Brain
Matter
The
Physics of
Quantum
Consciousness
Chemistry
Quantum
Consciousness
Chemistry
and
Tubulins
Quantum consciousness - Consciousness is one of the most perplexing problems outstanding in science, and one that reflects on our very nature and relation to reality. Most approaches to the problem of consciousness see the brain as a computer, with neurons and synapses acting as basic switches, or "bits". In this approach, consciousness is thought to "emerge" as a novel property of complex computation. However this approach fails to adequately deal with enigmatic features of consciousness and more radical approaches may be necessary.
Quantum mechanics describes the seemingly bizarre behavior of matter and energy at microscopic scales, e.g. that of atoms and sub-atomic particles. At that level particles may be in two or more places at the same time (quantum superposition), and particles widely separated in distance may nonetheless be intimately connected (quantum entanglement). These properties are used in quantum computation which offers potential solutions to the enigmatic features of consciousness. However quantum computation is disrupted by interactions with the environment ("decoherence"), and neurons and synapses seem too large for delicate quantum effects.
But neurons may be far more complicated than mere switches. If we look inside neurons and other cells, we see highly ordered networks (the "cytoskeleton") comprised of microtubules and other filamentous structures which organize cellular activities. Microtubules are cylindrical polymers of the protein tubulin arranged in hexagonal lattices comprising the cylinder wall. Cooperative interactions among tubulin subunits within microtubules have been suggested to process information, as in molecular scale "cellular automata". As the states of tubulin are controlled by quantum mechanical internal forces (van der Waals London forces), they may exist in quantum superposition of multiple states ("quantum bits, or "qubits"), and microtubules may be seen as quantum computers involved in cellular organization.
articles
Welcome To The Mind-Boggling World Of Brain/Mind Research. Check Your Tired, Old Assumptions At The Door.
Charles Seife
Calculations show that collapsing wave functions in the scaffolding of the brain can't explain the mystery of consciousness. Sir Roger Penrose is incoherent, and Max Tegmark says he can prove it. According to Tegmark's calculations, the neurons in Penrose's brain are too warm to be performing quantum computations--a key requirement for Penrose's favorite theory of consciousness.
Penrose, the Oxford mathematician famous for his work on tiling the plane with various shapes, is one of a handful of scientists who believe that the ephemeral nature of consciousness suggests a quantum process. In the realm of the extremely small, an object with a property such as polarization or spin may exist in any of a number of quantum states. Or, bizarrely, it may inhabit several quantum states at once, a property called superposition. A quantum superposition is extremely fragile. If an atom in such a state interacts with its environment--by being bumped or prodded by nearby atoms, for instance--its waveform can "collapse," ending the superposition by forcing the atom to commit to one of its possible states.
To some investigators, this process of coherence and collapse seems strikingly similar to what goes on in the mind. Multiple ideas flit around below the threshold of awareness, then somehow solidify and wind up at the front of our consciousness. Quantum consciousness aficionados suspect that the analogy might be more than a coincidence. Eleven years ago, Penrose publicly joined their number, speculating in a popular book called The Emperor's New Mind that the brain might be acting like a quantum computer.
"Between the preconscious and conscious transition, there's no obvious threshold," says Penrose's sometime collaborator Stuart Hameroff, an anesthesiologist at the University of Arizona in Tucson. Ideas start out in superposition in the preconscious and then wind up in the conscious mind as the superposition ends and the waveform collapses. "The collapse is where consciousness comes in," says Hameroff.
But what exactly is collapsing? From his studies of neurophysiology, Hameroff knew of a possible seat for the quantum nature: "microtubules," tiny tubes constructed out of a protein called tubulin that make up the skeletons of our cells, including neurons. Tubulin proteins can take at least two different shapes--extended and contracted--so, in theory, they might be able to take both states at once. If so, then an individual tubulin protein might affect its neighbors' quantum states, which in turn affect their neighbors'--and so forth, throughout the brain. In the 1990s, Penrose and Hameroff showed how such a tubulin-based quantum messaging system could act like a huge quantum computer that might be the seat of our conscious experience.
The idea attracted a few physicists, some consciousness researchers, and a large number of mystics. Quantum physicists, however, largely ignored it as too speculative to be worth testing with numerical calculations. Now Tegmark, a physicist at the University of Pennsylvania, has done the numbers. In the February issue of Physical Review E, Tegmark presents calculations showing just what a terrible environment the brain is for quantum computation.
Combining data about the brain's temperature, the sizes of various proposed quantum objects, and disturbances caused by such things as nearby ions, Tegmark calculated how long microtubules and other possible quantum computers within the brain might remain in superposition before they decohere. His answer: The superpositions disappear in 10-13 to 10-20 seconds. Because the fastest neurons tend to operate on a time scale of 10-3 seconds or so, Tegmark concludes that whatever the brain's quantum nature is, it decoheres far too rapidly for the neurons to take advantage of it.
Hameroff is unconvinced. "It's obvious that thermal decoherence is going to be a problem, but I think biology has ways around it," he says. Water molecules in the brain tissue, for instance, might keep tubulin coherent by shielding the microtubules from their environment. "In back-of-the-envelope calculations, I made up those 13 orders of magnitude pretty easily."
Some members of the quantum-consciousness community, however, concede that Tegmark has landed a body blow on Penrose-Hameroff-type views of the brain. "Those models are severely impacted by these results," says physicist Henry Stapp of Lawrence Berkeley National Laboratory in California. (Stapp's own theory of quantum consciousness, he says, is unaffected by Tegmark's arguments.)
Physicists outside the fray, such as IBM's John Smolin, say the calculations confirm what they had suspected all along. "We're not working with a brain that's near absolute zero. It's reasonably unlikely that the brain evolved quantum behavior," he says. Smolin adds: "I'm conscientiously staying away" from the debate.
Paola Zizzi's "Big Wow" theory. If consciousness is related to fundamental properties of the universe (as is suggested by pan-experiential philosophical approaches and Orch OR), then where/when/how did consciousness or its precursors originate? Italian cosmologist Paola Zizzi of the University of Padua has a novel idea.
The "Big Bang" model raises questions which are partially dealt with through "inflation" (as originally proposed by Guth). This suggests that in the early universe (i.e. within 10-33 seconds after the beginning of the Big Bang) the universe expanded rapidly, reached a threshold for the end of rapid inflation, and has expanded only slowly ever since.
Building on this idea, Zizzi proposes that during rapid inflation the universe was a quantum superposition of multiple possible spacetime geometries ("multiple worlds") and that the end of inflation was marked by a Penrose "objective reduction" ("OR"): the superposition reached a quantum gravity threshold for self-collapse due to instability in the spacetime separation, and reduced to a single universe. By the Penrose (and Orch OR) criteria, such an objective reduction would constitute a conscious moment. Consequently Zizzi has suggested that the end of inflation (in the context of the Big Bang) was marked by a cosmic conscious experience (the "Big Wow").
of Quantum Coherence in Brain Microtubules:
The "Orch OR" Model for Consciousness