The Cerebral Code
William H. Calvin, 1998

The Darwinian Theory of Mosaics in the Brain
This book represents the core statement of Calvin's Darwinian Mosaics theory. His
How Brains Think is a less technical presentation of the essential ideas.

Strange Vocabulary?
Calvin frequently uses the terms "chaos", "strange attractor" and "basin of attraction" to describe the behavior of groups of the hexagonal mosaics. Yet, he does not say just how these concepts are to be applied to that behavior or whether, indeed, he actually intends these terms to be understood with their common usage from the theory of nonlinear dynamical systems.

Although it is true that many. if not most, nonlinear systems do exhibit chaotic behavior and there is no question that the brain is a highly nonlinear system, still it is not at all clear how Calvin intends these terms to apply. He refers (CC p..) to a group of mosiacs, distributed over some area of cortical surface, each having a slightly different configuration derived from an original perceptual feature or other such input. That area of mosaics is said to constitute a "basin of attraction" and yet, neither the individual mosaics nor the area as a whole go through any sort of configurational cycles. There is no clear sense in which one could construct a phase space. Wilson presents a detailed discussion of chaotic neural behavior. The point is that the attractors he discusses occur at a lower level than the symbolic patterns Calvin pursues. How these different levels might be related is unknown.

One is led to the conclusion that the "basin" to which Calvin refers is, in fact, simply the cortical area over which these mosaics are distributed, that area being characterized by the distribution of suitability of the various mosaics to be matched by a different pattern being communicated by a linking system of fibers, such as from the other hemisphere via the corpus callosum.

Calvin's use of the term "attractor" seems to refer to the pattern-recognition-like effect which occurs when a communicating (linking) mosaic or mosaic set sufficiently matches the linked pattern such that ....... (what action occurs as a result?) This, of course, has nothing to do with the nonlinear meaning of the popularized term "strange attractor", used in the sense of a tendency for a chaotic system to remain close to a particular phase space trajectory.

Thus, it appears that none of these terms is used in the mathematical sense of describing nonlinear chaotic behavior.

Uncommitted Brain Areas for Darwinian Copying?
A major part of Calvin's theory, the Darwinian copying, depends on the existence of uncommitted areas of cerebral cortex, rather large areas in fact, if we are to be able to deal with highly complex topics. Unfortunately, according to
Bickerton (p43), no such brain area has yet been discovered. Certainly, there are cortical regions whose function we do not yet know, but that is not the same as saying that such areas are not genetically wired for any particular function. It has been fashionable for many years to refer to most of the frontal lobes as "association areas". But as more is learned, specific regions of this vast, unknown territory are region-by-region being assigned to particular functions.


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