Abstract
We consider approaches to brain dynamics and function that have been claimed to be Darwinian. These include Edelman’s theory of neuronal group selection, Changeux’s theory of synaptic selection and selective stabilization of pre-representations, Seung’s Darwinian synapse, Loewenstein’s synaptic melioration, Adam’s selfish synapse, and Calvin’s replicating activity patterns. Except for the last two, the proposed mechanisms are selectionist but not truly Darwinian, because no replicators with information transfer to copies and hereditary variation can be identified in them. All of them fit, however, a generalized selectionist framework conforming to the picture of Price’s covariance formulation, which deliberately was not specific even to selection in biology, and therefore does not imply an algorithmic picture of biological evolution. Bayesian models and reinforcement learning are formally in agreement with selection dynamics. A classification of search algorithms is shown to include Darwinian replicators (evolutionary units with multiplication, heredity, and variability) as the most powerful mechanism for search in a sparsely occupied search space. Examples are given of cases where parallel competitive search with information transfer among the units is more efficient than search without information transfer between units. Finally, we review our recent attempts to construct and analyze simple models of true Darwinian evolutionary units in the brain in terms of connectivity and activity copying of neuronal groups. Although none of the proposed neuronal replicators include miraculous mechanisms, their identification remains a challenge but also a great promise.
Highlights
How can neuronal group selection (NGS) be Darwinian, one might ask? What is meant by selection here? We propose that sense can be made in terms of a special formalism, frequently used in evolutionary biology, that of the eminent Price (1970), who made two seminal contributions to evolutionary biology
This involves the copying of a functional pattern of input connections from one neuron to another neuron and is a lower-boundary case of replication of synaptic connectivity patterns in small neuronal circuits (Young et al, 2007)
There is evidence that connectivity patterns can be entrained by stimuli (Johnson et al, 2010) and that this can occur during behavior (Isaac et al, 2009)
Summary
This is rather far from the truth, This is immediately clear from two reviews of Edelman’s book: one by Crick (1989), working in neuroscience and another by Michod (1988, 1990), an eminent theoretical evolutionary biologist. The appreciation by these authors of Edelman’s work was almost diametrically opposite. We believe that a precondition to success is to have some professional training in the theory (at least) of both the neural and cognitive sciences as well as of evolution Out of this comes a difficulty: neurobiologists are unlikely to follow detailed evolutionary arguments and, evolutionary biologists may be put off Frontiers in Computational Neuroscience www.frontiersin.org. If this analysis were to stimulate a good number of thinkers in both fields, the authors would be more than delighted
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