Re: no-go for the penrose-hameroff proposal
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 --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: no-go for the penrose-hameroff proposal
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 > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: no-go for the penrose-hameroff proposal
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/ --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
