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From thought to language

Communicating in Words

HelpLink : The Early PioneersLink : Paul Broca : Paris, FranceLink : The Arcuate Fasciculus
Research : DR. CARL WERNICKEResearch : DR. PAUL BROCAResearch : Paul Pierre Broca : A Brief BiographyResearch : Pierre Paul Broca
Original modules
Tool: Sign LanguageSign Language

Rethinking the Role of Broca’s Area in Language

A large proportion of the studies done on the brain’s language functions since the 19th century have involved establishing correlations between a particular language deficit and the locations of lesions in the brains of autopsy subjects. But a single lesion can sometimes cause damage to several brain structures at once, which makes interpreting such findings difficult.

Modern brain imaging techniques have made it possible to study the activation of the brain areas associated with language in healthy subjects while they perform specified language activities. These studies have confirmed the importance of Broca’s and Wernicke’s areas for language while also identifying them as part of a wider network of interconnected areas of the brain that contribute to language. This concept has now replaced the historical notion of language “centres”.

Tool : Brain Imaging

In bilingual people, the earlier in life the second language was acquired, the more similar the areas of the brain involved in understanding and producing the two languages. In contrast, brain-imaging studies have shown that when people learn a second language later in life, the areas of the cortex involved in understanding the two languages are not always the same. Interestingly, when bilingual people lose the use of one of their languages as the result of a brain injury, the language that they retain is not always necessarily their mother tongue.

Indeed, bilingualism is a complex phenomenon, and much about its functional bases remains unknown. For example, because Italian uses phonemes and syntax that are much closer to French than to Chinese, will the brain of someone who is bilingual in French and Italian operate differently from that of someone who is bilingual in French and Chinese? Among people who are bilingual in French and Chinese, are their differences between the brains of those whose mother tongue is Chinese and those whose mother tongue is French? How does the frequency with which a person uses a language affect the corresponding structures in their brains? Clearly, the number of factors that may influence the language-processing areas of the brains of bilingual persons is quite considerable.

Link : The Evidence Speaks Well of Bilingualism's Effect on KidsLink : Imagerie cérébrale du langageLink : Statistical non-parametric maps of brain activity, in response to first and second languageTool: Different Types of Bilingualism


The process of identifying the parts of the brain that are involved in language began in 1861, when Paul Broca, a French neurosurgeon, examined the brain of a recently deceased patient who had had an unusual disorder. Though he had been able to understand spoken language and did not have any motor impairments of the mouth or tongue that might have affected his ability to speak, he could neither speak a complete sentence nor express his thoughts in writing. The only articulate sound he could make was the syllable “tan”, which had come to be used as his name.

Paul Broca

Tan’s brain

When Broca autopsied Tan’s brain, he found a sizable lesion in the left inferior frontal cortex. Subsequently, Broca studied eight other patients, all of whom had similar language deficits along with lesions in their left frontal hemisphere. This led him to make his famous statement that “we speak with the left hemisphere” and to identify, for the first time, the existence of a “language centre” in the posterior portion of the frontal lobe of this hemisphere. Now known as Broca’s area, this was in fact the first area of the brain to be associated with a specific function—in this case, language.

Ten years later, Carl Wernicke, a German neurologist, discovered another part of the brain, this one involved in understanding language, in the posterior portion of the left temporal lobe. People who had a lesion at this location could speak, but their speech was often incoherent and made no sense.

Carl Wernicke

Brain with a lesion causing Wernicke’s aphasia

Wernicke's observations have been confirmed many times since. Neuroscientists now agree that running around the lateral sulcus (also known as the fissure of Sylvius) in the left hemisphere of the brain, there is a sort of neural loop that is involved both in understanding and in producing spoken language. At the frontal end of this loop lies Broca's area, which is usually associated with the production of language, or language outputs . At the other end (more specifically, in the superior posterior temporal lobe), lies Wernicke's area, which is associated with the processing of words that we hear being spoken, or language inputs. Broca's area and Wernicke's area are connected by a large bundle of nerve fibres called the arcuate fasciculus.

This language loop is found in the left hemisphere in about 90% of right-handed persons and 70% of left-handed persons, language being one of the functions that is performed asymmetrically in the brain. Surprisingly, this loop is also found at the same location in deaf persons who use sign language. This loop would therefore not appear to be specific to heard or spoken language, but rather to be more broadly associated with whatever the individual’s primary language modality happens to be.

In addition to Broca’s and Wernicke’s areas, a third area of importance for language, located in the parietal cortex, has been described more recently.


A general problem encountered in any attempt to determine the locations of brain functions is that every brain is unique. Just as every normal human hand has five fingers, but everyone’s hands are different, all human brains have the same major structures, but the size and shape of these structures can vary from one individual to another—by as much as several millimetres. Average measurements can be used, of course, in studying the brain, but the fact remains that the same type of lesion will not always cause exactly the same type of deficit in several different individuals.

With functional brain maps standardized for the sizes of various brains, we obtain a reference that is useful but does not really correspond to the brain of any one particular individual.

Tool : Brain Imaging


Often, when you have a word on the tip of your tongue, you can remember what letter it starts with, or what sound it ends with, or how many syllables it has, though you have not yet recalled the word itself. This shows that accessing a word when you are preparing to speak is not an all-or-nothing process: you can retrieve its various characteristics independently of one another.

In general, women’s overall reading abilities are better than men’s, and this gender difference often makes itself apparent when children are still in primary school. Researchers are still investigating how much of this difference is inborn and how much is acquired, but part of the answer would seem to be that girls have a greater taste for reading. Thus at least part of the reason that girls are better readers might simply be that they spend more time reading, while boys often spend more time playing sports. Some experts believe that increasing the time that boys spend reading and writing, and offering them content that interests them, could reduce this gap between boys and girls substantially.

Girls also seem to be better at spelling. The explanation here might be that females use both hemispheres of the brain in processing sounds, while males tend to use mainly the left side. If girls are therefore better at isolating the various sounds in a word, it would make sense that they would also be better at decoding it and spelling it.


A first model of the general organization of language functions in the brain was proposed by American neurologist Norman Geschwind in the 1960s and 1970s. This “connectionist” model drew on the lesion studies done by Wernicke and his successors and is now known as the Geschwind-Wernicke model. According to this model, each of the various characteristics of language (perception, comprehension, production, etc.) is managed by a distinct functional module in the brain, and each of these modules is linked to the others by a very specific set of serial connections. The central hypothesis of this model is that language disorders arise from breakdowns in this network of connections between these modules.

According to this model, when you hear a word spoken, this auditory signal is processed first in your brain’s primary auditory cortex, which then sends it on to the neighbouring Wernicke’s area. Wernicke’s area associates the structure of this signal with the representation of a word stored in your memory, thus enabling you to retrieve the meaning of the particular word.

In contrast, when you read a word out loud, the information is perceived first by your visual cortex, which then transfers it to the angular gyrus, from which it is sent on to Wernicke’s area.

Whether you hear someone else speak a word or you read the word yourself, it is the mental lexicon in Wernicke’s area that recognizes this word and correctly interprets it according to the context. For you then to pronounce this word yourself, this information must be transmitted via the arcuate fasciculus to a destination in Broca’s area, which plans the pronunciation process. Lastly, this information is routed to the motor cortex, which controls the muscles that you use to pronounce the word.

The Wernicke-Geschwind model is thus based on the anatomical location of areas of the brain that have distinct functions. On the whole, this model provides a good understanding of the primary language disorders, such as Broca’s aphasia or Wernicke’s aphasia. But is also has its limitations. For one thing, its assumption that the various areas involved in processing speech are connected in series implies that one step must be completed before the next one can begin, which is not always actually the case. Because this model also fails to explain certain partial language disorders, other models have been proposed to address these shortcomings.

In addition to semantic memory, which lets us retain the various meanings of words, we must use other specialized forms of memory in order to speak. For example, to pronounce any given phoneme of a language that you know how to speak, you must place your tongue and mouth in a particular position. They assume this position unconsciously, but obviously you must have stored it in memory somewhere in your brain.

In some languages, such as Spanish, the relationship between spelling and pronunciation is fairly straightforward, so it is fairly easy to retrieve the pronunciation of a word when you read it. But in other languages, the exact same string of letters may be pronounced very different ways in different words—for instance, the “ough” in “thought”, “tough”, “through” and “though”, in English, or the “ars” in “jars”, “mars”, and “gars”, in French. These arbitrary variations must be memorized as such, with no logical rules to help.

Tool : The Human Vocal Apparatus


Link : WHAT IS BRAIN LATERALIZATION?Link : Approche de la dominance cérébrale chez les peintres gauchersLink : Surprenant langageLink :
Experience : Right Side/Left Side

The brain hemisphere in which the main language abilities reside has often been referred to as the “dominant” hemisphere for language. But since we now know that the other hemisphere also contributes to language, it would be more accurate to describe the two hemispheres as sharing responsibility for the many aspects of language, rather than one hemisphere’s somehow exercising dominance over the other.

Anthropologists have been able to investigate handedness in ancient cultures by examining their tools. For example, by examining the marks left on a flint ax by the blows struck to make it, researchers can tell whether the person who did this work was right-handed or left-handed. Researchers have also examined ancient art to see what proportions of people are depicted using their right hand and what proportion using their left.

Researchers can generally estimate how right-handed or left-handed someone is by asking him or her a simple set of questions, such as “What hand do you write with?”, “What hand do you use to throw a ball?”, and “What hand do you use to brush your teeth?”

Tool : The Hand


Perhaps the most striking anatomical characteristic of the human brain is that it is divided into two hemispheres, so that it has two of almost every structure: one on the left side and one on the right. But these paired structures are not exactly symmetrical and often differ in their size, form, and function. This phenomenon is called brain lateralization.

The two most lateralized functions in the human brain are motor control and language. When a function is lateralized, this often means that one side of the brain exerts more control over this function than the other does. The side that exerts more control is often called the “dominant hemisphere” for this function, but this expression can be somewhat misleading (see sidebar).

Lateralization of motor control is what determines whether someone is right-handed or left-handed. When someone is ambidextrous—when they can use either hand as easily as the other—it means that their brain is only partly lateralized or not at all lateralized for motor control.

In right-handed people, the “dominant” hemisphere for motor control is the left, while in left-handed people, it is the right. The reason for this inversion is that the motor pathways of the nervous system cross over to the other side of the body as they go down the spinal cord. Thus the movements of one side of the body are controlled by the hemisphere on the opposite side.

About 9 out of 10 adults are right-handed. This proportion seems to have remained stable over many thousands of years and in all cultures in which it has been studied (see sidebar).

Now, what about language—what is its “dominant” hemisphere? And is there any correlation between handedness and language lateralization? Considering how easily we can determine whether someone is right-handed or left-handed, if there were such a correlation, it might prove very useful for research. And indeed, this correlation does exist, but it is not perfect. In the vast majority of right-handed people, language abilities are localized in the left hemisphere. But contrary to what you might expect, the opposite is not true among left-handed people, for whom the picture is less clear. Many “lefties” show a specialization for language in the left hemisphere, but some show one in the right, while for still others, both hemispheres contribute just about equally to language.

Though handedness does influence the brain hemisphere that people use to speak, the left hemisphere does seem to have a natural predisposition for language, and this predisposition is reflected anatomically.


Link : One Brain...or Two?Link : Two Ways of KnowingLink : Drawing on the Right Side of the Brain

Even though language has a sort of “music” to it, from a neurological standpoint, music and language are distinct functions, because the sounds of music and the sounds of language are processed in different parts of the brain. Here are two famous cases demonstrating that language functions and musical functions are independent.

The first case is the French composer Maurice Ravel. After suffering an injury to the left side of his brain, he became aphasic. As a result, he could no longer transcribe melodies, but he could still recognize them, which showed that his ability to perceive music (as opposed to writing or performing it) had been preserved.

The other example is Ernesto “Che” Guevara. Though Che was a brilliant speaker, he suffered from congenital amusia, which made him completely unable to perceive music. Some nasty wits might say that the only reason Che made revolution was to take out his frustration at not being able to tell a salsa from a tango. But of course, they’d be wrong.


Verbal language is not the only way that two people communicate with each other. Even before they open their mouths, they are already communicating through various non-verbal mechanisms.

First of all, their physical appearance, the way they dress, the way they carry themselves, and their general attitude all form a context that lends a particular coloration to their verbal messages. Next, the particular position of their bodies during conversation, the way their eyes move, the gestures they make, and the ways they mimic each other will also impart a certain emotional charge to what they say. There is also what is often called the music of language—the variations in tone, rhythm, and inflection that alter the meanings of words.

When we are talking about language, it is therefore useful to distinguish between verbal language—the literal meaning of the words—and everything that surrounds these words and gives them a particular connotation. That is the big difference between denoting and connoting: the message that is perceived never depends solely on what is said, but always on how it is said as well.

Another good reason to distinguish between the denotative and connotative aspects of language is that they call on different parts of the brain. In the great majority of people, it is the left hemisphere that formulates and understands the meaning of words and sentences, while the right hemisphere interprets the emotional connotation of these words.

For example, if you ask someone who has right hemisphere damage to tell you which of the two pictures here best portrays the expression “She has a heavy heart”, that person will point to the woman with the big heart on her sweater rather than to the woman in tears. Similarly, if you remarked in a sarcastic tone that someone was a really nice guy, a person with right-hemisphere damage would think you really meant it.

When scientists first began to investigate what functions are performed by the parts of the right hemisphere that are homologous to the language areas of the left hemisphere, most of their initial findings came from studying people who had lesions in these parts of the right hemisphere.

Because the sign language used by the deaf involves so many visual and spatial tasks, you might expect it to be controlled by the right hemisphere. But in fact, the proportion of people who are left-lateralized for language is just as high among deaf people who use sign language as it is among people with normal hearing.

Tool: Sign Language

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