At the roots of neuro-psycho-physiology

At pre-Socratic times, questions about the nature and the way the psyche acts upon the body formed the core of ideas, from which the first phylogenetic seeds of future neuro-psycho-physiology started to grow. At first, these ideas took the form of platonic dualism, giving emphasis on the rational psyche, residing in the brain. In the Aristotelian cardiocentric conceptual scheme, the vital pneuma is conducted by the blood vessels to the various organs, activating their psyche, in the sense of their inherent propensity for action. With Galen, the brain becomes once again the central organ of perception; the psychic pneuma, formed inside the brain, is conducted along the nerves to the periphery. These concepts will prevail until the development of the Cartesian mechanistic model, in the 17th century; according to the latter, large blood particles serve to nourish the brain, whereas finer ones are transformed into animal spirits, which flow through the hollow nerves, conducting impulses to the periphery. During the 18th century, Haller's concepts of excitability and sensibility as properties of living organisms coincide with an increasing interest in electricity. The advances in physics will mark the whole century: Bertholon introduces the notion of “animal electricity”, which does not yet constitute an elaborated theory. The deficiencies will be met by the methodical investigations of Luigi Galvani. Based on the hallerian concept of irritability, as well as his famous experiments with frogs, Galvani creates a theoretical model, according to which animal electricity is accumulated in the muscles, whereas the nerves have merely a conductive function. These new ideas represent a great advance for a time when the concepts of the cell and the cellular membrane had not yet been developed, however, they will be disputed, particularly by Alessandro Volta. The latter vividly questions the existence of a natural electrical disequilibrium: his experimentations will be structured on a different basis and will result in the invention of the voltaic pile, the huge success of which will lead to the temporary abandonment of electrophysiological research. Research in this area will revive in the mid-19th century, mainly through the works of Emil du Bois-Reymond, who will present significant evidence in favour of the view that the neural conduction is electrical in nature. Moreover, his theoretical model of electrical molecules closely resembles the modern theories of neural conduction, these are actually based on Berstein’s concept of injury currents, but they only attained their final form in the 20th century through the investigations of Hodgkin, Huxley and Katz, as well as that of later researchers.

Key words: History of neuroscience, electrophysiology, neuro-psycho-physiology, animal electricity, Plato, Aristotele, Galvani, Volta, du Bois-Reymond.