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

Did We Only Use 10% of our Brain?

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Did We only Use 10% of our Brain?

It is often said that humans only use 10% (sometimes 20%) of their brain. Where did this myth come from? Some say it came from Einstein, who responded once during an interview that he only used 10% of his brain. Early research on the brain may have supported this myth.

In the 1930s, Karl Lashley explored the brain using electric shocks. As many areas of the brain did not react to these shocks, Lashley concluded that these areas had no function. This is how the term “silent cortex” came into circulation. This theory is now judged to be incorrect. Dubious interpretations of the brain’s functioning have also fuelled this myth.





Today, thanks to imaging techniques, the brain can be precisely described in functional areas. Each sense corresponds to one or several primary functional areas: a primary visual area, which receives information perceived by the eye; a primary auditory area, which receives information perceived by the ear, etc.

Several regions are linked to the production and comprehension of language. They are sometimes described separately by physiologists, and the public which remembers these partial descriptions may gain the impression that the brain functions area by area. This would be consistent with the image that, at any one moment, only a small region of the brain is active but this is not what occurs.

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