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At least 253 records · Page 14Linked to original sources
PubMed1976

A cybernetic approach to the origin of the genetic coding mechanism. I. Methodological principles.

It is postulated that some quasi-deterministic code features (universality, connectedness, systematic degeneracy, symmetry, regularity and so on) resulted from unique (and therefore universal) relization of a stochastic evolutionary process. The evolution of real genetic systems should satisfy the principle of succession; that is, loss of a feature that is necessary for a genetic system means death to its carrier. The hypothesis of unique key coincidence is proposed which indicates the mechanisms of arising of the primary correspondence between the linear structures of polynucleotides and polypeptides. If the collinear coincidence was to appear in the key positions of pra-protein with, at least, some of the primitive properties of the pra-amino-acyl-t-RNA-synthetase required for the accelerated recognition of the key positions of pra-template, the positive feed-back mechanism in the system would be most short-circuited so that the repetitive reproduction of pra-synthetase would be much accelerated.

Amino Acyl-tRNA Synthetases↗
PubMed1988

Cybernetic origins of replication.

An evolutionary progression leading toward replication is resolved into several phases; (a) the replication of RNA segments by self-priming and -templating, (b) the replication of single stranded molecules by elongation and controlled scission, (c) replication of complementary duplexes and (d) replication of DNA. The initial phase is suggested by evidence for the existence of tandem repeats in an early population of molecules presumed to be ancestral to today's structural RNAs. Relics of these repeats are seen in the positioning of sequence matches between transfer and ribosomal RNAs. Conservation of the positions of the matches is indicated by persistence of a periodicity in their spacings along the molecules. Selection is viewed as a vector, with a source and a focus. The evolutionary progression entails shifts in the source of selection, from external catalysts to the replicating molecule itself, and in its focus, from substrate to replicator, to the products of the replicator's activity. When the source and focus of selection are the same selection becomes internalized, and replication and Darwinian evolution follow. Catalytic specificity is regarded as an antecedent to natural selection. Shifting of the source and focus of selection and switches in evolution's 'vehicle', the most fundamental thing that evolves, result in profound changes in the modes of evolution. Control provides a conceptual framework within which entry into a Darwinian mode of evolution, and ultimately liberation from Darwinian evolution might be explained.

Biological Evolution↗
PubMed2005

Estimating position and velocity of a submerged moving object by the clawed frog Xenopus and by fish--a cybernetic approach.

The lateral-line system is a unique facility of aquatic animals to locate predator, prey, or conspecifics. We present a detailed model of how the clawed frog Xenopus, or fish, can localize submerged moving objects in three dimensions by using their lateral-line system. In so doing we develop two models of a slightly different nature. First, we exploit the characteristic properties of the velocity field, such as zeros and maxima or minima, that a moving object generates at the lateral-line organs and that are directly accessible neuronally, in the context of a simplified geometry. In addition, we show that the associated neuronal model is robust with respect to noise. Though we focus on the superficial neuromasts of Xenopus the same arguments apply mutatis mutandis to the canal lateral-line system of fish. Second, we present a full-blown three-dimensional reconstruction of the source on the basis of a maximum likelihood argument.

Animals↗
PubMed1984

Paradox in psychotherapy: a cybernetic perspective.

Recent uses of the term "paradox" in the field of psychotherapy have distracted attention from the concept's broader implications. All therapy can be seen as paradoxical because of the recursive nature of self-evaluation. Using agoraphobic problems as illustrative, and starting from the notion that the core issue for the agoraphobic is a demand for absolute control of his environment, we argue that therapy requires the bonding of two observers--the therapist and the "client-as-observer". Negotiations issuing from this bond are crucial to outcome, even when behavioral techniques, often considered to have automatic effects, are used. Behavior therapy, like all other psychotherapy, is not simply action--it is action contextualized by a specific, negotiated social contract.

Agoraphobia↗