Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Other Theories of the Quantum Brain

  1. Apr 13, 2014 #1
    I am aware that the most popular version of the quantum brain theory i.e. the Penrose and Hameroff version has been disproved experimentally many times. But I was wondering what the status of other such attempts such as Vitiello and Freeman's dialog model is, in the scientific community ? Is there a lot of skepticism about such theories even if they haven't been disproved ? And more importantly is there any sign that advanced physics, more than just electrical circuits, will be needed to obtain a complete description of the brain ?
     
  2. jcsd
  3. Apr 13, 2014 #2

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    Before this thread continues, please note that since this area of study is STILL being debated, and that nothing concrete has been established yet, then all arguments and discussion MUST be accompanied by valid sources, not just opinions!

    BHL20: please start by providing appropriate papers so that others can understand exactly the theories you are referring to.

    Others planning on participating: If you are presenting your point, please provide appropriate references/papers to support your point.

    Zz.
     
  4. Apr 13, 2014 #3
    Tegmark's criticism of the quantum mind:

    http://arxiv.org/abs/quant-ph/9907009

    Abstract:
    Based on a calculation of neural decoherence rates, we argue that that the degrees of freedom of the human brain that relate to cognitive processes should be thought of as a classical rather than quantum system, i.e., that there is nothing fundamentally wrong with the current classical approach to neural network simulations. We find that the decoherence timescales ~10^{-13}-10^{-20} seconds are typically much shorter than the relevant dynamical timescales (~0.001-0.1 seconds), both for regular neuron firing and for kink-like polarization excitations in microtubules. This conclusion disagrees with suggestions by Penrose and others that the brain acts as a quantum computer, and that quantum coherence is related to consciousness in a fundamental way.
     
    Last edited: Apr 13, 2014
  5. Apr 13, 2014 #4
    Alfinito and Vitiello respond to Tegmark here:

    http://arxiv.org/abs/quant-ph/0006066

    page 4:
    Finally, we remark that some criticisms recently advanced [21(Tegmark)] on the use of quantum formalism in brain modeling are quite easily turned down. Such criticisms are founded on the computation of the decoherence time of the neuron and of the microtubule. Such a decoherence time is found to be many order of magnitude shorter than typical dynamical times associated with neuron activity and kink-like microtubule excitations. The ”conclusion” that neurons and microtubules are classical objects is ”then” reached. As a matter of fact, Stuart, Takahashi and Umezawa have anticipated such a ”discovery” noticing [12], with a pleasant sense of humor, that ”it is difficult to consider neurons as quantum objects”. A careful reading of the literature thus shows that, since 1967 [6], the conclusion of ref. [21(Tegmark)] was taken to be a rather obvious fact by the authors of the papers where the quantum model of brain and its developments have been discussed. The ”quantum”variables entering the formalism are the dynamical variable mentioned above, not to be confused with neurons and other cells. The neurons are purposely not even considered to be ”the fundamental units of the brain” [6]
     
    Last edited: Apr 13, 2014
  6. Apr 13, 2014 #5
    Hagan, Hameroff, Tuszyński respond in more detail here:

    http://arxiv.org/abs/quant-ph/0005025

    Abstract:
    The Penrose-Hameroff (`Orch OR') model of quantum computation in brain microtubules has been criticized as regards the issue of environmental decoherence. 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 assumptions behind Tegmark's calculation 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) Tegmark predicts decreasing decoherence times at lower temperature, in direct contradiction of the observed behavior of quantum states, 3) recalculation after correcting Tegmark's equation for differences between his model and the `Orch OR' model (superposition separation, charge vs. dipole, dielectric constant) lengthens the decoherence time to 10^−5−10^−4 s and invalidates a critical assumption of Tegmark's derivation, 4) 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), and 5) phases of actin gelation may enhance the ordering of water around microtubule bundles, further increasing the decoherence-free zone by an order of magnitude and the decoherence time to 10^−2−10^−1 s. These revisions bring microtubule decoherence into a regime in which quantum gravity can interact with neurophysiology.
     
    Last edited: Apr 14, 2014
  7. Apr 14, 2014 #6
    Stapp offers a possible mechanism for Von Neumann's interpretation:

    http://arxiv.org/abs/0803.1633

    Abstract:
    A simple exactly solvable model is given of the dynamical coupling between a person's classically described perceptions and that person's quantum mechanically described brain. The model is based jointly upon von Neumann's theory of measurement and the empirical findings of close connections between conscious intentions and synchronous oscillations in well separated parts of the brain. A quantum-Zeno-effect-based mechanism is described that allows conscious intentions to influence brain activity in a functionally appropriate way. The robustness of this mechanism in the face of environmental decoherence effects is emphasized.
     
  8. Apr 14, 2014 #7

    MathematicalPhysicist

    User Avatar
    Gold Member

    You mean "back up your stance with works of established professors".

    Just to point out that even if you back up your stance with what established professors say, it may still be wrong; These sources as far as I can tell are also just opinions, some are educated some aren't but most are rather speculative.
     
  9. Apr 14, 2014 #8

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    As long as they are published in our accepted peer-reviewed journals, these are valid discussion points. It is a fallacy that we do not allow a certain amount of speculation. We do! The whole forum on Beyond The Standard Model is speculative devoid of experimental evidence! It is just how the speculation is done, ie via peer reviewed journals, which ensures the quality of the speculation and ensures that these are by people who are experts in such fields.

    And BTW, not everyone who published papers are "professors"!

    craigi: simply posting sources isn't carrying a discussion. It requires no understanding at all to just post these. If you have a point to make, then do it, and use these sources to back it up. Otherwise, no one knows what it is that you are trying to convey.

    Zz.
     
    Last edited: Apr 14, 2014
  10. Apr 14, 2014 #9
    I've provided links to the key papers which debate the role of decoherence in the primary theories of the role of quantum processes in human mind. It's critcal to the academic debate. The quotes provided convey the argument well. I don't see any need to dumb it down, demonstrate my own understanding, or speculate further than that.
     
    Last edited: Apr 14, 2014
  11. Apr 14, 2014 #10

    DevilsAvocado

    User Avatar
    Gold Member

    I don't know about Vitiello and Freeman, but Hameroff and Penrose has recently launched a new 'proof' confirming the hypothesis of Orch-OR (29 March 2014), based on research by Anirban Bandyopadhyay.

    I'm just a layman; but when watching a presentation by Bandyopadhyay on Microtubule, not only were the 'alarms' flashing red, but so did my face... it was just embarrassing, the way he handle 'difficult questions' from the audience. I love Penrose, he's a highly intelligent man, but it's beyond my imagination how he can be 'collaborating' with this man...

    Other very well funded projects are the Blue Brain Project and the Human Brain Project, which are afaik mainly based on "electrical circuits". However, co-director Felix Schürmann dedicated his master thesis to the simulation of quantum computing.

    https://www.youtube.com/watch?v=LS3wMC2BpxU
    http://www.youtube.com/embed/LS3wMC2BpxU
    (Again, a highly respected man stating highly speculative claims...)

    https://www.youtube.com/watch?v=2qTuZlMvFgY
    http://www.youtube.com/embed/2qTuZlMvFgY

    https://www.youtube.com/watch?v=_UFOSHZ22q4
    http://www.youtube.com/embed/_UFOSHZ22q4
     
  12. Apr 15, 2014 #11
    Could you elaborate on this?

    Very recent discoveries relating to microtubules in the brain (which you linked yourself); photosynthesis; the sense of smell; and navigation in birds: indicate that he was completely correct about warm coherent quantum states.

    Hamerhoff (and Penrose for that matter), came under very heavy criticism for their inital views. Do you think that they have, at least in part, been vindicated?

    Personally, I find it fascinating that an anesthesiologist can predict discoveries of this kind, in the face of so much resistance from physicists.
     
    Last edited: Apr 16, 2014
  13. Apr 15, 2014 #12
    Tegmark's most recent offering on the subject, doesn't address any of the recent discoveries pertaining to warm coherent states, with only a passing reference to Penrose. Hopefully, he'll follow up on them soon.

    http://arxiv.org/abs/1401.1219

    Abstract:
    We examine the hypothesis that consciousness can be understood as a state of matter, "perceptronium", with distinctive information processing abilities. We explore five basic principles that may distinguish conscious matter from other physical systems such as solids, liquids and gases: the information, integration, independence, dynamics and utility principles. If such principles can identify conscious entities, then they can help solve the quantum factorization problem: why do conscious observers like us perceive the particular Hilbert space factorization corresponding to classical space (rather than Fourier space, say), and more generally, why do we perceive the world around us as a dynamic hierarchy of objects that are strongly integrated and relatively independent? Tensor factorization of matrices is found to play a central role, and our technical results include a theorem about Hamiltonian separability (defined using Hilbert-Schmidt superoperators) being maximized in the energy eigenbasis. Our approach generalizes Giulio Tononi's integrated information framework for neural-network-based consciousness to arbitrary quantum systems, and we find interesting links to error-correcting codes, condensed matter criticality, and the Quantum Darwinism program, as well as an interesting connection between the emergence of consciousness and the emergence of time.
     
  14. Apr 16, 2014 #13

    DevilsAvocado

    User Avatar
    Gold Member

    It's a little bit hard to elaborate when you change the quote to make it look like something else...

    [my emphasis]
     
  15. Apr 16, 2014 #14

    I apologise for misquoting you. Have my assurance that it wasn't intentional.

    Was it Bandyopadhyay's talk from the Google workshop on Quantum Biology, that you watched?
     
    Last edited: Apr 16, 2014
  16. Apr 16, 2014 #15

    DevilsAvocado

    User Avatar
    Gold Member

    Yup, but now you've changed your own post :smile:, so let me answer the original question first.

    Do you know who Deepak Chopra is? If not, real professors of biology define his views as "a lot of scientifically-sounding psychobabble". I find it quite unlikely that Sir Roger Penrose would ever visit Chopra's show ONE WORLD to talk about real science (even if one could never be sure).

    Anirban Bandyopadhyay, on the other hand, goes there apparently without any doubts.

    In a Google Workshop on Quantum Biology, Anirban Bandyopadhyay gets a question about the "topological qubits" he has 'discovered' (and shown flashy graphics on for 40 min). However in the answer he provide, it's clear that Bandyopadhyay doesn't even understand what a qubit is, as he defines it as "a sudden change in resistance"...

    As I said, I'm only a layman, but I think I could take my soldering iron and knock together something that would give a "sudden change in resistance", but I would never dream on calling it a "topological qubit", since it would be a little bit too embarrassing, even for me.

    Anyone can hold a talk, showing flashy graphics, using fancy cutting edge terminology, but it's a completely different enchilada to put real coherent science behind the words, i.e. in a field like this.

    To me he looks like a fraudster, but of course I could be wrong...
     
  17. Apr 16, 2014 #16
    I can empathise with your opinion but this is philosophy and politics and not relevant to his scientific work. Hameroff indulges much of the same speculation. Penrose is open to it too, but is much more conservative.

    Bandyopadhyay is a serious scientist with a wide range of publications:
    http://nims.academia.edu/anirbanbandyopadhyay
     
    Last edited: Apr 16, 2014
  18. May 11, 2014 #17
    Thinking about consciousness and what we mean by consciousness.
    Consciousness is one thing that we cannot deny is the fact that we are conscious. It is probably the only absolute certainty that we have is that we are experiencing beings. Right now, for example, we could all be plugged into the Matrix and all be having this wonderful simulated experience of living on planet Earth…
    So, we could actually doubt whether this is real but we couldn't doubt that we are still experiencing it, maybe an illusion, but we are still experiencing it. In fact that is what Descartes saw with his famous ‘Gogito ergo sum’, he was looking for the absolute truth and he found that he could doubt everything, any idea, any philosophy, he even doubted he had a body, he doubted his experience and this is 350 years before virtual reality. Then he realised the one thing that he couldn't doubt was that he was experiencing. Yet this is something which science has consistently ignored. You cannot weigh it and you cannot use the normal scientific ways of looking at things to measure consciousness which leads to the interesting corollary that there is no scientific evidence whatsoever for consciousness, because there is no way of measuring it, there is no actual experiment to prove that someone is conscious. We believe that they are and also science is interested in the objective, the real world and consciousness is subjective. Science is looking for the truth which is common to all observers that everyone can agree upon and independent of the observer.
    The universe works perfectly well without any understanding of consciousness. We do not need consciousness to explain the universe; in fact we get this rather interesting paradox that science would be much happier if there wasn't a phenomenon as consciousness. Yet without consciousness there wouldn't be any science, so this strange paradox.
    Things are beginning to change these days in academic circles driven by the discoveries in quantum physics. There are things in quantum mechanics which are counter-intuitive to our way of viewing the usual natural order of events that implicate consciousness and the observer in some way. All the work that has been going on in the recent decades to do with the brain; neurophysiology, neuropsychological research, et al, they are all beginning to bring up this question what is consciousness and we cannot deny or cannot ignore that we are conscious any longer. Of course, in this current time there is this interest in society in the mind and personal development and spiritual growth which again is all around consciousness and the nature of consciousness.


    What I want to start of by doing is actually defining what we mean by consciousness. We use the word in many different ways in our cultures but the Eximo’s have twenty different words for snow because they have all these different meanings for snow. We just talk about snow in the singular. It is the same with consciousness; we use the word without
    The aspects of consciousness and this could mean many different things.
    We find in Sanskrit about a dozen different words for consciousness which have meaning for clearly delineated aspects of what we loosely call consciousness.
    So what do we mean when we say that someone is conscious? Let us look at some of the different meanings. The first obvious one is that if someone is awake they are conscious and we say that if someone is asleep they are not conscious. But we dream when we are asleep, we have experiences. Dreams happen in consciousness. So what we really mean is that sleeping people are not conscious of the exterior world but are still conscious of their interior world. So there is still consciousness. Sometimes we talk about conscious; “I wasn't conscious of what I was doing”, meaning that I was not paying attention. But there is still consciousness there, an experience everyone has many times a day. If you were totally conscious of your consciousness there would be no time in which to actually complete any tasks. This is a part of the syndrome, within a spectrum, science calls autism.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Other Theories of the Quantum Brain
  1. Quantum brain teazer (Replies: 1)

  2. Quantum brain (Replies: 7)

Loading...