Information Handling in the Nervous System: An Analogy to Molecular-Genetic Coder-Decoder Mechanisms

INFORMATION HANDLING IN THE NERVOUS SYSTEM: AN ANALOGY TO MOLECULAR-GENETIC CODERDECODER MECHANISMS BERNARD L. STREHLER* Pattern recognition and appropriate response appear to be the common elements in all adaptive behavior ofliving systems. Ifthe responses elicited by a patterned input impinging upon such a system result in an increase in the probability that the responding organism will transmit its genes to descendants and they to theirs et sequitur, those genes and gene combinations which enable their carriers to meet these response requirements most adequately will tend, in competitive natural environments, to be selectively perpetuated—a restatement of the Darwinian evolutionary dogma. The nature ofthe patterned input to a system is by itselfnot the relevant parameter. Rather, the relationship ofinput patterns to possible alternative responses is the key element in such evolutionary interactions between organism and environment. This relationship is usually incorporated into the genome ofa living system in the form ofsome kind ofcomplementarity between an internal pattern1 (structure) and the patterns imposed * Department ofBiological Sciences, University ofSouthern California, Los Angeles, California 90007. 1 wish to thank ProfessorsJacek Szafran, Bernard C. Abbott, John Petruska, and Dr. Edwin Perkins for perceptive criticisms and comments during the preparation ofthis manuscript. A portion ofthis work was carried out with support derived from National Science Foundation grant GB-7493 and Atomic Energy Commission contract AT(n-i)-ii3 PA 20. 1 A pattern is defined as an improbable regularity, either in the arrangement ofobjects or in the time order ofevents. Because of the natural decrease in order which results fiom the operation of thermodynamic principles, as time passes, pattern (order) will decrease in any closed system unless potential energy is expended to generate or maintain such patterns within a system. The presence ofpattern is determined experimentally by comparing the linear distances between elements (objects) or the time distances between events. Unrigorously stated, if the measurements obtained exhibit a higher frequency ofcertain numerical values than ofothers (that is, ifthe numbers are not random), then one may conclude that a pattern exists, spatially or temporally, as the case may be. Most important , the observation ofany regularity or pattern within a given randomly selected part ofa system makes it more highly probable that a similar pattern will be encountered in an adjacent part ofthe 584 Bernard L. Strehler · Information Handling in the Nervous System Perspectives in Biology and Medicine · Summer 1969 by the environment. Further, such complementarity, by virtue ofdirect or indirect interaction between environmental patterns and internal patterns , increases the probability that the system will do work directed to the "selected" objective, the long-term survival ofthe line. Such complementarities are encountered in various forms at all levels of biological organization and function. At the level of DNA-RNA function, it is the complementarities between purine and pyrimidine base structures which determine the kinds of DNA and RNA molecules that will be synthesized under the influence ofthe template pattern [l]. At the level of tRNA amino acylation, it is the complementarities existing among the structures of the tRNA molecules, the acylating enzymes , and the appropriate amino acids that regulate the specificity ofthe tRNA charging reactions [2]. At the level of enzymatic catalysis, it is primarily the complementarity between the tertiary structure of the enzyme and its substrate that selectively accelerates given reactions [3]. At the level of adaptive enzyme formation (e.g., Operon model and allosteric modulation ofenzymes), it is the complementarity between the repressor and inducer (or allosteric agent and enzyme) which yields information that confers a capacity for an adaptive response that furthers survival [4]. These and many other stereotyped responses ofliving systems to patterned inputs have been directly incorporated into the genes ofall living systems. However, as sensory receptors evolved (sensory receptors are, of course, another kind of system in which complementarity between input and internal patterns elicits a specific output), particularly those subserving the detection of events at a distance, patterned information, whose accurate interpretation has survival value, became more and more available and complex in its form. Consequently, the ordinary trial-anderror regimen which operates in the genetic fixation of stereotyped response became inadequate to provide optimum adaptation (and rate of adaptation), except in highly restricted environmental niches. This fact conferred particular...