The problems of the age-linked and comparative physiology of the central 

 nervous system were of great interest to such prominent representatives of 

 Pavlovian physiology as L. A. Orbcli (1933-1955) and K. M. Bykov (1946- 

 1949), 



I. P. Pavlov, on the basis of the "mean" results of many investigations 

 noted a "natural decline of the stimulation process" in old age. The inhibition 

 process suffers to an even greater extent: "With aging, there is first a weakening 

 of the inhibition process, and then the mobility of the nerve process suffers, 

 with an increase in inertia." He formulated his views as to senile changes in 

 higher nervous activity in more detail, in the following manner: "... On the 

 basis of all the material at our disposal, we can say that the inhibition process is 

 the first to succumb to old age, and after this, it would appear that the mobility 

 of the nervous processes is affected. This is evident from the fact that a large 

 percentage of our aging dogs ceased to tolerate the previous more complex 

 conditioned-reflex system. The responses become chaotic, the effects fluctuate 

 in an entirely irregular fashion, and good results can be obtained only by sim- 

 plifying the scheme. I think that this can very legitimately be ascribed to the 

 fact that mobility decreases with the years. If we have a distinct effect in 

 a large system, this means that one stimulus does not interfere with another and 

 does not spread its effect to the next nerve process. When a nerve process is 

 delayed, however, the remaining traces of each stimulus become prolonged and 

 influence the succeeding ones, i.e., we have a chaotic state and confusion." 

 (Pavlovian Environments, vol. 2, pp. 121-122, Izd-vo AN SSSR, M.-L., 1949). 



In addition to this, I. P. Pavlov's pupils established cases of exceptionally 

 long maintenance of full higher nervous activity (as, for example, in the case of 

 the dog Postrel in Fedorov's experiments.) 



In her extensive experiments on the nervous systems of dogs aging under 

 various conditions of functional stress, M. K. Petrova established the very great 

 significance of the preservation of the nervous system in longevity. As a result 

 of this, Petrova is inclined to regard a progressive weakening of the nervous 

 system as the principal cause of the age-associated changes in the organism: 

 ". . . In our dogs, we were able to observe both normal physiological and 

 pathological old age. Our experimental findings indicate that the major and 

 leading role in the process of aging of the organism is played by the central 

 nervous system, and particularly by the cerebral cortex and the other systems 

 associated with it." (On the Role of the Functionally Weakened Cerebral 

 Cortex in the Genesis of Various Pathological Processes in the Organism, 

 Medgiz, L., p. 70, 1946). 



Having indicated that there can be no doubt of the great significance of 

 the nervous system for the organism as a whole and for its age-linked changes 

 in particular, A. V. Nagorniy (1954) suggests that it may indeed be a major 

 factor in longevity. "It can be shown that of all the systems of the intact 

 organism (in the absence, of course, of pathological manifestations), the most 

 stable, the most plastic, the most intensely functioning and longest-lived is the 

 system of the cerebral hemispheres" (p. 26). 



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