Alcmaeon: Pioneer of experimental Brain Research

Some may rub their eyes in amazement, but the history of scientific brain research actually began with the ancient Greeks. Specifically, in the 6th century BC. At that time, the Greek natural philosopher Alcmaeon of Croton emphasized the crucial role of the brain in human cognition: "It is the brain that allows the perceptions of hearing, seeing, and smelling; from these arise memory and imagination, but from memory and imagination, when they have settled and come to rest, knowledge is formed."

This may sound obvious to us today, but at that time it was by no means so. After all, there was a long-standing controversy in ancient times as to whether the brain or the heart was the seat of thought and feeling.

We know very little about Alcmaeon as a person: he lived in the late 6th and early 5th centuries BC and “was young when Pythagoras grew old.” He probably had a close relationship with Pythagoras, and both lived in Croton, today's Crotone – southern Italy was settled by Greeks at that time. Whether Alcmaeon was actually a Pythagorean cannot be proven conclusively. Like them, he believed in the immortality of the soul and the divinity of the stars. However, Pythagorean numerology does not appear in his work at all. There is little doubt, however, that he was a physician. And as such, he did groundbreaking work!

Alcmaeon is considered an anatomist from the very beginning. In ancient times, he was reputed to be the one “who first dared to perform a dissection.” At the very least, he experimented on dead animals and cut out their eyeballs. In doing so, he discovered the strands of the optic nerves that lead from the eye to the brain, which he regarded as hollow, “light-bringing” channels. For he describes the “two narrow paths that lead from the brain, where the highest and most decisive power of the soul is rooted, to the cavities of the eyes.”

Alcmaeon is thus not only credited with discovering the first cranial nerve in history: the optic nerve (according to anatomical counting, the II cranial nerve). He also recognized the brain as the central organ of all sensory perception. These, as Theophrastus quotes Alcmaeon, “suffered damage when this (the brain) was shaken and its position changed.” Alcmaeon's belief that the sense of smell came about because we draw the air we breathe up to the brain is not entirely correct, but it was astonishingly modern for its time.

Last but not least, Alcmaeon correctly recognized that a mechanical impact – a blow – to the eyes can lead to a visual sensory perception, to the perception of light effects, of photomes, or in everyday language: of “stars.” Alcmaeon himself stated that the “fire in the eye sparks.” With today's knowledge, this makes more sense than it did to the ancient Greeks – the visual cortex processes the impulses of the visual sensory cells in the only way possible.

Alcmaeon can therefore rightly be considered a pioneer of visual natural physiology. His findings were based not only on pure philosophical speculation, but also on empirical experiments.