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of features from the myriads of possibilities. When primed cell assemblies subsequently become activei.e., when the corresponding predictions are verifiedthe associations involved are strengthened by the mechanisms of (3). The resulting network of associations constitutes a model of the environment within the CNS. The model is dynamic in the sense that it takes sensory data as input and primes different temporal sequences on the basis of the model's predictions. Introspection confirms that, for the human CNS, models of the environment are indeed used to compare alternative courses of action. This model is ultimately dedicated to keeping primitive needs fulfilled, but it incorporates "leading indicators," etc., so that needs rarely become acute enough to determine action directly.) |
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How can the  framework help in analyzing this model? Certain analogies with other processes are suggestive. Individual cell assemblies act, in part, like the detectors in pattern recognizers: they are activated by particular features of the environment, features presumably relevant to the organism's needs. At the same time, the configuration of cell assemblies active at any given time defines the organism's response to the environment. In the terms used earlier, such a configuration is an element of the system's repertory. Assuming that the set of all cell assemblies is fixed (as it might be, to a first approximation, in a mature organism) or, at least, that the potentially available cell assemblies can be enumerated, the set of all possible assembly configurations constitutes the system's repertory of techniques for confronting the environment. |
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When cell assemblies are in mutual negative association (cross-inhibition), they act much as the alleles of a chromosomal locus; any active configuration can contain at most one of the assemblies, because it will actively suppress the others in the set. Positive associations between cell assemblies which favor particular configurations are analogous to the linkage of coadapted alleles in a chromosome. Indeed there are many potentially fruitful "genetic" analogies. As the CNS gains experience, some assemblies in a cross-inhibited set are likely to be expressed in a broadened range of environmental conditions, at the expense of others in the seta process suggestive of the evolution of (partial) dominance. Various genetic operators such as crossover and inversion find their counterparts in the ways in which cell assembly associations are modified. Temporal associations correspond to feedback among gene-products and sequential expression of genes. The list can be extended easily. |
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The needs of the organism define its goals, and ultimately set a criterion on |
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