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Spier, Thomas & HameroffQuantum consciousness: Reply to Spier & Thomas Stuart Hameroff Trends in Cognitive Science http://www.cell.com/trends/cognitive-sciences/ In this paper, Hameroff replies to criticisms of the Orch OR model by Spier and Thomas. Hameroff justifies the unusual nature of the proposals in the Orch OR model, and its integration of ideas from neuroscience, computing and physics, by the fact new concepts are required to solve ‘the hard problem’ of consciousness. The theory is argued to be non-dualist, because it is based on in fact merely an extension of existing physical sciences including neuroscience. The theory stems from Penrose’s notion that there is an element of non-computability within brain processes. Most physical processes are deterministic, and Penrose has singled out wave function collapse as the only non-deterministic aspect of nature. This is conventionally understood as being a random process, not apparently of much value to human cognition. Penrose, however, proposes an additional form of wave function collapse, objective reduction (OR), which is suggested to occur when the quantum wave is not collapsed by interaction with the environment or by a measurement. The quantum wave represents superpositions of the different possible states of a quantum particle. Each superposition of a particle is viewed as having its own spacetime geometry, with each superposition possessing a slightly different geometry, and the separation between these comprising a form of blister or bubble in spacetime. When this separation reaches the Planck length, it reaches a critical threshold of instability, and rapidly collapses to a single state of the particle. It is suggested that in this case the choice of state is not random, but based on a non-computable process that is neither deterministic nor random. This process is suggested to be based on the configuration of networks that make up and drive the dynamic development of spacetime. Hameroff suggests that qualia, raw subjective experiences such as the redness of red, are encoded in the spin networks that may constitute space time. The sensation of having free will is also suggested to be a function of this non-computable process. Penrose sometimes describes the spacetime where mathematical understanding and other aspects of the mind are suggested to be encoded as the Platonic realm. This refers back to Plato’s idea that the physical world reflected ideals or ideas embodied in a separate realm. This has tended to be a target of ridicule for modern critics, such as Patricia Churchland. Spiers and Thomas advance the somewhat odd objection to Orch OR that if human ideas were derived from a Platonic realm or Platonic logic all human opinions would be the same. Hameroff’s counter view is that spacetime geometry is dynamic and evolving, and also that only part of the influence on individual minds derives from spacetime, with the mind also be governed by conventional inputs from inheritance and environment. Spier and Thomas appear to have something of a mantra to the effect that protein molecules are the basic computational elements in neurons. Hameroff in fact agrees with this, but suggests that the conformation is governed by quantum van der Waals forces, occurring mainly in hydrophobic pockets within the proteins. Anaesthetic molecules which oblate consciousness are thought to bind in such pockets. Spier and Thomas somewhat weaken their case by trundling out the old argument that microtubules are too unstable to form a basis for consciousness. This at least is easily answered by the fact that brain microtubules are much more stable and form part of a dense cytoskeletal structure. The argument moves on to the issue of single celled creatures, such as paramecium. Hameroff has suggested that these can navigate and respond to their environment without a nervous system as a result of microtubule processing. Spier and Thomas counter with the example of bacteria, which can also navigate themselves but lack microtubules. Hameroff quotes a study (Lowe & Amos, 1.) indicating that bacteria have protein based circuits resembling tubulin, the protein from which microtubules are built. References:- 1.) Lowe, J. & Amos, L. (1998) - Crystal structure of the bacterial cell-division protein - Nature, 1998, 391, pp. 203-206 Smolin, L. (1997) - Life of the Cosmos - Oxford Press Franks, N. & Lieb, W. (1982) - Molecular mechanisms of general anesthesia - Nature, 1982, 361 pp. 349-351 Stuart Hameroff reply to Michael Shermers article in Scientific American (292) Keywords: neurotransmitters, quantum consciousness, microtubules, Orch OR, Michael
Shermer’s article refers to a book by Victor Stenger of the University
of Colorado, which claims that for a system to be described quantum
mechanically mass, speed and distance must be of the order of the Planck
constant. Shermer says that neurotransmitter molecules are too large
and slow in crossing the synapse to be quantum mechanical. Microtubules
are dismissed as mere scaffolding for the cell in Shermer's view. Hameroff
has made a reply to Shermer that has not apparently been published by
Scientific American. Hameroff stresses that the Orch OR model did not
look for quantum activity at the synapses, which is what Shermer sought
to disprove, but in microtubules within the neurons. He points out that
in addition to their structural functions, microtubules are responsible
for molecular transport within the cells and synaptic changes. They
would appear to be the basis for the ability of single cell organism to
survive in an environment without any brain or nervous system.
Furthermore, the microtubule subunits are regulated by van der Waal
forces in intra-protein non-polar pockets. Hameroff
goes on to put his case for thinking that the action of anaesthetic
gases gives a clue as to the basis of consciousness. He points out that
anaesthetic gases erase consciousness while many non-conscious processes
in the brain continue. The action of the anaesthetics is thought to be
related to the control of protein conformation, occurring in brain
structures including the cytoskeleton. For this reason Hameroff thinks
that consciousness is related to one of the areas of the brain acted on
by anaesthetic gases. |
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