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Cited by 389Quantum Mechanics and ApplicationsBiofield Effects and BiophysicsPhilosophy and Theoretical Science

Quantum computation in brain microtubules: decoherence and biological feasibility

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Hagan, S., Hameroff, S. R., Tuszyński, J. A.·2002·Physical Review E
DOI 10.1103/physreve.65.061901
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Abstract

The Penrose-Hameroff orchestrated objective reduction (orch. OR) model assigns a cognitive role to quantum computations in microtubules within the neurons of the brain. Despite an apparently "warm, wet, and noisy" intracellular milieu, the proposal suggests that microtubules avoid environmental decoherence long enough to reach threshold for "self-collapse" (objective reduction) by a quantum gravity mechanism put forth by Penrose. The model has been criticized as regards the issue of environmental decoherence, and a recent report by Tegmark finds that microtubules can maintain quantum coherence for only 10(-13) s, far too short to be neurophysiologically relevant. Here, we critically examine the decoherence mechanisms likely to dominate in a biological setting and find that (1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the orch. OR theory with a soliton in superposition along the microtubule; (2) recalculation after correcting for differences between the model on which Tegmark bases his calculations and the orch. OR model (superposition separation, charge vs dipole, dielectric constant) lengthens the decoherence time to 10(-5)-10(-4) s; (3) decoherence times on this order invalidate the assumptions of the derivation and determine the approximation regime considered by Tegmark to be inappropriate to the orch. OR superposition; (4) Tegmark's formulation yields decoherence times that increase with temperature contrary to well-established physical intuitions and the observed behavior of quantum coherent states; (5) incoherent metabolic energy supplied to the collective dynamics ordering water in the vicinity of microtubules at a rate exceeding that of decoherence can counter decoherence effects (in the same way that lasers avoid decoherence at room temperature); (6) microtubules are surrounded by a Debye layer of counterions, which can screen thermal fluctuations, and by an actin gel that might enhance the ordering of water in bundles of microtubules, further increasing the decoherence-free zone by an order of magnitude and, if the dependence on the distance between environmental ion and superposed state is accurately reflected in Tegmark's calculation, extending decoherence times by three orders of magnitude; (7) topological quantum computation in microtubules may be error correcting, resistant to decoherence; and (8) the decohering effect of radiative scatterers on microtubule quantum states is negligible. These considerations bring microtubule decoherence into a regime in which quantum gravity could interact with neurophysiology.

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  • Hagan et al. pointed out that Tegmark assumed tubulin proteins would have to form superpositions of distinct positions separated by an unrealistically large distance.

    “However, as pointed out by Hagan et al. (2002) shortly thereafter, Tegmark assumed tubulin proteins (MT subunits) would have to form superpositions of distinct positions separated by an unrealistically large distance.”

    From A quantum microtubule substrate of consciousness is experimentally supported and solves the binding and epiphenomenalism problems (2025) · cites this paper as Hagan et al. 2002

  • Hagan et al. used Tegmark's same formula and recalculated microtubule decoherence times using Orch OR stipulations, finding 10^-4 to 10^-3 seconds, or longer.

    “Hagan et al. [162] used Tegmark's same formula and recalculated microtubule decoherence times using Orch OR stipulations, finding 10 -4 to 10 -3 seconds, or longer.”

    From Consciousness in the universe (2014) · cites this paper as [162]

  • Mitochondria are involved in the action of anaesthetics.

    “Turin et al. cite a number of instances in which it has been shown that mitochondria are involved in the action of anaesthetics 65,[90][91][92] .”

    From Quantum effects in the brain: A review (2020) · cites this paper as [65]

  • General anaesthetics cause a change in spin.

    “Discounting free electron spin signals from melanin pigments the results of the experiment lead them to conclude that general anaesthetics cause a change in spin.”

    From Quantum effects in the brain: A review (2020) · cites this paper as [65]

  • Spin changes differ for anaesthetic resistant flies.

    “Further verification for the hypothesis is offered by the fact that spin changes differ for anaesthetic resistant flies.”

    From Quantum effects in the brain: A review (2020) · cites this paper as [65]

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Authors
Hagan, S., Hameroff, S. R., & Tuszyński, J. A.
Affiliations
  • British Columbia Institute of Technology (CA)
  • University of Arizona (US)
  • University of Alberta (CA)
ORCID
Venue
Physical Review E
Publisher
American Physical Society (APS)
Published
2002-06-10
Volume
65
Issue
6
Pages
061901-061901
ISSN
  • 1063-651X (ISSN-L)
  • 1095-3787
DOI
10.1103/physreve.65.061901
OpenAlex
W2031284984
Cited by
389
References
64
Citations by year
2026: 23 · 2025: 17 · 2024: 9 · 2023: 4 · 2022: 14 · 2021: 6 · 2020: 13 · 2019: 18 · 2018: 10 · 2017: 15 · 2016: 17 · 2015: 12 · 2014: 21 · 2013: 21 · 2012: 18
FWCI
10.03
Type
journal article
Language
en
Open access
Licence
link.aps.org/licenses/aps-default-license (vor)
Locations
  • Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
  • arXiv (Cornell University)
Funders
University of Arizona
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Mechanics and Applications
  • Health Sciences › Medicine › Physiology › Biofield Effects and Biophysics
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Philosophy and Theoretical Science
Keywords
Orchestrated Objective Reduction, microtubules, environmental decoherence, decoherence time, Debye layer, actin gels, water ordering, topological quantum computation, quantum gravity, consciousness
MeSH terms
Actins, Biophysics, Brain, Cognition, Electrophysiology, Humans, Microtubules, Models, Neurological, Quantum Theory, Temperature, Tubulin, Biophysical Phenomena

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