |id=Sw_WcQAACAAJ}} |year=1934 |publisher=University of Pennsylvania Press |location=Philadelphia, Pennsylvania |language=en-us}}
* {{cite journal |last1=Wigner |first1=Eugene P. |title=Physics and the explanation of life |journal=Foundations of Physics |year=1970 |volume=1 |issue=1 |pages=35–45 |doi=10.1007/bf00708653 |bibcode=1970FoPh....1...35W |s2cid=121081834}}
{{refend}}

==External links==
* [http://consciousness.arizona.edu/ Center for Consciousness Studies], directed by [[Biography:Stuart Hameroff|Stuart Hameroff]]
* [https://philpapers.org/browse/philosophy-of-mind PhilPapers on Philosophy of Mind], edited by David Bourget and [[Biography:David Chalmers|David Chalmers]]
* [http://plato.stanford.edu/entries/qt-consciousness/ Quantum Approaches to Consciousness], entry in [[Stanford Encyclopedia of Philosophy]]
* [http://www.quantum-mind.co.uk/ Quantum-Mind], founded by Simon Raggett

{{Quantum mechanics topics|state=expanded}}
{{Roger Penrose}}

[[Category:Quantum mind| ]]
[[Category:Fringe science]]
[[Category:Quantum mechanics]]
[[Category:Theory of mind]]

{{Sourceattribution|Quantum mind}}