[ intro ].

Back in World War One,. British soldiers wore a helmet called a Brodie helmet, which basically looked like an upside-down mixing bowl.

Any helmet is better than none, but this helmet in particular had some fatal design flaws, including the fact that it left the back of the soldier's skull completely exposed— right over the part of the brain responsible for vision. But similar-looking helmets were pretty common at the time, including in other countries and wars. And during the wars of the early 20th century, many soldiers were shot in the exposed area.

But in spite of the fact that they suffered irreparable brain damage, many of them lived —and went on to be treated and studied by doctors. Because of that, these injuries led to an enormous breakthrough in neuroscience — an accurate brain map of our sense of vision that's on par with the most sophisticated maps we can produce with modern technology. It might sound unusual that so many soldiers survived wounds like this, but that had a lot to do with another technology of war: bullets.

Towards the end of the 19th century , bullet designs went from round to cylindrical, and guns were able to shoot them at higher speeds. That meant they entered the body more cleanly. So instead of causing a bunch of peripheral brain damage like older bullets did, they often produced damage only in the specific region the bullet had passed through.

And because of the shape of helmets at the time, many of these gunshot wounds damaged the visual cortex, the area of the occipital lobe where we process vision. So, while many soldiers lived, they often lost some aspect of their vision. During the Russo-Japanese War in 1904 and ‘05, the Japanese doctor Tatsuji Inouye noticed that, in general, soldiers with these injuries weren't completely blind, even though many of them had impaired vision.

And after a while, he started to notice a pattern between where in the brain a soldier had been shot and the problems they had with their vision. Inouye decided to try and map out these connections. He invented a measurement tool called a cranio-coordinometer, which helped draw a straight line from the entry wound to the exit wound and approximate which brain tissues were affected.

Then, to figure out patients' symptoms, he had a target on the wall with four quadrants, and he tested the soldiers to see which regions were visible to them. In total, he studied 29 soldiers. And in 1909, he published a report with his findings.

Which were… surprisingly significant, considering that today, we're used to studying the brain with fancy, super expensive machines. In it, he identified the part of the brain responsible for seeing things at the center of your visual field, what's called foveal vision. He also reported that outside that region, the brain works to process things in your peripheral vision.

Inouye's work unfortunately didn't get a ton of attention at the time, but it did lay the groundwork for researchers who came after him. Notably, a few years later, in World War One, an Irish physician named Gordon Holmes built on Inouye's work with new data from the soldiers he treated. Holmes placed a circular map on the wall and had soldiers report which part of it they couldn't see anymore.

And like Inouye, he noticed that his patients' pattern of blindness seemed to be linked to the location of their injuries. Over time,. Holmes worked with a few other doctors to gather enough reports to draw a map of the brain.

Holmes' map expanded on the one Inouye had made and included more detail about how the brain processes information in the center of your visual field. And researchers found it nice and accessible. So, before long, it was pretty popular.

I mean, as far as maps of the brain go, anyway. In addition to the map,. Holmes also wrote detailed reports about some phenomena that he didn't entirely understand at the time.

For instance, one patient had trouble keeping his eyes fixed on moving objects. He also didn't have a blink reflex, and he couldn't reach out and touch objects precisely, even though he could see them. Holmes didn't know exactly what to make of that, but he wasn't the only one seeing cases like this.

A Scottish physician named George Riddoch, who was working with soldiers around the same time, recorded some similar cases. For instance, he described how some patients could detect motion, but had lost the ability to see discrete shapes and colors. So they were basically blind, but they could see things if they were moving.

As a result, Riddoch suggested that the visual cortex didn't just process different regions of sight, like foveal or peripheral vision, but completely different aspects of sight. In other words, things like motion, shape, and color all seemed to be linked to different parts of the brain. Which is kind of amazing when you consider how unified all those aspects of vision seem when you see, say, a car drive by.

This concept is called functional partitioning. And today, we know it's a major factor in how the brain processes all our senses. But at the time, it was a pretty radical idea.

Even Holmes, who'd done all that work mapping the brain, didn't accept Riddoch's conclusion that things like shape and color were separate in your brain. But Riddoch was right, and his findings gave us a huge new insight into how the brain works. In fact, the precise maps all these wartime doctors made kicked off even more research to learn how the rest of the senses— like smell, touch, and hearing— are processed in the brain, especially as better technology became available.

And what's bonkers is that in spite of today's cutting-edge technology, our modern map of vision is not much better than the one those 20th-century doctors made with pencils and paper. Thanks for watching this episode of SciShow Psych! And a special thanks to our patrons on Patreon, who make it possible for us to create episodes like this.

Everything you contribute goes toward making science education free on the internet, and we couldn't do it without you! If you're not a patron but want to learn about supporting SciShow, find out more at patreon.comSciShow. [ outro ].