A History of the Brain

radioBroadcaster: BBC Radio 4
Year: Originally broadcast 2011 (repeated periodically)
Genre: Radio, Documentary, History of Science
URLs: See below for each episode

Review by Eunice Muruako
Dr Geoff Bunn (Manchester Metropolitan University) presents a series of ten 15-minute programmes spanning 5000 years of cultural and scientific progress in understanding how the brain works.

Episode 1: A Hole in the Head (https://learningonscreen.ac.uk/ondemand/index.php/clip/90227)
The series begins with an introduction to one of the earliest forms of brain surgery, trepanation (3.00). Trepanation was the process by which a small piece of skull was cut away to relieve pressure believed to be caused by the build-up of fluid. Bunn explains that, even in the ancient world, connections were being made with how particular areas of the brain affected certain functions. We learn that Egyptian physician, Imhotep, understood that injury to one side of the brain could paralyse limbs on the opposite side (10.38).

Episode 2: The Blood of Gladiators
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90228)
Various philosophers had conflicting ideas about the role of the brain and its connection to the location of the soul. Aristotle, for example, considered the heart to have primacy over the brain because it was centrally located and developed first in the embryo (9.09). Whereas Galen agreed with Hippocrates that the body was ruled by the brain (12.37). Ailments which were previously attributed to the gods could instead be understood in terms of natural causes affecting the brain.

Bunn tells us that Hippocrates’ rejection of supernatural causes for conditions like epilepsy marked a turning point in the understanding of the brain (6.13).

Episode 3: The Origin of Common Sense
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90229)
Episode three focuses on the brain’s ventricles (2.19), the historical cultural ideas about their role in the communication of thought and the resulting conclusions about the connection between brain and soul.

Galen considered them responsible for the production of “animal spirits” (3.16) which he claimed was the mechanism that made thinking possible while da Vinci attributed cognition, sensation and memory to each of the ventricles (1.46). Da Vinci’s demonstrations that a frog without a heart could survive for a short period of time while one without a brain could not (9.44), was a contradiction to the Aristotelean idea that the heart controlled human action.

Bunn introduces the contributions of the Islamic world to the modern understanding of the brain, including the scholar Al Razi and physician Ibn Sina. Sina believed that thoughts travelled around the brain through the ventricles in a pattern (6.01). Beginning at the front, imprints from the senses accumulated into a “common sense” before moving to the middle ventricle to be judge and, finally, to the back to be stored as memory.

Episode 4: Spirits in the Material World
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90230)
Once it generally held that the brain and soul were separate, the problem shifted to consideration of how an immaterial soul could interact with a material body. Descartes hoped that the solution to the conflicting mind-body duality could lie in the brain (4.46). He proposed that the pineal gland provided a suitable medium between brain and soul due to its position at the centre of the brain and his belief that it was delicate enough to be moved by an immaterial soul. Descartes connected the position of the pineal gland with mood swings; its rocking motion accounted for the experience of conflicting emotions.

Descartes’ theory was rejected by Thomas Willis because animals, who lack a soul, also have this gland and some even larger than humans. Willis’ model of brain function was hierarchical (8.48); “superior acts” were based in the cerebrum at the top, and instruction sent to the cerebellum at the back for lowly actions.

Willis’ curiosity about a man who in life had displayed no symptoms of a brain tumour, but had died from it, led him to discover the function of the cerebral arterial circle (10.28) or “Circle of Willis” (2.28).

Episode 5: The Spark of Being
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90231)
By the middle of the 18th century, electrical impulses in the brain were being recognised as the spark for human consciousness and electricity was being sold as a cure for a wide array of diseases (7.36). John Walsh was able to prove that the animal nervous system was powered by electricity by observing the spark generated by an eel on a tin plate (0.24).

This new electrical discovery led people like Luigi Galvani to experiment on the effect of electrical impulses on the nervous system. Galvani was able to make a severed frog leg twitch by applying an electric charge to the spinal cord (9.48). This led to the question of the brain’s ability to remain sentient when disconnected from the body. Karl August Weinhold claimed to have be able to use electricity animate a cat whose brain he had removed and replaced with a mixture of zinc and silver (10.40). In the wake of these new discoveries Mary Shelley published Frankenstein.

Episode 6: The Beast Within
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90232)
In this episode Bunn explores the effects of localised damage to the brain with a focus on the four lobes (3.47). Bunn explains how Paul Broca arrived to his conclusions about the localisation of language in the frontal lobe of the left hemisphere (9.07).

The programme offers a brief summary of phrenology and Franz Josef Gall’s idea of the brain as a collection of 27 different faculties which happen to reflect hierarchical structures within society (5.37). Gall’s phrenology posits that the more desirable faculties – benevolence, conscientiousness, etc – were located at the roof of the brain and kept the undesirable faculties (located at the base) in check.

Bunn presents the evolution of brain science from phrenology to John Hughlings Jackson’s ideas of regression and regeneration (12.11) in his theory of brain function.

Episode 7: Mind the Gap
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90233)
Mind the Gap explains how neurologists began to study the structure of brain cells (2.44) with the use of the microscope and staining techniques.

In the 19th century, Camillo Golgi created his “black reaction” (5.47) a process which randomly stains 1/20 cells in a sample. Potassium dichromate was used to harden the pieces of brain under examination which were then reacted with silver nitrate. The stains produced were silver-black against a yellow background and provided the clearest impression of the cell. To resolve the question of how neurons interacted with each other Golgi supported the nerve net theory; he thought of the brain as a unified network where impulses could freely communicate both backwards and forwards.

Santiago Ramón y Cajal used Golgi’s black reaction on bird cerebellum cells (8.54). Unlike Golgi, Cajal concluded that nerve net theory must be false (10.40); he found that axons projected towards the brain in sensory nerves and away in motor nerves and so axons must send impulses while dendrites receive them. This suggested that nerve impulses could only travel in one direction which contradicts the to and fro travel presented by nerve net theory.

Bunn also talks about Sigmund Freud’s involvement in neurology during the early stages of his career and describes Bernhard von Gudden’s creation and use of the Gudden microtome to study the brain (7.25).

Episode 8: The Agony and the Ecstasy
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90234)
After the rejection of the nerve net theory the question of how impulses where transmitted remained. There was an assumption that the transmittance would be electrical, however it was discovered that extract from the adrenal gland would speed up a frog heart (2.28), suggesting that chemicals played a role. This led to the work of Otto Loewi and Henry Dale.

Loewi and Dale established that impulses travelled via chemical synaptic transmission (5.45) when they discovered the neurotransmitter (1.05) acetylcholine. Unfortunately, this research would go on to be used by Richard Kuhn, a Nazi sympathiser, to create Soman nerve toxin which interferes with the function of the nervous system by disabling the enzyme that breaks down acetylcholine (10.42).

This episode is the first in the series to address a negative aspect in the development of neurology.

Episode 9: All or Nothing
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90235)
In 1925 Hans Berger accidentally discovered brain waves while looking for psychic energy. He created his “brain mirror” by recording the brain’s electrical signals using electrodes on a person’s head and attached to an electric meter (3.31). This was eventually to be become the technique we now know as Electroencephalography (EEG).

The episode title comes from the principle that a nerve impulse can only occur above a certain threshold or it does not occur at all (2.24).

Episode 10: Einstein’s Brain
(https://learningonscreen.ac.uk/ondemand/index.php/clip/90237)
In his final instalment, Bunn brings us up to date with modern advances in neuroscience, for example the first successful study using an fMRI scan was published in the 90s, and lists other emerging fields such as neuro-aesthetics, social-neuroscience and cultural neuroscience (5.36). In the area of cultural neuroscience, Bunn describes 2007 research from Peking University in Beijing which found that the brain reflected the difference in western individualistic culture and the more collectivist Asian culture (11.55).

We also find out what happened to Einstein’s brain after he died and the various claims that were made to explain his genius.

At the time of writing the episodes are also available on the BBC website for the series.

 

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