If we take consciousness, as Karl Popper did, to be important for "solution of problems of the non-routine kind," then shaping up quality courses 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. ⁶ The way in which quality is achieved using this process has long occupied the best minds in evolutionary biology. 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 algorithm⁶, 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 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 multifaced 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".⁷

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 neocortex, that of the patterned recurrent excitatory connections between neighboring pyramidal neurons. 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.

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 seen⁸ 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. Like an express train, these axon skip the intermediate stops. That's what makes synchronized triangular arrays likely to form on occasion.

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-tail 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.⁹ 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. 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. 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.