Mes chers camarades, bien le bonjour! If you were shown this emoji, you'd immediately recognize the iconic organ of thought: the brain. But how long have we known what it looks like and what it does? After all, for millennia, we didn't go around opening people's skulls, unless it involved some weaponry, and even then, there wasn't much to analyze! Plus, we had no clue that pain felt in our hands or feet was actually created by the brain. But are you even sure you're up to date on this? Does a brain really look like that? Luckily, for this episode, we have a partner at the forefront of research in this field: CEA. In fact, we even made a Nota Bonus episode to narrate the history of CEA, which involves Marie Curie, espionage in Norway, and fighting against the Nazis – it's quite the story, so don't forget to check it out after this episode.

From This to That: Evolution of Brain Knowledge

It took quite a while for us to go from this... to that! Today, thanks to comparative anatomy, we know a lot about our brains, but it's quite challenging to comprehend it when you put it next to the scattered network of a jellyfish, the starfish's ring, the mushroom-shaped ganglion of insects, or the cartilage-encased lobes of an octopus. However, when we compare ourselves to other vertebrates, it suddenly becomes much clearer. You see, we all have a Central Nervous System, composed of two parts: first, there's a long hollow spinal cord protected by vertebrae. And then, there's a big bulge at the end of this tube – a series of cavities surrounded by nervous tissue. They are folded, compact, and enclosed in a little box formed around them to protect them; that's what we call the bony skull. In essence, we have something like a "carnival balloon." It's the brain: all vertebrates have one, whether you're a human, a cat, a rhinoceros, or a chicken. There's really not a significant difference.

At this point, you might think, "I just got a mini biology lesson," but don't worry; it'll be over soon. These cavities and the spinal cord canal are filled with fluid. So, to remember: when we draw a brain, we're only depicting part of a system that actually occupies a significant portion of our body, along with the spinal cord, our eyes, and the entire peripheral nervous system. We can thank modern science for this understanding because back in the prehistoric era, they probably didn't know all of this!

Unraveling the Brain's Secrets Throughout History

Believe it or not, most prehistorians believe that some people of that time may have had an inkling of what a brain could look like! How, you ask? Through trepanation, the process of drilling a hole in the skull to treat an ailment. Considering the time it took to bore through such hard bone, one can bet that the person doing it took a moment to peek inside. Back then, they used flint tools for trepanation! If it sounds medically questionable or downright gruesome, rest assured that there is evidence of patients who survived such operations and healed. This practice still exists today, particularly when it comes to brain surgery for tasks like removing hematomas or tumors. But don't worry; they don't use flint anymore! Another widespread prehistoric practice was cannibalism, and when you dine on your fellow humans, you don't leave the brain and spinal cord behind. They're quite tender and tasty. "Tell me what you eat, and I'll tell you who you are" – well, in this case, that saying is quite literal!

During the prehistoric era, there's no evidence of artistic representations, such as statues or cave paintings, depicting the brain. They knew about it, but to what extent remains uncertain. It wasn't until the emergence of written language that the first descriptions of this organ came about, particularly in the form of hieroglyphs. For example, the famous Edwin Smith Papyrus, dating back 1500 years before our era, is considered the oldest surgical treatise ever discovered. It contains symbols like these – which don't make much sense when translated into emojis. In plain French, it roughly means "brain." The papyrus also lists traumatic war injuries, including a case of an injured individual with an open skull who felt pulsations and palpitations when their exposed brain surface was touched. The author witnessed the removal of the skullcap and likened the brain to "folds similar to those forming on molten copper." So, you might be thinking, "Did the Egyptians identify some brain functions?" Well, maybe, but they didn't really care. For them, the soul resided in the heart, and during mummification, along with other organs, the heart was meticulously removed and preserved in a fancy canopic jar. As for the brain? Well, they removed it through the nose! With a spoon, they sucked it out, and then they discarded it. That's how little they cared! This situation didn't improve much during antiquity, especially among the Greeks.

Ancient Debates on Brain and Heart Dominance

In antiquity, dissections were performed, often with trephination, which provided a fairly precise understanding of the brain. They could distinguish between the two hemispheres, meninges, and nerve roots. However, between the 5th and 4th centuries BCE, a debate raged between two schools of thought. On one side were the cerebrocentrists, such as Alcmaeon of Croton and Hippocrates of Kos, who believed that the brain was the central organ of thought. On the other side were the cardiocentrists, like Aristotle, who thought the Egyptians were right, and that the heart was the key. For them, the brain was just a cold, wet organ – essentially, a cooling system for the body, lowering blood temperature and inducing sleep. Quite the opposite of our modern complaint about thoughts racing in our brains when we can't sleep! Nevertheless, a physician named Claude Galen of Pergamon would later challenge this perspective. Galen treated several Roman emperors and numerous gladiators. After studying their injuries, he became convinced of the brain's essential role in thinking and hypothesized that nerves were hollow tubes through which a psychic pneuma fluid flowed, particularly in the brain's ventricles. However, Galen found himself somewhat isolated in this view, as the cardiocentrists eventually prevailed. Aristotle's doctrine held firm, with minimal serious questioning, until the Renaissance.

The Middle Ages didn't witness significant advancements in brain anatomy due to religious prohibitions on dissection by the Church. But it wasn't just for religious reasons; there were also philosophical, technical, ethical, and prophylactic concerns, meaning they wanted to prevent diseases. Dissection was deemed useless, difficult to perform, sacrilegious, and posed a risk of deadly infections from cadaver manipulation. The few violations of these rules barely revealed that the brain was akin to intestines. These observations reinforced the idea that the brain certainly didn't contain the human mind. A few rebels, however, continued to promote Galen's ideas in