Ivan Pavlov

Ivan Pavlov (born September 14 [September 26, New Style], 1849, Ryazan, Russia—died February 27, 1936, Leningrad [now St. Petersburg]) was a Russian physiologist known chiefly for his development of the concept of the conditioned reflex. In a now-classic experiment, he trained a hungry dog to salivate at the sound of a metronome or buzzer, which was previously associated with the sight of food. He developed a similar conceptual approach, emphasizing the importance of conditioning, in his pioneering studies relating human behaviour to the nervous system. He was awarded the Nobel Prize for Physiology or Medicine in 1904 for his work on digestive secretions.

Life

Pavlov, the first son of a priest and the grandson of a sexton, spent his youth in Ryazan in central Russia. There, he attended a church school and theological seminary, where his seminary teachers impressed him by their devotion to imparting knowledge. In 1870 he abandoned his theological studies to enter the University of St. Petersburg, where he studied chemistry and physiology. After receiving the M.D. at the Imperial Medical Academy in St. Petersburg (graduating in 1879 and completing his dissertation in 1883), he studied during 1884–86 in Germany under the direction of the cardiovascular physiologist Carl Ludwig (in Leipzig) and the gastrointestinal physiologist Rudolf Heidenhain (in Breslau).

Having worked with Ludwig, Pavlov’s first independent research was on the physiology of the circulatory system. From 1888 to 1890, in the laboratory of Botkin in St. Petersburg, he investigated cardiac physiology and the regulation of blood pressure.

He became so skillful a surgeon that he was able to introduce a catheter into the femoral artery of a dog almost painlessly without anesthesia and to record the influence on blood pressure of various pharmacological and emotional stimuli. By careful dissection of the fine cardiac nerves, he was able to demonstrate the control of the strength of the heartbeat by nerves leaving the cardiac plexus; by stimulating the severed ends of the cervical nerves, he showed the effects of the right and left vagal nerves on the heart.

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Faces of Science

Pavlov married a pedagogical student in 1881, a friend of the author Fyodor Dostoyevsky, but he was so impoverished that at first they had to live separately. He attributed much of his eventual success to his wife, a domestic, religious, and literary woman, who devoted her life to his comfort and work. In 1890 he became professor of physiology in the Imperial Medical Academy, where he remained until his resignation in 1924. At the newly founded Institute of Experimental Medicine, he initiated precise surgical procedures for animals, with strict attention to their postoperative care and facilities for the maintenance of their health.

During the years 1890–1900 especially, and to a lesser extent until about 1930, Pavlov studied the secretory activity of digestion. While working with Heidenhain, he had devised an operation to prepare a miniature stomach, or pouch; he isolated the stomach from ingested foods, while preserving its vagal nerve supply. The surgical procedure enabled him to study the gastrointestinal secretions in a normal animal over its life span. This work culminated in his book Lectures on the Work of the Digestive Glands in 1897.

Laws of conditioned reflex

By observing irregularities of secretions in normal unanesthetized animals, Pavlov was led to formulate the laws of the conditioned reflex, a subject that occupied his attention from about 1898 until 1930. He used the salivary secretion as a quantitative measure of the psychical, or subjective, activity of the animal, in order to emphasize the advantage of objective, physiological measures of mental phenomena and higher nervous activity. He sought analogies between the conditional (commonly though incorrectly translated as “conditioned”) reflex and the spinal reflex.

According to the English physiologist Sir Charles Sherrington, the spinal reflex is composed of integrated actions of the nervous system involving such complex components as the excitation and inhibition of many nerves, induction (i.e., the increase or decrease of inhibition brought on by previous excitation), and the irradiation of nerve impulses to many nerve centres. To these components, Pavlov added cortical and subcortical influences, the mosaic action of the brain, the effect of sleep on the spread of inhibition, and the origin of neurotic disturbances principally through a collision, or conflict, between cortical excitation and inhibition.

Beginning about 1930, Pavlov tried to apply his laws to the explanation of human psychoses. He assumed that the excessive inhibition characteristic of a psychotic person was a protective mechanism—shutting out the external world—in that it excluded injurious stimuli that had previously caused extreme excitation. In Russia this idea became the basis for treating psychiatric patients in quiet and nonstimulating external surroundings. During this period Pavlov announced the important principle of the language function in human beings as based on long chains of conditioned reflexes involving words. The function of language involves not only words, he held, but an elaboration of generalizations not possible in animals lower than humans.