The roots of Western brain research
ABSTRACT: In the 6th/5th century BC Greek thinkers began to question the validity of their prevailing allegoric worldview, seeking a rationalization of the world around them. Their search for the primordial substance that formed living creatures including human beings led to the concept that all living beings consist of a combination of four elements i.e. water, air, fire and earth.
Subsequently, these natural philosophers, joined by medical doctors, debated the relationship between the body and the soul-mind. Pretty soon the brain became special and the discussion which organ, heart or brain, was governing our body took off. For this presentation I selected some relevant ideas and data from ancient and more recent past that illustrate the development of Western Brain Research. It will become evident that this research did not proceed in isolation. In fact, on several critical moments the path of Western Brain Research crossed that of learned African and Asian philosophers, physiologists, anatomists and medical doctors.
In the heart vs brain discussion the position of Aristotle (4th c.) is remarkable. Based on the composing elements and their qualities he described the brain as a cooling device balancing the heat produced by the heart. Hence, he was the most powerful advocate of the ruling role of the heart. This so called hegemonikon debate was firmly closed by Galen (2nd, beginning 3rd c. AD), most likely, in modern terms, the first experimental and clinical neuroscientist. This physician, anatomist and philosopher was a giant who brought to a close the ancient Greek era of knowledge about the brain in order to spread new insights like a herald. Galen’s writings on the anatomy and physiology of the brain are high points in the history of Western Brain Research, and over a fifteen hundred years later his influence was still noticeable. He was the first to properly describe the brain cavities (ventricles) and his pneuma physiology concept was leading throughout the Middle Ages. Galen confirmed that the brain is the seat of cognitive functions but he was not clear about the localization of these functions within the brain, that is: in tissue or in ventricles. Later, unfortunately, influential writers who cited his work, such as St Augustine (4th/5th c.), implied that Galen advocated a strict ventricular localization. This notion is amplified by influential Arabic philosophers and physiologists (Costa ben Luca, 9th c., Avicenna, 10th/11th c.) who were also read in the Western world. Thus the ventricular notion dominated medieval thinking about the brain, often leading to absurd assumptions (f.i. Berengario 1521).
At the turn of the 15th to 16th c. Leonardo da Vinci became interested in the brain and he performed some unique experiments. However, as his data reached the public domain only as late as the end of the nineteenth century Leonardo had hardly any influence on the development of Western Brain Research. This does not hold for the Flamish anatomist Vesalius, working in Italy, who in his book De humani corporis fabrica (1543) refuted the medieval ventricle assumptions and concluded that the ventricles were but cavities containing liquor. Time for alternative approaches.
At around 1640 the French philosopher Descartes, for the first time, proposed a neural mechanism for memory consolidation, whereas the English physician and anatomist Willis (1664) related different brain regions to different cognitive functions. In the nineteenth century the ideas on tissue localization of brain function culminated in the phrenology as formulated by Gall (ca. 1800. – it became a public hype-), who proposed that manual inspection of the skull would provide information on the relative size of functional brain regions.
Eventually, the whole of Western Brain Research changes dramatically when by the end of the nineteenth beginning of the twentieth century it became clear that brain tissue consists of discrete cells and that neurones act in networks, in concert. Actually marking the beginning of modern Western Neuroscience.