Summary

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 neuronal 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 (like mass, spin or charge) which is accessed by particular neuromolecular quantum processes in the brain. Roger Penrose*s proposed objective reduction (OR) is a self-organizing quantum gravity process at the most basic level of spacetime geometry. A mechanism by which the OR process occurs in intra-neuronal microtubules and links cognition with "funda-mental" experience has been proposed in the Penrose-Hameroff model of "orchestrated objective reduction" ("Orch OR"). Here the model is summarized and applied to cognitive activities such as facial recognition and volitional choice.

Introduction - A Burning Issue

Can conscious experience*feelings, qualia, our "inner life"*be accommodated within present-day science? Those who believe it can (e.g. physicalists, reductionists, materialists, functionalists, computationalists) see conscious experience as an emergent property of complex neural network computation. Others see conscious experience either outside science (dualists), or believe science must expand to include experience (idealists, panpsychists, pan-experientialists, "funda-mentalists"). These philosophical battle lines were originally drawn in ancient Greece between Socrates, who believed the cerebrum created consciousness, and Aristotle, Democritus, Thales and others who argued that mental processes were properties of fundamental reality. Perhaps they were all correct.

Brain = Mind = Computer?

The basic physicalist idea is that the mind is a computer functioning in the brain's neural networks. The current leading candidate for an underlying "neural correlate" of consciousness involves synchronously oscillating thalamo-cortical feedback loops. Higher frequencies (collectively known as "coherent 40 Hz") have been suggested to mediate temporal binding of conscious experience (e.g. Singer, Gray, Crick and Koch, etc.). Proposals vary, for example as to whether coherence originates in thalamus or resonates in cortical networks, but "thalamo-cortical 40 Hz" stands as a prevalent view of the substrate for consciousness. But how do synchronized neural firings and synaptic transmissions produce experiential qualia, emotions or free will? Physicalists believe this to be relatively straightforward (brain = mind = computer!) however others find the question intractable, or as vexing as trying to coax a reluctant genie from a magic lamp. I see three problems with the brain = mind = computer analogy:

1) Is consciousness classical computation? In a controversial stance Roger Penrose has asserted that essential aspects of consciousness are non-computable. But regardless, classical computers appear to be evolving toward quantum computers. Beginning in the early 1980*s Benioff, Feynman and others proposed that states in a system---bits in a computer---could interact while in quantum superposition of all possible states, effecting near-infinite massive parallelism. Rather than classical Boolean bit states 1 or 0, quantum computers would utilize interactive "qubits" of 1 and 0. If quantum computers can ever be constructed they will have huge advantages in important applications. As the brain/mind has always been cast as current information technology, consciousness may inevitably be seen as some form of quantum computation.

2) Are neural firings the "fine grain" of consciousness? Cells and synapses are far more complex than simple on-off switches. Consider the paramecium, a single cell organism which gracefully swims, avoids predators, learns to escape from capillary tubes, and finds food and mates. Lacking synapses, paramecium utilizes its cytoskeleton for communication and organization. Neurons have a rich and dynamic set of cytoskeletal microtubules which regulates synapses, and increases computational capacity. More importantly, neurons are alive and we don't yet know what that implies for consciousness.

3) Details which don*t fit the brain = mind = computer scheme are overlooked. For example: a) Neurotransmitter vesicle release and cognitive reaction times are "noisy", and exhibit apparent probabilistic randomness (?non-computable quantum indeterminacy). b) Axonal firing patterns (rather than average frequency) and dendritic-dendritic processing may be relevant to consciousness22. c) Apart from chemical synapses, primitive electrotonic gap junctions couple neurons and glia synchronously and may play an important role in consciousness. d) Glial cells (80% of the brain) are ignored in the brain-as-computer view.

Quibbling aside, the physicalist view fails to explain the difficult issues of consciousness. For example the problem of 'binding' in vision and self is often attributed to temporal correlation (e.g. coherent 40 Hz), but why temporal correlation per se should bind experience is unclear without an explanation of experience. Regarding transition from pre-conscious or implicit processing to consciousness itself, the physicalist view is that consciousness emerges at a critical level of complexity. But no threshold is apparent, nor is there a reasonable suggestion why such an emergent property should have conscious experience. As physicalism is based on deterministic computation, it is also unable to account for free will or Penrose's proposed non-computability. But the major problem remains experience, for which physicalism offers no testable predictions. Something is missing.

Panpsychism Meets Modern Physics

Perhaps panpsychists are in some way correct and components of mental processes are fundamental, likemass, spin or charge. Following the ancient Greek panpsychists, Spinoza (1677) saw some form of consciousness in all matter. Leibniz (1766) portrayed the universe as an infinite number of fundamental units (monads) each having a primitive psychological being. Whitehead (e.g. 1929) was a process philosopher who viewed reality as a collection of events occurring in a basic field of proto-conscious experience ("occasions of experience"). Abner Shimony25 observed that Whitehead's occasions were comparable to quantum state reductions---actual events in physical reality (see below). But what of Whitehead's "basic field" of proto-conscious experience? How could experience (qualia) simply exist in empty space? What is empty space?

This question also stems from the ancient Greek philosophers. Democritus argued that empty space was a true void whereas Aristotle contended that it was in fact a plenum (a background filled with substance)---a medium in which heat and light traveled. Siding with Aristotle, Maxwell's 19th century theory of the luminiferous ether described a plenum that carried electromagnetic waves much as water carries waves across its surface. However attempts to detect this ether failed (e.g. the Michelson-Morley experiment) and the rise of Einstein*s special relativity in 1905 reverted back to Democritus in that empty space was seen as an empty void. Ten years later, however, Einstein's general relativity with its curved space and distorted geometry forced him to reverse his stand and opt for a richly-endowed plenum, which he termed the spacetime metric.

We now know that at very small scales space and time are not smooth, but quantized. This granularity occurs at the incredibly small dimensions of the "Planck scale" at 10-33 centimeters and 10-43 seconds. Roger Penrose portrays this basic makeup of the universe as a dynamical spider-web of quantum spins. These "spin networks" create an evolving array of Planck scale geometric volumes defining four dimensional spacetime. Penrose applies Einstein*s general relativity (in which mass equates to curvature, or perturbation of spacetime) all the way down to this near-infinitesimal geometry. Thus everything that exists and occurs is in reality particular arrangements of spacetime geometry. Building on these ideas, Lee Smolin suggests that self-organizing processes at the level of spin networks (which he likens to Leibniz monads) constitute a flow of time, raising the issue of whether the universe at its most basic level contains information and is in some sense alive. Could infinitesimally small, weak and fast processes be coupled to macroscopic effects in biological systems? A reasonable possibility seems to be Penrose*s objective reductions---a particular type of quantum state reduction.

At the Edge of Reality: Quantum State Reductions and Consciousness

Quantum theory describes the bizarre wave/particle duality of energy and matter at very small scales. The behavior is so strange that the American physicist Richard Feynman once commented "anyone who claims to understand quantum theory is either lying or crazy."

Strange as it is, quantum theory offers features which may be relevant to consciousness. One is that large collections of quantum particle/waves can merge into coherent unitary states of macroscopic size and influence. Superconductors, Bose-Einstein condensates and lasers are unitary states in which component atoms or molecules give up individual identity and behavior. Such coherent quantum states have been suggested to occur among brain proteins to provide unitary "binding" in vision and self29,30.

Another feature involves "quantum superposition". Components of isolated small scale systems can exist in different states or locations simultaneously. Obviously this is contrary to our perceived macroscopic world in which objects have well defined positions and are decidedly concrete. The problem is the transition*why and how do microscopic quantum superposed states become classical and definite in the macro-world? This problem is called quantum state reduction, or collapse of the wave function, and it may be the key to both consciousness and reality.

Experimental evidence in the early part of this century led great theorists Bohr, Heisenberg and Wigner to conclude (the "Copenhagen interpretation") that objects can remain in wave-like quantum superposition until they are observed by a conscious human being*that consciousness causes collapse of the wave function! To illustrate the apparent absurdity of this conclusion, in the 1930's Schr"dinger devised his famous thought experiment¿Schr"dinger's cat. A living cat is placed in a box into which poison can be released by a quantum event, e.g., sending a photon through a half-silvered mirror. So after the photon has been sent there are equal possibilities that the cat is either dead or alive. But according to the Copenhagen interpretation until a conscious being opens the box and observes, the cat is both dead and alive. Schr"dinger's point was that the conscious observer interpretation was absurd.

Many physicists now believe that intermediate between tiny quantum-scale systems and "large" cat-size systems some objective factor disturbs the superposition to cause collapse, or "objective reduction (OR)". According to Roger Penrose1,2,32 this objective factor is an intrinsic feature of spacetime itself. As mass is equivalent to spacetime curvature, Penrose begins with the notion that quantum superposition¿actual separation (displacement) of mass from itself¿is separation in underlying spacetime. According to this view superposed mass separated from itself is equivalent to simultaneous curvatures in opposite directions, causing "bubbles", or separations in fundamental spacetime geometry down to the Planck scale of quantum spin networks. Penrose reasons that these bubble-like separations are unstable and reduce to specific states and locations after a critical degree of separation. OR thus describes a self-organizing process of events rooted in the Planck scale. If proto-conscious experience exists there, then objective reductions may be conscious events¿Whitehead*s occasions of experience33.

Could OR events actually occur in the brain? The critical spacetime separation precipitating Penrose's OR is given by the uncertainty principle E=h/T. E is related to the superposed mass, h is Planck's constant over 2p, and T is the coherence time until reduction. The size of a superposed system (it*s spacetime separation) is inversely related to the time T until self-collapse. If isolated, a large system (e.g. Schr"dinger's one kilogram cat) will undergo OR very quickly, e.g. in only 10-37 seconds. A small system such as a single isolated superposed atom would undergo OR only after 107 years. OR in the brain would likely be linked to neural processes occurring over time scales in the range of tens to hundreds of milliseconds, for example 25 millisecond intervals in coherent 40 Hz. If T=25 millisecond OR events coincide with coherent 40 Hz oscillations, each would require E= roughly 3 nanograms (3 x 10-9 gram) of superposed brain mass.

Nanograms of what? To utilize the OR process a biological structure must function as a quantum computer, avoid environmental decoherence and couple to neural activities. Microtubules are the leading candidates.

Are Microtubules Quantum Computers? - The Penrose-Hameroff "Orch OR" Model

Interiors of neurons and glia are functionally organized by webs of protein polymers¿the cytoskeleton. Its major components are microtubules, actin and intermediate filaments. Microtubules are self-assembling hollow cylinders whose walls are crystalline lattices of subunit proteins known as tubulin. Evidence links the neuronal cytoskeleton to cognitive functions, and theoretical models suggest microtubule subunits function as molecular automata capable of computation and information processing in the nanosecond time scale.

Roger Penrose and I have developed a model in which quantum superposition supporting quantum computation occurs in microtubule automata within brain neurons and glia. Microtubule-associated-proteins (MAPs) provide feedback and "tune" the quantum oscillations; the proposed OR is thus self-organized ("orchestrated objective reduction"¿"Orch OR"33,35,36). In the Orch OR model microtubule quantum computation is isolated from decoherence and continues until threshold is met (E=h/T) and an OR event occurs. For example E=1010 tubulins (roughly 20,000 neurons) would maintain superposition for T=25 milliseconds for an OR event coinciding with one 40 Hz cycle.

Quantum computation in the Orch OR scheme differs from technological proposals in that superpositions in the latter reduce to output states by environmental decoherence---computation is terminated by intervention and choice of states has an element of randomness. On the other hand, in the Orch OR scheme isolated superpositions eventually self-reduce due to instability in spacetime separation. The choice of outcome states, according to Penrose, is therefore neither completely deterministic nor random, but has an element of non-computability---influenced by Platonic logic embedded in spacetime.

Penrose also argues that aspects of human understanding and consciousness exhibit elements of non-computability, a controversial and widely assailed claim. Although outnumbered by his critics, Penrose34 has thoroughly and systematically answered them. Non-computability is a clue, a subtle but significant thread with which to unravel the mystery of consciousness.

Orch OR and Cognition

Each proposed Orch OR event consists of an isolated quantum computing phase identified with pre-conscious, implicit processes. The pre-conscious quantum phase culminates in instantaneous reduction corresponding with a discrete conscious event*a Whitehead "occasion of experience", the "now". Each event selects (non-computably) particular configurations of Planck-scale experiential geometry, and classical states of microtubule automata which regulate synaptic/neural functions. Sequences of such events (e.g. at 40 Hz) give a "stream" of consciousness

Can Orch OR be understood in the context of cognition? Consider two cognitive tasks: facial recognition and deciding what to order for dinner. Each may occur in a series of steps yielding intermediate solutions, however for the purpose of illustration consider how single Orch OR conscious events could accomplish these tasks. (Although classical neural-level parallel computation can partially explain these functions, the Orch OR scheme provides far greater information capacity, conscious experience, binding, and non-computability consistent with free will.)

Imagine you see a familiar woman's face. Is she Amy, Betty, or Carol? All possibilities may superpose in a quantum computation. For example during 25 milliseconds of pre-conscious processing, quantum computation occurs with information (Amy, Betty, Carol) in the form of "qubits", superposed states of microtubule automata. As threshold for objective reduction is reached, superposed tubulin qubits reduce (collapse) to definite states, becoming bits. Now, you recognize Carol as a particular experiential geometry is selected! (Many more than three possibilities, in fact an astronomically high number of possibilities could be superposed in microtubule quantum computing.)

In a volitional act possible choices may be superposed. Suppose you are selecting dinner from a menu. During pre-conscious processing, shrimp, sushi and pasta are superposed. As threshold for objective reduction is reached, the quantum state reduces to a single classical state whose selection is influenced by Platonic logic ingrained in the Planck scale. A choice is made. You'll have sushi!

Conclusion

The Orch OR model is consistent with known neurophysiological processes, generates numerous testable predictions39 and is at least the type of multi-level theory necessary to encompass the difficult issues related to consciousness. Life and consciousness may indeed be subtly linked to fundamental spacetime geometry.

Isolated Macroscopic Quantum States in the Brain?

At first glance the brain is a noisy, thermal environment, hardly hospitable to delicate quantum effects which require (in the technological realm) extreme cold to prevent thermal excitations. Nature however may have solved the problem of quantum state isolation. For example Dan Sacketta of NIH has recently shown that microtubules may be isolated from thermal noise by a condensed layer of charges which surround them like a sleeve.

Another protective mechanism may isolate quantum superposition in microtubules as they become isolated from environmental decoherence by phases of actin gelation. Among the most primitive of biological activities are "sol-gel transformations". Cytoplasm within living cells alternates between phases of 1) "sol" (solution, liquid), and 2) "gel" (gelatinous, solid) caused by disassembly (sol) and assembly (gel) of cytoskeletal actin (regulated by calcium ion). Sol-gel transformations play essential roles in many cell functions, can occur rapidly (e.g. 40 sol-gel cycles per second), be quite solid, and deformable without transmitted responsed. Cyclical encasement of microtubules by actin gels may be an ideal quantum isolation mechanism.

Key quantum events may also be shielded either in hollow microtubule cores or intra-protein hydrophobic pockets (where anesthetic gases are known to act).

But even if quantum coherent superposition could be isolated and maintained in cytoplasm of individual neurons and glia, how could quantum states traverse membranes and synapses to become macroscopic and occur among microtubules in cells throughout the brain? One possibility involves quantum tunneling through gap junctions, primitive electrotonic windows between neurons and glia. Neurons interconnected by gap junctions form networks which fire synchronously, "behaving like one giant neuron"f, and possibly accounting for synchronized 40 Hz neural activity. Unlike chemical synapses which separate neural processes by 30-50 nanometers, gap junction separations are 3.5 nanometers, within range for quantum tunneling. Gap junctions are widespread but unevenly distributed throughout the brain. By immunolabeling of gap junction protein (connexin) precursor, Micevych and Abelsonh found high levels in thalamic sub-nuclei, layers 2 and 3 of cortex, and midbrain. Thalamo-cortical networks of gap junction-connected neurons with actin gelation/solution phases coupled to synchronized 40 Hz activity could isolate MT across large brain volumes and provide cycles of macroscopic quantum coherence.