Have We Two Brains? (3)

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“Is There One ‘Left-Brain’ & Another ‘Right-Brain’?” (3)
The 60s, Studying the “Split Brain Alive”

Until the 1960s, methods for observing the dominant role of the left hemisphere in language use and processing (lateralisation of language) were based on studies postmortem of patients with brain lesions. Some neurologists nevertheless claimed that language might not be entirely a left hemisphere function in that it was impossible to conclude no role for the right hemisphere on the basis of lack of lesions there among those who had had language impairments. Lesions only on the left side could be random.






The pertinence of this intuition was underlined by studies carried out on “split-brain” patients.The corpus callosum of these patients was severed in order to stop epileptic attacks from one hemisphere to the other.While the primary goal of the operation was to reduce epileptic fits, it also allowed researchers to study the role of each hemisphere on these patients.






The first such studies were conducted in the 1960s and 1970s, with Medicine Nobel Prize winner Roger Sperry and his team from the California Institute of Technology playing a dominant role.

They succeeded in supplying information to a single hemisphere in their “split-brain” patients and asked them to use each hand separately to identify objects without looking at them.
This experimental protocol built on the fact that basic sensory and motor functions are symmetrically divided between the two hemispheres of the brain - the left hemisphere receives almost all sensory information from and controls movements to the right part of the body and vice versa.Sensory information from the right hand is received in the left hemisphere and that from the left hand in the right hemisphere.

When patients touched an object with their right hand, they could easily name the object but not when they touched it with the left hand. Here was proof that the left hemisphere is the seat of principal language functions.




This unequal localisation of language functions created the idea of the left hemisphere as the verbal one and the right hemisphere as the non-verbal one. Since language has often been perceived as the noblest function of the human species, the left hemisphere was declared “Dominant".






Other experiments with the same type of patients helped to clarify the role of the right hemisphere. A video made by Sperry and Gazzaniga about the split-brain patient W.J. gives a surprising demonstration of the superiority of the right hemisphere for spatial vision. The patient was given several dice, each with two red sides, two white sides, and two sides with alternating white and red diagonal stripes. The task of the patient was to arrange the dice according to patterns presented on cards. The beginning of the video shows W.J. quickly arranging the dice in the required pattern using his left hand (controlled, remember, by the right hemisphere). He had great difficulty, however, completing the same task using his right hand – he was slow and moved the dice indecisively. Once his left hand intervenes, he became quick and precise but when the researchers hold it back he again became indecisive.

Other research by Roger Sperry et al. (1969) confirmed the domination of the right hemisphere in spatial vision. This role was then confirmed by clinical case studies. Patients suffering from lesions in the right hemisphere were not able to recognise familiar faces; other patients had difficulty with spatial orientation.

Some patients with lesions in the right hemisphere have shown defects in identifying the emotional intonation of words and in recognising emotional facial expressions. Behavioural studies back up the clinical studies: speech rhythms are best perceived when the sounds are received by the left ear so that the information goes to the right hemisphere and images seen by the left visual field provoke greater emotional reaction. It was deduced from this that the right hemisphere was also specialised in the processes related to emotions.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 115

(To be continued...)

Have We Two Brains? (2)

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“Is There One ‘Left-Brain’ & Another ‘Right-Brain’?” (2)
A Myth that Began in the 19th Century

This “left brain/right brain” opposition originated in the First neurophysiology research. Intellectual capacities were often then described in two classes: critical and analytical aptitudes, on the one hand, and creative and synthetic aptitudes, on the other.



One of the major doctrines of neurophysiology from the 19th century associated each class to a hemisphere. In 1844, Arthur Ladbroke Wigan published A New View of Insanity: Duality of the Mind. He describes the two hemispheres of the brain as independent, and attributes to each one its own will and way of thinking: they usually work together but in some diseases they can work against each other.


This idea caught the imagination with the publication of Robert Louis Stevenson’s famous The Strange Case of Doctor Jekyll and Mister Hyde in 1866 which exploits the idea of a cultivated left hemisphere that opposes a primitive and emotional right hemisphere, which easily loses all control.



Paul Broca, a French neurologist, went beyond fiction to localise different roles in the two hemispheres. In the 1860s, he examined postmortem the brains of more than 20 patients whose language functions had been impaired. In all the brains examined, he noticed lesions in the frontal lobe of the left hemisphere, whereas the right hemisphere was still intact. He concluded that the Production of spoken language had to be located in the front part of the left hemisphere.



This was completed a few years later, by the German neurologist Carl Wernicke who also examined postmortem brains of those who had had language development disorders; he suggested that the capacity to Understand language is situated in the temporal lobe of the left hemisphere.

Thus, Broca and Wernicke associated the same hemisphere of the brain, the left, to two essential components of processing language – comprehension and oral production.

Brain Autopsy



Diagram of the Left Cerebral Hemisphere



Photograph of the Left Hemisphere "Normal"



Photograph of the Left Hemisphere "With the Damaged Broca's Area"

"Understanding the Brain", The Birth of a Learning Science, 2007, page 114, 115

(To be continued...)

Have We Two Brains? (1)

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“Is There One ‘Left-Brain’ & Another ‘Right-Brain’?” (1)
Two Brain Hemispheres Very Good Connected

The brain is made up of neuronal networks, it has functional areas that interact among themselves, and it is composed of Left and a Right Hemispheres. Each hemisphere is more specialised in certain fields than in others.

Do these facts justify the strange statements to be heard in everyday life, such as: “me, I’m more “Left-Brained””? or “women have a more developed “Right Brain”?”, Is there really a right “brain” and a left “brain”?



A rapid overview of the origin of these terms is needed to determine whether they correspond to facts, or if it is again a matter of questionable extrapolations of scientific data.

The Corpus Callosum Connects the Two Haves of the Brain

But to begin with, it needs to be underlined that the two hemispheres are not separate functional and anatomic entities: nerve structures connect them together (the Corpus Callosum) and many neurons have their cell nucleus in one hemisphere and extensions in the other. This alone should prompt reflection.






Lateralization of Brain Function:
It has been said that the “Left Brain” is the seat of rational thinking, intellectual thinking, analysis, and speech. It also processes numerical information deductively or logically. It dissects the information by analysing, distinguishing, and structuring the parts of a whole, by linearly arranging the data. The left hemisphere is the best equipped to deal with tasks related to language (writing and reading), algebra, mathematic problem-solving, logical operations. Thus, it can be believed that people who are rational, intellectual, logical, and have a good analytical sense “Preferentially Use their ‘LeftBrain’” and tend to be mathematicians, engineers, and researchers”.



The “Right Brain” has been called the seat of intuition, emotion, non-verbal thinking, synthetic thinking, which allows representations in space, creation, and emotions. It tends to synthesise, recreates three-dimensional forms, notices similarities rather than differences, and understands complex configurations. It recognises faces and perceives spaces. From this stems the Complementary Myth that people who are intuitive, emotional, imaginative, and easily find their way around, “Preferentially Use their ‘Right Brain’” and engage in the artistic and creative professions”.


However, despite the relative location of highest cerebral functions in the brain, it is always necessary to remember that this is One Brain with Two Hemispheres that are usually very well connected...

2-D images of the Corpus Callosum

"Understanding the Brain", The Birth of a Learning Science, 2007, page 114

(To be continued...)

The Brain Is 100% Active

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Did We only Use 10% of our Brain? (3)
The Brain Is 100% Active!

Neuroscience findings now show that the brain is 100% active. In neurosurgery, when it is possible to observe the functions of the brain on patients under local anaesthetic, electric stimulations show no inactive areas, even when no movement, sensation, or emotion is being observed.


No areas of the brain are completely inactive, even during sleep; if they were, it would indicate a serious functional disorder.




Similarly, loss of very much less than 90% of brain tissue leads to serious consequences as no region of the brain can be damaged without causing physical or mental defects.

The cases of people who have lived for years with a bullet lodged in the brain or similar trauma do not indicate “useless areas”. If it is possible to completely recover from such a shock, it is the demonstration of the brain’s extraordinary plasticity: neurons (or networks of neurons) have been able to replace those that were destroyed and in such cases the brain reconfigures itself to overcome the defect.



The myth is implausible for physiological reasons, too. Evolution does not allow waste and the brain, like the other organs but probably more than any other, is moulded by natural selection. It represents only 2% of the total weight of the human body but consumes 20% of available energy. With such high energy cost, evolution would not have allowed the development of an organ of which 90% is useless.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 113

Did We only Use 10% of our Brain? (2)

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Did We only Use 10% of our Brain? (2)
The 10% of Brain's Cells Are Neurons

The primary areas are surrounded by secondary areas, so that, for example, information from images perceived by the eye is sent to the primary visual areas, and then is analysed in the secondary visual areas where the three-dimensional reconstitution of the perceived objects takes place.
Information from the memory of the subject circulate in the brain to recognise objects, while semantic information from language areas comes into play so that the person can quickly name the object seen.

At the same time, the brain areas that deal with posture and movement are in action under the effect of nerve signals from the entire body, allowing the person to know whether (s)he is sitting or standing, with the head turned to the right or the left, etc. . Therefore, a partial, fragmented description of the areas of the brain can lead to a misinterpretation of how it works.

The 10% of Neural Brain's Cells Are Neurons

Another origin of the myth may be found in the fact that the brain is made up of ten glial cells (neuroglia) for every neuron. Glial cells have a nutritional role and support nerve cells, but they do not transmit any information. In terms of transmission of nerve impulses only the neurons are recruited (or 10% of the cells comprising the brain) so that this offers a further source of misunderstanding on which the “10% myth” might come.

But this vision of cell functions is simplistic: while the glial cells play a different role from that of the neurons, they Are No Less essential to the functioning of the whole.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 113