| By Tré LaRosa NeuLine Health |
The history of neuroscience is marked by a series of milestones, all of which were developed by previous milestones. As is the way of science, not every milestone in the history of neuroscience has proven to be true. Some milestones are revelatory and novel in their way of thinking, and instead of proving to be true, offering scientists and philosophers a new way of looking at perplexing problems. Not even every milestone in neuroscience was a milestone in the field, some milestones are built off discoveries in other fields. Science is remarkable not because it always provides clear answers, but because the answers provide clarity and yet still reveal more unanswered questions.
This is the history of neuroscience, told through major milestones.
Early societies speculate the brain is responsible for intelligence
Before the brain was known to be the seat of human intelligence, the heart was believed to be the key. The Egyptians believed the heart to be the most important of all human organs and crucial to one’s character and wisdom, and the ticket to the afterlife. Some 2,400 years ago, Hippocrates — the namesake of the Hippocratic Oath — proposed that it wasn’t the heart, but actually “from the brain alone, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears.” He concluded “the brain is the interpreter of consciousness.” At the time, he disagreed with philosophical titans including Aristotle.
Some argue it was actually Pythagoras who introduced the idea of cephalocentrism — the idea that the brain was the seat of human intelligence, as opposed to cardiocentrism. Or perhaps it was actually Alcmaeon, who lived during Pythagoras’ time and may have even been a student of Pythagoras.
The struggles of early scientists to determine which organ was responsible for cognition is one that reverberates through the millennia as it depicts the challenges of science, the limits of understanding at a given time in history, and the incredible importance of improving our understanding of the world around us a discovery at a time. As time has progressed forward, it’s not helpful to identify milestones as the singular most important milestones. Science builds and collapses; progress is made, hypotheses are presented, experiments conducted, only to reveal there is more to be learned. It wasn’t feasible for scientists during Hippocrates’ time to present a deeply detailed description of the cells and tissues of the nervous system. They didn’t have the technology nor did they have the generations of discoveries that we have today. In fact, it’s due to their curiosity, their early discoveries, and their pioneering spirit that we have the science we have today — for they are the ones who invented neuroscience. Every achievement today is built on the blocks they established at the foot of the foundation of neuroscience.
Galen of Pergamon Advances Understanding of the Brain
Galen of Pergamon, a leading physician during the era of the Roman empire, is one of the most important figures in the history of neuroscience and medicine. While it’s hard to trace the origin of ideas, Galen is believed to have produced hundreds of writings on the human body. A student of the school of Hippocrates, Galen was also one of the very first researchers to rely on experimentation to evaluate his hypotheses, especially his belief that the brain gives rise to the mind.
At the time, the belief that the mind was rooted in the brain wasn’t yet consensus and required further research. Galen significantly advanced this understanding. Galen discovered that all five senses terminated in the brain, which supported his belief that the brain was responsible for intelligence. He wasn’t exactly on the mark, though, as he also believed that personality and emotion were generated by other parts of the body, including the heart and liver. It’s impossible to fault any figure for their beliefs in theories that have since been disproven; after all, their hypotheses were borne of the eras that preceded them, so human history’s prior belief at the time that the heart was responsible for passion and intellect remained in many theorists’ writings. Galen also advanced a crucial understanding of the association between the brain and the voice: It was Galen who discovered recurrent laryngeal nerves — through his practice of experimentation — and their role in generating voice production, which at the time, was a crucial part of a Roman culture where rhetoric reigned supreme. Galen concluded that since the recurrent laryngeal nerves branch from the base of the brain, the brain is the seat of rationale, a belief that has proven true over the subsequent 2000 years.
Jason Pratensis publishes De Cerebri Morbis, the first book on neurological disorders
De Cerebri Morbis was published in 1549 by Jason Pratensis. De Cerebri Morbis wasn’t remarkable for any particular discovery, but instead for its importance as the first collection of neurological disorders. As time and medicine progressed, it became increasingly important to consolidate knowledge in a centralized way. De Cerebri Morbis consolidated knowledge from Greek, Roman, and Arabic scientists and physicians as well as contemporary discoveries in astrology and pharmaceuticals, and included classifications of conditions based on symptom complexes of many conditions including epilepsy.
The description of myelinated and unmyelinated axons
In the early 19th century, Robert Remak became the first person to describe myelinated and unmyelinated axons, a discovery that would prove crucial to the understanding of multiple sclerosis, the most common demyelinating condition. Myelin is the fatty insulation around axons and allows for electrochemical signals to be rapidly propagated from the brain to the rest of the body.
While Robert Remak didn’t know exactly the significance of myelin at the time, he did know that it was crucial for the functioning of the nervous system. In describing myelinated and unmyelinated axons, Robert Remak gave contemporary and future scientists a critical piece of knowledge that would help inform nerve impulses, a hypothesis that was a generation away.
Julius Bernstein hypothesizes that a nerve impulse is a “wave of negativity”
For the brain to control the rest of the body, signals have to be transmitted somehow. The discovery that neurons are electrically excitable required understanding action potentials, which are electrical gradients generated by differing amounts of positively- and negatively-charged ions traveling across the membrane of cells. This example demonstrates how the history of science is a story of convergent and divergent ideas across a vast array of different fields. Advancements in the fields of physics, anatomy and physiology, and chemistry, were all required before the idea of membrane potential and neural conduction could even be postulated.
It was Julius Bernstein who contributes two major milestones in the understanding of signal transduction: First, in 1868, he described the remarkable phenomenon of action potentials in 1868; then, in 1902, he theorizes membrane theory, the first explanation of bioelectric events. These discoveries would inspire many revelations in neuroscience, including for why the myelin sheath is so critical for the functioning of the nervous system.
Julius Axelrod discovers the reuptake of neurotransmitters
While Julius Bernstein is a major figure in the understanding of the electrical conductance of neurons, Julius Axelrod won the 1970 Nobel Prize for contributing a major discovery for the chemical portion of neural functioning: The reuptake of neurotransmitters. Dr. Axelrod discovered that neurons reuptake neurotransmitters after they’ve been released and reuse them for future transmissions of signals. His discovery was monumental — it led to the development of today’s antidepressants: selective serotonin reuptake inhibitors.
Resources:
- Chen, I., & Lui, F. (2022). Neuroanatomy, Neuron Action Potential. In StatPearls. StatPearls Publishing.
- Finger, S. (2005). Hippocrates: The Brain as the Organ of Mind. In S. Finger (Ed.), Minds Behind the Brain: A history of the pioneers and their discoveries (p. 0). Oxford University Press.
- Freemon, F. R. (1994). Galen’s ideas on neurological function. Journal of the History of the Neurosciences, 3(4), 263–271.
- Julius Bernstein (1839–1917): Pioneer neurobiologist and biophysicist | SpringerLink. (n.d.).
- Pandya, S. K. (2011). Understanding Brain, Mind and Soul: Contributions from Neurology and Neurosurgery. Mens Sana Monographs, 9(1), 129–149.
- Pestronk, A. (1988). The first neurology book. De Cerebri Morbis…(1549) by Jason Pratensis. Archives of Neurology, 45(3), 341–344.
