Journal of Consciousness Studies 5(4)389-404 (1998)

Competing for Consciousness:

A Darwinian Mechanism at an Appropriate Level of Explanation

William H. Calvin

University of Washington

Department of Psychiatry and Behavioral Sciences

725 9th Avenue, Box 2605

Seattle WA 98104-2086 USA

WCalvin@UW.edu | WilliamCalvin.org

Abstract

Treating consciousness as awareness or attention greatly underestimates it, ignoring the temporary levels of organization associated with higher intellectual function (syntax, planning, logic, music). The tasks that require consciousness tend to be the ones that demand a lot of resources. Routine tasks can be handled on the back burner but dealing with ambiguity, groping around offline, generating creative choices, and performing precision movements may temporarily require substantial allocations of neocortex. Here I will attempt to clarify the appropriate levels of explanation (ranging from quantum aspects to association cortex dynamics) and then propose a specific mechanism (consciousness as the current winner of Darwinian copying competitions in cerebral cortex) that seems capable of encompassing the higher intellectual function aspects of consciousness as well as some of the attentional aspects. It includes features such as a coding space appropriate for analogies and a supervisory Darwinian process that can bias the operation of other Darwinian processes.

Introduction

Francis Crick likes to observe that people once worried about the boundary between the living and the nonliving. Today, the boundary seems meaningless; we instead talk about all the varied aspects of molecular biology. Today's brain researchers think it likely that much of the present scientific and philosophical concern about consciousness will soon become equally obsolete, that we will simply come to talk of the various physiological processes involved with attention and creative problem-solving.

This is not to say that consciousness will disappear as a useful word in our vocabularies. Nor will the philosophers' cautions about classical mistakes cease to be relevant. Just as "living" has continued to be a useful shortcut, so will "conscious" and "mind." Even those of us who come to understand all the contributing physiological processes will still need the C word, not only for

communicating with those outside the field but even for thinking about the subject.

So let me attempt a neurophysiologist's introduction to the subject, one that I hope will remain useful as we build our knowledge about what Dan Dennett called "the last surviving mystery." A mystery, Dennett said, "is a phenomenon that people don't know how to think about -- yet." Here I will attempt to clarify the appropriate levels of explanation and then propose a candidate mechanism, a Darwin Machine (Calvin 1987, 1996) that seems capable of encompassing the higher intellectual function aspects of consciousness as well as some of the attentional aspects. [Portions of this article are adapted from my two 1996 books, How Brains Think (Basic Books, New York) and The Cerebral Code (MIT Press, Cambridge MA).].

Consciousness is the tip of the iceberg, in the sense that many other things are going on in the brain at the same time, hidden from view. Indeed, we are incapable of reporting on most of what our brain does for us. I cannot report on my blood pressure without a lot of external instrumentation, even though my brain measures and regulates my systolic and diastolic pressures. It is simply not accessible for verbal reporting.

For the brain, we need to span multiple levels of mechanism -- from synapses to cells to circuits to modules, and more. And also span multiple levels of phenomenological explanation -- such as attributes, objects, categories, analogies, and metaphors. Layers of middlemen are familiar from everyday economics, and we expect to see many layers of representation standing between our consciousness and the real world.

As Derek Bickerton noted: [T]he more consciousness one has, the more layers of processing divide one from the world. . . . Progressive distancing from the external world is simply the price that is paid for knowing anything about the world at all. The deeper and broader [our] consciousness of the world becomes, the more complex the layers of processing necessary to obtain that consciousness. There are subconscious trains of thought, however, and they vie for "attention." The layer immediately underlying consciousness might well involve a mechanism for competition.

Though the obvious analogy is to the television viewer who surfs the channels (and our nighttime dreams often seem like switching between soap operas in progress), there need not be a central place where choices are viewed. The "best" channel need only temporarily win out over the others in the battle for access to output pathways such as speech and other body movements. Soon, another channel comes to dominate and we speak of "our attention shifting" -- but there need not be an agent which makes the decision or performs the action, not any more than ice needs an agent to help it melt.

Output need not involve overt movements: silent speech is an important way in which we reason, generate alternatives, and choose amongst them. The mental rotation of complex objects illustrates a nonlanguage mode of conscious thought. But, to a neurophysiologist, there is nothing in this overview that demands a central place. The "center of consciousness" could, instead, shift from moment to moment: from language to nonlanguage areas, from frontal to parietal lobe, from left to right hemisphere, and maybe even from cortical to subcortical structures -- anywhere, I suspect, with the potential for generating novel patterns of movement. And, of course, it seems possible to do several things at once, just as one can sew, or listen to the radio, while watching television. Not everything we do has to pass through the current center of consciousness.

Karl Popper noted that posing alternatives seemed especially “conscious”: Much of our purposeful behaviour (and presumably of the purposeful behaviour of animals) happens without the intervention of consciousness.... Problems that can be solved by routine do not need consciousness. [The biological achievements that are helped by consciousness are the solution of problems of a non-routine kind.] But the role of consciousness is perhaps clearest where an aim or purpose... can be achieved by alternate means, and when two or more means are tried out, after deliberation.

While I think that Popper is on to something here, I'd state it more generally: the tasks that require consciousness tend to be the ones that demand a lot of resources. Routine tasks can be handled on the back burner but dealing with ambiguity, groping around, generating creative choices, and performing precision movements may temporarily require substantial allocations of neocortex.

Consciousness and Levels of Explanation

A mystery, Dennett said, "is a phenomenon that people don't know how to think about -- yet." What constitutes an explanation? To explain consciousness in any serious way, we must avoid using mathematical concepts to dazzle rather than enlighten. And we must watch out for "proofs by want of imagination," as when we conclude, out of arrogance or impatience, that there are no other alternatives to the answers we have found. When it comes to the brain, in particular, we must be careful to pitch our theories at the right level of mechanistic explanation.

Brain function involves at least a dozen levels, and finding appropriate levels for aspects of consciousness has not been easy. Everyone tends to extrapolate their favorite subject of study and proclaim its relevance to consciousness. Since I'm about to do the same thing myself, indulge me in a few words about levels, particularly as they relate to emergent properties and those "changes of state," for I have two major points to make in this short summary of (and borrowing from) my longer works, How Brains Think and The Cerebral Code.

. One is a proposal for a specific consciousness mechanism (as the current winner of Darwinian copying competitions in association cortex) and the other is an argument about what's a correct level at which to seek a consciousness mechanism. I hope both are correct, but the level analysis ought to be more generally useful; it's certainly intended as a critique of much that has been written on the subject.

What's missing from most discussions of consciousness is, surprisingly, the whole concept that there are levels of explanation. Douglas Hofstadter (1985) gives a nice example of levels when he points out that the cause of a traffic jam is not to be found within a single car or its elements. Traffic jams are an example of self-organization, more easily recognized when stop-and-go achieves an extreme form of quasi-stability -- the crystallization known as gridlock. An occasional traffic jam may be due to component failure, but faulty spark plugs aren't a very illuminating level of analysis--not when compared to merging traffic, comfortable car spacing, driver reaction times, traffic signal settings, and the failure of drivers to accelerate for a hill or high-rise bridge.

The more elementary levels of explanation are largely irrelevant to traffic jams. Such decoupling was emphasized by the physicist Heinz Pagels (1988), who noted:

“Causal decoupling” between the levels of the world implies that to understand the material basis of certain rules I must go to the next level down; but the rules can be applied with confidence without any reference to the more basic level. Interestingly, the division of natural sciences reflects this causal decoupling. Nuclear physics, atomic physics, chemistry, molecular biology, biochemistry, and genetics are each independent disciplines valid in their own right, a consequence of the causal decoupling between them....

Such a series of “causal decouplings” may be extraordinarily complex, intricate beyond our current imaginings. Yet finally what we may arrive at is a theory of the mind and consciousness — a mind so decoupled from its material support systems that it seems to be independent of them — and “forgot” how we got to it.... The biological phenomenon of a self-reflexive consciousness is simply the last of a long and complex series of “causal decouplings” from the world of matter.

Stratified Stability and Emergents

Closely related is the notion of emergent properties: traffic jams and crystals emerge from combinations, and we expect emergence to play a large role in the transient levels of organization involved with higher intellectual function (language, planning, games, etc.). In our search for a level corresponding to consciousness, it is well to recall that levels arise from what Jacob Bronowski (1973) called stratified stability:

Nature works by steps. The atoms form molecules, the molecules form bases, the bases direct the formation of amino acids, the amino acids form proteins, and proteins work in cells. The cells make up first of all the simple animals, and then the sophisticated ones, climbing step by step. The stable units that compose one level or stratum are the raw material for random encounters which produce higher configurations, some of which will chance to be stable.... Evolution is the climbing of a ladder from simple to complex by steps, each of which is stable in itself. The tumult of random combinations occasionally produces a new form of organization. Some forms, such as the hexagonal cells that appear in the cooking porridge if you forget to stir it, are ephemeral (as, indeed, are the contents of our consciousness).

Other forms may have a "ratchet" that prevents backsliding once some new order is achieved. While crystals are the best known of these quasi-stable forms, molecular conformations are another, and it is even possible that there are quasi-stable forms at intermediate levels -- such as the microtubule quantum states where the consciousness physicists would like the action to be:

“Accordingly, the neuron level of description that provides the currently fashionable picture of the brain and mind is a mere shadow of the deeper level of cytoskeletal action — and it is at this deeper level where we must seek the physical basis of mind!” --Roger Penrose, Shadows of the Mind, 1994.

While I hope that quantum field effects on consciousness exist (as you will presently see, when I get to technological possibilities), there are a number of problems with such proposals, not the least of which is the scanty evidence relating quantum fields to cortical synchrony, or relating synchrony to perceptual binding, or relating binding to attention, or relating attention to the much broader range of phenomena associated with consciousness (the word has many connotations, and they surely don't all share the same mechanism).

To limit myself to the initial leap from QM (my abbreviation for all the “quantums” reviewed by Jibu and Yasue 1995) to synchrony, one should always be suspicious of any mechanism that claims to tunnel through a dozen levels of organization to produce a striking effect. As I explained in How Brains Think:

[A] more appropriate level of inquiry into consciousness is probably at a level of organization immediately subjacent to that of perception and planning: likely (in my view) cerebral-cortex circuitry and dynamic self-organization involving firing patterns within a constantly shifting quilt work of postage-stamp-sized cortical regions.

Consciousness, in any of its varied connotations, certainly isn't located down in the basement of chemistry or the subbasement of physics. This attempt to leap, in a single bound, from the subbasement of quantum mechanics to the penthouse of consciousness is what I call the Janitor's Dream. Quantum mechanics is probably essential to consciousness in about the same way as crystals were once essential to radios, or spark plugs are still essential to traffic jams. Necessary, but not sufficient. Interesting in its own right, but a subject related only distantly to our mental lives -- and not to be confused with the temporary levels of organization associated with higher intellectual function.

Darwinian Bootstrapping of Quality

An existence proof for a good alternative is potentially far more persuasive than the best critique of quantum-mechanical spirits and little-man-inside reasoning, so let me shift gears here. If we take consciousness to be important for Popper's "solution of problems of the non-routine kind," then shaping up a good-to-excellent ("quality") course of action in thought is a key aspect of consciousness, one that goes well beyond mere awareness or shifting attention.

We no longer have to take it on faith that there are mechanisms capable of recursively bootstrapping random novelties into something of quality. For the last 160 years, there has been an existence proof, the Darwinian process (Calvin 1996b, 1997). The way in which quality is achieved using this process has long occupied the best minds in evolutionary biology (see, for example, Maynard Smith and Szathmáry 1995). And the slow evolution of species, on the time scale of millennia, is no longer the only example: the immune response is now known to be another Darwinian process, operating on the time scale of days to weeks as a better and better antibody is shaped up in response to the challenge of a novel antigen. For decades, computer science has used a solution-finding procedure, called the genetic algorithm (Holland 1992), that mimics an expanded version of the Darwinian process on a time scale limited only by computer size and speed.

It would be surprising if the brain did not make some use of this fundamental principle for bootstrapping quality. Can this same well-known process operate quickly enough in the brain, on the time scale of thought and action? Can it account for much of what we call "consciousness"? I undertook to answer such questions in one of my 1996 books, The Cerebral Code, which analyzes the recurrent excitatory circuitry of mammalian neocortex. I showed that this widespread wiring principle was capable of running the six essential features of the classical Darwinian process:

• a pattern (spatiotemporal firing pattern of a Hebbian cell-assembly, in this case) that

• copies with occasional

• variation where

• populations of the variants compete for a limited work space,

• their relative success biased by a multi faceted environment (both memorized and real-time, in this case), and

• with further variations centered on the more successful of the current generation (Darwin's inheritance principle).

This full-fledged Darwinian process is what is associated with the recursive shaping up of quality; it should not be confused with mere selective survival of a single pattern and other "sparse sets" that utilize only a few of the "six essentials" (Calvin 1997).

The best way of demonstrating what I consider an appropriate level of explanation, that of circuits involving stamp-to-postcard-sized areas of cerebral cortex (we have enough neocortex to fill four sheets of typing paper), is to take the reader through an example. It's not the only possible example, just the one due to Darwin, but I expect that competing theories will also come to occupy the same level of explanation, that of emergent properties in the shifting dynamics of substantial areas of cortex. After I explain enough of the circuitry so that the reader can imagine how a Darwinian process could operate in neocortex, I will briefly return to Quantum Consciousness, trains of thought, and the explanatory coverage needed for a theory of mind.

The Brain's Darwinian Circuitry

The cortical circuitry that makes a full-fledged Darwinian process possible is not an obscure feature known only to a few neuroanatomists: it is easily the most prominent wiring principle seen in cerebral cortex, that of the patterned recurrent excitatory connections between neighboring pyramidal neurons in the top layers of neocortex. It has just taken a while to realize one of the implications of it, an emergent property of the circuit not possessed by any of the individual elements: synchronized triangular arrays of pyramidal neurons, with nodes about 0.5 mm apart, is what you expect to observe, some of the time.

Each pyramidal neuron has an axon that branches nearly 10,000 times. Some travel through the white matter but most of the branches never leave the cortical layers, terminating in a synapse within a millimeter or so. The axon travels sideways to excite other cortical neurons, mostly other pyramidal neurons. The deep-layer (V and VI) pyramidal neurons have such sideways axons that remain within the cortical layers, some terminating nearby and others more distantly.

It's the wiring seen (e.g., Lund et al 1993) in the branching of the axon of the superficial-layer pyramidal neurons (layers II and III), however, that is so striking. Their terminations are patterned: their axons are like express trains that skip a long series of intermediate stops, concentrating their synaptic outputs in zones about 0.5 mm apart. That's what makes synchronized triangular arrays likely to form on occasion.

Though the 0.5 mm spacing is similar to that of macrocolumns (say, the orientation columns of visual cortex) and though it may be related to helping organize such macrocolumns during development (Calvin 1995), the analogies to macrocolumns (as we currently know them) are limited.

What's intriguing is their relation to minicolumns (orientation columns are the best known examples), which are vertical columns of about a hundred neurons that are organized around a dendritic bundle in the manner of stalks of celery; the distance between neighboring bundles is about 0.023-0.031 mm (in monkey; twice that in cat: Peters and Yilmaz 1993). The nearest outputs of a superficial pyramidal neuron's axon are not 0.5 mm away but to immediate neighbors. Cells within a minicolumn tend to share interests, as in elongated visual stimuli of a particular orientation, and this local recurrent excitation is one of the reasons.

The longer axon branches tend to skip making synapses for 0.4-0.6 mm, but the express-train analogy is too one-dimensional to capture the reality: axon branches go in many radial directions. I tend to draw the result, looking down from the top, as an annular ring; while no one cell's axon branches will fill in the annulus, there are 39 superficial pyramidal neurons in a given minicolumn doing similar jobs. So think of the output pattern as something like a mal-focused flashlight beam: a central minispot, then a bright ring in the periphery. Actually, because many axons continue their express run for another 0.5 mm, you need to imagine additional annuluses at 0.5 mm spacings, more like a bull's eye target with fading shades of gray.

Synchrony on a Small Scale

One consequence of the express-train axon is that cells 0.5 mm apart will tend to talk to one another: they will recurrently excite. While a chasing-their-tails loop is one possibility if synaptic strengths are quite high, even weak synaptic strengths have an important consequence: entrainment. Since 1665, when the Dutch physicist Christiaan Huygens noticed that pendulum clocks on the same shelf synchronized their ticks within a half hour, much additional work has been done on entrainment.

A dramatic example from the Philippines was reported in Science by Hugh Smith in 1935: Imagine a tree thirty-five to forty feet high, apparently with a firefly on every leaf, and all the fireflies flashing in perfect unison at a rate of about three times in two seconds, the tree being in complete darkness between flashes. Imagine a tenth of a mile of river front with an unbroken line of mangrove trees with fireflies on every leaf flashing in synchronization, the insects on the trees at the ends of the line acting in perfect unison with those between. Then, if one’s imagination is sufficiently vivid, he may form some conception of this amazing spectacle. Even small tendencies to advance the next flash when stimulated with light will suffice to create a "rush hour." Furthermore, you usually do not see waves propagating through such a population, except perhaps when the flashing is just beginning or ending.

Relaxation oscillators like neurons and fireflies will get in sync much more quickly than harmonic oscillators, and even weak interconnections will suffice (Somers and Kopell 1992). So, if several neurons 0.5 mm apart are firing for some reason (perhaps they both respond to the color yellow), there is a good chance that they will get in sync some of the time.

This has an interesting consequence: entraining additional yellow neurons located 0.5 mm from each of the original pair, to form an equilateral triangle of synchronized superficial pyramidal neurons (as seen, looking down on the cortex from above). Of course, yellow-2 and yellow-3 might themselves entrain a fourth. What we have is a mechanism for forming a triangular array of synchronized cells, one that can extend its reach to wherever there are cells already firing, or close to firing.

Suppose now that we have some other cells responding to another attribute of a yellow banana, say its curvature. They too can form their own triangular array. What is the largest number of triangular arrays? Try to define an area containing only one member of each triangular array. It turns out to be hexagonal in shape (corresponding points in adjacent hexagons are connected by equilateral triangles), 0.5 mm across, and containing a few hundred minicolumns. Most potential arrays will, of course, be silent; I tend to imagine fewer than a dozen actively firing, but the silent ones are likely also important (were they to become active, they might "fog" the characteristic spatiotemporal firing pattern).

What we now have is a hexagonal mosaic, formed of the active and silent triangular arrays. The adjacent hexagons are nearly identical in their firing patterns. The curved array and the yellow array need not be synchronized with one another (as a common form of the binding theory assumes); indeed, they are likely displaced in time. But the spatiotemporal firing pattern within the hexagon is now the minimal one: it contains one member of everything, but never a redundant one. The microcircuitry within that 0.5 mm hexagon may resonate with the spatiotemporal pattern. An imposed pattern might be memorized via long-term potentiation and depression; indeed, one can imagine reconstituting the spatiotemporal pattern if it is halted, thanks to the lingering alteration of synapse strengths from the imposed rhythms creating a new basin of attraction, conforming any near-fit spatiotemporal patterns to the stored standard.

It's a minimal Hebbian cell-assembly, potentially capable of recording the various features of an object or the details of a movement program. And a hexagon's spatiotemporal firing pattern is potentially a cerebral code, what represents an object or idea. Such a pattern is like a little tune (map each of the several hundred minicolumns to a note on a musical scale). There will be a different tune characterizing Apple than the tune for Banana.

The musical analogies also tell us that a hexagonal mosaic is like a plainchant choir, singing in the lockstep of a Gregorian chant. As the triangular arrays recruit followers on the edges, additional hexagons are added to the mosaic. Perhaps choosing between an apple and a banana for a snack is a matter of how big their respective choirs are, that only large choruses can gain access to the output pathways associated with silent speech.

Dueling Choirs for Concept Competition

Now imagine dueling choirs, abutting hexagonal mosaics singing different tunes, trying to recruit members at the expense of the other. Along the battlefront, there are hexagons that have both tunes superimposed, just as in a symphonic work. If the combination resonates well with the local neural network, we might speak of harmony, just as we do for the major and minor scales. Borderline superpositions (as well as the more extensive ones that can be created by long corticocortical bundles) illustrate a powerful recombination principle, a way of doing associative memories that can represent relationships with the same 0.5 mm hexagonal code space as used for objects.

Another lesson of levels is that mechanisms that suffice at one level may prove to be shaky foundations, that other ways of doing the same thing are more extensible. Hexagonal codes are a much better foundation for superstructures (such as coding for analogies) than are the better-known associative memory mechanisms at the level of synaptic mechanisms for classical conditioning.

This isn't the place for showing the many implications of a cerebral coding scheme based on the spatiotemporal firing pattern within one of the recurrent-excitation-defined hexagons, a book-length project that I tackled in The Cerebral Code. But with the notion of hexagonal mosaics that transiently compete for space in association cortex, you can now appreciate how a Darwinian process could operate in association cortex via the spatiotemporal patterns copying themselves sideways. Like the classical examples of a full-fledged Darwinian process, there is

• a pattern,

• that is copied (indeed, what is reliably copied defined the hexagonal-shaped spatiotemporal pattern),

• variations occur (dropouts, off-focus nodes, superpositions),

• populations of variant patterns compete for a work space,

• their relative success is biased by a multifaceted environment (current sensory as well as resonances with memorized patterns), and

• the more successful of the current patterns tend to produce more of the next round of variants (Darwin's inheritance principle) is implemented because bigger mosaics have more perimeter, and the perimeter is where dropouts and off-focus nodes can escape the standardization enforced by six surrounding nodes all firing at the same time).

Unlike the generation times spanning days to decades of the usual Darwinian examples, cortex operates on a time scale of milliseconds to seconds, though its operations are biased by memories that span far longer time scales. Within seconds to minutes, neocortex ought to be capable of implementing all of the classical means of accelerating the rate of evolution (systematic recombination, parcellation, rapid "climate change," and refilling empty niches).

A Web of Darwinian Competitions

Because of its distributed nature and corticocortical connections between regions, cortex isn't limited to the standard Darwinian productions. It might well utilize some additional features, such as a supervisory Darwinian process that can bias the operation of other Darwinian processes.

Yet it need not be some grand supervisor with even more intelligence. Until something fancier is clearly indicated, the default assumption ought to be that any regulatory process is essentially stupid, perhaps only chaotic phenomena on a grander or slower scale.

Indeed, there are some situations that might qualify for such two-level interactive evolution, such as the orbital frontal cortex role in monitoring progress on an agenda, a meta-sequence that seems to tick along on a different time scale than individual thoughts and sentences. There's no requirement that darwinian variations have to be truly random; a slow darwinian process could bias or skew the general direction of the variants of a faster darwinian process that deals with lower-level matters, such as perception and movement on the time scale of seconds. There could be a cascade or web of such darwinian processes that operate on different levels in the attributes-to-metaphors spectrum, or on different time scales in the milliseconds-to-hours range.

The neocortical Darwin Machine theory seems to me to be at the right level of explanation for consciousness; it's not down in the synapse or cytoskeleton but up at the level of dynamics involving tens of thousands of neurons, generating the spatiotemporal patterns that are the precursors of movement -- of behavior in the world outside the brain.

Composite cerebral codes, formed by superpositions and shaped up by darwinian copying competitions, could explain much of our subconscious mental lives. The codes themselves are suitably arbitrary, just as a century of argument about symbols has emphasized. Copying competitions suggest why we humans can get away with many more novel behaviors than other animals (we have offline evolution of nonstandard movement plans judged for safety). It suggests how we can engage in analogical reasoning (relationships themselves can have codes that can compete). Because cerebral codes can be formed from pieces, you can imagine a unicorn and form a memory of it (resonances that can reactivate the spatiotemporal code for unicorn). Best of all, a darwinian process provides a machine for metaphor: you can code relationships between relationships, and then shape them up into something of quality.

None of these things naturally flow from Quantum Consciousness. But let us not throw out the baby with the bath water: there are interesting aspects of some of the quantum field proposals.

The Quantum's Revisited

Picking up on the notions of synchronization for binding the dispersed aspects of the analysis on an object in the brain, some have invoked a synchronizing influence of quantum fields, suggesting a connection between QM and object recognition (and, in the process, conflating perception with consciousness). I hesitate to note that my synchronized triangular arrays for pattern cloning show another possible application of the same reasoning, extending the potential realm of QM beyond the object-feature binding aspects of consciousness and into the realm of higher intellectual function.

While it is possible that quantum-level phenomena could influence some aspects of consciousness via encouraging synchrony, extraordinary claims (QM mediating a key aspect of consciousness) require extraordinary evidence. If the consciousness physicists were serious about their proposal, they would examine alternative ways of achieving synchrony in the brain -- which are legion -- and explain why their synchronizing explanation was preferable to simpler explanations that are a dozen levels of organization closer to higher intellectual function.

A caution, however: If I were to announce yet another way of achieving cortical synchronization via some new synaptic mechanism, everyone would yawn: given how many ways there are of encouraging entrainment (even recurrent inhibition can entrain; more generally, see Winfree 1967), the name of the game is not possible mechanisms but probable mechanisms.

How strong is your candidate's synchronizing influence? Do other known mechanisms seem to interdigitate with it? Does it do anything that needs doing? (I'm convinced of the need for a Darwinian process to bootstrap quality, but some of us are not convinced that object attributes typically need synchrony to bind them together after what-where divergence.) The existence of other synchronization mechanisms means that any QM effect could be easily swamped, so proponents not only need to show a QM effect on entrainment but to show the conditions when it can dominate the others, and so bring Quantum Consciousness to the fore.

Such has led me to wonder if quantum-mechanical proposals are not solutions in search of a problem. I'm not convinced that brain science needs quantum-mechanical mechanisms when we already have so many candidates at the level of the emergent properties of circuits to accomplish the never mind getting from synchrony to binding, from binding to attention, from attention to other aspects of consciousness).

But that's science -- and technology may well be another matter, given my other role for entrainment, that of providing the foundation for a hexagonal mosaic that can engage in a Darwinian competition. Encouraging entrainment, or breaking it up, via externally applied fields could provide an interface with the Darwinian brain processes that shift the contents of consciousness. If the postulated quantum effects prove strong enough, and external fields can be focused sufficiently well to elevate them to dominate other entrainment influences, such a QM spotlight might make for an interesting technology. For psychiatry, imagine breaking up obsessive patterns of thought or suppressing hallucinations. For neurology, imagine retraining cortical areas to take over a function lost elsewhere to a tumor or stroke. For anesthesiology, imagine disrupting those choirs that lead to memorizing unpleasant events. Studying for exams with a quantum assist might aid in learning new material; focusing the assist in other areas might aid in recall.

The Stream of Consciousness

Resonances are better known these days as part of the rubric of chaotic attractors. I imagine each hexagon's neural network as supporting a number of characteristic spatiotemporal patterns, just as spinal cord circuitry supports a number of gaits, the particular spatiotemporal pattern that you get depending on how you precondition the circuitry via the facilitation from other imposed patterns. And that may have something to say about the "stream of consciousness."

Manipulating the landscape of a basin of attraction is reminiscent of William James's train of thought, that series of mental states that preceded your current one, each one fading into the background but overlain on its predecessors -- and all capable of contributing to what connections you're likely to make right now.

Just imagine those various fading attractors as like that Japanese technique of finely slicing some raw fish, then tilting the block sideways (fallen dominos are another analogy, if you are sashimi impaired). The bottom layer may be hardest to reach but it goes back furthest. Stage-setting with multiple layers of fading schemas may be handy for promoting creativity, getting the right layers of attractors in about the right order and so adjusting their relative strengths. (The Sashimi Theory of Creativity would, of course, be a suitably raw successor to all those half-baked right-brain schemes).

But such histories can also be distracting, and we often try to let them fade, try to avoid re-exciting them with further thinking. There are various mind-clearing techniques; Donald Michael (personal communication 1995) suggests that forming large quasi-stable hexagonal territories might be what meditation with a mantra is all about, preempting the everyday concerns that would otherwise partition the work space and plate out new short-term attractors. By replacing it all with the mantra's nonsense pattern, and holding it long enough for temporary synaptic strength alterations to fade back to normal, the meditator gets a fresh start (for things other than the mantra!).

An ordinary mantra won't, of course, wipe the work space clean: to prematurely erase those fading attractors, you'll need a fancier mantra that disrupts instead. Short of fogging with seizures, as in electroshock therapy, I don't know of any such eraser schemas -- though one can imagine mental viruses (Dawkins 1993) that might preempt entry into those fading basins of attraction, more analogous to an obscuring coat of paint than to a true eraser.

Higher Aspects of Consciousness

Once they finish with things as basic as perceptual transformations and memory phenomena, theories of brain function must explain abstractions and associations as diverse as categories, abstracts, schemas, scripts, syntax, and metaphor. If we are to venture past the elementary notion of consciousness as mere awareness or shifting attention, we are going to need to account for:

• How items of our vocabularies are represented.

• How memories are stored and recalled.

• How Darwinian shaping-up takes place.

• How “new ideas” arise, perhaps as pattern variants or superpositions.

Those four, at least, have pretty much fallen out of our search for the darwinian essentials. The rest are harder:

The existence of hallucinations and dreams.

Déjà vu experiences. Abnormally widespread cloning of an input pattern (perhaps due to lack of competition) might produce the conscious experience usually associated with strong memory resonances that allow widespread cloning.

Unreliable memories. Because the long-term synaptic connectivities can be modified by a new active pattern, this could often happen. Similarly, we’d like something appropriate for concrete thinking and the idée fixe.

How the various connotations of a word such “comb” are linked, given that they’re likely stored

• in different cortical areas.

• The presence of specialized cortical regions that can also participate in nonspecialist tasks.

The ability to hold a behavioral set, after selecting it from among possibilities. What might an agenda look like?

Serial-order specialties for language and speculative planning, not to mention all the small muscle sequencing that a child needs to tie a shoelace.

Speed-of-thought correlates, mechanisms that could vary from time to time in the same individual.

During the transitions of manic-depressive illness, a person can go from a fluidity of making connections and decisions to a slow, labored train of thought that lingers too long and fails to make obvious connections. And back again.

The impression of a narrator, juggling decisions, and speculating about tomorrow. Any explanation needs to be consistent with the neurological evidence that no partial cortical lesion abolishes the “self.”

That's the kind of coverage needed for a useful theory of mind (and this neocortical Darwin Machine enables predictions to be made, all across this spectrum; Calvin 1996b). It may not have to explain all of two centuries of neurology, one century of psychology, and a half-century of neurobiology and cognitive neuroscience -- but it can't be truly inconsistent with any of it. A theory of mind needs a lot of explanatory power, while still being specific enough to make experimental predictions.

So far, we've actually needed two metaphors: a top-down metaphor that maps thoughts onto ensembles of neurons, and a bottom-up metaphor that accounts for how ideas emerge from those apparently chaotic neuron ensembles. But the neocortical Darwin Machine may well do for both metaphors -- it might, indeed be more mechanism than metaphor, thanks to those express-train patterns in the cortex.

Let me turn now to how complex patterns might self-organize, using such Darwinian competitions to embed suitable resonances in the neural feltwork as we gain experience.

The Search for Hidden Patterns

Our passion for discovering patterns seems to have a lot to do with our notions of consciousness. If we are to have meaningful, connected experiences -- ones that we can comprehend and reason about -- we must be able to discern patterns to our actions, perceptions, and conceptions. Underlying our vast network of interrelated literal meanings (all of those words about objects and actions) are those imaginative structures of understanding such as schema and metaphor, such as the mental imagery that allows us to extrapolate a path, or zoom in on one part of the whole, or zoom out until the trees merge into a forest.

Early childhood contains a number of pattern-finding challenges, and children seem extraordinarily acquisitive of ever-more-complex patterns hidden in the sounds and events that surround them. In our first year of life, we discovered phonemes within words. After another year of acquiring words, we were busy discovering schemas and syntax within word strings, and then we went on to discover nested embedding and narrative principles among more extended discourses.

The hexagonal superpositions, so like the different voices of a symphonic performance, show us a way that new associations can be represented in the brain -- and the Darwinian aspect suggests how quality could be shaped up via the usual variation, competition, and inheritance.

When we think seriously as adults, we think even more abstractly. We conjure up simplified pictures of reality called concepts or models. We can even discover patterns in speculative scenarios, as when we create a forwards-leaping chain of inferences (especially handy for speculating about consciousness!). As Paul Valéry once said, thought is all about "that which does not exist, that which is not before me, that which was, that which will be, that which is possible, that which is impossible."

Passive awareness (and its neural correlates) may be much simpler than the creative constructs implied by the James-Piaget-Popper levels of consciousness; a pop-through recognition of a familiar object may not need to utilize a cloning competition with alternatives in the manner of an ambiguous percept or a novel movement. Hexagonal mosaics surely aren't everything going on in the brain; indeed, they are probably just one mode of operation of some expanses of neocortex, and regulated by other brain regions such as hippocampus and thalamus. But here-this-minute, gone-the-next mosaics seem quite suitable for explaining many aspects of mind, aspects that have been difficult to imagine emerging from quantum mechanics, chemistry, neurotransmitters, single neurons, simple circuits, or even the smaller neocortical modules such as minicolumns. In some regions, at some times, hexagonal competitions might be the main thing happening.

There emerges from this view of our brain, with its relentless rearrangement from moment to moment, some glimpses of the neural foundations on which we construct our utterances and think our thoughts, some possibilities for implementing our kind of language and rational thought.

Dueling choirs are at a level of explanation that looks as if it might be appropriate for creativity and decision-making. It will be interesting to see how much of an explanation for talking-to-yourself consciousness can be provided by the same quality-bootstrapping process that Charles Darwin discovered back in 1838.

References

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Jacob Bronowski (1973), The Ascent of Man (Little, Brown), pp. 348-349.

William H. Calvin (1987), “The brain as a Darwin Machine,” Nature 330:33-34.

William H. Calvin (1995), “Cortical columns, modules, and Hebbian cell assemblies,” in Handbook of Brain Theory and Neural Networks, M. A. Arbib, ed. (MIT Press), pp. 269-272.+

William H. Calvin (1996a). How Brains Think: Evolving Intelligence, Then and Now (Basic Books, New York).

William H. Calvin (1996b). The Cerebral Code: Thinking a Thought in the Mosaics of the Mind (M.I.T. Press, Cambridge MA).

William H. Calvin (1997). “The six essentials? Minimal requirements for the Darwinian bootstrapping of quality,” Journal of Memetics 1:1, at http://www.fmb.mmu.ac.uk/jom-emit/1997/vol1/calvin_wh.html

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