Mini Museum Entry 2: The discovery of the Neuron and the Neuron Doctrine by

1. Reticular Theory vs. Neuron Doctrine (Early 1800s–1891)

mcgreer6 — 2025-04-01 00:57:51 UTC

In the late 19th century (1800s) the scientific community was divided over the structural organization of the nervous system. The main theory, the reticular theory by Camillo Golgi, stated that the brain was a continuous network of interconnected fibers, functioning as a unified whole (Golgi, 1873). Golgi's belief was based on his observations using a staining technique he developed, which appeared to show a seamless web of neural tissue. We will touch on this more in the next section.

Also, Santiago Ramon and Cajal introduced the Neuron Doctrine, asserting that the nervous system is composed of discrete, individual cells called neurons (Cajal, 1891). Through meticulous observations and detailed drawings, Cajal demonstrated that neurons are separate entities that communicate at specific junctions (Shepherd, 1991). This finding fundamentally changed our understanding of neural structure and established base knowledge for modern neuroscience.

Sources:

Cajal, S. R. (1891). Textura del sistema nervioso del hombre y de los vertebrados. Madrid, Spain.

Golgi, C. (1873). On the Structure of the Nervous System. Italian Academy of Sciences.

Shepherd, G. M. (1991). Foundations of the Neuron Doctrine. Oxford University Press.

Hunched Over a Microscope, He Sketched the Secrets of How the Brain Works - The New York Times

2. Golgi’s Silver Staining Technique (1873)

mcgreer6 — 2025-04-01 01:02:36 UTC

In 1873, italian scientist Camillo Golgi developed the black reaction. The black reaction is a groundbreaking staining method that used silver nitrate to visualize nervous tissue under a microscope (Golgi, 1873). This technique selectively stained a limited number of neurons in their entirety, revealing their complex structures against a transparent background. This allowed scientists for the first time to observe the detailed morphology of individual neurons (Public Domain Review, 2017). They were able to view a lot including their cell bodies, dendrites, and axons.

Golgi's method was revolutionary, providing unprecedented insights into the architecture of the nervous system. However, his interpretation of the results led him to support the Reticular Theory, believing the stained structures formed a continuous network.

Sources:

Golgi, C. (1873). On the Structure of the Nervous System. Italian Academy of Sciences.

Public Domain Review. (2017). Illustrations of the Nervous System. Retrieved from https://publicdomainreview.org/collection/illustrations-of-the-nervous-system-golgi-and-cajal

What is the Golgi stain? — Brain Stuff

Hunched Over a Microscope, He Sketched the Secrets of How the Brain Works - The New York Times

3. Cajal’s Evidence for Individual Neurons (1887–1891)

mcgreer6 — 2025-04-01 01:03:47 UTC

Spanish neuroscientist Santiago Ramon and Cajal refined Golgi's staining technique and applied it to his studies of the nervous system. During the years 1887-1891 Cajal produced detailed observations and drawings that provided solid evidence for the existence of individual neurons. His work demonstrated that neurons are discrete cells that communicate through specialized contact points which challenged the idea of a continuous neural network.

Overall, Cajal used Golgi’s staining technique, but came to the conclusion that neurons are distinct cells that communicate at contact points (Cajal, 1891).

Cajal's meticulous studies revealed the directional flow of information within neurons, which is from dendrites to axons, supporting the concept of functional polarization (Shepherd, 1991). His microscopic observations and also his neuron drawings provided the first clear evidence of the individual neurons (Public Domain Review, 2017). His findings supported the neuron doctrine which would change our understanding of brain structure and function and lead to endless scientific developments still present today.

Sources:

Cajal, S. R. (1891). Textura del sistema nervioso del hombre y de los vertebrados. Madrid, Spain.

Shepherd, G. M. (1991). Foundations of the Neuron Doctrine. Oxford University Press.

Public Domain Review. (2017). Illustrations of the Nervous System. Retrieved from https://publicdomainreview.org/collection/illustrations-of-the-nervous-system-golgi-and-cajal

4. Charles Sherrington and the Concept of the Synapse (1897)

mcgreer6 — 2025-04-01 01:04:41 UTC

After the findings relating to the Neuron Doctrine, the British physiologist Charles Sherrington introduced the term "synapse" in 1897 to now officially describe the junctions where neurons communicate (Sherrington, 1897). Through extensive research on reflexes and neural pathways, Sherrington illustrated that neural transmission involves discrete interactions between neurons at these synaptic points.

He identified that synapses could either be excitatory or inhibitory which means that they could enhance or suppress neural signals (Sherrington, 1906). This discovery was pivotal in understanding the integrative actions of the nervous system, explaining how complex behaviors and processes arise from simple neural interactions. His findings are also important when trying to understand mental disorders (Silvestri et al., 2019).

Sources:

Sherrington, C. S. (1897). On the reflex action of the spinal cord. Journal of Physiology, 21(3), 233–258.

Sherrington, C. S. (1906). The Integrative Action of the Nervous System. Cambridge University Press.

Silvestri, L., Costantini, I., Sacconi, L., & Pavone, F. S. (2019). Brain structural and functional connectivity: A review of light microscopy and diffusion-based imaging techniques. Frontiers in Cellular Neuroscience, 13, 66. https://www.frontiersin.org/articles/10.3389/fncel.2019.00066/full

Why the First Drawings of Neurons Were Defaced | Quanta Magazine

5. Wilhelm Waldeyer Coins the Term "Neuron" (1891)

mcgreer6 — 2025-04-01 01:05:06 UTC

In 1891, German anatomist Wilhelm Waldeyer synthesized existing research and formally introduced the term "neuron" to describe the individual nerve cells that constitute the nervous system (Waldeyer, 1891). His work consolidated the findings of contemporaries like Cajal and provided a term that helped further research and communication within the scientific community.

Wilhelm Waldeyer's acceptance and usage of the Neuron Doctrine and his efforts in standardizing the new official vocabulary were instrumental in the widespread acceptance of the concept that the nervous system is composed of discrete cellular units (Silvestri et al., 2019). Coining new terms noy only makes communication within a community of scientists easier, but teaching neuroscience to the future general population, as well.

Sources:

Waldeyer, W. (1891). Über einige neuere Forschungen im Gebiete der Anatomie des Centralnervensystems.

Silvestri, L. et al. (2019). Brain structural and functional connectivity: A review. Frontiers in Cellular Neuroscience, 13, 66. https://www.frontiersin.org/articles/10.3389/fncel.2019.00066/full

https://www.frontiersin.org/articles/10.3389/fncel.2019.00066/full

Contemporary: Modern Neuroscience Imaging and the Human Connectome Project

mcgreer6 — 2025-04-01 01:05:51 UTC

The Human Connectome Project (HCP) is a modern research initiative aimed at mapping the complex network of neural connections in the human brain. Utilizing advanced imaging technologies such as functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging, the HCP provides detailed insights into the brain's structural and functional connectivity. These imaging techniques are used for a variety of other things as well for anything involving mapping brain activity by detecting changes in blood flow. It helps researchers and doctors' study which brain regions are active during tasks like thinking, feeling emotions, or moving.

This modern imaging technology allow scientists to visualize and analyze neural pathways with true precision to validate and expand on the base of knowledge established by the concept of the Neuron Doctrine. The Human Connectome Project's findings have significant options to study for understanding brain function, diagnosing neurological disorders, and even for developing targeted treatments.

Sources:

Van Essen, D. C., et al. (2013). The Human Connectome Project: Progress and Prospects. Neuron, 80(3), 607–620. https://www.frontiersin.org/articles/10.3389/fncel.2019.00066/full

Human Connectome Project | Mapping the human brain connectivity

Who is my docent: Eric Kandel

mcgreer6 — 2025-04-01 01:06:18 UTC

Eric Kandel is a renowned neuroscientist whose research has profoundly influenced our understanding of memory and learning. Born in 1929, Kandel's work focuses on the molecular mechanisms that underlie synaptic plasticity. Synaptic plasticity is the ability of synapses to strengthen or weaken over time. This is believed to be fundamental to learning and memory.

By studying the sea slug aplysia californica, Kandel uncovered how changes at the synaptic level contribute to the formation of memories. Kandel's work provided crucial evidence supporting the neuron doctrine. By explaining the mechanisms of synaptic changes, Kandel bridged the gap between the structural principles of the neuron doctrine and some of the functional processes of behavior and thinking. His contributions were recognized in 2000 when he was awarded the Nobel Prize in Physiology or Medicine, alongside Arvid Carlsson and Paul Greengard, for their collective discoveries concerning signal transduction in the nervous system.

He is the perfect docent to not only cover the basics of neurons and the information found relating to the concept of the neuron doctrine, but a Nobel Peace Prize winning neuroscientist who could explain the details we know about learning and memory in modern day.

Sources:

Eric Kandel | Biography, Nobel Prize, & Facts | Britannica

Eric Kandel - Alchetron, The Free Social Encyclopedia