What we now have is a hexagonal mosaic, formed of the active and silent triangular arrays. A hexagon is simply the largest cortical area that contains one, and only one, of the participating triangular arrays. The adjacent hexagons are nearly identical in their firing patterns.

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 choirs are.

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 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 the 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).

Though our recording methods currently lack sufficient resolution to see how often the various cortical areas actually utilize this Darwinian mode of operation (it could, for example, be restricted to a tune-up period early in life and seldom used thereafter), the time scale question is somewhat clearer

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).

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 random; a slow darwinian process could bias 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.