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Golgi, Cajal and The Neuron Doctrine

When I tell someone out of the field that I study neuroscience, I often get a similar response. They either ask “How is that different than neurology?” or “So, something like biology?” If the response is neither one of these, it is probably because they are looking at me with a confused expression to see if I misspoke or if they misunderstood. This posts aims to clear up some of that confusion and go into a little bit of detail about how it all began.

Neuroscience is the study of the nervous system. It used to be a branch of biology, but grew to be its own field due to the increasing number of scientist studying various aspects of the nervous system. This is probably the reason why some people use neuroscience and neurobiology interchangeably, however I would say that it is incorrect. The term neurobiology refers to only the biology of nervous system; neuroscience incorporates the interdisciplinary characteristic of the field and refers to the entire science of the nervous system. I think this is a not-so-trivial difference, considering that neuroscience collaborates fields such as medicine, psychology, chemistry, physics, mathematics, engineering, computer science, philosophy as well as the more recent inclusions law, economics, education and ethics. I will address some of these interesting collaborations (e.g. neurolaw, neuroeconomics) in my future posts.

So how did it all start? The earliest reference to the brain in any human record comes from a couple of surgical papyri from ancient Egypt and dates back to 17th c BC. Archeological studies have even found evidence dating back to Neolithic times, from people using techniques such as trepanation to cure epileptic seizures, migraines and mental disorders. Although interesting, these early techniques were only performed for practical purposes (and sometimes even spiritual) and not as much to understand the function of the brain. In the following eras, the gradual improvement in the scientific thought and methods allowed physicians to dissect and structurally analyze the healthy and diseased brain. However, again, these studies were mostly at the level of structural anatomy. In fact very few advances were seen on actually understanding the function of the brain and its parts until as far as 19th century.

Scientific research in general started to develop much more rapidly after the invention and popular usage of the light microscopy; this was also true for neuroscience. Two talented physician-scientists, Camillo Golgi (1843–1926) and Santiago Ramon y Cajal (1852-1934), were the ones to establish the foundations of modern neuroscience and receive the 1906 Nobel Prize in Medicine, “in recognition of their work on the structure of the nervous system.” Interestingly, they had the exact opposite idea about the structure of the nervous system! Golgi was convinced that the nervous system was formed of a continuous arbor, not from single cells, an idea that is called the “reticular theory.” On the other hand, the evidence that Cajal provided was in favor of the “neuron doctrine”, the idea that the nervous system, as other tissues, was composed of cells, which were later named as “neurons.”

In order to analyze what he believed to be the reticular structure of the nervous system Golgi developed a silver staining procedure, the Golgi stain, to visualize neurons under light microscopy. In Golgi staining, fixed (~killed, for practical purposes) neurons are impregnated with chemicals that produce silver chromate crystals that appear as dark black deposits on a yellow background. It stains neurons randomly, the reason of which we still do not know; but for the ones that it does stain, it shows the entire neuron with exquisite detail.

arin 1Drawing by Golgi of a hippocampus stained with the Golgi stain.

Cajal also used the Golgi staining to analyze neuronal structures and even improved it by performing double impregnation. Obviously, during those days it was not possible to connect a computer to a camera and a desktop computer to have a digital image of the structure seen under the microscope. But that certainly did not stop Cajal. As an avid painter and artist, whose talent was not much appreciated by his father in his young days, he drew every structure that he saw under the microscope. He had hundreds of such drawings that illustrated the detailed arborizations of different kinds of brain cells and their connections. These drawings are still used for educational and training purposes. So using the Golgi staining that show individual cells rather than a continuous neural network, he was able to refute Golgi’s “reticular theory” and prove the “neuron doctrine.”

arin 2Drawing by Cajal of a hippocampus. Notice how a circuit diagram is drawn (arrows), showing neurons as individual units with information flowing between them. The circuit that he drew a century ago is consistent with the recent findings.

arin3Drawing by Cajal of cerebellar purkinjee cell using Golgi staining

arin4Drawings by Cajal of various cerebellar cells using Golgi staining.


Drawings by Cajal of structures of mammalian retina.


Modern imaging of Golgi stained pyramidal neuron from a cerebral cortex. Notice the fine details that can be observed

The silver staining technique that Golgi developed and its use by Cajal to prove “Neural doctrine” is considered to be the foundation of modern neuroscience. If you want to know more, check out the links below:

Nobel Prize in Physiology or Medicine 1906:

Cajal’s Butterflies of the Soul by Javier DeFelipe:’s+Butterflies+of+the+Soul:+science+and+art&hl=en&sa=X&ei=UoZwUqfzBome2wW3-IHAAw&ved=0CC4Q6wEwAA

Advice for a Young Investigator by Santiago Ramon y Cajal:


Image source: Flickr

Arın Pamukçu


  1. Wow, this piece of writing is fastidious, my sister is analyzing these things, therefore I am going to let know her.

  2. There is certainly a great deal to learn about this subject.
    I love all of the points you have made.

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