Systems Neuroscience Pt. 1: A Brief History of (Almost) Everything
Preface
It’s been a year since I’ve written an article. Up to date, I’ve only published articles on topics relating to technologies such as artificial intelligence, but I’ve decided to write about all things that interest me.
So, this will be a two-part series on systems neuroscience examined through the lens of brain disorders. I hope you enjoy this recap of some of history’s most influential neuroscientists and their discoveries and look forward to next week’s article (which I’ll discuss in the conclusion).
Phrenology (Franz Gall)
Developed in 1796, phrenology was one of the earliest forms of brain mapping that we know of. Essentially, Gall found different “archetypes” of people (e.g. priests, criminals, intellectual professors, etc.) and tried to deduce the differences in their mental traits by feeling the outside of their skulls. For example, if Gall found that the top of criminals’ skulls tended to abnormally protrude (compared to those who had never committed a crime), he would ascribe the top of the brain to man’s moral compass. Using this method, he created a generalised “map” of the brain, ascribing different parts of the brain to different mental traits like ambition, self-reflectiveness, and more.
Of course, we now know this method of brain mapping is almost complete bogus, so this section serves as more of an interesting tidbit of history than anything else.
Cytoarchitecture (Korbinian Brodmann & Santiago Ramón y Cajal)
Korbinian Brodmann
Next comes cytoarchitecture, a much more accurate method of studying the brain’s structure developed around the early 1900s in particular. Brodmann examined the brain tissue of people who had died under a microscope, allowing him to map out the brain much more effectively than predecessors like Gall. He carefully mapped out the number of cells in different parts of the brain, how densely these parts were connected, and what the different layers of the brain looked like. Most notably, however, Brodmann defined 52 distinct brain regions in the Brodmann areas.
It turns out his drawings were quite accurate: the Brodmann areas are still used to identify different parts of the brain to this day. For example, we know Brodmann area 17 to be located in the occipital lobe. However, despite highly accurate mapping of the brain's physical architecture, Brodmann never addressed the function of these different parts.
Santiago Ramón y Cajal
Ramón y Cajal got even more detailed than Brodman and examined individual cells under a microscope. Rather than creating a generalised system to map out the brain, Ramón y Cajal mapped out individual cells and cell types. Again, he was highly detailed and accurate, and his drawings are still referred to when discussing the anatomy of cells in the brain to this day. However, like Brodmann, Ramón y Cajal abstained from addressing the function of the parts of the brain.
Functional mapping (Pierre Broca, Gustav Fritsch, Eduard Hitzig, Wilder Penfield, & Tatsuji Inouye)
Pierre Broca
Broca was the first to notice that distinct parts of the brain serve distinct functions. As stated in the title, much of neuroscience was made possible due to the study of brain disorders. During the mid-1800s, Broca studied patients who had had strokes in a certain part of the temporal lobe; every patient that had had a stroke in this part of the brain lost the ability to speak. Broca thus concluded that this area of the brain was responsible for speech. This conclusion proved correct, and we still refer to this area of the brain as “Broca’s area”. Patients with strokes in Broca’s area are also referred to as having “Broca’s aphasia”.
Gustav Fritsch & Eduard Hitzig
Fritsch and Hitzig built upon Broca’s work by electrically stimulating different parts of a dog’s brain and seeing how it would react. Specifically, they determined the function of the primary motor cortex; they found that by electrically stimulating different areas on this strip of brain matter, they could elicit certain movements.
Wilder Penfield
Similarly, Penfield electrically stimulated the brains of epilepsy patients to localise where these seizures were occurring. At the same time, he noticed that by stimulating a certain part of an area of the brain known as the somatosensory cortex, he could elicit feelings in certain body parts. Note that this differs from the primary motor cortex, as the primary motor cortex elicits movements while the somatosensory is responsible for receiving and processing sensory information.
Tatsuji Inouye
While the neuroscientists we’ve talked about so far mapped out areas of the brain responsible for physical movements and feelings of the body, Tatsuji Inouye did most of his work on an area of the brain responsible for vision, known as the occipital lobe.
Inouye’s story is especially interesting: as an army physician, he was able to figure out the mechanisms of vision by looking at different patients from the Russo-Japanese war. This war was the first time soldiers used a specific type of gun loaded with a specific type of bullet that would leave a discrete lesion on other soldiers’ helmets. This meant that when such bullets came into contact with the heads of soldiers, they would cause damage to very specific parts of the brain, whereas larger bullets would have destroyed much larger areas. Coincidentally, many of the injuries that Inouye treated were injuries to the back of the head, which housed the occipital lobe. When certain parts of the occipital lobe were damaged, soldiers would lose sight in parts of their fields of vision. Using this knowledge, Inouye carefully mapped out which parts of the occipital lobe were linked to which parts of one’s field of vision.
Conclusion
Above is a brief recap of some of the most important developments in systems neuroscience history. Again, this is the first part of a two-part series, and the next article I’ll release will be a comprehensive breakdown of the different parts of the brain and how they work together to help us function.
As seen in this article, brain disorders have been fundamental in furthering our knowledge of the brain’s inner mechanisms. This idea will be further explored in part two of this series, so please look forward to that sometime next week. Thanks for reading!
If you have any questions or would like to connect, feel free to email me at: alexander.chow911@gmail.com
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