no-go for the penrose-hameroff proposal

[Miroslav Dobsicek]

Somebody might  be interested in ..

PHYSICAL REVIEW E 80, 021912 2009

Penrose-Hameroff orchestrated objective-reduction proposal for human
consciousness is not biologically feasible

From the abstract:

------------
   Penrose and Hameroff have argued that the conventional models of a
brain function based on neural
networks alone cannot account for human consciousness, claiming that
quantum-computation elements are also
required. Specifically, in their Orchestrated Objective Reduction Orch
OR model R. Penrose and S. R.
Hameroff, J. Conscious. Stud. 2, 99 1995 , it is postulated that
microtubules act as quantum processing units,
with individual tubulin dimers forming the computational elements. This
model requires that the tubulin is able
to switch between alternative conformational states in a coherent
manner, and that this process be rapid on the
physiological time scale. Here, the biological feasibility of the Orch
OR proposal is examined in light of recent
experimental studies on microtubule assembly and dynamics. It is shown
that the tubulins do not possess
essential properties required for the Orch OR proposal, as originally
proposed, to hold. Further, we consider
also recent progress in the understanding of the long-lived coherent
motions in biological systems, a feature
critical to Orch OR, and show that no reformation of the proposal based
on known physical paradigms could
lead to quantum computing within microtubules. Hence, the Orch OR model
is not a feasible explanation of the
origin of consciousness.
-----------

 Mirek


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[Bruno Marchal]

Actually Tegmark already proposed a similar no go theorem.

BTW, it is weird people that continue to talk about the Penrose-
Hameroff argument.
Hameroff is OK with the idea that a brain could be a machine (of the  
quantum kind).
Penrose is not OK, with that idea. Penrose, in his book and papers,  
makes a proposition that brain are not machine, not even quantum  
machine, i.e. that brain are really not turing emulable. It is the  
only example of non-comp position made by a scientist. I recall, with  
Quentin recently, that quantum computer are Turing-emulable (albeit  
very slowly).

Bruno


On 18 Aug 2009, at 13:33, Mirek Dobsicek wrote:

>
> Somebody might  be interested in ..
>
> PHYSICAL REVIEW E 80, 021912 2009
>
> Penrose-Hameroff orchestrated objective-reduction proposal for human
> consciousness is not biologically feasible
>
> From the abstract:
>
> ------------
>   Penrose and Hameroff have argued that the conventional models of a
> brain function based on neural
> networks alone cannot account for human consciousness, claiming that
> quantum-computation elements are also
> required. Specifically, in their Orchestrated Objective Reduction Orch
> OR model R. Penrose and S. R.
> Hameroff, J. Conscious. Stud. 2, 99 1995 , it is postulated that
> microtubules act as quantum processing units,
> with individual tubulin dimers forming the computational elements.  
> This
> model requires that the tubulin is able
> to switch between alternative conformational states in a coherent
> manner, and that this process be rapid on the
> physiological time scale. Here, the biological feasibility of the Orch
> OR proposal is examined in light of recent
> experimental studies on microtubule assembly and dynamics. It is shown
> that the tubulins do not possess
> essential properties required for the Orch OR proposal, as originally
> proposed, to hold. Further, we consider
> also recent progress in the understanding of the long-lived coherent
> motions in biological systems, a feature
> critical to Orch OR, and show that no reformation of the proposal  
> based
> on known physical paradigms could
> lead to quantum computing within microtubules. Hence, the Orch OR  
> model
> is not a feasible explanation of the
> origin of consciousness.
> -----------
>
> Mirek
>
>
> >

http://iridia.ulb.ac.be/~marchal/




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[Brent Meeker-2]

Mirek Dobsicek wrote:
> Somebody might  be interested in ..
>
> PHYSICAL REVIEW E 80, 021912 2009
>
> Penrose-Hameroff orchestrated objective-reduction proposal for human
> consciousness is not biologically feasible

It has long been noted that microtubles are ubiquitous in the cells of other organs, not
just in the brain.  It is sometimes said that males think with an organ other than the
brain, but this is generally metaphorical.

Brent

>
>>From the abstract:
>
> ------------
>    Penrose and Hameroff have argued that the conventional models of a
> brain function based on neural
> networks alone cannot account for human consciousness, claiming that
> quantum-computation elements are also
> required. Specifically, in their Orchestrated Objective Reduction Orch
> OR model R. Penrose and S. R.
> Hameroff, J. Conscious. Stud. 2, 99 1995 , it is postulated that
> microtubules act as quantum processing units,
> with individual tubulin dimers forming the computational elements. This
> model requires that the tubulin is able
> to switch between alternative conformational states in a coherent
> manner, and that this process be rapid on the
> physiological time scale. Here, the biological feasibility of the Orch
> OR proposal is examined in light of recent
> experimental studies on microtubule assembly and dynamics. It is shown
> that the tubulins do not possess
> essential properties required for the Orch OR proposal, as originally
> proposed, to hold. Further, we consider
> also recent progress in the understanding of the long-lived coherent
> motions in biological systems, a feature
> critical to Orch OR, and show that no reformation of the proposal based
> on known physical paradigms could
> lead to quantum computing within microtubules. Hence, the Orch OR model
> is not a feasible explanation of the
> origin of consciousness.
> -----------
>
>  Mirek
>
>
> >
>

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[Johnathan Corgan]

On Tue, 2009-08-18 at 11:09 -0700, Brent Meeker wrote:

> It has long been noted that microtubles are ubiquitous in the cells of other organs, not
> just in the brain.

While I find the Penrose/Hameroff proposal very unconvincing for other
reasons, this is not one of them.

There are many shared organelles that are in both neuronal and
non-neuronal cell bodies.  It is a matter of organizing them for use one
way or another.  The voltage-gated sodium ion channel pore used for
propagating an event potential down an axon is also present in cells
outside the nervous system, yet the brain is able to use them to effect
(dare I say?) computation.

So it is at least plausible that microtubules, though ubiquitous
throughout the body, have been recruited and honed by evolution to
operate in the fashion proposed by Penrose/Hameroff in the nervous
system.  

Personally, I think their whole agenda is misguided, an example of
"brains are mysterious, quantum mechanics is mysterious, therefore,
brains operate using quantum mechanics."

The "mystery" of quantum mechanics largely disappears with no-collapse
and decoherence anyway.

Johnathan Corgan


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