Since the second half of the nineteenth century, continuing the tradition of phrenology, pioneer neurologists studied the brain and its functions. The study of language disorders provides an example of how lesions in the brain were supposed to cause neurological problems. This week we will explore how pioneer neurological research studied the localisation of brain functions and on what kind of experiments this research was based.
P. Broca, 'Remarks on the Seat of the Faculty of Articulated Language, Following an Observation of Aphemia (Loss of Speech)', in Bulletin de la Société Anatomique, vol. 6 , pp 330-357. Trans. C. D. Green. Available on line at http://psychclassics.yorku.ca/Broca/aphemie-e.htm
T. Engelhardt ' John Hughlings Jackson and the Mind-Body Relation', Bulletin of the History of Medicine 49 (1975): 137-151.
R. E. Graves, 'The Legacy of the Wernicke-Lichtheim Model', Journal of the History of Neurosciences 6 (1997): 3-20.
S. H. Greenblatt, 'Hughlings Jackson's First Encounter with the work of Paul Broca: The Physiological and Phylosophical Background', Bulletin of the History of Medicine 44 (1970): 555-570.
S. H. Greenblatt (ed), A History of Neurosurgery: In its Scientific and Professional Contexts, chapters 8 and 9 pp. 131-152 (1997).
S. H. Greenblatt, 'The Development of Hughlings Jackson's Approach to Diseases of the Nervous System 1863-1866: Unilateral Seizures, Hemiplegia and Aphasia', Bulleting of the History of Medicine 51 (1977): 412-430.
A. Harrington, Medicine, Mind, and the Double Brain: A Study in Nineteenth-Century Thought (1987).
A., Harrington, 'Beyond Phrenology: Localization in the Modern Era,' in P. Corsi (ed), The Enchanted Loom: Chapters in the History of Neuroscience (1991), pp. 207-225.
L . S. Jacyna, 'Constructing Silence: Narratives of Language Loss in Early Nineteenth-Century France', Journal of the History of Medicine and Allied Sciences 49 (1994): 333-61.
L..S. Jacyna, 'The Discourse of Aphasia' in Lost Words (2000), pp. 81-122.
T. Kaitaro, 'Biological and Epistemological Models of Localization in the Nineteenth Century: From Gall to Charcot', Journal of the History of Neurosciences 10 (2001): 262 - 276.
P. J. Koehler, ' Brown-Séquard and Cerebral Localisation as Illustrated by his Ideas on Aphasia', Journal of the History of Neurosciences 5 (1996): 26-33.
J. Oppenheim. Shattered Nerves: Doctors, Patients, and Depression in Victorian England (1991).
Until the 19th century physicians complained that while they had reached a reasonable level of knowledge about various body functions, they didn't know much about the brain. This lecture will introduce you briefly to the history of neurology in the second half of the 19th century. This will focus on the study of cerebral localisation, or the attempt to locate the areas of the brain involved in the performance of specific functions such as language, movement like those of the legs, and feelings.
Phrenology: the story of cerebral localisation shows how phrenological ideas continued to be important within medical communities in the 19th century. It can perhaps even show how scientific and other popular ideas today have been influenced by phrenology.
At the beginning of the 19th century, the German physician Franz Joseph Gall had localised the language faculty in the frontal lobes of the cortex. Indeed, he placed all the high intellectual faculties in the frontal lobes, and all the instinctual faculties in the posterior lobes, arguing that a person was more intelligent in proportion to his frontal lobe development.
The phrenological belief that there was a link between frontal lobe functions and the highest intellectual functions continued in medical science throughout the 19th century as physicians focussed in particular on finding in what part of the brain the language faculty resided. This interest was in part the result of the observations of aphasia, a mental/neurological disorder that caused speech loss. It was possible for physicians to do an autopsy of individuals who had suffered from aphasia and when these individuals died, physicians looked for brain lesions to explain the relationship between language and parts of the brain.
This kind of research initially developed especially in France, where the physician, Jean-Baptiste Bouillaud, had been impressed with Gall's phrenological work. Bouillaud believed that Gall had been right to put the language faculty in the frontal lobes. For 40 years he collected more than 100 cases of brain damage in human beings supposedly demonstrating a link between frontal lobe damage and loss of speech.
Some historians have suggested that there were political reasons for the development of such research in France. For the many French intellectuals who were free thinkers and republicans (against the old regime), science was an obvious way of challenging traditional authorities
and religion. They thought that if they were able to demonstrate that everything in the universe was natural, and subject to natural laws, the Church and its political allies would be stripped of their authority. Physicians who devoted their research to discovering where mental functions were located in the brain wanted to demonstrate that psychological reactions, emotions, and human mental operations had a cerebral origin, not a religious one. Localising the brain functions involved rejecting the idea of the soul.
A major French researcher in the area was Paul Broca, who was a physician, anatomist and anthropologist. Broca was also a troublemaker well accustomed to fighting with the local church. Authorities denounced Broca as a subversive, a materialist (he did not believe in the soul), and a corrupter of youth after he founded a society of freethinkers who sympathised with Charles Darwin's theories. Broca was also the founder and driving force behind the Paris Anthropological Society (1859, Paris Societé d'Anthropologie), an organisation that became notorious for attracting left wing, anticlerical intellectuals.
Broca's Anthropological Society was particularly interested in the study of 'advanced surgery' in non-European populations. In 1867, a Peruvian skull with cross-hatched cuts was discovered.This skull came from an Inca cemetery in the valley of Yucay, and was discovered by an archaeologist, by Ephraim George Squier, and had been trepanned. Broca himself experimented with trepanation and found that a hole could very easily be made in the skull of a deceased 2-year-old child using a simple glass scraper. While the entire procedure took him around 4 minutes on a child, it took about 50 minutes when performed on an adult's skull.
But Broca's main claim to fame was for his neurological studies on aphasia. At the French asylum Bicêtre, Broca had a patient known as 'Tan' because that was the only word he could say. Tan suffered from speech loss, even though his tongue and lips were not paralysed and he was able to understand what was said to him. When Tan died, Broca did an autopsy and found that Tan's frontal lobes were damaged. Broca understood Tan's speech loss as a memory disorder and he argued that there was a link between this and his frontal lobe damage. Yet this was not the only case Broca dealt with; 6 months after his initial study of Tan, Broca found a similar case and as his studies into this phenomenon progressed, He discovered that all of the autopsies in these cases appeared to confirm a relationship between frontal lobe damage and aphasia.
Most of Broca's cases seemed not only to confirm a connection between frontal lobe damage and speech loss, they also appeared to point to a link between speech loss and damage of the LEFT side of the brain. The discovery of the asymmetrical nature of language's localisation transformed the way neurologists regarded higher mental functioning in the human brain. At Broca's time, most neurologists, anatomists, and physicians believed that the brain was composed of different organs, but the left and right parts of the brain were believed to be symmetrical. As men had symmetrical eyes, arms, and legs, so too did the brain follow this pattern. Broca was not initially prepared to accept the idea that nature could create 2 apparently identical structures that functioned differently.
The belief in the in the innate functional symmetry of the brain was deeply imbedded in French physiological thinking. In an attempt to compromise this view, Broca proposed that there were DEVELOPMENTAL differences between the 2 sides of the brain, suggesting that the LEFT frontal lobe grew slightly faster than the right. According to Broca, in childhood, when we are forced to master the complex manual and intellectual skills (i.e. articulate language), we tend to rely on our slightly more mature left frontal lobe. In other words, we learn to speak with the left half only of our brain.
One of the consequences of Broca's interpretation of the asymmetry data was to encourage a view of the left side of the brain as the intelligent, educated, 'human' side; and the right side of the brain was responsible for a wide range of dark, psycho-physiological processes that were dominated by instincts.
Some physicians came to believe that the right hemisphere was especially well developed in certain supposedly inferior human groups, such as small children, women, non-white races, madmen and criminals. In short, people dominated by animalistic passions rather than reason, which dominated white European men.
In the first decades of the 20th century, evidence suggesting that patients with right hemisphere damage were more likely to suffer from certain perceptual and attention problems, especially those involving spatial orientation, began to accumulate. Today, the exact role of the two brain hemispheres in differing forms of emotional expression and perception remain unclear, although the language faculty does seem to be located in the left side of the brain.
Broca's research on cerebral localisation focussing on speech loss became very famous within the international scientific community. In Germany in 1874, the neuropsychiatrist Carl Wernicke, began a new era in the history of language localisation with the publication of his classic monograph on the problem of language loss and cerebral localisation, Der Aphasische Symptomencomplex . In his work, Wernicke contrasted the loss of speech studied by Broca with another new type of language disturbance that he believed had not yet received proper recognition. This was a type of language disturbance or aphasia characterised by a loss of the ability to comprehend speech. While Broca focussed on subjects who could not speak, but who could understand other people, Wernicke focussed on more severe cases: individuals who could neither speak nor understand other people. Wernicke linked this disorder to damage of a posterior region of the cortex in the left side of the brain.
Wernicke also believed that the old phrenological idea that one can localise complex psychological characteristics had been misguided. He thought that it was possible to locate only simpler functions, what he called primitive 'memories' of past sensory and motor-sensory activity. These 'memories' of past sensory and motor experiences served as basic units for all mental functioning and interacted and combined with each other in the brain according to so-called 'laws of association'. Rather than the psychological characteristics such as 'ambition' 'love' etc., which phrenologists thought dominated an individual's brain, Wernicke believed that it was possible to locate physiological reactions that dominated human behaviour. In other words, Wernicke believed that it was possible to locate sensory motor reflexes, which ruled our behaviour.
Today, both Broca and Wernicke have an area of the brain named after them; Broca's area and Wernicke's area, indicating that these scientists made a major scientific contribution to their field.
Broca's and Wernike's discoveries were largely based on their observations during autopsies and also research on living humans affected by aphasia. In the 19th c. the research of cerebral localisation also advanced thanks to experimental research on the brain. Still, until the mid 19th century, surgeons were quite limited in what they could do to treat afflictions of
the nervous system. The most common study was the study of the brain of dead patients. Those patients with neurological or mental deficits had their brain studied after their death in an attempt to correlate mental disorders with detectable alterations in the brain tissue.
Broca performed trepanation on the skulls of dead people, but trepanation had been practiced on living people for a long time, with some historians believing that it has been happening since ancient times.
However, because the exact location of a lesion in the brain could not be diagnosed by a neurological examination, and because surgical exposure of the brain was limited to a very small area the surgeon had to be guided by external clues such as a depressed skull fracture. Surgeons had also a major problem when performing such a operation. The expected consequence of any operation was an infection. Surgeons avoided opening the skull unless there was a strong evidence of blood or pus. Therefore, skull operations were rarely performed.
Only in the early 1860s did Louis Pastor and Claude Bernard understand that micro-organisms infecting animals and humans caused disease (germ theory). This led to the discovery of antiseptic methods in surgery (i.e. the sterilisation of surgical tools to avoid infection) at the end of 1860s. However, it took a while for antiseptic methods to become applied regularly, not to mention in operations on the skull.
Therefore it was more common for those physicians interested in understanding how the brain functioned to carry out experiments on animals.Around the 1820s anatomists and physiologists had developed new experimental methods to intervene directly in the brain and to see the results of these interventions on the behaviour of animals. These methods were:
Marie Jean Pierre Flourens, a French physiologist, conducted experiments on the brain of rabbits and pigeons to locate different brain functions. He was able to demonstrate convincingly for the first time that the main divisions of the brain were responsible for largely different functions. By removing the cerebral hemispheres in pigeons and rabbits, he