The Physics of
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.
|A Slide Show|
Welcome To The Mind-Boggling World Of Brain/Mind Research. Check Your Tired, Old Assumptions At The Door.
|Consciousness, Microtubules and The Quantum World|
Numbers Unmake the Quantum Mind
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.
|Do all scientists agree?|
our neurons have anything at all to do with our thinking,
if all these electrical firings correspond in any way to
our thought patterns, we are not quantum computers,"
says Tegmark. The problem is that the matter inside our
skulls is warm and ever-changing on an atomic scale, an
environment that dooms any nascent quantum computation before
it can affect our thought patterns. For quantum effects
to become important, the brain would have to be a tiny fraction
of a degree above absolute zero.
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.
and the early universe
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
|Features of consciousness difficult to understand in terms of conventional neuroscience have evoked application of quantum theory, which describes the fundamental behavior of matter and energy. In this paper we propose that aspects of quantum theory (e.g. quantum coherence) and of a newly proposed physical phenomenon of quantum wave function “self-collapse(objective reduction: OR-Penrose, 1994) are essential for consciousness, and occur in cytoskeletal microtubules and other structures within each of the brain's neurons. The particular characteristics of microtubules suitable for quantum effects include their crystal-like lattice structure, hollow inner core, organization of cell function and capacity for information processing. We envisage that conformational states of microtubule subunits (tubulins) are coupled to internal quantum events, and cooperatively interact (compute) with other tubulins. We further assume that macroscopic coherent superposition of quantum-coupled tubulin conformational states occurs throughout significant brain volumes and provides the global binding essential to consciousness. We equate the emergence of the microtubule quantum coherence with pre-conscious processing which grows (for up to 500 milliseconds) until the mass-energy difference among the separated states of tubulins reaches a threshold related to quantum gravity. According to the arguments for OR put forth in Penrose (1994), superpositioned states each have their own space-time geometries. When the degree of coherent mass-energy difference leads to sufficient separation of space-time geometry, the system must choose and decay (reduce, collapse) to a single universe state. In this way, a transient superposition of slightly differing space-time geometries persists until an abrupt quantum classical reduction occurs. Unlike the random, “subjective reduction (SR, or R) of standard quantum theory caused by observation or environmental entanglement, the OR we propose in microtubules is a self-collapse and it results in particular patterns of microtubule-tubulin conformational states that regulate neuronal activities including synaptic functions. Possibilities and probabilities for post-reduction tubulin states are influenced by factors including attachments of microtubule-associated proteins (MAPs) acting as “nodesEwhich tune and “orchestrateEthe quantum oscillations. We thus term the self-tuning OR process in microtubules “orchestrated objective reduction(EB>Orch OR, and calculate an estimate for the number of tubulins (and neurons) whose coherence for relevant time periods (e.g. 500 milliseconds) will elicit Orch OR. In providing a connection among 1) pre-conscious to conscious transition, 2) fundamental space-time notions, 3) non-computability, and 4) binding of various (time scale and spatial) reductions into an instantaneous event (“conscious now, we believe Orch OR in brain microtubules is the most specific and plausible model for consciousness yet proposed.|
|Age-old battle lines over the puzzling nature of mental experience are shaping a modern resurgence in the study of consciousness. On one side are the long-dominant "physicalists" (reductionists, materialists, functionalists, computationalists. . ) who see consciousness as an emergent property of the brain's neural networks ("brain = mind = computer"). On the alternative, rebellious side are those who see a necessary added ingredient: proto-conscious experience intrinsic to reality, perhaps understandable through modern physics (panpsychists, pan-experientialists, "funda-mentalists"). It is argued here that the physicalist premise alone is unable to solve completely the difficult issues of consciousness (e.g. experience, binding, pre-conscious conscious transition, non-computability and free will) and that to do so will require supplemental panpsychist/pan-experiential philosophy expressed in modern physics. In one such scheme proto-conscious experience is a basic property of physical reality accessible to a quantum process associated with brain activity. The proposed process is Roger Penrose's objective reduction (OR), a self-organizing "collapse" of the quantum wave function related to instability at the most basic level of spacetime geometry. In the Penrose-Hameroff model of "orchestrated objective reduction" ("Orch OR"), OR quantum computation occurs in cytoskeletal microtubules within the brain's neurons and links cognition with proto-conscious experience and Platonic values embedded in spacetime geometry. The basic idea is that consciousness involves brain activities coupled to self-organizing ripples in fundamental reality.|