The Discovery of Bioelectricity:

Brain Ventricles and Theories of the Mind

The ventricular system of the brain has been since its discovery divided into four, the two lateral ventricles, the third and connected by a small tube, the fourth. Herophilus placed the soul in the fourth ventricle and the "animal spirits" (intellectual, motor system) in the brain itself (cerebrum). Taking information available from Herophilus concerning the ventricular localization of the soul and the concepts elaborated by Galen, a doctrine emerged which explained the function of the mind. This "Cell Doctrine" localized the mind to the ventricular system of the brain. The two lateral ventricles were considered to represent the first cell, the third ventricle the second and the fourth ventricle the third. information was synthesized in the back part of the first cell or in the second cell to form imaginativa (imagination) and "fantasia" (fantasy). The second cell was also the seat of reasoning. Words used for function processing in this cell included "aestimativa" (judgement), "cognitativa" (thought) and "ratio" (reason). In the third cell, "memorativa" (memory) resided. In the 10th century, a new concept arose that there was a flow or a dynamic element to the process, starting in the first cell and terminating in the third. This conceptual model of brain function superimposed on the ventricular anatomy of the brain captivated the mind of Medieval thinkers and theologians. Many variations of this scheme were produced and manuscript drawings outlining the basic concepts of this model are plentiful.

Leonardo turned his attention to the exact location of the soul in the brain. A series of drawings exist which outline this quest. On a sheet from about 1487 clustered among a series of fourteen drawings are three which deal directly with the issue of cerebral localization (K/P 4r). In the central figure, the optic nerves converge on the anterior ventricle labeled 'imprensiva'. The olfactory and auditory nerves course towards the middle ventricle labeled 'senso comune' while the last ventricle contained the word 'memoria'. Leonardo has labeled the anterior ventricle 'intelletto' (intellect) and 'imprensiva'; the middle ventricle is labeled with the words 'volonta' (will) and 'senso comune' and the posterior ventricle with 'memoria' (memory). In this drawing, Leonardo associates intellect with the ventricle towards which the optic nerves run. Imprensiva, a term introduced by Leonardo and used only by him, denotes the concept that sensory information has a direct effect on intellect. 'Volonta' or will (voluntary motion or action) he places in the middle ventricle. Therefore, both sensation and action arise from the middle ventricle being influenced by intellectual input from the anterior ventricle and memory from the third ventricle. he applies his skills as a sculptor to more accurately model the shape of the ventricular system using the brain of an ox (K/P 104r). Leonardo injected wax into the floor of the third ventricle by using an injection syringe and made two "vent-holes" in the horns of the lateral ventricles to allow for escape of fluid. After the wax had set, he dissected away the brain leaving the cast of the ventricular system. He was left then with a relatively accurate model of the ventricular system on which he then located the 'imprensiva', 'senso comune' and 'memoria'.

Albertus Magnus, Philosophia pauperum. 1496.

Drawing by Leonardo da Vinci of the ventricle system of the brain

The  "pores" of the brain matter, connected to the ventricles, as imagined by René Descartes

Internet Resources

Renato M.E. Sabbatini, PhD
Brain & Mind Magazine
Copyright (c) 1998 The State University of Campinas, Brazil
Center for Biomedical Informatics

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