Two sides of reflex: Pavlov’s and Sherrington’s branches of reflexology

Pavlov started using the term “conditional reflex” in 1903, more than a half a century before the term “neuroscience” appeared. By that time such basic concepts concerning the body / mind problem already existed as “blood-brain barrier" by M. Lewandowsky, membrane theory for cells by J. Bernstein, and cytoarchitecture of anthropoid cerebral cortex by A.W. Campbell.

Developing the theory of conditioning, Pavlov inherited ideas and elaborations of notable Russian physiologists, among which were Vladimir Bechterev and Ivan Sechenov.

Sechenov was the first person to appreciate the significance of inhibition and reflex action. During work in Germany and France Sechenov showed that by placing salt crystals in certain parts of a frog’s brain he could reversibly inhibit its leg-withdrawal reflex. He returned to St. Petersburg and in 1863 published a major classic “Reflexes of the Brain”. In it he suggested that thinking is based on reflexes within the brain and mental activity has to be considered as a subject of experimental investigations.

Sechenov's description of reflex had begun to diverge from Descartes' notion of simple fixed “reflections” of stimuli. First, Sechenov suggested that the strength of stimuli and the responses they elicited need not be similar - very weak stimuli might trigger quite intense reactions. Second, Sechenov suggested that reflexes are ubiquitous and flexible, for example, he suggested that, as it was his habit to think of politics before going to bed each night it might happen that if he were to lie down in the daytime the properties of his bedroom might elicit thoughts of politics in him. Sechenov felt that inhibition played a significant role in both of these extensions of Descartes' concept of the reflex. Having demonstrated the existence of centrally mediated inhibition of reflexes, however, Sechenov did not go on to test these later inferences. Sechenov’s pioneering work in the field of reflexes led him to the hypothesis that the psyche was actually a function of the brain and that psychical activity can be explained by reflex activity, either innate or learned.

Another famous Russian physiologist and physician, Sergei Botkin, who had accompanied Sechenov on some of his studies in Germany, became Professor of Clinical Medicine at the Military Medial Academy in Moscow where he maintained an animal laboratory for the experimental study of physiology. In 1878, Botkin appointed a highly recommended young physiologist from St. Petersburg, Ivan Pavlov to be its director. Pavlov transformed Sechenov's theoretical attempt to discover the reflex mechanisms of psychic activity into an experimentally proven theory of conditional reflexes.

V.M. Bekhterev was interested in the study of conditioning, under the terminology of associative reflexes. After graduating in 1878 he held a position at the psychiatric clinic in St. Petersburg. He was then awarded a fellowship to study and conduct research abroad. In 1884-1885 he worked with Wilhelm Wundt who is generally acknowledged as the founder of experimental psychology, and the psychiatrist and neurologist Paul Emil Flechsig in Leipzig. In 1895 he returned to Russia to become professor of psychiatric diseases at the University of Kazan. At Kazan he established the first laboratory for research on the anatomy and physiology of the nervous system. In 1907 he established a psycho neurological institute with his own means. This later had subsidiary institutes and was made into the State Psychoneurological Academy. Bekhterev served as the institute’s first director even after he was forced to resign his medical school appointment under governmental pressure in 1913, and he founded the State Institute for the Study of the Brain, which today bears his name, also in St. Petersburg.

Bekhterev was an academic competitor and faculty colleague of Pavlov, with whom he was frequently in open conflicts at meetings and there was much acrimonious debate between workers from his laboratory and those from Pavlov’s. Bekhterev’s work and theories were published as seven-volumes “Foundations of Knowledge About the Functions of the Brain”, in Russian in 1903 – 1907, and later in German, French and English. His 3-volumes “Objective Psychology” was published in Jena, in 1907-1912 (see: Bekcheterv, 1926, 1928 (1973); V. M. Bekhterev's Collective Reflexology translated and published in 1994). Bekhterev’s fundamental books about mind and life moved many scientists in Russia to investigate mental processes. In particular, his books inspired a young student of Moscow University, Nadezhda Ladygina, to ask herself a question: at what level do living creatures start to possess consciousness? This became the central research problem in her life and generated many impressive results obtained on wolves, birds, as well as on a chimpanzee and a child of her own (see details in Chapters 15, 16).

It is worth to note that Bekhterev diagnosed Stalin as suffering from " grave paranoia." A couple of days after he had visited the Kremlin he suddenly died.

Another branch of reflexology, based on ideas of associations between neurones, was elaborated by the most notable nerve physiologist of the time, Charles Scott Sherrington (the Noble laureate of 1932). Sherrington, eight years younger than Pavlov, was introduced to the neurology through histology. He studied neurophysiology with Santiago Ramon Y Cajal, who shared with Camillo Golgi the Nobel Prize in 1906 for their work on the structure and function of nerve cells. Sherington’s research focused on individual neurones, on the base of which all reflexes really act. At this background he studied spinal reflexes as well as the physiology of perception and reactions and arrived to the theory of the synapse. Sherrington concentrated on studying peripheral nervous system, in particular, on the efferent nerve supply of muscles. He was also studying the connection between the brain and the spinal cord by way of the pyramidal tract. In 1897 Sherrington introduced the term “synapse”. After series of papers, in 1906 he published the book “The Integrative Action of the Nervous System”, which was considered the landmark in physiological studies.

Studying the salivary reflexes in dogs, Pavlov was basing on Sherrington’s investigations of the pyramidal tract. He sought analogies between the conditional reflex and the spinal reflex. According to 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.

With E. Adrian, Sherrington is often referred to as one of the founders of modern neurophysiology, while Pavlov, with his discovered elemental units of behaviour as conditional reflexes, became one of the fathers of behaviourism. Pavlov enriched this branch of behavioural sciences by the main idea that physiological methods could be used to study psychological phenomena and that these phenomena must be described and explained in physiological terms if they are to be understood.

Although Pavlov’ work contradicted with some ideas concerning processes of central inhibition, the two great physiologists maintained scientific contacts. Sherrington visited Pavlov’s laboratory in St. Perersburg in 1916, and Pavlov visited Sherington in 1928.