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Born in modern day Teheran in 864, Rhazes wrote over 200 scientific articles, resulting in a large impact on the development of medicine in Europe.

These writings not only helped to further medicine and help those who are sick, but his findings helped to further neuroscience. In his manuscripts Kitab al-Hawi and Al-Mansuri Fi At-Tibb, Rhazes wrote the first description of neurons. He described 7 cranial nerves and 31 spinal nerves. He further classified the spinal nerves into 8 cervical, 12 thoracic, 5 lumbar, 3 sacral, and 3 coccygeal nerves.

Not only did Rhazes write the first description of nerves, he also stated that the nerves had different functions. Some being for motor and some being for sensory. This finding would launch a new field of neuroscience that looked at the neurons, not just the brain, and how they are used for communication.

Source:

https://pubmed.ncbi.nlm.nih.gov/16009898/

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2. The Finding of a Specific Neuro Pathway

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2. The Finding of a Specific Neuro Pathway

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Born in 1543 in Bologna, Constanzo Varolio was the first to describe a specific neurological pathway, specifically the optic nerve pathway.

Varolio was a neuroanatomist who decided to look at the brain in slices from the bottom up. While doing this, he made sure to take detailed notes of what he found. He named different structures including the pons, and the hippocampus, and he also found the optic nerve and wrote detailed descriptions of the path it took and what structures it went through.

In his book, De Nerves Opticis, Varolio drew detailed images of the neuroanatomy involving the optic nerve. He wrote descriptions of the different structures that it passed through, as well as where it ended. His work in this helped other doctors in Europe and neuroscientists further their education and help with the treatment of sick individuals.

Source:

https://link.springer.com/article/10.1007/s00381-017-3515-x

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3. The Localization Theory of Ventricles

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3. The Localization Theory of Ventricles

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In the dark ages, it became common knowledge that the brain is the control center of the body. However, despite findings of specific nerves and their pathways, people still believed that the soul of the body lived in the ventricles, giving the brain control of the body.

The localization theory of ventricles states that each ventricle is associates with a different type of function. Specifically, the front ventricle being in control of perception, the middle in control of cognition, and the posterior ventricle in control of memory. The idea of this, mainly coming from Galen's anatomical drawings.

Despite this knowledge being wrong, it did give idea to the accurate topic of localization of the brain. Certain areas being specialized for different functions. Think the occipital lobe being specialized for vision. With the idea of specialization present, neuroscientists were able to look for other areas of specialization in the brain.

Source:

https://pubmed.ncbi.nlm.nih.gov/12720323/

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Rene Descartes was born in 1596 in France. He studied math, philosophy, and psychology.

His ideas of neuroscience stemmed from Galen, the dark ages, as well as Vesalius. However, he held a strong belief in the idea of nerves being a pathway for animal spirits to travel through, giving power and control to the brain.

His spirit theory, would later give the definition of a reflex. He believed that each nerve contained filaments, which contained valvules which allowed for the control of the flow of the animal spirits.

His process went something like this, an external stimuli stimulated a nerve, the nerve would then have the valvules open in ventricles where the animal spirits would be released. The release of the animal spirits would then result in the reflex. This is also known as the reflex arc.

Descarts' ideas on the animal spirit action, helped for future neuroscientists find causes for reflexes, as they are not related to the brain but instead the spinal cord.

Source:

https://www.acsu.buffalo.edu/~duchan/new_history/early_modern/descartes.html

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Thomas Willis of Oxford was a neuroscientist who looked not only at anatomy, but the physiology of the anatomy. In the 1660s, Willis made many discoveries in neuroscience that would aide in the development of neuroscience.

The Circle of Willis was found by Willis in 1664, it is a junction of arteries at the bottom of the brain, helping blood flow to the front and back of the brain. This finding helped to refocus attention to the brain as a source of control. He also found the correct differentiations between the cerebral functions which include memory and perception, and the brainstem functions which including basic life functions such as breathing and a heartbeat. Willis also found the corpus striatum and how it relates to motor functions.

Most importantly, Willis had extremely detailed illustrations of his brain dissections, and his classification system for the cranial nerves. A classification system that is still being used today, and has helped thousands of neuroscientists in their research and furthering of neuroscience.

Source:

https://www.medicalnewstoday.com/articles/circle-of-willis

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Multiple Sclerosis, MS, is a chronic neurological autoimmune disorder that affects the entire nervous system. In 1868, Jean Martin Charcot gave a series of lectures describing MS and its effect on the nervous system. This was the first time that the nerves themselves were the focus of a neurological disease, rather than a lesion of a brain structure.

Charcot found that in those with MS, they showed both physical symptoms, tremors when moving as well as visual and sensory problems, in addition to problems seen via autopsy. In autopsies of those who had passed with MS, Charcot found that the myelin sheaths had thinning or complete loss, which led to the buildup of plaques forming around the axons of the nerves.

The description of the nerves of those with MS helped doctors come up with possible solutions to be able to treat MS. And while there is no cure currently, we have been able to find ways to lessen the symptoms all thanks to the work of Charcot. He laid the groundwork for looking at individual neurons to see if they have any abnormalities as a cause or result of a disease.

Source:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6262215/

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6. Confirming the Presence of Electricity in Nerves

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6. Confirming the Presence of Electricity in Nerves

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In the late 18th century, neuroscientists were beginning to think of ways that neurons communicated with each other. Animal spirits and blood were out of the question, and the idea of electricity was beginning to be talked about.

In the 1780s, Luigi Galvani conducted a series of experiments on frog legs using electricity. He severed the frog legs at the base of the spine, ensuring that the nerves were still exposed. When the nerves were given a jolt of electricity, the leg would contract or extend, performing a reflex.

Scientists began to understand that the electricity was inherent in the animal itself, much like a Leyden jar. It was observed that a sort of circuit was formed from the nerves to the muscles which produced electricity, which resulted in the movement of the frogs leg. The finding that electricity was already present in nerves as it came from within the body, helped other neuroscientists with their findings of neurons.

Source:

https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/frogs/frogs-and-animal-electricity

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In 1944, Joseph Erlanger and Herbert Spencer Gasser earned the Nobel Prize for Physiology and Medicine for their findings of differentiated functions of single nerve fibers.

The pair found that different types of nerve fibers served different purposes. Type A fibers are subdivided into four categories: Aα (motor to skeletal muscle), Aβ (cutaneous touch and pressure), Aγ (motor to muscle spindle), and Aδ (Cutaneous temperature and pain). Type B nerve fibers are sympathetic preganglionic and type C are cutaneous pain afferents and sympathetic postganglionic.

The finding that there is more differences to neurons other than just sensory or motor allowed for other neuroscientists to realize that there is an importance of specialization for function for not only brain structures, but for the neurons themselves.

Source:

http://doccdn.simplesite.com/d/15/43/282319408838099733/e4e839f5-0eb0-4f94-86a8-0aca07feb9d2/7.3%20Alhashli%20Nerve%20Fibers.pdf

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Born in 1857, Charles Scott Sherrington would go on to make great discoveries in neuroscience, the most famous of which was his findings in his knee jerk studies in the early 1900s.

Using a bottom up approach, Sherrington studied the nervous system starting with the spinal cord rather than the brain. Prior to this study, there were two main beliefs about reflexes. The first was held by Wilhelm Erb who believed that it was a true reflex in the sense that a nerve to the spinal cord and then a second nerve going from the spinal cord back to the extensor muscle. The second belief was held by Carl Westpal who believed that it was just a mechanical twitching of the muscle and the nerves were not actually involved.

In Sherrington's studies, he would find that Erb was correct. The nervous system was involved. In his two papers detailing this study, Sherrington made four claims. The first being that the reflex arc contains both motor and sensory nerves. The motor neurons extended to the muscle while the sensory neurons originated in the muscle. Finally, he found that no matter what was done, unless the nerves were severed nothing could block the reflex from occurring.

These findings would inspire other neuroscientists to continue their research in individual neurons and how they work.

Source:

https://neuroscientificallychallenged.com/posts/history-of-neuroscience-charles-scott-sherrington

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Schematic for the three stage amplifier and electrometer

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9. The First Isolation of Single Motor Neurons

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9. The First Isolation of Single Motor Neurons

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With the findings of the neuron doctrine in the decades prior, scientists were now studying individual neurons. It had been found that neurons fire in an all or nothing way, and it had been found that as a stimulus increases, the firing rate of a neuron also increases. However, a single neuron had not been isolated, that is until 1928 when Edgar Adrian and Detlev Bronk did exactly that.

Adrian and Bronk were able to isolate and record the firing of a single motor neuron. Sensory neurons had already been measured, but never a motor neuron. They discovered that in order to record a single neuron, they would need amplification. They also needed tools to isolate the electrical field of a single neuron as the micro electrode had not yet been invented.

So instead, they isolated the neuron by cutting away neighboring neurons to keep it separate. They first described the firing of the phrenic neurons. In their second paper, they recorded the discharge of motor neuron axons to muscles in the leg during a stimulus, such as the knee jerk. Both of these recordings were recorded with sound and amplified so that one can hear the firing rate of the neuron.

Source:

https://marlin.life.utsa.edu/adrian-and-bronk.html

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In 2014, John O'Keefe, May-Britt Moser, and Edvard Moser won the Nobel Prize in Physiology and Medicine for their findings on cells that constitute a positioning system in the brain.

For centuries, neuroscientists have been trying to piece together the information they have to understand how  the brain can create a map of the space surrounding us and how that map is used to navigate our complex environments.

The team found groups of cells in the hippocampus that are always active when a rat was at a certain location in the box, they called these cells place cells. The cells are not only able to register what they can see, but also what they can not see, all aiding in the building of a map of the environment within the brain.

In addition to place cells, grid cells form a hexagonal grid pattern when the rat passes through multiple locations, each individual cell activating in unique patterns.

These findings will hopefully lead to better understanding of the spatial losses that occur in neurological diseases such as Alzheimers.

The work of Erlanger and Gasser would benefit these neuroscientists as they looked at the specialization of neurons. It is more than just motor vs sensory. The place and grid neuron cells function very differently, yet need to work together to achieve the end goal of building a mental gps system.

Source:

https://www.nytimes.com/2014/10/07/science/nobel-prize-medicine.html

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Joseph Erlanger and Herbert Gasser were the winners of the Nobel Prize in Physiology and Medicine in 1944. Let's take a deeper look into the life of Joseph Erlanger.

Born in 1874 in San Francisco, Erlanger would go on to study  chemistry at University of California and later medical school at Johns Hopkins. After medical school, Erlanger went on to become a professor at the Johns Hopkins medical school. He would eventually accept a position as the first professor of physiology at the University of Wisconsin medical School. He would eventually retire from teaching at Washington University in 1946.

He began to work with Gasser in the early 1920s, when they adapted the cathode-ray oscillograph to be able to study action potentials. This work would lead to the pair earning the Nobel prize in 1944.

In addition to his work in neuroscience, Erlanger also did work on the metabolism of dogs who have a shortened intestine and those with traumatic shock, additionally, he did research on the mechanism of the production of sound in arteries.

His work inspired hundreds of other neuroscientists to always look deeper, as there is always something unknown about the brain. Had it not been for his work with Gasser, the specialization of nerve fibers would not have been known and our current knowledge of neuroscience would be much different.

Joseph Erlanger would go on to live a life with his wife and three children, and would die in December of 1965.

Source:

https://www.nobelprize.org/prizes/medicine/1944/erlanger/biographical/