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Evolving Understanding of the Brain

Neuroletter, Volume 2 Issue 1

The brain is a fascinating organ. Over thousands of years of evolution, our understanding of the brain has also evolved.

In the 4th century B.C. Aristotle considered the brain a radiator meant for cooling the heart and seat of the spirit. He defined the term sensus communis as the space where all spirits united. By the 1st century A.D, the basic structure of the brain had been identified. The following century saw Roman physician Galen support Aristotle’s theory of the brain being the house of the animal soul. However, after observations of how brain injuries affected mental activities, Galen concluded that mental activities took place in the brain and not in the heart.

Eventually, the brain anatomy had been consolidated into three main components called ventricles - the anterior ventricle was responsible for imagination, the posterior for memory, and the ability to reason was located somewhere in between in the brain.

The fifteenth century Renaissance scientists dissected the brain further and by 6th century we had a much better understanding of the anatomy of the brain. By the first decade of the sixteenth century, Leonardo da Vinci’s illustrations of the brain showed the more intricate anatomical details of the brain.

He began examining the relationship between the brain, the olfactory, and optical nerves by injecting wax in order to develop a model of the ventricles within the brain. However, during the same century, Belgian anatomist Andreas Vesalius created a detailed map of the nervous system while also refuting the idea of the ventricles being the seat of brain functions. In the 17th century, Thomas Willis and Nicolaus Steno’s publications on brain anatomy criticized the previously celebrated ideas of ventricles being the seat of

common sense and drove home the importance of how evolution has resulted in the intricate designs within the brain.

18th-century Italian scientist Luigi Galvani discovered that electrical impulse is an important property of the nervous system. In 1848, in an unfortunate accident involving American construction worker Phineas Gage, an iron rod went through his head destroying most of his left frontal lobe. This incident famously known as the “American Crowbar Case” resulted in several behavioral changes in Gage. The case propelled the discussion of functional specialization - specific brain regions specialize in certain functions. Following this, Broca and Wernicke’s work showed how specific parts of the brain were

involved in different components of speech.

The early 1900s saw a huge influx of microscopic and staining techniques used to study brain tissue. In 1906, Cajal and Golgi won the Nobel Prize for identifying neurons as the building blocks of the nervous system. Sir Sherrington and Edgar Adrian bagged the Nobel in 1932 for the functional characterization of neurons. In 1963, Hodgkin, Huxley and Sir John Eccles won the Nobel Prize for discovering how neurons can communicate via both electrical and chemical signaling.

However, amidst the growing interest in the field of neuroscience, sometime in 1953, a man going by the name of Henry Molaison, was admitted to Hartford Hospital, Connecticut. He was suffering from epileptic seizures and was referred to William Beecher Scoville, who was a famous neurosurgeon of his time. Scoville surgically removed the medial temporal lobe from both the hemispheres of Molaison’s brain. This surgery partially relieved him of his epileptic seizures but presented a new problem. Molaison developed amnesia. This was arguably the most famous patient in the history of neuroscience - Patient

H.M. His case became a textbook case and revolutionized our understanding of memory. In the 2017 book “Patient H.M.: A Story of Memory, Madness, and Family Secrets” written by Scoville’s grandson Luke Dittrich, Dittrich talks about how his grandfather was a huge champion of the controversial surgery of lobotomy which involved severing brain connections as a treatment for mental disorders. During his interview with WIRED, Dittrich mentions how patients like H.M. and several other psychotic asylum inhabitants were merely “psychiatric material” with almost little to no agency.

However, today we have many advanced molecular and imaging tools to study the structure and function of different brain regions and neural circuits. We have come a long way in terms of ethics concerning research and also our understanding of the brain and mental disorders.



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