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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Physiology of higher nervous activity. History and essence of scientific discovery
Directory / The most important scientific discoveries The work of the brain for many years remained an unsolved mystery for humanity. Not only the clergy, but also scientists who professed idealism associated all mental processes in the body with a mysterious soul. The soul was a "forbidden place" for scientific research. For centuries, science has been dominated by dualistic ideas about the body and soul, the material and the mental, as two heterogeneous principles. The mechanistic views of materialist philosophers were considered the most progressive. The latter asserted that "thought is the secretion of the brain," that "the brain secretes thought in the same way that the liver secretes bile." The Russian physiologist Sechenov was the first who was not afraid to invade the complex world of the human psyche. His goal was to explain this world, to show physiological mechanisms, to prove the materialistic essence of human mental activity. Ivan Mikhailovich Sechenov (1829-1905) was born in a village in the Nizhny Novgorod province, where he spent his childhood. Then the boy was assigned to a military school so that he began to study as an engineer. In 1843, Ivan went to St. Petersburg, where in a few months he prepared and successfully passed the entrance exams to the Main Engineering School. However, Sechenov did not get along with his superiors and was not admitted to the senior class of the school to become a military engineer. With the rank of ensign, he was released and sent to an ordinary sapper battalion. Two years later, Sechenov resigned, left military service and entered the medical faculty of Moscow University. A thoughtful and diligent student, Sechenov initially studied very diligently. Interestingly, in his junior years, he dreamed, by his own admission, not of physiology, but of comparative anatomy. In his senior years, after becoming acquainted with the main medical subjects, Sechenov became disillusioned with the medicine of that time. Sechenov became interested in psychology and philosophy. In his senior years, finally convinced that medicine was not his vocation, Sechenov began to dream of physiology. After graduating from the course, Sechenov, among the three most capable students, passed not the usual medical, but more difficult - doctoral exams. Having successfully passed them, he received the right to prepare and defend his doctoral dissertation. After a successful defense, Sechenov went abroad "with the firm intention of studying physiology." From that time on, physiology became his life's work. Starting in 1856, he spent several years abroad, working with the largest physiologists in Europe - Helmholtz, Dubois-Reymond, Bernard. In the same place, he writes his doctoral dissertation - "Materials for the Physiology of Alcohol Intoxication", for which he puts experiments on himself! Returning to Russia, after defending his dissertation on March 8, 1860, he became a professor at the St. Petersburg Medical Academy. From the very beginning of his work at the Department of Physiology, Sechenov resumed intensive scientific research. In the autumn of 1862, the scientist received an annual leave and went to Paris. He was led to the capital of France by the desire to get to know the research of the famous Claude Bernard and to work in his laboratory himself. The most significant result of the research conducted by Sechenov in Paris was the discovery of the so-called central inhibition - special mechanisms in the frog brain that suppress or depress reflexes. Sechenov reported this in a work published in 1863, first in French, and then in German and Russian. In the same year, the Russian journal Medical Bulletin published Sechenov's article "Reflexes of the Brain". The scientist showed for the first time that the entire complex mental life of a person, his behavior depends on external stimuli, and not on some mysterious "soul". Any irritation causes one or another response of the nervous system - a reflex. Reflexes are simple and complex. In the course of experiments, Sechenov established that the brain can delay excitation. This was a completely new phenomenon, which was called "Sechenov's inhibition." “The path I have chosen to explain the origin of mental processes,” he wrote in the preface to a separate edition of Reflexes of the Brain, “if it does not lead to a completely satisfactory solution of the issues related to this, then at least it turns out to be fruitful in developing them. ... The time has already come when the voice of a physiologist can be useful in working out questions concerning the mental life of a person. The phenomenon of inhibition discovered by Sechenov made it possible to establish that all nervous activity consists of the interaction of two processes - excitation and inhibition. Sechenov experimentally proved that if a dog's sense of smell, hearing and vision are turned off, then it will sleep all the time, since no signals from the outside world will enter its brain. This article immediately, as contemporaries testify, became known in the widest circles of Russian society. "The thoughts expressed in the Reflexes were so bold and new, the naturalist's analysis penetrated into the dark realm of mental phenomena and illuminated it with such skill and talent that the amazing impression made by the Reflexes on the whole thinking society becomes quite understandable" - wrote a prominent Russian physiologist N.M. Shaternikov. “The most important thing in Sechenov’s teaching was that he considered the mental process as a reflex one in terms of the way it was carried out (origin), writes M.B. Mirsky in a book about the scientist. ended with a resounding success. Of course, Sechenov did not at all reduce the human psyche only to reflexes: the concept of "reflex" embraced only the general form and mechanism of mental processes. And the content of the psyche, the scientist argued, is a reflection of the objective world, a product of human cognitive activity. Having created the doctrine of the reflexes of the brain, extending the concept of a reflex to the activity of the higher department of the nervous system, Sechenov laid the foundation for the natural-scientific substantiation of the materialistic theory of reflection. His teaching was truly revolutionary. It was the basis of all subsequent development of the physiology of mental processes, the foundation on which the greatest achievement of science of the present century arose - the doctrine of I. P. Pavlova about higher nervous activity. The continuity of Sechenov's theory and Pavlov's teachings was repeatedly pointed out by both domestic and foreign physiologists, and first of all by Ivan Petrovich himself. In a speech on the occasion of the fiftieth anniversary of the publication of "Reflexes of the Brain", delivered on March 24, 1913, Pavlov said: "Exactly half a century ago (in 1863) the Russian scientific article "Reflexes of the Brain" was written, in a clear, precise and captivating form containing the main idea of what we are developing at the present time. What a force of creative thought was required then to give birth to this idea! And having been born, the idea grew, matured and has now become a scientific lever guiding the huge modern work on the brain. " In 1904, Pavlov was awarded the Nobel Prize for his work on digestion, and in 1907 he was elected a member of the Russian Academy of Sciences. At this time, the scientist carried out work on the physiology of higher nervous activity. At the institute, which was located not far from St. Petersburg, in the town of Koltushi, Pavlov created the only laboratory in the world for the study of higher nervous activity. Its center was the famous "Tower of Silence". It was a special room that made it possible to place the experimental animal in complete isolation from the outside world. While conducting his experiments, the scientist noticed that salivation in a dog can occur even in response to the steps of a person who brings her food at the same time. This means that the dog developed a conditioned connection between the sound of steps and receiving food. Thus, food is an unconditioned, innate stimulus that causes salivation. Steps are a conditioned stimulus. The connection itself, which is formed in the cerebral cortex, is called a conditioned reflex. A bell, light, heat, cold, and much more can serve as a conditioned stimulus. “Pavlov also introduced the concepts of lower nervous activity and higher nervous activity into science,” writes A.E. Asratyan. “How do these concepts relate to each other, whether lower nervous activity consists of unconditioned reflexes, and higher nervous activity consists of conditioned reflexes or the correlations between these concepts did not fit into such a simple formula?What brain structures are associated with these types of nervous activity? Pavlov's point of view on these rather complicated questions is summarized as follows. Higher nervous activity was understood by him as a mental activity and was defined as a reflex regulation of the relationship of the organism with its external environment, and lower nervous activity as a reflex regulation of its own intraorganismal relationships. The first ensures the precise, subtle and perfect adaptation of the body to the factors of the external world, to the ever-changing conditions of existence, ensures unity and continuous interaction with the external environment, and the second determines the internal consistency in the work of the organs and systems of the body, ensures its unity, harmonic integrity and well-coordinated flow. its manifold functions; which is also a necessary prerequisite for the successful implementation of his subtle relationships with the outside world. Pavlov wrote: “The activity of the cerebral hemispheres with the nearest subcortex, the activity that ensures the normal complex relations of the whole organism to the outside world, can legitimately be called instead of the former term “mental” - higher nervous activity, the external behavior of the animal, contrasting it with the activity of further sections of the brain and spinal cord, chiefly in charge of the correlations and integration of the parts of the body among themselves under the name of lower nervous activity. In one of his works, summarizing what was said on this fundamentally important issue, he notes: “I imagine the whole set of higher nervous activity, partly repeating what has already been said for systematization, so. In higher animals, up to and including humans, the first instance for complex relationships of an organism with its environment is the subcortex closest to the hemispheres with its most complex unconditioned reflexes (our terminology), instincts, drives, affects, emotions (various conventional terminology). Hence the limited orientation in the environment and, at the same time, weak adaptation.The second instance is the cerebral hemispheres, but without the frontal lobes.Here, with the help of conditional connection, association, a new principle of activity arises: the signaling of a few unconditional external agents by an innumerable mass of other agents, constantly together with themes analyzed and synthesized, giving the possibility of a very large orientation in the same environment, and themes already of much greater adaptation. In his writings, Pavlov also speaks of a third instance - a specifically human signaling system. With his "... research, Pavlov," notes E.A. Asratyan, "not only enriched the physiology of the central nervous system with the most valuable facts regarding the specific features of the qualitatively new and higher type of reflex discovered by him - the conditioned reflex, but also firmly established the fundamental for this important section physiology, the position that the development of heterogeneous and varied conditioned reflexes is one of the essential functions of the cerebral cortex of the brain, that these reflexes, as elementary mental acts, not only underlie simple and complex behavioral acts, but also constitute the main fund of the higher nervous, or mental activities of higher animals and man. As Pavlov wrote: "Thus, with the fact of a conditioned reflex, a huge part of the higher nervous activity, and perhaps all, is given into the hands of the physiologist." Author: Samin D.K.
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